Download Worksheet 1: Cells—crossword

Worksheet 1: Cells—crossword
Across
3
membrane
4
diffusion
5
phospholipid
10
Golgi
13
mitochondria
18
organic
20
carbohydrate
21
active
Down
1
vacuole
2
lipid
5
prokaryote
6
omega3
7
protein
8
murein
9
osmosis
11
chloroplast
12
facilitated
14
ribosome
15
eukaryote
16
organelle
17
nucleus
19
nucleic
Worksheet 2: Gadget gallery—cell organelles
1
From top to bottom: nucleus, Golgi apparatus, rough endoplasmic reticulum (or endoplasmic reticulum with
ribosomes), mitochondria, cell membrane, cytoplasm, chloroplast, vacuole, cell wall
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Organelle
Description
nucleus
dense spherical body in cytoplasm
mitochondrion
organelle featuring folded inner
membranes
stack of flat, membranous sacs
Golgi apparatus
A: endoplasmic
reticulum
B: ribosomes
chloroplast
network of membranous
interconnected tubules
tiny spherical bodies either in
cytoplasm or associated with ER
organelle containing green pigment
Function
contains genetic information and
controls cell activities
cellular respiration
package materials for export from the
cell
transport of material within cells
protein production
photosynthesis
Worksheet 3: Model membranes
1
2
Plasma membranes are described as having a ‘fluid’ nature because the phospholipid molecules they contain are
able to move about within the phospholipid layer. ‘Mosaic’ refers to the presence of proteins scattered throughout
the phospholipid bilayer.
3
a Cholesterol molecules provide stability for the membrane structure and reduce permeability of small watersoluble molecules.
b Carbohydrate molecules attached to the membrane surface are involved in cell recognition.
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Process
Description of process
Example of material
exchanged
Simple diffusion
Passive process in which particles
move from an area of high
concentration to an area of low
concentration, along a concentration
gradient
oxygen, carbon dioxide,
urea
Facilitated
diffusion
Passive process—particles move along
a concentration gradient but their
movement is assisted by protein
channels embedded in the membrane
Special kind of diffusion that involves
the passive movement of water
molecules through a partially permeable
membrane from a region of high
concentration of free water molecules to
a region of low concentration of free
water molecules.
Energy-requiring process in which
particles move from a region of low
concentration to an area of high
concentration
amino acids, glucose
Osmosis
Active transport
Component of
plasma membrane
involved
Diffuse directly
through the
phospholipids bilayer
by passing between
the phospholipids
molecules
Protein channel
embedded in plasma
membrane
water
Diffuse directly
through the
phospholipids bilayer
by passing between
the phospholipid
molecules
materials that are
required in relatively high
concentrations by cells,
e.g. mineral ions by plant
root hair cells; digested
nutrients by gut epithelial
cells in animals
Protein channels
embedded in plasma
membrane
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Worksheet 4: Enzyme ABC—amazing biological catalysts
1 Correct order of terms: catalysts, protein, metabolism, biomolecules, anabolic, photosynthesis, catabolic,
cellular respiration, substrate specific, optimal, temperature, coenzymes, active site, denatured, deficiency
2
Enzymes are needed in small amounts.
Enzymes are not used up in chemical reactions.
Enzymes can be used over and over again.
Enzymes do not affect the final amount of product in a reaction.
Enzymes decrease the activation energy required to initiate reactions.
Worksheet 5: Active enzymes
1
2
Enzymes are specific for a particular substrate, in the same way a key is specific for a particular lock. A given
enzyme will only catalyse a reaction involving the substrate molecules that fit its active site.
3
An enzyme's active site can be compromised by extremes in pH and temperature (excessively high temperature).
4
When the active site of an enzyme is denatured, its shape is altered so that it no longer ‘fits’ the substrate
molecule. When this happens, the ability of the enzyme to catalyse a reaction ceases, i.e. no further reaction
occurs.
5
In the "induced fit" model the interaction between the substrate and the enzyme alters the shape of the active site
to precisely fit the shape of the substrate molecule.
6
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7
Graph B represents a reaction in which energy is released—this makes it an exergonic reaction. Energy stored in the
sucrose molecule is present in the chemical bonds of the molecule. When the chemical bond between the glucose
and the fructose molecule is broken, energy is released.
Worksheet 6: Energy transformations
1
From top to bottom: mitochondrion, lactic acid, electron transport, exergonic reaction, chloroplast, Krebs cycle,
endergonic reaction, energy, ATP, anaerobic respiration
2
• The energy-rich molecule ATP is generated from ADP and inorganic phosphate in a cycle that continues to make
energy available for cells.
• First step in breakdown of glucose—glucose molecule is split (glycolysis) to produce two pyruvate molecules (3C
molecules), generating 2 molecules of ATP.
• The process of photosynthesis combines carbon dioxide and water in the presence of light and chlorophyll to
construct energy-rich glucose molecules. Oxygen and water are also produced.
Worksheet 7: Mighty mitochondria
1 Cellular respiration is the process in which complex organic compounds such as glucose are broken down to
release energy. Carbon dioxide and water are byproducts.
2
C6H12O6 + 6O2 → 6CO2 + 6H20 + energy (36–38 ATP)
3
Correct order of terms: Krebs cycle, electron transport, glycolysis, electron transport, mitochondria
4
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Mitochondria make energy available to cells, which is used to power or drive metabolic processes. They represent
the cell’s power generator, and so are likened to a powerhouse.
Worksheet 8: Zooming in on photosynthesis
1 Correct order of terms: grana, light-dependent, stroma, light-independent (or dark)
2
3 Any two of:
• CO2 concentration—the higher the CO2 concentration, the greater the rate of photosynthesis.
• Light intensity—the greater the light intensity, the greater the rate of photosynthesis.
• Temperature—rate of photosynthesis increases with increasing temperature until optimal temperature is
reached.
• Water availability—water is an important ingredient in photosynthesis; reduced water availability reduces
the rate of photosynthesis.
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Worksheet 9: Energy transformations in cells: cellular respiration and photosynthesis—a concept
map
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Worksheet 10: Cell’s user manual—a concept map
Worksheet 11: Nuclear puzzle—same pieces, different picture!
1
P: phosphate molecule; S: sugar group (deoxyribose sugar or ribose sugar); A, T, C, G: adenine, thymine,
cytosine, guanine respectively
2
Consistency of colour coding important, e.g. adenine—red, thymine—orange, cytosine—green, guanine— blue
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3
Ensure strand is antiparallel.
4
Feature 1: number of hydrogen bonds—adenine and thymine share three hydrogen bonds, and so can only bond with
one another; cytosine and guanine share two hydrogen bonds.
Feature 2: size of base molecules—adenine and guanine are purines (double ring structure) so are large
molecules; each bonds with a purine (single ring), thymine and cytosine respectively; this results in consistency
of size at the ‘rungs’ of the DNA helix, keeping the strands parallel.
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5
6
mRNA strand should follow structure shown in Figure 3.27, using the following order of bases: G U G G A G U G
A
Worksheet 12: Hypothetical halitosis
1
a Subjects 1 and 5.
b Subject 1 tests positive for both salivary proteins JM and PU, i.e. two positives for bad breath proteins. Subject 5
tests positive for three proteins, both JM and PU, and NS, which has no smell and so doesn’t cancel the effect of
either JM or PU.
2
While Subject 4 tests positive for both JM and PU, the presence of protein TP cancels the effect of one of these. This
effectively reduces the magnitude of the halitosis.
3
Neither Subjects 3 nor 6 tests positive for either of the bad breath proteins JM or PU. They both test positive for one
salivary protein. Subject 3 tests positive for TP, which results in a pleasant odour, while Subject 6 tests positive for
protein NS, which has no smell. Subject 3 has the most pleasant breath. Based on the SPIT results alone, Subject 3
gets the date.
4
Subjects 1 and 5—equal first place, followed by Subject 4, then Subjects 2 and 6—equal third, and Subject 3 with
least halitosis.
Worksheet 13: Homeostasis—crossword
Across
1
hormone
3
environment
5
receptor
6
stimulus
8
stomata
12
effector
13
diabetes
Down
1
homeostasis
2
internal fluid
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4
osmoregulator
7
insulin
9
osmoconformer
10
glucagon
11
response
Negative feedback system: stimulus–response system in which the response reduces the magnitude of the initial
stimulus.
Disturbance detector: receptor that detects a change in internal or external environment that may lead to a change in
that particular internal factor.
Misalignment detector: receptor that detects a change in an internal factor that is under homeostatic control.
Oxygen debt: the amount of oxygen that is required to break down the lactic acid accumulated during a period of
anaerobic respiration.
Worksheet 14: Breathe deep—respiratory gases and negative feedback
1
Correct order of terms: response, reduced, limits, carbon dioxide, oxygen
2
receptor: chemoreceptors in arteries and brainstem
effector: diaphragm and intercostal muscles
response: increased breathing rate
feedback: decreased blood level of carbon dioxide
3
The negative feedback mechanism restores blood pH by reducing the amount of hydrogen ions that dissociate from
H2CO3. This occurs as a result of the increased ventilation rate that maintains a high concentration gradient between
the blood and the alveolar air, resulting in increased diffusion of carbon dioxide out of the blood at the alveoli.
Worksheet 18: Hormonal plants—plant growth regulators
1
Coleoptile A is the control against which the experimental set-ups B and C are compared. There should be no
change to the control. Any change to the control suggests that extraneous factors have influenced the test and this
would render any results from the experimental set-ups inconclusive.
2
The mica sheets establish an impermeable barrier between cells at the tip and cells below the mica. Any
materials present in the tip that might diffuse downwards and influence the bending response are blocked.
3
A plant growth regulator that is present in the tip and affects cells below is unable to diffuse downwards due to the
mica. B establishes that when such a chemical is blocked from moving down the coleoptile away from the light
source, no bending response can occur.
4
The experimental results support the hypothesis. Coleoptile C did show a bending response towards the light
source when a chemical present in the tip after exposure to light was able to move down the side of the coleoptile
away from the light source.
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Experimental design: Set up a number of coleoptiles into two groups, half with no foil cap (Group A) and half
with foil cap (Group B). Expose all of the coleoptiles to a light source from one direction only for a period of 24
hours.
Results: It is expected that Group A coleoptiles show a growth response (bending) towards the light source, and
that Group B coleoptiles show no bending at all.
Hypothesis: If only those coleoptiles that had their tips stimulated by light showed the bending response, then the
hypothesis would be supported.
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Worksheet 15: Transpiring trees and other vascular plants
Worksheet 16: Critical signals—detecting and responding to signals
1 Correct order of responses: true, true, false, false, false, false, true, false, true, true, false, true, false, true
2
• Different kinds of receptors are sensitive to different stimuli. For example, chemoreceptors are sensitive to
chemical stimuli; mechanoreceptors are sensitive to physical stimuli; photoreceptors are sensitive to light;
thermoreceptors are sensitive to changes in temperature.
• Neurotransmitter is a signalling molecule released from the pre-synaptic membrane of nerve cells;
neurotransmitter is a chemical messenger but it is not a hormone. Hormones are different kinds of chemical
messengers that travel in the bloodstream.
• Excitability of nerve cells depends in part upon the unequal distribution of sodium ions and potassium ions inside
and outside the cells (high concentration of sodium ions outside the cell, high concentration of potassium ions inside
the cell).
• The pituitary gland is sometimes called the master gland of the endocrine system because of its role in
coordinating the release of hormones from other endocrine glands.
• The intensity of a stimulus is important in the generation of an action potential—a stimulus must polarise a nerve
cell sufficiently to reach the threshold potential in order for an action potential to occur.
• Misalignment detectors and disturbance detectors together ensure the stability of the internal environment. For
example, in temperature regulation, disturbance detectors in the skin are sensitive to changes in the external
environment and misalignment detectors in the brain fine-tune mechanisms that regulate core temperature.
• Plant hormones include auxins, gibberellins, abscisic acid and ethylene.
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Worksheet 17: Signalling cells—cell communication
1
2
a An action potential or nerve impulse is a wave of electrical change that moves along a nerve cell.
b An action potential is generated when a nerve cell is sufficiently polarised by the difference in charge between
the inside and outside of a cell to trigger depolarisation. This is called the threshold potential.
3
a acetylcholine
b Acetylcholine is called a signalling molecule because it binds with receptor sites on target cells and signals an
instruction to respond in a particular way, i.e. it stimulates the target cell, causing a response.
3
a A → Z; B → Y; C → W; D → X
b receptor site
c The receptor sites on target cells are specific to particular signalling molecules, i.e. they bind with only the
signalling molecules they fit.
d neurotransmitter (acetylcholine), hormone
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Worksheet 19: Pathogens—crossword
Across
3
Organism that hosts the juvenile form of a pathogenic organism, also called secondary host.
5
Protista that features branching hyphae that penetrate host cells to absorb nutrients.
7
A condition that impairs the normal functioning of an organism.
10
Kingdom of heterotrophs that includes pathogens such as ringworm and tinea.
11
Organism that is host to the adult form of a parasite.
13
Organism that lives in a close relationship with a host organism, receiving a benefit from the host and the host
is harmed.
14
Protein coat surrounding the nucleic acid core of a virus particle.
16
Disease-causing organism.
Down
1
A type of virus that manufactures DNA from viral RNA.
2
Organism that carries a pathogen from one host to another.
4
A kind of disease that is caused by a living organism.
6
Virus that infects a bacterium.
8
Pathogen characterized by a DNA or RNA core surrounded by a protein coat.
9
Collective name for roundworms, hookworms and threadworms.
12
Single-celled eukaryote, some cause disease (eg. malaria) while others do not.
14
Individual organism that is infected by a pathogen without showing symptoms, but can transmit the pathogen
and therefore disease to others.
15
Agent of disease composed only of protein.
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Worksheet 20: Clean kitchens—preventing pathogens
Suggested guidelines:
Guidelines
Wash hands thoroughly using soap and water before
handling foods.
Wash kitchen surfaces thoroughly before using surface
for food preparation.
Keep uncooked foods separate from cooked foods.
Do not handle cooked or fresh foods, such as salad
items, on same surface or with same utensils as have
been used on uncooked foods.
Store meats and cooked foods in the refrigerator.
Use cling wrap or sealed containers to cover foods for
storage.
Explanation
Prevents transfer of bacteria from hands to food.
Prevents transfer of bacteria from kitchen surfaces
to food.
Prevents transfer of bacteria from uncooked food to
cooked food.
Prevents transfer of bacteria from uncooked food to
cooked food.
Cold conditions slow spoilage rate.
Keeps food fresh longer, prevents dehydration.
Worksheet 21: Self-defence mechanisms
1
a specific, physical, antibiotics, ciliated, phagocytic, complement, inflammation, interferons
b
specific adaptive, memory
c humoral, T-lymphocytes
d antigens, antibodies
e plasma
f transplant
g encapsulation, bacteriocidal
h enzymes
2
Pyrogens: chemical that acts on brain causing body to reset set-point for core body temperature at a new and higher
level; produced by bacteria Mast cells: found in walls of blood vessels, gut and respiratory system; involved in
allergic reactions; release histamines
Lymphatic system: system of glands involved in defending the body against pathogens
Cytokines: chemical produced by T-helper cells that control the function of B cells, cytotoxic T-cells and
phagocytes NK cells: ‘natural killer’ cells are lymphocytes involved in destroying virus-infected cells and cancerous
cells
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Worksheet 22: Target practice—aiming antibodies at invaders
Worksheet 23: Immunology—matchmaker
1
2
Correct order of terms: naturally acquired active immunity, histamine, self, MHC complex, resolvins, antigen,
immunity, autoimmune disease, allergy, antibody, passive immunity, vaccine
Antihistamine: substance that acts to counteract inflammation
Immunoglobulin: antibody
Non-self: describes antigen/proteins on the surface of cells that are not recognised by the body as belonging to ‘self’
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Artificially acquired active immunity: immunity conferred by the administration of a vaccine that provokes antibody
production
Toxoid: inactivated toxins (e.g. produced by bacteria) that are used in vaccines to produce antibodies in an immune
response
Allergen: substance that provokes an allergic reaction
Worksheet 24: Horrible hayfever and other allergies
1
2
antibody
3
IgE
4
Mast cells are located in the walls of blood vessels, and in the lining of gut and respiratory passages.
5
The release of histamines causes dilation of blood vessels in a local area, resulting in leakage of white blood cells as
well as an increased volume of tissue fluid, which leads to swelling.
6
Allergen particles combine with IgE immunoglobulins on mast cells, triggering the release of histamines and an
allergic reaction. The reaction becomes increasingly lessened as fewer and fewer antibody sites are available for
allergen particles. Eventually all sites are taken, so the incoming allergen cannot combine with immunoglobulin and
no reaction occurs.
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Worksheet 25: Molecular genetics—crossword
Across
1 polymerase
2 transcription
4 translation
6 intron
7 exon
10 trait
13 guanine
15 anticodon
16 codon
17 diploid
18 gene
19 genome
Down
1 pyrimidine
3 polypeptide
5 gene regulation
8 nucleotide
9 chromosome
11 adenine
12 ribosome
14 uracil
Worksheet 26: Counting characteristics—variation in a group
2
Figures entered into the table are dependent on class/sample size. It is expected that a ratio pattern of 3:1 will
emerge. However, this will depend on the make-up of the sample and in particular on the sample size. The larger the
sample size, the closer to a 3:1 ratio will be expected.
3
A pattern of ratio 3:1 is expected to emerge. Very small sample sizes may vary significantly from this. Any
sample size is a random sample, so a ratio that is different from the expected result is possible.
4
Larger sample sizes are more likely to be representative of a population than smaller sample sizes. For example, a
random sample of 2 marbles from a bucket containing 4 reds and 8 blues may net 2 red marbles. The sample is not
representative of the ratio that exists in the entire ‘marble population’. Taking a random sample of 20 marbles from
a bucket that contains 40 reds and 80 blues (the same ratio) is likely to net at least some of each colour. The larger
the sample, the more representative it is likely to be, and therefore the more reliable.
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Worksheet 27: Genetic dictionary—reading the code
1
2
a During transcription, the DNA template strand is copied to produce a single-stranded molecule of mRNA.
b During translation, the nucleotide sequence in mRNA is interpreted using the genetic code—amino acids are
arranged in a linear sequence to produce a polypeptide chain.
3
4
AUG is a start codon—it initiates polypeptide production. UAG is a ‘stop’ codon—it signals the end of polypeptide
production.
polypeptide
Summary: The role of genes is to direct the production of polypeptides (proteins).
Worksheet 28: GTT—genetic tools and technology
1
Correct order of terms: genetic modification, endonucleases, polymerase chain reaction, Taq polymerase, gel
electrophoresis, DNA sequencing, DNA probes, recombinant DNA
2
Cloning: technology used to create genetically identical individuals
Primers: short, single-stranded DNA sequences that bind to specific DNA sequence in the larger DNA molecule;
used to target a particular section of DNA, e.g. for the purposes of amplification
Plasmid: circular thread of bacterial DNA
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DNA ligase: enzyme that rejoins cut ends of DNA molecule
DNA profiling: technology used to produce a DNA banding pattern unique to an individual; banding pattern
identified using technique such as gel electrophoresis Genome: full complement of genes in a particular
individual
Worksheet 29: PCR—a gene amplification technology
1
Target DNA is the section of a DNA molecule that has been identified for amplification.
2
The DNA polymerase adds nucleotides to the unzipped DNA strands, thereby constructing new copies of the
original strands.
3
Taq polymerase functions normally at temperatures that are excessive for human DNA polymerase. PCR
requires high temperatures, e.g. to denature the DNA molecule.
4
Primers are short, single-stranded DNA sequences that bind to a specific section of the DNA molecule. They are
used in PCR to target the section of the DNA molecule to be amplified, i.e. they indicate the point along the DNA
molecule at which amplification begins.
5
Adenine, thymine, cytosine, guanine. These nucleotides have been added to the buffer solution to provide the
building materials for the construction of the DNA fragments to be copied.
6
The PCR reaction produces are very large number of target DNA copies in a relatively short time.
7
PCR technology makes large quantities of identical DNA fragments available for analysis using other techniques,
when only very small amounts (not enough for meaningful analysis) may have been recovered at a crime scene, for
example.
Worksheet 30: Cell reproduction—matchmaker
1 Correct order of terms: somatic cells, crossing-over, homologous chromosomes, gamete, differentiation, diploid,
polyploid, homeotic genes, mitosis, haploid, non-disjunction, meiosis
2
Cell division: process in which a cell separates (divides) into two new cells
The following four terms represent sequential stages during the process of mitosis:
Prophase: duplicated chromosomes appear as fine strands, condensing to form double stranded chromosomes
composed of two chromatids
Metaphase: chromosomes are arranged about the centre of the spindle attached by their centromeres
Anaphase: centromeres divide so that sister chromatids are separated, each moving to opposite poles
Telophase: nuclear membrane begins to reform and cell membrane pinches inwards in readiness for cell
division
Cytokinesis: Dividing cell becomes completely separated into two new cells as cytoplasm is divided and cell
membrane is formed between the cells
Interphase: Stage that occurs between mitotic divisions; chromosomes not visible during this stage;
chromosome replication occurs as well as cell growth and metabolic processes
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Worksheet 31: Modelling mitosis and meiosis
1
Mitosis
Meiosis
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2
•
•
Mitosis
Results in two daughter cells genetically
identical to each other and to the cell
from which they have arisen
Resulting cells usually diploid
•
•
Meiosis
Results in daughter cells that are
genetically different from one another
and from the cell from which they have
arisen
Resulting cells are haploid
Worksheet 32: True or false?—karyotypes, alleles and mutations
1
Correct order of responses: false, true, true, false, false, true, false, true, true, false
2
• In a karyotype the full set of chromosomes of a cell or an individual are set out in a formal arrangement with
chromosomes displayed in homologous pairs, the pairs usually arranged in order from largest to smallest.
• Metacentric, submetacentric and acrocentric are terms used to identify the approximate position of the
centromere on chromosomes as ‘central’, ‘nearer one end than central’ and ‘close to one end’ respectively.
• In humans, females are said to homogametic because of the presence of similar sex chromosomes, while males
are said to be heterogametic due to the presence of sex chromosomes that are not similar.
• A mutation is a change in the sequence of bases in a strand of DNA. This may result in damage or disease in the
individual in which it occurs or to whom it is passed on. When silent mutations occur there is no observable
change in phenotype of an individual.
• Frameshift mutations are generally more damaging than missense mutations because the addition or deletion of a
single nucleotide in the DNA sequence results in a ‘shift’ in the codons so that during translation all subsequent
amino acids placed in the polypeptide chain are altered.
Worksheet 33: Counting on karyotypes—chromosomal diagnoses
1
Individual A: Female, normal
Individual B: Male, trisomy 21 (Down syndrome)
Individual C: Male, XXY—extra X chromosome (Klinefelter’s syndrome)
Individual D: Female, XO—missing one X chromosome (Turner’s syndrome)
2
Sex determination, chromosomal abnormalities such as extra or missing chromosomes, translocation
conditions in which one chromosome is physically connected to another.
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3
Karyotyping does not provide information about gene mutations that might confer a genetic disease, because the
shape of the chromosome in such instances remains unchanged.
4
The technique of ‘chromosome painting’ uses fluorescent dyes to identify particular chromosomes so that they are
distinguishable from other chromosomes on the basis of colour. Each homologous pair takes up a different coloured
fluorescent dye. Arranging homologous chromosomes in a karyotype can be done with greater accuracy.
Worksheet 34: Genotype, phenotype and crosses—crossword
Across
6
Describes the state of having only one allele of a pair rather than two; eg, X chromosome in human males.
7
Describes a characteristic that is observed in the phenotype of a heterozygote.
8
Genetic make-up of an individual in relation to one or more genes.
11
Describes a characteristic that is observed in the phenotype of an individual homozygous for a particular allele,
but not observed in the heterozygote.
12
Alternative form of a gene.
Down
1
Describes alternative forms of a characteristic that are observed in intermediate form in the phenotype of a
heterozygote
2
Describes alternative forms of a characteristic that are fully expressed in the phenotype of a heterozygote
3
Cross between individuals that takes into account one particular characteristic
4
State of an individual that carries two different forms of a gene in relation to a particular characteristic
5
Cross between individuals that takes into account two different characteristics
6
State of an individual that carries identical alleles for a given gene
9
Cross between an individual displaying a dominant phenotype and an individual displaying a recessive
phenotype (homozygous) for the purposes of determining whether the dominant individual is heterozygous or
homozygous
10
Physical expression of a particular genotype
Worksheet 35: Mendel’s spin on meiosis—Mendel’s principles
1
During meiosis alleles for a given gene separate so that gametes are formed that each contain one copy of an
allele for that gene.
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2
The
Principle of Independent Assortment means that the order in which one pair of homologous chromosomes is arranged and
subsequent movement to the poles during meiosis is not influenced by other homologous pairs.
Worksheet 36: Linkage and pedigrees
1
Correct order of terms: linkage, recombinant, crossing-over, gene complex, sex-linkage, X-linked, Y-linked,
pedigree, stud books, discontinuous, continuous, polygenic
Worksheet 37: Puzzling pedigrees—analysing family histories
A
B
1
I i, I i respectively.
2
The expression of the alleles that determine A antigens and B antigens on red blood cells are codominant— they
are fully and equally expressed in the phenotype. The expression of the i allele is recessive to both A and
B.
3
The mode of inheritance for haemophilia is X-linked recessive. Males that carry the allele that confers
haemophilia have only one X-chromosome—there is no homologue with an allele for the expression of
normal clotting factor to mask the effect of the haemophilia allele.
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4
Haemophilia appears in descendants of Queen Victoria who are not descendants of Leopold. Victoria’s second
daughter must be a carrier to pass the condition on to her second son; at least two of her daughters in the pedigree
also have sons with the condition so she has passed the affected allele onto them.
5
Worksheet 38: Evidence from the past—crossword
Across
2
continental drift
6
isotope
8
amber
14
half life
15
radiometric dating
16
fossil
17
gondwana
18
absolute
Down
1
stratigraphy
3
evolution
4
trilobite
5
indicator fossil
7
thermoluminescence
9
biogeography
10
radiocarbon dating
11
relative
12
stromatolites
13
cast
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Worksheet 39: Snapshots in time—change on a grand scale
1
Geological
time-scale
205–141
million years
ago
146–65
million years
ago
55–38
million years
ago
23–16
million years
ago
Geography
Australia still part of
supercontinent called
Pangaea; Australia and
entire landmass much
further north
Australia still joined to
Antarctica, New Zealand
and South America, this
remnant of Gondwana
placed Australia further
south than its current
position
Australia still connected to
Antarctica via land bridge
across Tasmania;
Australian land still
relatively close to South
Pole
Australia completely
separated from
Antarctica—an island
continent; positioned much
further north and closer to
the equator
Climate,
conditions
Relatively hot and
dry
Flora
Fauna
Conifers, ferns,
horsetails,
gingkos,
clubmosses
Fish and amphibians
Cool and wet, with
dark and icy
winters
Conifer forests
covered much of
Australia; ferns,
cycads, ginkgos,
clubmosses,
horsetails; first
flowering plants
Dinosaurs, early birds,
giant marine reptiles,
first mammals including
platypus ancestors
Wet but warmer
conditions
Rainforests are
dominant
vegetation
Warm and wet in
the north; cooler
and drier by late
Miocene
Rainforests in the
north of the
continent
Rainforests
limited to coastal
regions; open
forests and
woodlands
dominate the
drier interior
Eucalyptus and
acacia (wattle)
dominate the
landscape;
wildflowers
10.4–5
million years
ago
Positioned further north and
connected to South East
Asian Islands; isolated from
other major landmasses
Becoming drier
5–1.6 million
years ago
years ago
Australia almost in present
position with northern
boundary in equatorial
region
Warm and wet
1.6 million
years ago –
10,000 years
ago
Close to present global
positioning
Fluctuations in
polar ice-caps
mean fluctuating
climate change
from cold, dry
conditions to warm
and wet
Vegetation
adapted to dry
conbditions;
pattern of forests,
grasslands and
desert changing
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Mammals including
monotremes,
marsupials and
placentals; flightless
birds, reptiles,
amphibians
Marsupials such as
kangaroos, possums
and koalas existed as
well as marsupial lion;
bats; reptiles including
crocodiles, snakes,
lizards; various bird
species, insects
Megafauna such as
diprotodont; marsupial
lions and thylacines;
kangaroos evolve to
move on hind legs only
Kangaroos, wallabies,
parrots, crocodiles,
snakes including giant
pythons; rats and mice
migrate from South
East Asia
Megafauna are
dominant animals
27
Geological
time-scale
10 000 years
ago –
present
2
Geography
Already in present position
Climate,
conditions
Relatively wet until
about 5000 years
ago when the
continent became
drier
Flora
Fauna
Open eucalypt
forests,
woodlands and
grasslands,
wildflowers
Megafauna have
disappeared; present
day species unique
marsupials, birds
including emu, parrots;
reptiles, amphibians;
European settlement
has meant extinction for
many species
110 million years ago, Australia was still connected to the southern landmass that once formed Gondwana. Its
global position was much nearer the South Pole, so its climate was much colder and wetter than it is today. Since
then it has became separated to form an isolated continent and has slowly moved northward to its present
position, with its northern-most parts in the tropics. As a result, its climate has become much warmer and drier.
Conifer forests have given way to eucalypts and wattles, rainforests in the warm and wet north-east coastal
region, and desert conditions at the interior. Megafauna species have disappeared and the dominant species are
the marsupial mammals and colourful birds. Australian plants and animals are unique in the world, having
evolved in a cradle of long-term geographical isolation.
Worksheet 40: Evidence of evolution from anatomy and molecules—matchmaker
1
Correct order of terms: mitochondrial DNA, molecular clock, analogous structures, genetic linkage group,
homologous structures, von Baer’s law, comparative anatomy, DNA hybridisation, comparative embryology,
thermal stability
2
Chloroplast DNA: DNA contained within chloroplasts
Tetrapod: vertebrate organism that features four limbs
Phylogenetic tree: simple tree diagram indicating evolutionary relationship between related organisms based
on structural similarities
Fossil DNA: remnant DNA fragments extracted from remains of fossilised organisms
Vestigial structure: reduced structure present on an organism with no apparent function; suggests a remnant of a
function in an evolutionary ancestor
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Worksheet 41: Homologous hands—comparative anatomy
2
Homologous structures are anatomical features in different organisms that are fundamentally similar in form or
structure.
3
Homologous structures suggest that the organisms in question share a common ancestor from which the
different forms diverged.
Worksheet 42: Population change—matchmaker
1
Correct order of right-hand column
Box 7: A population of rabbits has some individuals that are resistant to calicivirus and some that are sensitive.
Box 6: Feather colouration in the tawny frogmouth makes it well camouflaged in its natural environment.
Box 1: Two pink-flowering snapdragon plants produce some red-flowering and some white-flowering
offspring.
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29
Box 3: Dieldrin-resistant blowflies increase in a population exposed to the pesticide, while the frequency of
sensitive individuals declines.
Box 2: A dairy farmer deliberately retains cows for breeding that produce large volumes of milk. Box 4: A small
population that is isolated on an island shows change in allele frequency resulting from chance only.
2
Box 5: Migration from one population into another introduces new genetic variation into the second population.
Variation: different forms of a particular characteristic that exists in a population
Adaptations: features of organisms that make them well-suited to their particular environment or lifestyle Sexual
reproduction: form of reproduction that involves the mixing of genetic information from two parents, thereby
generating variety in offspring
Natural selection: process of evolutionary change within species such that individuals with favourable
characteristics have an increased chance of survival and reproduction compared with individuals with less
favourable characteristics
Biologically fit: individuals that are well adapted to the environment in which they live; produce more offspring
than their less biologically fit counterparts
Artificial selection: process of change within a population/species that is driven by human intervention, whereby
only those individuals featuring the most desirable characteristics are selected for breeding
Genetic drift: change in allele frequencies in a population that occur as a result of chance alone Gene flow: exchange
of genes between populations of a species as a result of breeding between individuals in those populations
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30
Worksheet 43: Superbugs—a modern tragedy in natural selection
1
Variation exists within a population of Staphylococcus bacteria, i.e. some are resistant to the antibiotic and some are
not resistant.
Resistant individuals have the favourable phenotype in the presence of the antibiotic, i.e. they are more
biologically fit
↓
These resistant individuals are adapted to an environment in which the antibiotic is present—they have a
survival advantage - an increased chance of surviving and reproducing—they are ‘selected for’
↓
Through reproduction (transfer of plasmids that contain antibiotic resistant genes) they pass on the alleles that
confer the survival advantage to the next generation (and to other bacteria)
↓
Non-resistant individuals are sensitive to the antibiotic, i.e. they have an unfavourable phenotype and are less
biologically fit
↓
Non-resistant individuals have a decreased chance of surviving and reproducing—they are ‘selected against’
↓
Individuals with unfavourable phenotype decline in the population
↓
Over time and generations there is a shift in the allele frequencies and the associated phenotypes in the
population, such that those with the resistant phenotype increase in frequency and those with the nonresistant phenotype decrease in frequency.
2
Increased use of antibiotics exposes bacteria to the selection pressure, accelerating the process of natural
selection that has led to increasing levels of antibiotic resistance. When new and more potent antibiotics
are developed and applied, a bacterial mutation that confers resistance is passed to offspring (and to other
bacteria through transfer of plasmids), leading to an entire population of resistant individuals. Failure to
complete a course of antibiotics also contributes to the problem—taking only part of a course of
antibiotics will be effective at destroying the most susceptible bacteria causing an infection, leaving any
resistant individuals that may be present to increase in number before causing a relapse. Re-application of
the same antibiotic will be less effective because the remaining population are resistant.
Worksheet 44: The truth of the matter—patterns in evolution
1
Correct order of responses: true, false, true, false, false, true, true, true, false, true
2
• Divergent evolution occurs when related species diverge from a common ancestral species.
• The presence of 13 different species of finches on the Galapagos Islands is understood to be an example of divergent
evolution.
• Parallel evolution occurs when different but related species diverge from a common ancestral group and then
independently evolve similar structural features.
• When paired chromosomes fail to separate during meiosis, the resulting offspring feature multiple sets of
chromosomes. This is called polyploidy and is responsible for sudden speciation. Polyploidy is common is some plant
groups.
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Worksheet 45: Adaptive radiation—Darwin’s finches
1 Adaptive radiation is the rapid divergence of one or more species from an ancestral population.
2
3
a Seeds; Species A features a large, strong beak that is suitable for crushing large seeds.
b Insects; Species F beak is most similar to the beak of species B which is an insect eater.
4
• Ancestral mainland population included variation, e.g. in size and shape of beak.
• Ancestral population migrate to islands. Initially expect proportions of variants to be representative of
original population.
• Different environmental pressures (food sources available on different islands) favour particular
phenotypes, e.g. a large, strong beak adapted to crushing seeds is favoured on some islands, whereas a
long, fine beak adapted to extracting nectar is favoured on other islands.
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• Birds with phenotypes that confer a survival advantage are favoured on some islands, whereas
different phenotypes are favoured on other islands. The most biologically fit individuals increase in
number on each island, whereas less fit individuals leave less offspring and their numbers decline.
• Over time and many generations, distinct races appear on each of the islands.
• Cessation of gene flow between populations on the different islands means races become increasingly
adapted to their particular environment, and increasingly different from one another.
• When gene flow is no longer possible between members of the different populations, speciation is said
to have occurred.
Worksheet 46: Human evolution and interventions—crossword
Across
2
Oldest known hominid fossil, dated at about 6 million years old
4
Fully bipedal, human-like primates 6 Describes members of species in the Genus Homo that co-existed with Homo
sapiens but became extinct about 30 000 years ago; fossils originally discovered in the Neander river valley in Germany
10 Practice of using fire to remove dense vegetation and promote new growth; used by Australian Aborigines
15 Late Palaeolithic (Stone Age, 40 000 years old) humans whose fossil remains show evidence of culture
16 Species name of most recently discovered humans whose fossil remains on the Indonesian island of Flores
reveal complex culture
Down
1 Genus of robust hominids that used tools
2
Artificial selection, i.e. selecting only those organisms with the most desirable characteristics for breeding purposes
3
Technical term used to describe testing procedure to determine the presence or absence of genetic defects in
IVF embryos before implanting
5
Class to which the four hominid genera belong
7
Genus of robust hominid that includes the famous ‘Lucy’ fossil
8
Species to which modern humans belong
9
Describes ‘giant’ animal species including mammals, reptiles and emu-like birds that became extinct in the
last 35 000 years
11 Knowledge accumulated and passed from generation to generation through various forms of communication
12 Mobility that involves walking on two legs
13 Order of animals featuring grasping hands, bicuspid teeth, binocular vision, well-developed brain; includes
monkeys, apes, humans 14 Genus to which modern humans belong
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Worksheet 47: Fluorofish—a controversial application of gene transformation
1
Fluorescence gene isolated from jellyfish
↓
Specific gene promoters (skin, muscle) isolated from zebra fish
↓
Hybrid gene produced that is composed of zebra fish gene promoter sequence and jellyfish fluorescence gene
↓
Hybrid gene injected into zebra fish embryos by microinjection at early stage of development—one or two-cell stage
↓
Transgenic zebra fish allowed to develop
↓
Fluorescence observed in relevant differentiated tissue, e.g. skin tissue
2
The transgenic zebra fish will likely die as a result of predation—the fluorescence means it is not camouflaged in its
natural environment.
3
Ethical issues include: unknown consequences of this kind of intervention for a species, especially if transgenic animals
escape to wild populations; may be seen as ‘playing God’; animal rights issues.
4
Sheep have been successfully engineered in the UK to include a human gene that results in the production of a protein in
sheep milk. This represents a potential treatment for the genetic disease cystic fibrosis.
GM cattle: include a human gene that results in production of milk that contains a protein that may be useful in treating
multiple sclerosis.
Research into the development of GM cats that are hypo-allergenic.
Worksheet 48: Homo hobbit—the lost tribe of Flores
1
The fossil evidence of upright stance, bipedalism, flattened nose, and arms shorter than legs indicates that Homo
floresiensis was indeed a human species. Artefacts such as cooking utensils, stone tools and evidence of use of fire
indicate relatively advanced intelligence and culture.
2
The general pattern observed in hominid evolution shows an increased brain-case size from older to more recent
fossils, a pattern that suggests a larger brain together with increasing intelligence. Homo floresiensis was a species that
3
stood at only 1 metre tall with a brain-case of only 380 cm , and yet showed the hallmarks of advanced intelligence.
3
Homo sapiens and Homo floresiensis appear to share a common ancestor that diverged to yield different lines, one
leading to Homo erectus and Homo floresiensis (which appear to be closely related) and the other giving rise to Homo
heidelbergensis, from which Homo neanderthalensis and Homo sapiens evolved.
4
Possible geographical isolation of ancestral population on island (Flores) due to rise in sea levels. No gene flow with
original population, together with unique environmental pressures over millennia, would steer island population
towards adaptations that suit its unique environment. Population becomes increasingly different from the ancestral
population, eventually evolving into distinct species.
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