Download Final Review Answer Key - Mercer Island School District

Final Review: 2nd Semester Biology
1.
What is the purpose of cellular respiration? What are the reactants? What
are the products?
The purpose of cellular respiration is to produce ATP (the energy currency of
the cell). Glucose (C6H12O6) and oxygen (O2) are the reactants in the overall
reaction. Carbon dioxide (CO2) and water (H2O) are the products. The
energy released in the process is used to create ATP (from ADP + P).
2. Describe an ATP molecule, including which bond is a high energy bond.
ATP is adenosine triphosphate. It has an adenine (nitrogen base), a ribose
sugar and three phosphate groups attached. The bonds between the
phosphate groups are high energy bonds.
3. Complete the ATP/ADP cycle below. Explain which has higher energy :
ATP or ADP + P group. Indicate which reaction requires energy ATP 
ADP + P group or ADP + P group ATP, and indicate which processes
can provide this energy or use this released energy.
ATP
The energy released when ATP
is broken down into ADP + P
can be used for many cell
processes- allowing movement,
providing energy for other
chemical reactions….
Energy from food is used to
make ATP in cellular
respiration.
Energy from the sun is used to
make ATP as an intermediate
step in photosynthesis.
ADP + Phosphate group
4. Make a Venn diagram to compare and contrast aerobic respiration and
anaerobic fermentation.
Fermentation:
 Anaerobic (Does not
use O2)
 Produces less ATP
(only from glycolysis)
Both:
 Start with
glycolysis
(“splitting of a sugar”)
 Produce ATP –
Energy currency
Cellular Respiration:
 Requires O2 (Aerobic)
 Produces more ATP per
sugar
5. Name the two types of anaerobic fermentation and give examples of
organisms that can perform each.
Lactic acid fermentation:
Our muscles perform lactic acid fermentation when we can not deliver enough
oxygen to them (running fast etc.).
Also certain bacteria used in yogurt-making.
Alcohol fermentation: certain yeast and bacteria.
6. Explain the difference between the following terms: DNA, gene, allele and
chromosome.
DNA is the material that stores genetic information.
A gene is a piece of DNA that controls one trait.
An allele is a form of a gene (For example: for your earlobe gene, you may inherit
the allele for free earlobes or attached earlobes.)
A chromosome is a long strand of genes, which has the information for many
traits.
7. What occurs in interphase prior to mitosis.
The chromosomes are replicated (two identical copies of each).
8. Name the four main phases of mitosis, describe what happens in each
phase and draw a simple diagram of each.
Prophase: Chromosomes condense into thicker, shorter bands- becoming visible
under the microscope. But the chromosomes are still jumbled up.
Metaphase: Chromosomes line up along the spindle in the middle of the cell.
Anaphase: Sister chromatids (identical copies created when DNA is replicated
during interphase) split apart.
Telophase/Cytokinesis: Sister chromatids move to far poles/ cell begins to divide.
Define the following terms:
9. Diploid: Two copies of each chromosome. The pair of chromosomes are
called homologous pairs. Homologous pairs are chromosomes that are the same
length and have the same type of gene, but can have different alleles (forms) of
those genes. Body cells in most eukaryotic organisms are diploid.
10. Haploid: One copy of each chromosome. Gametes (egg or sperm) are
haploid.
11. If a snake has 10 chromosomes in its gametes (egg or sperm) how many
chromosomes would be in its body cells?
A. 5
C. 15
B. 10
D. 20
Correct answer is 20. Gametes are haploid (only one copy of each chromosome).
Body cells are diploid ( two copies of each chromosome). So there would be
twice as many.
12. Fill in the chart to contrast mitosis with meiosis.
Purpose
Number of DNA
replications
Number of Cell
Divisions
Number and Type of
Cells Produced
Mitosis
Growth (new cells) &
Repair (replace cells)
1 during interphase
Meiosis
Produce gamete (egg or
sperm)
1 during interphase
1
2
2/ diploid (identical to
original cell)
4/ haploid (half the
chromosomes of the
original
13. Heterozygous: an organism that has two different alleles for a trait.
Example: Pp- a purple flower allele and a white flower allele
14. Homozygous: an organism that has two of the same alleles for a trait.
Example: PP- two purple alleles.
15. Genotype: the two alleles possessed by an organism for a trait
Examples: PP, Pp or pp are all possible genotypes
16. Phenotype: the expression (physical appearance etc.) for a trait.
Examples: purple or white flowers are possible phenotypes.
17. Two cats both have long whiskers. They have the same phenotype for this
trait. If long whiskers is a recessive trait they must also have the same
genotype. However, if long whiskers is a dominant trait, they could have
either a homozygous dominant or heterozygous genotype.
18. Describe what a Punnett square is, why it is useful, and what the two sides
of a Punnett square represent.
A Punnett square is a tool for determining the possible offspring from two
parents and the possibility of each. Each side represents the possible alleles
that could be in the gametes for each parent for the trait(s).
Example: If a mother is heterozygous for free ear lobes (a dominant
trait) her eggs can have either a F allele or f allele.
If the father is homozygous recessive for attached ear lobes, his
sperm always have the f allele.
Eggs from mother
Sperm from father
F
f
f
f
19. The allele for tasting a substance called PTC is dominant (T). Non-tasters
of PTC are homozygous recessive (tt). If a couple are both heterozgyous
for this gene (Tt), what is the probable offspring for this trait of this couple?
T
t
T
t
TT
Tt
Tt
tt
Phenotype ratio 3:1 (dominant to recessive)
Probability of taster: 75%
Probability of non-taster: 25%
Genotype ratio 1:2:1 (TT:Tt:tt)
Probability of homozygous dominant: 25%
Probability of heterozygous: 50%
Probability of homozygous recessive: 25%
20.
A
a
a
Aa
aa
a
Aa
aa
Phenotype Ratio : 1:1
Probability of normal pigmentation: 50%
Probability of albino: 50%
21. What is a dihbyrid cross?
A dihybrid cross is a Punnett square that studies two traits.
22. If parents are both heterozygous for both of the traits being studied in a
dihybrid cross (AaBb), what allele combination for the gametes will be
written on each side of the dihybrid Punnett square.
If the parents are AaBb, their gametes could contain AB, Ab, aB or ab.
(Gametes always have one copy of each gene. Through independent assortment
A can pair with B or b etc.)
23. The probable outcomes for a dihybrid cross will not be accurate if the two
genes are linked closely on the same chromosome because the dihybrid
cross assumes that the genes are independently assorting.
24. In pea plants, the round seed allele is dominant (R) over the wrinkled seed
allele (r). The purple flower allele (P) is dominant over the white flower
allele (p). If two pea plants that are heterozygous for seed shape and
flower color are crosses (RrPp x RrPp) what are the probable outcomes.
RP
RP
Rp
rP
RRPP RRPp RrPP
rp
RrPp
RRPp RRpp
RrPp
Rrpp
RrPP
RrPp
rrPP
rrPp
RrPp Rrpp
rrPp
rrpp
Rp
rP
rp
Phenotype ratio 9:3:3:1 (standard ratio when both parents heterozygous for both
traits)
Fraction Round, Purple: 9/16
Fraction Round, White: 3/16
Fraction Wrinkled, Purple: 3/16
Fraction Wrinkled,White: 1/16
25. Explain what an X-linked trait is. Give two examples of human traits that are Xlinked. Which gender is more likely to express a recessive X-linked trait. Explain
why.
Males only have one X chromosome (XY). So if their only X chromosome has the
recessive trait, they will express it. Women (XX) have to inherit copies of the
recessive trait from each parent.
26. In order for a man to inherit red-green colorblindness, what must be true
regarding his parents (be specific).
His mother must at least be a carrier.
He inherits a Y from father, so his inheritance not affected by whether or
not father is colorblind.
In order for a woman to inherit red-green colorblindness, what must be true
regarding her parents (be specific).
Her mother has to be at least a carrier AND her father must be colorblind.
(She has to inherit this recessive trait from both parents, and she inherits
father’s only X chromosome)
27. Duchene’s muscular dystrophy is a recessive X-linked trait (Xd). If a mother is a
carrier of Duchene’s muscular dystrophy (XDX d) and the father does not have
muscular dystrophy (XDY), what is the probability of their having children with
muscular dystrophy?
XD
XD
Y
Xd
XDXD XDXd
XDY
XdY
Probabilities:
Daughter having MD: O% (For this wording, look only at probability within daughters).
Daughter not having MD: 100%
Son having MD: 50% (For this wording, look only at probability within sons).
Son not having MD: 50%
28. What are two ways that genetic variation is created during meiosis?
Explain each.
Independent assortment and crossing over are the two ways that genetic variation
occurs during meiosis.
Independent assortment means that each pair of chromosomes lines up
independently during meiosis (I).
Crossing over allows genetic variation of genes on the same chromosome, because
non-sister chromatids can exchange segments during prophase of meiosis I.
29. DNA is a chain of nucleotides.
Explain the structure of each of these subunits. Draw a simple diagram and
label the parts.
Each nucleotide is made of three parts: a sugar (deoxyribose in DNA), a
phosphate group and a nitrogen base. There are 4 possible nitrogen bases:
adenine, thymine, guanine and cytosine.
30. How are these DNA subunits arranged in the DNA molecule? Draw a simple
diagram and label the parts.
DNA is a double helix- 2 strands of nucleotides chains that are twisted like a spiral
staircase.
The sugar- phosphate groups form the backbone of the chains and pairs of nitrogen bases
form the “rungs” of the double helix.
31.
What are the complementary pairings of nitrogen bases in DNA? If one
strand of the DNA molecule is CATGAG, what will the other strand of DNA be?
GTACTC
Adenine always pairs with Thymine.
Cytosine always pairs with Guanine
32. Explain the process of DNA replication. When does DNA replication occur?
What enzymes are involved? In the final result, what part of the two DNA
molecules that is produced is original and what part is new?
DNA replication occurs just prior to cell division.
The enzyme helicase unwinds the double helix, separating the two strands. The enzyme
DNA polymerase constructs the new DNA by adding the complementary nucleotides. In
the end, each of the 2 DNA molecules produced contains one original strand of
nucleotides (that served as the template) and one new strand of nucleotides.
33. Each gene is the information to build one protein (or polypeptide strand
of a protein) . There are two steps in expressing this information. The first
is transcription which results in the production of a mRNA molecule. This
first step occurs in the nucleus . The second step is translation where the
protein is actually produced. The process occurs in the ribosome. In this
process each 3 nucleotide sequence in the mRNA, called a codon is paired
with another type of RNA called tRNA which has a complementary
anticodon . Each of these tRNA’s has an attached amino acid. These
subunits are joined together in building the protein (or polypeptide)
encoded by the gene.
34. Explain 3 differences between a DNA molecule and an mRNA molecule.
DNA is a double strand of nucleotides, RNA is a single strand
DNA uses the sugar deoxyribose in nucleotides, RNA uses the sugar ribose
In DNA, one of the nitrogen bases is thymine (A, C, G and T), in RNA the
nitrogen base uracil is used (A, C, G and U)
35. Compare and contrast the structure of an mRNA molecule with a tRNA
molecule.
Both mRNA and tRNA are made of nucleotides. mRNA is an RNA copy of a gene
(single strand). tRNA is folded piece of RNA that has three exposed nucleotides
(the anticodon) and has an attached amino acid.
mRNA being transcribed.
36. Explain the process of transcription. Where does it occur, what enzyme is
involved, what is produced …?
Transcription occurs in the nucleus on an ongoing basis, as new proteins are
needed.
The enzyme RNA polymerase unwinds region of DNA for the gene that is
being transcribed. The enzyme adds the complementary RNA nucleotides.
37. If the gene sequence on the DNA is TAGCAT what mRNA transcript will be
produced?
AUCGUA
C pairs with G,
Since RNA uses U instead of T, A pairs with U (T on DNA pairs with A)
38. Explain the process of translation. Where does it occur, what molecules are
involved. Include the terms codon, anticodon and amino acid.





Translation occurs in the ribosome.
The mRNA is attaches to a ribosome and a tRNA complementary to start
codon.
A tRNA with a complementary anticodon to the next codon (series of 3
nucleotides) attaches bringing the corresponding amino acid.
The amino acids are joined together and the mRNA slides down the
ribosome, moving the next codon into the ribosome binding site.
This process continues to build the protein.
39. What does it mean that the genetic code is universal? Why is this
important for biotechnology processes such as recombinant DNA?
All types of organisms translate the codons in the mRNA in the same way
(add the same amino acid). For example, if an mRNA strand has the codon
UUU, all organisms with add the amino acid phenylalanine to the protein.
Recombinant DNA technology is possible because of the fact that the
genetic code is universal. For example, a gene from a human, such as
insulin, can be inserted into a bacteria and it will produce the same protein.
40. If a protein is made of 210 amino acids, how many nucleotides must have
encoded this protein? Explain your answer.
630 nucleotides. Each amino acid is encoded by a 3 nucleotide sequence called a
codon.
A codon of 3 nucleotides  1 amino acid
Solving for nucleotides
 multiply by 3
Solving for amino acids
 divide by 3
630 nucleotides  210 amino acids
On the other hand if 210 nucleotides :
210 nucleotides  70 amino acids
41. What is a recombinant plasmid? Explain the basic process of creating a
recombinant plasmid. Include the terms restriction enzyme and sticky ends.
A recombinant plasmid is when scientists create a piece of DNA from two
different sources, for example a fish gene inserted into a bacterial plasmid. (It is
the recombining of DNA from two sources.) Scientists do this by cutting both
types of DNA with special enzymes called restriction enzymes. These enzymes
leave “sticky ends”- single stranded ends. The complementary bases of the
different pieces of DNA allow them to join together.
42. Homeostasis is an equilibrium (balance) of conditions (temperature, pH,
salt concentrations) in the internal environment of an organism that is
suitable for life. For example, we maintain our temperature at
approximately 98.5 F. Explain how the blood vessels in the skin are
involved in maintaining homeostasis (What happens to the blood vessels
when you are hot and when you are cold? And how does this help
maintain homeostasis?)
When you are hot, the blood vessels in your skin dilate (get wider). This is
why you might look flushed when you are hot as more blood goes
towards the surface of your skin. The heat can radiate from the surface of
your skin.
When you are cold, the blood vessels in your skin constrict (get narrower),
especially to your extremities. This reduces the amount of heat lost from
the surface of your skin.
43. Why are viruses not considered to be alive by many scientists? How do
viruses reproduce?
Viruses do not exhibit the characteristics of living things on their own. They
cannot reproduce on their own, and they do not metabolize on their own (build
molecules etc.)
Viruses reproduce by attaching to a host cell (each type of virus may be specific
for certain types of host cells that it can attach to). The virus’ genetic material
(DNA or RNA)is injected into the host cell. The host cell’s organelles and enzymes
are used to make more viral DNA and viral proteins (for the viral coat). When
the new viruses are replicated, they are released from the host cell which may
destroy the host cell in the process.
44. Of what kind of cells are bacteria composed? Describe the characteristics of
this cell type.
A bacterium (plural bacteria) is a microorganism made of a prokaryotic cell,
which is a cell that does not contain a nucleus or other membrane-bound
organelles. The DNA for the bacterial cell is found in the cytoplasm of the
cell (without a nuclear membrane surrounding it.
Bacteria have a circular chromosome (that is a single copy- not diploid
strands as in eukaryotic cells.)- they may also have additional smaller
plasmid chromosomes.
Bacteria cells are typically much smaller than eukaryotic cells since they are
less organized and efficient.
Antibiotics may be used to kill of bacteria, because they can disrupt some
of the processes necessary for life in these living things.