Download MCA Review Part 3 File

MCA REVIEW PART III:
EVOLUTION IN LIVING
SYSTEMS
Genetics

Standard 1.1-3: Genetic Information found in the
cell provides information for assembling proteins,
which dictate expression of traits in an
individual.
Genetics
(Pg 130) Terms:
DNA: a double stranded molecule made of four different subunits called
nucleotides, deoxyribonucleic acid
Genes: a specific region of DNA that codes for a particular protein
Chromosome: one long continuous strand of DNA that consists of numerous genes
Explain the relationships among DNA, genes, and chromosomes: In the nucleus, DNA
is a double stranded molecule that has specific regions that code for a particular
(gene)protein, all coiled up and condensed into a chromosome.
Genetics
(pg 170-172) Terms:
Phenotype: physical trait or appearance
Genotype: the genetic makeup of a specific set of genes (the letters: TT, Tt, tt)
Allele: any alternative form of a genes (individual letters T or t)
Homozygous: two of the same alleles at a specific location ( TT or tt)
Heterozygous: two different alleles at a specific location (Tt)
Dominant Allele: expressed when two different or two dominant alleles are
present (Tt or TT)
Recessive Allele: expressed only when two copies are present (tt)
Genetics
2. Suppose you cross a pea plant that is heterozygous
for purple flowers with a pea plant that is
homozygous recessive for white flowers; P=purple, p
=white. (6.5)
a. Draw and fill out a punnett square:
P
p
p
Pp
pp
p
Pp
pp
b. What is the expected Genotypic Ratio for the
offspring?
2:2  1:1
c. What is the expected Phenotypic Ratio for the
offspring?
2:2  1:1
Genetics
3. Suppose you cross two purpleflowered pea plants that are both
heterozygous.
a. Draw and fill out a punnett square:
P
p
P
PP
Pp
p
Pp
pp
b. What is the expected Genotypic
Ratio for the offspring?
1:2:1
c. What is the expected Phenotypic
Ratio for the offspring?
3:1
DNA to Proteins
Proteins are what dictate expression of traits in an individual. DNA provides the directions
for making proteins. How do we go from DNA to Proteins? We will now review
replication, transcription, and translation. For questions 4-5, use pg 216-219.
4. Describe DNA’s Structure:
A double helix made up of nucleotides:
1. Phosphate Group
2. Deoxyribose - Sugar
3. Nitrogen Base (A, T, C, G)
5. What are the base pairing rules for DNA?
A-T
C-G
6. Summarize the main steps of DNA Replication including where it occurs (pg 221-224):
-Occurs in the Nucleus
-DNA unzips
-Free floating nucleotides (A, T, C, G) pair up with exposed bases on each strand
-Two identical DNA molecules result, each contains one original strand and one
new strand
DNA to Proteins
7. (Pg 225-226) Summarize the central dogma of
molecular biology. Include a summary of the
three processes involved.
Central Dogma:
DNA  RNA  Proteins
1. Replication copies DNA
2. Transcription converts a DNA
message
into an RNA molecule
3. Translation interprets an RNA
message
into a string of amino acids
 polypeptide
8. RNA differs form DNA in what three ways?
1. Single Stranded
2. Contains Uracil (U) instead of
Thymine (T); AUCG
3. Sugar is ribose (instead of
deoxyribose)
Transcription (DNA to RNA)
9. Summarize the main steps of Transcription including where
it occurs in a cell (pg 226):
-DNA molecules unzips
-RNA nucleotides form base pairs with the DNA
template (A-U, C-G)
-The growing RNA strand hangs freely
-The DNA strand closes back together
-The complete RNA molecule separates from the DNA
template
a. What three types of RNA does transcription produce?
1. Messenger RNA (mRNA): intermediate
message translated to form a protein
2. Ribosomal RNA (rRNA): forms part of
ribosomes
3. Transfer RNA (tRNA): brings amino acids from
the cytoplasm to a ribosome to help make proteins
Translation (RNA to Proteins)

10. Summarize the main steps of
Translation including where it occurs
in a cell (pg 229-233):
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


Occurs on a ribosome
Converts an mRNA transcript into a
polypeptide/protein
1. The exposed codon attracts a
complementary tRNA that is
carrying an amino acid
2. The tRNA anticodon pairs with
the mRNA codon
3. Another complementary tRNA
molecule is attracted to the next
exposed mRNA codon and the
process continues until the amino
acid sequence/protein is complete
DNA – RNA - Proteins
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11. Replicate, transcribe, and translate the following
DNA strand. Note: you will need the chart on pg 244 for
translation.
Right Strand: TAC GCC TAA CGT CTG AGG TAC ACT
Left Strand: ATG CGG ATT GCA GAC TCC ATG TGA
mRNA:
UAC GCC UAA CGU CUG AGG UAC ACU
Amino Acid: Tyr Ala Stop Arg Leu Arg Tyr Thr
Protein A
**PROTEINS ARE MADE UP OF AMINO ACIDS!!
Proteins/Enzymes
READ!!!! Now, how proteins/enzymes help to carry out most of the work
done by cells. Remember, enzymes are a type of protein.
Your cells are BUSY, and they need to be in order to carry out all the
chemical reactions necessary to keep you alive. Enzymes are
catalysts that speed up chemical reactions. Without them, the
chemical reactions in your body simply do not take place fast
enough.
AGAIN, enzymes are a type of protein, and proteins are made up of
amino acids. Thus, enzyme function, meaning what it does, depends
on the amino acid sequence that dictates each enzyme’s specific
shape.
Proteins/Enzymes
1. (pg 52-54) How exactly do enzymes speed up chemical
reactions? In other words, what do they do to chemical
reactions?
Enzymes are catalysts that lower activation energy
which is the energy required for a chemical reaction to
start.
2. What are some examples of enzymes in your body? What do
they do? Give at least two examples.
-Enzymes that help to break down food
Ex: Amylase – breaks down starch into sugars, in
saliva
Ex: Lipase – breaks down fats
3. Enzymes are “sensitive” meaning they work under a specific
set of conditions. What are two conditions that enzymes are
“sensitive” to? What happens when these conditions
change?
1. Temperature
2. pH – acidity or basicness
Proteins/Enzymes
4. What do I mean by: “Enzymes are
highly specific!”
-Each enzymes is specific for a
particular substrate
-”Lock and Key” Model
5. What would happen if the amino
acid sequence changes? What
could this result in?
Enzymes are a type of protein,
proteins are made up amino
acids. Thus, if the amino acid
sequence changes, the structure
of the enzyme changes, and it
may not work at all.
Variation

Standard 2.1-3: Variation within a species is the
natural result of new inheritable characteristics
occurring from new combinations of existing
genes or form mutations of genes in reproductive
cells.
Variation
Mendel’s law of segregation and
independent assortment explain how
sorting and recombination (crossing over)
of genes during sexual reproduction
(meiosis) increases the occurrence of
variation within a species.
(pg 160-166) Terms:
Gamete: sex cells
Egg: female sex cell
Sperm: male sex cell
Meiosis: a form of nuclear division that
divides a diploid cell (2n) into a haploid
cell (n)
Variation
1. What is the result of meiosis?
Produces genetically UNIQUE, haploid cells (n)
2. (pg 179-181). Explain the two processes that
take place during meiosis/sexual reproduction
that result in genetic variation.
a. Independent Assortment of Chromosomes:
allele pairs separate independently during the
formation of gametes.
In other words, it is due to chance alone which
parental pairs will end up in each individual
gamete
b. Crossing Over: the exchange of
chromosome segments between homologous
chromosomes during prophase I of meiosis.
Sexual vs Asexual Reproduction
3. There are both advantages and
disadvantages to both sexual and asexual
reproduction. Fill in the charts below:
Sexual Reproduction:
(+) Genetic Variation – more traits =
more suitable environments
(-) Requires more energy
(-) requires 2 parents
Asexual Reproduction (go back to 5.4):
(+) Time Efficient (no mate required)
(+) Requires less energy
(-) No Genetic Variation (If the parent has
a genetic disorder/disease, so does the
offspring)
Mitosis vs Meiosis
Genetically
identical cells
Genetically
Unique Cells
Diploid Cells
Haploid Cells
Throughout an
organism’s life
Only at certain
times
Asexual
Sexual
Mutations
In addition to sexual reproduction, new, inheritable characteristics can occur from
mutations that occur in genes of reproductive cells.
(pg 238-241) Terms:
Mutation: a change in an organism’s DNA
Point Mutation: a mutation in which one nucleotide is substituted for another
Frameshift Mutation: involves the insertion or deletion of a nucleotide in the
DNA sequence
1. Explain how mutations may or may not affect phenotype:
-Chromosomal mutations affect a lot of genes and tend to have a big
effect. Gene mutation are smaller in scale and can have either a large
or small effect depending on how it affects the amino acid sequence.
Ex: AAG to CAG changes glutamine to lysine
-There is more than one codon for every amino acid, sometimes a
mutation still results in the same amino acid
2. TYPO! Why are mutations that occur in body cell not passed on to offspring?
Because body cells are not passed from one generation to another
3. What factors can causes mutations to occur?
Replication Errors and Mutagens
Evolution

Standard 3.1-6: Evolution by Natural Selection is
a scientific explanation for the history and
diversity of life on Earth.
Evolution
(pg 280-296) Terms:
Evolution: the process of biological change by which descendants
Variation: the difference in the physical traits of an individual from those of other
individuals in the group to which it belongs
Adaptation: a feature that allows an organism to better survive in its environment
Artificial Selection: when humans change a species by breeding it for certain traits
Heritability: the ability of a trait to be passed down from one generation to the next
Natural Selection: a mechanism by which individuals that have inherited beneficial
adaptations produce more offspring on average than do other individuals
Fitness: a measure of the ability to survive and produce more offspring relative to
other members of the population in a given environment
Evolution
In the 1700s scientists began to observe how organisms change from one generation to the next.
Then, came Darwin who “put the pieces together”.
1. Read through 10.3 and explain how several key insights led Darwin to his idea for natural
selection:
a. Artificial Selection
b. Struggle for Survival (from Malthus): Food, water, shelter
2. Identify and describe the four main principles to the theory of natural selection:
1. Variation: the heritable differences, or variations, that exist in population are the basics
for evolution
2. Overproduction: results in competition between offspring for resources
3. Adaptation: sometimes a certain trait allows an individual to survive better than others,
these individuals are “naturally-selected” to live longer
4. Descent with Modification: Over time, natural selection will result in species with
adaptations that are well suited for survival and reproduction
3. Why must there be variation in a population in order for natural selection to occur?
Without variation, everyone is the same, if the environment changes  no new traits to
choose from means no survivors
Evolution
4. Identify and describe the four evidences that Darwin
used to support his argument for evolution:
1. Fossils
2. Geography: he saw that island plants and animals
looked like, but were not identical to species on the
South American continent
3. Embryology: embryos of vertebrates are
extremely hard to tell apart
4. Anatomy: comparing the body parts of different
species. Homologous structures, though they can
differ in their function, they are the result of a
common ancestor
5. Compare homologous structures to analogous structures:
Homologous structures provide evidence for a
common ancestor because they are composed of the
same structures. Analagous structures are structurally
different and therefore do not indicate common
ancestry.
Evolution
6. Natural Selection can change the distribution
of a trait in one of three ways. Write the
definition for each type of selection, draw
the graph the represents each type, and give
at least one example for each type (pg 310313):
a. Directional Selection: a type of selection
that favors phenotypes at one extreme of a
trait’s range.
Ex: Antibiotic Resistance
b. Stabilizing Selection: the intermediate
phenotype is favored and becomes more
common in the population
c. Disruptive Selection: occurs when both
extreme phenotypes are favored,
individuals with intermediate phenotypes
are selected against
Evolution
7. (pg 327-331) What is convergent evolution? What
types of structures are common examples of
convergent evolution? Give at least one example.
Evolution toward similar characteristics in
unrelated species.
Ex: Wings on birds and insects
Ex: Tails fins on dolphins and sharks
8. What is divergent evolution? What types of structure
are common examples of divergent evolution? Give
at least one example.
When closely related species evolve in different
directions and become increasingly different.
9. What is co-evolution? Give at least one example.
The process in which two or more species evolve
in response to changes in one another.
Evolution

10. What is adaptive radiation? The
adaptive radiation of mammals
followed the extinction of the
dinosaurs. How do these events
support the theory of punctuated
equilibrium?
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Adaptive Radiation: the
diversification of one ancestral
species into many descendant
species
When dinosaurs were dominant,
most mammals were small,
nocturnal insect-eaters. After the
extinction of dinosaurs, which left
many niches empty, there was a
period of sudden and rapid
evolution of mammals, during
which thousands of new and
diverse species evolved to fill those
niches.
Evolution