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BIO 121 Lecture Notes - Lecture 16: Allele Frequency, Genetic Drift, Genetic Variation

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School
Syracuse University
Department
Biology
Course
BIO 121
Professor
Dr.Wiles

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Document Summary

This is because evolution causes genetic changes over time. Microevolution : altered frequency of alleles in a population over generations. Mutations, gene rearrangements change the sequence of dna. Rapid reproduction leaves room for dna replication errors. Mutations that alter the phenotype are often harmful. Harmful mutations can be hidden from selection in recessive alleles. Mutations that result in a change in phenotype are sometimes beneficial. Populations can evolve -- although evolution acts on individuals, the individuals. Only cannot change the frequency of their alleles. Hardy-weinberg equation is used to test whether a population is evolving. Quantitative ; measures the frequencies of the alleles in the population. Model that represents the absence of evolution. Genetic drift : random events changing survival and reproduction. Has a greater impact on smaller than larger populations. Consists of the movements of alleles among populations. Natural selection is the only mechanism that consistently causes adaptive radiation. Evolution by ns involves both chance and sorting .

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Related Questions

Which of the following provides evidence for evolution?

All of these answers are correct
Comparing DNA sequences between species
Looking at the geographic distribution of similar species
Comparing similarities in embryonic development between species
Analyzing transitional fossils

Which one of the following statements is true?

Natural selection works on non-heritable traits.
Mutations only give rise to harmful traits.
Natural selection works on variation already present in a population.
Individuals evolve through natural selection.

Which one of the following can create new alleles?

Genetic drift
Natural selection
Gene flow
Mutation

Which of the following is true concerning evolution?

An individual can evolve
Genetic drift is a non-random part of natural selection
An organism's fitness is determined by how long it survives
Natural selection occurs through a change in allele frequency

All living things need carbon. How does carbon enter the living portion of an ecosystem?

Atmospheric carbon dioxide taken in by photosynthesis.
Atmospheric carbon dioxide taken in by soil bacteria.
Elemental carbon taken in by plant roots.
Elemental carbon taken in by cellular respiration.
Elemental carbon taken in by cellular transpiration.

The burning of fossil fuels:

Releases excess carbon dioxide into the atmosphere.
Removes pollutants from the atmosphere.
Was developed by scientists to combat global climate change.
Has no effect on the carbon cycle.
Is good for the environment

__________ conducts water and dissolved minerals from the __________ to the ___________.

Phloem; roots; shoots
Xylem; roots; shoots
Phloem; shoots; roots
Xylem; shoots; roots

What is a disadvantage of growing traditional crops such as corn, soy or sugar cane for making biofuel?

they require lots of land and fresh water
they take carbon dioxide out of the atmosphere
they release oxygen into the atmosphere
they release water through their stomata

______ is the source of the oxygen gas released by a photosystem.

NADPH
H2O
C6H12O6
CO2
Chlorophyll

Through what structure(s) do plants obtain most of their water?

interior cells
stems
leaves
roots
stomata

1. A) Explain how changes in the environment drive evolutionary change. B) Provide and explain an example

2. A) Explain how the Hardy-Weinberg equation allows us to find evidence of evolution. B) Could processes other than Natural Selection result in deviation from the Hardy-Weinberg equilibrium? List and explain each one: C) define what the process is and D) the effect it has on the allele frequency.

3. A gene that is responsible for multiple traits (pleiotropy), for example the same allele causes sickle-cell anemia and provides resistance to malaria. Would a gene that controls these two traits respond equally to natural selection favoring malaria resistance as a non-pleitropic gene that only controls malaria resistance? Explain your answer.

4. A) Explain how lack of genetic variation limits evolution and provide an example. B) Explain how epistasis limits evolution and provide an example

Questions 5-6 are based on the following:

Let’s say you are studying a population of Japanese four o’clock plants. In these plants, the allele for red color flower shows incomplete dominance over the allele for white flowers. This is very convenient for this experiment because you can distinguish the heterozygous (pink flowers) from the homozygous dominant (red flowers). For your experiment, you produced a large number of plants, 25% had red flowers, 25% had white flowers and 50% had pink flowers. You transplanted them into different habitats and left some in the lab (using the same proportions in all the habitats). You waited a few years, while plants reproduce for a few generations and then you go back and resample the populations you’ve transplanted.

5. In the lab you ensured that all individuals receive all requirements to grow and reproduce and mate randomly. A) What do you expect the distribution of the phenotypes after a few generations breeding in the lab? B) Is the lab population in Hardy-Weinberg equilibrium? Yes/No, explain

6. In habitat A, you find that you only have red flowering plants and white flowering plants but there are no pink flowering plants. A) Is the population in habitat A in Hardy-Weinberg equilibrium? Yes/No, explain. B) Which one(s) of the five agents of evolutionary change could be responsible for these results? Explain. C) What type(s) of selection (stabilizing, disruptive, directional, oscillating, etc...) could be responsible for the results in habitat A? Explain

1. Characters that show a continuous range of variation, such as height and eye color, usually are controlled:

a. by a single gene with two alleles that are codominant.
b. by many genes with an additive effect.
c. by epistatic interactions between two genes.
d. mainly by the environment, with only a small genetic component.

2. In humans, red-green colorblindness is inherited as a sex-linked recessive trait. In order for a woman to be red-green colorblind, which of the following statements must be true.

a. Her mother must be red-green colorblind.
b. All of her brothers must be red-green colorblind.
c. Her father must be red-green colorblind.
d. All of the above statements must be true if a woman is red-green colorblind.

3. The x-ray crystallography data collected by Rosalind Franklin suggested to Watson and Crick that the:

a. structure of DNA is a double helix.
b. two strands of the DNA molecule are joined by hydrogen bonds between the bases.
c. four bases within DNA pair in a specific way.
d. two strands of the DNA molecule are joined by covalent bonds between the bases.

4. In the genetic code, _________ one amino acid.

a. one nucleotide specifies
b. two nucleotides specify
c. three nucleotides specify
d. four nucleotides specify

5. During Meiosis I, a homologous pair of chromosomes may not separate, resulting in daughter cells that have extra chromosomes or are missing chromosomes. This can lead to genetic disorders, including Down Syndrome. This phenomenon is called:

a. independent assortment.
b. nondisjunction.
c. segregation.
d. crossing over.

6. You are a human geneticist studying the incidence of retinitis pigmentosa in the residents of Tristan de Cunha, a group of small islands in the middle of the southern Atlantic Ocean. The allele for retinitis pigmentosa, which causes a form of blindness, is inherited as an autosomal recessive. You have determined that the frequency of this allele (r) in the population is 0.4 (40%). Using the principles of the Hardy-Weinberg rule, you would estimate the frequency of individuals who are heterozygous for this allele (Rr) in the population to be:

a. 0.16 (16%)
b. 0.24 (24%)
c. 0.36 (36%)
d. 0.48 (48%)

7. Natural selection acts at the level of the:

a. phenotype.
b. gene.
c. population.
d. nucleotide.

8. You are working with pea plants, trying to recreate the experiments that Mendel performed. You are doing a dihybrid cross with a plant that is heterozygous for both seed shape and seed color, with the genotype RrYy. Which allelic combinations would you expect to find in the gametes produced by this plant?

a. This plant would produce only RY and ry gametes.
b. This plant would produce only RrYy gametes.
c. This plant would produce RY, Ry, rY, and ry gametes.
d. You cannot determine which gametes this plant can produce without knowing the genotypes of its parents.

9. Biochemist Erwin Chargaff found that in DNA there is a special relationship between the four bases that we now call Chargaff's rule. His observation was that, in an organism's genome the:

a. percentage of A nucleotides = the percentage of T nucleotides, and the percentage of C nucleotides = the percentage of G nucleotides.
b. four bases all occur in an equal frequency (25%) within each organism.
c. percentage of A nucleotides = the percentage of G nucleotides, and the percentage of C nucleotides = the percentage of T nucleotides.
d. genetic material is composed of proteins, not DNA.

10. During DNA replication:

a. each strand of the double helix acts as a template for the synthesis of a new strand.
b. the enzyme DNA polymerase adds nucleotides to the strand being synthesized.
c. the bases A,C,G and T are required.
d. All of the above are true of DNA replication.

11. During translation, amino acids are joined by peptide bonds to make polypeptides. The formation of these peptide bonds is catalyzed by:

a. DNA.
b. mRNA.
c. tRNA.
d. rRNA.

12. If an allele (R) at a gene with two alleles shows complete dominance, individuals with the genotypes ______ will have the same phenotype.

a. RR and rr.
b. RR and Rr
c. Rr and rr
d. Each of the three possible genotypes will have a different phenotype.