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Module 5 Self-Evaluation

Terms in this set (112)

man blood type is determined by three alleles IA, IB, and IO. The alleles IA and IB are co-dominant to each other, and both are dominant to IO. Within a large, randomly mating population (540,000 individuals), the frequencies for the blood type alleles are 0.3 for the IA allele; 0.6 for IO, and 0.1 for the IB allele.
a. Calculate the expected numbers of people in the population having each blood type A, B, AB, and O.
b. Determine the percentage of type B people that are heterozygotes (IBIO)
a) A person with blood type A has a combination IAIA or IAIO
p= frequency of A
q= frequency of O
for IAIO:
p2 + 2pq +q2
= (0.3)^2 + 2(0.3)(0.6) + 0.6^2
= 0.81
for IAIA:
= (0.3)^2 + 2(0.3)(0.3) + (0.3)^2
= 0.36
subtract the values: 0.81-0.36 = 0.45 or 45%
Blood Group A people is 45% of the population which = 540,000(.45) = 234,000
Do the same for the remaining blood groups
Blood Group B is 13% = 70,200
Blood Group AB are 6% = 32,400
Blood Group O is 36% = 194,400

b) (p+q+r)^2
where p= frequency of A
q = frequency of B
r = frequency of O
(0.3+0.1+0.6)^2 = 92.3%
Describe two mating patterns that have an impact on the genetic composition of a population.
Inbreeding: preferential mating with close relatives
Assortative mating: preferential mating with individuals of dissimilar or similar genotype or phenotype.
You are studying a population of kangaroo rats. You calculate the expected frequencies of the alleles for coat color. When you compare these to the observed genotype frequencies, there is a large discrepancy. What can you deduce, based on these findings?
If the expected genotype frequencies and the observed genotype frequencies are very different, then the population is not in Hardy-Weinberg equilibrium. At least one of the assumptions must be being violated.
Provide an explanation of the differences between differentiation and determination. Provide examples of each process and indicate how each is involved in development.
Determination is the early commitment of a cell to an eventual developmental fate. Differentiation is the set of functional and structural changes associated with the expression of that developmental fate. When nuclei of the developing Drosophila embryo reach the blastoderm stage, they become determined. Differentiation of the cells of the imaginal disks in Drosophila occurs during metamorphosis. Development, therefore, probably depends first on the determination of cells, then on the differentiation of cells.
You and a close friend from the University of Tennessee go hiking in the mountains. You are surprised to see a salamander that is bright orange in color. Thinking that some overzealous Tennessee fans have painted this particular amphibian, you walk on. As you continue your hike, you find other salamanders of this species and note that there is variation in the coloration: some individuals are bright orange, but others are drab in color. You also note that these salamanders often eat bright orange insects. How might you explain the presence of the color polymorphism in this salamander species?
You need to test to see if the coloration is totally environmental: the orange salamanders ate orange bugs and turn orange. The variation comes from the fact that there is variation in what salamanders eat. You can test this by doing a common garden experiment where you feed an experimental group of salamanders the orange bugs and see if they all turn orange (an environmental effect). If they do not, at least some of the coloration variation is due to genetics.
What is the term given to a random subset of individuals who are selected for measurement in a particular study?
sample
In the early part of this century, Nilsson-Ehle, East, and others described experiments showing that multiple loci may be involved in the inheritance of certain traits. Such patterns are often called ________.
additive alleles?
A classic example of selection in natural populations involves the peppered moth Biston betularia in England. Industrial gases killed the lichens and mosses on buildings, trees, etc., and soot deposited on the landscape. Dark-colored moths gained a selective advantage. In this case, one would say that there was selection against the light-colored moths.

Which morph, light or dark, would have the highest fitness?
dark
Given an inheritance pattern of incomplete dominance and 81 flowers are red (R1R1), 18 flowers are pink (R1R2), and 1 flower is white (R2R2), what is the frequency of the R1 allele?
0.90
_______ is a measure of the degree to which the phenotypic variation of a given trait is due to genetic factors.
broad-sense heritability?
Name two mammalian traits with relatively high heritability (h2) values.
epilepsy and eye color
One of the Hardy-Weinberg assumptions states that the population is infinitely large. What influence might small populations have on a Hardy-Weinberg equilibrium?
Sampling error would cause random and possibly significant fluctuations in gene frequencies
What the term for the equation used to examine the relative importance of genetic versus environmental factors?
narrow sense heritability (h2)
In a population that meets the Hardy-Weinberg equilibrium assumptions, 81 percent of the individuals are homozygous for a recessive gene.

What percentage of the individuals would be expected to be heterozygous for this gene in the next generation?
18
In a population of 10,000 individuals, where 3600 are MM, 1600 are NN, and 4800 are MN, what are the frequencies of the M alleles and N alleles?
M = 0.6
N = 0.4
Mutations that eliminate a contiguous region in the Drosophila embryo's segmentation pattern are called
a. linkage genes
b. gap genes
c. compartment genes
d. segment genes
e. homeodomains
b. gap genes
Flower diameter in sunflowers is a quantitative trait. A plant with 6-cm flowers, from a highly inbred strain, is crossed to a plant with 30-cm flowers, also from a highly inbred strain. The F1 have 18-cm flowers. F1 × F1 crosses yield F2 plants with flowers ranging from 6 to 30 cm in diameter, in approximately 4-cm intervals (6, 10, 14, 18, 22, 26, 30).
An 18-cm F1 plant is crossed to a 6-cm plant. What is the probability of an offspring with one additive allele, if all genes that influence this trait are unlinked?
a. 1/6
b. 1/16
c. 1/4
d. 3/8
e. 1/3
d. 3/8
Which of the following is a concern of population genetics?
a. How proteins fold under different pH conditions
b. Why is cancer a difficult disease to treat?
c. How the cell copies its DNA
d. What causes sickle cell anemia?
e. How many people have color blindness in Utah
e. How many people have color blindness in Utah
Which of the following polymorphisms is the most efficient for use in population genetics studies?
a. Variable number of tandem repeats
b. Chromosomal polymorphisms
c. Complete sequence variation
d. Restriction site variation
e. Amino acid sequence polymorphisms
c. Complete sequence variation
Two highly inbred tobacco plants are crossed. One has dark green leaves. The other has yellow leaves. The F1 have light green leaves. Five hundred progeny from F1 × F1 crosses are analyzed. Their leaves show continuous variation in color, but none has dark green or yellow leaves. What do these data suggest about the number of genes determining this trait?
a. There are 2 genes that determine this trait.
b. There are 3 genes that determine this trait.
c. There are 4 genes that determine this trait.
d. There are more than 4 genes that determine this trait.
d. There are more than 4 genes that determine this trait.
To establish that evolution by natural selection is operating in a population, one must demonstrate variability for a trait, heritability of that trait, differential reproductive success based on that trait, and:
a. progress.
b. increased complexity of the organism.
c. nothing else.
d. random mating.
e. continuous change in the environment.
c. nothing else.
If 64% of the people in a population are blue-eyed and the population is in Hardy-Weinberg equilibrium, what is the percentage of heterozygotes in the population?
a, 36%
b. 20%
c. 32%
d. It cannot be determined from these data.
e. 16%
c. 32%
Which of the following is NOT an example of nonrandom mating?
a. positive assortative mating
b. inbreeding
c. negative assortative mating
d. panmixis
e. outbreeding
d. panmixis
Evolution occurs:
a. only via natural selection, genetic drift, migration, or mutation.
b. magic
c. only through natural selection.
d. only when the environment is changing.
e. by altering physical traits but not behavioral traits.
a. only via natural selection, genetic drift, migration, or mutation.
In a human population, the genotype frequencies at one locus are 0.5 AA, 0.4 Aa, and 0.1 aa. The frequency of the A allele is:
a. 0.20
b. 0.50
c. 0.32
d. 0.90
e. 0.70
e. 0.70
QTL mapping requires all of the following except:
a. genetic markers.
b. an estimate of homozygosity in the population.
c. a controlled cross.
d. a genetic map.
e. offspring.
b. an estimate of homozygosity in the population.
In a population in Hardy-Weinberg equilibrium, what will be the proportion of matings between homozygotes?
a. 4p2q2
b. p2 + 2pq
c. p4 + q4 + 2p2q2
d. P4
e. p4 + q4
c. p4 + q4 + 2p2q2
The heterozygote genotype frequency term for a gene with two alternate alleles A (frequency of p) and a (frequency of q) in the Hardy-Weinberg equation is:
a. P+2pq+q2
b. (p+q)
c. 2pq
d. q2
e. p2
c. 2pq
A Mendelian population is defined by individuals
a. living in close proximity.
b. migrating.
c. inbreeding.
d. interbreeding.
e. evolving.
d. interbreeding.
Which of the following evolutionary forces does NOT change allele frequencies?
a. nonrandom mating
b. drift
c. selection
d. mutation
e. migration
a. nonrandom mating
Immediately after fertilization of a Drosophila egg, the zygote nucleus undergoes a series of divisions. Subsequent nuclear migration generates a ________.
a. maternal effect
b. syncytial blastoderm
c. cleavage nucleus
d. zygote
e. homeodomain
b. syncytial blastoderm
In Drosophila, segmentation genes function in a sequential manner in the following order:
a. gap, segment-polarity, pair-rule.
b. transdeterminal, gap, pair-rule.
c. segmentational, helical, spherical.
d. pair-rule, transdeterminal, gap.
e. gap, pair-rule, segment-polarity.
e. gap, pair-rule, segment-polarity
Total phenotypic variance can be decomposed into all but one of these components:
a. heritability.
b. genetic-environment interaction variance.
d. genetic variance.
e. environmental variance.
a. heritability.
Human albinism is an autosomal recessive trait. Suppose that you find a village in the Andes where 1/4 of the population is albino. If the population size is 1000 and the population is in Hardy-Weinberg equilibrium with respect to this trait, how many individuals are expected to be heterozygotes?
a. 50
b. 250
c. 750
d. 500
e. 300
d. 500
How will variation for a gene in a given population be increased?
If migration from other populations brings into the recipient population gene alleles that are not already in the population or are present at a lower frequency.
Define the term "fitness".
Fitness is the relative probability of survival and reproduction of a genotype or phenotype.
What are three critical points to keep in mind when measuring fitness?
Critical to assessing fitness is understanding that it is measured: a) relative to other genotypes/phenotypes in the population; b) in a specific environment; c) by reproductive success.
How does genetic drift alter the genetic variation in a population? Why is it a relatively insignificant agent of evolution in all but the very smallest populations?
Genetic drift, one of four agents of evolution, is characterized by a random change in allele frequencies. Because in altering allele frequencies it can produce fixation of one allele or another, genetic drift decreases the genetic variation in a population over time.
Explain how inbreeding can have a positive effect on population fitness.
Many deleterious recessive alleles are weeded out by natural or artifical selection so that the population becomes homozygous for beneficial alleles. In this way, the harmful effects of inbreeding may eventually be eliminated leaving a population that is homozygous for beneficial traits.
What must be true for a population to be in Hardy-Weinberg equilibrium?
-No mutation
-No selection
-Infinitely large population
-No migration
-Random mating
The difference between fitness of a given genotype and another genotype considered as optimal is called the selection coefficient (s). What is the selection coefficient for a genotype (aa) when 99 of every 100 organisms successfully reproduce?
0.01
The __________ hypothesis suggests that many factors or genes contribute to the phenotype in a cumulative or quantitative manner.
multi-factorial traits?
What does the expression 2pq represent?
heterozygote genotype frequency
Suppose that a given gene undergoes a mutation to its dominant allele such that two out of 100,000 offspring exhibit the new mutant phenotype.

Assuming that these offspring are heterozygous, what is the mutation rate for the gene?
1/100,000
Assume that you are studying a trait determined by a number of polygenes. If there are seven phenotypic categories, how many genes are probably involved?
2
Huntington's disease is inherited in humans as an autosomal dominant gene. Affected individuals show progressive brain deterioration from cell death in the cerebral cortex. Onset of the disease usually occurs between ages 30 and 50. Give two possible reasons for the observed variation in the age of onset of this disease.
- variance in external environment
- variable genetic background
- variance in internal physiological environment
A certain form of color blindness in humans is sex-linked. Assume that 8% of the males in a population are color blind.

What percentage of the females in this population are expected to be color blind?
64%
In zoo animals, inbreeding often occurs because there is a lack of a sufficient pool of breeding individuals. Under such conditions, what characteristics often attend inbred organisms?
higher frequency of aberrant phenotypes and higher mortality rates
Which of the following is NOT a feature of Darwin's theory of natural selection?
a. Individuals with poor fitness never produce offspring.
b. B and C
c. There is no heritable variation among individuals.
d. A and B
e. A population adapts to its environment due to the variable reproductive success of individuals.
b. B and C
Development appears to occur as a result of successive subdivisions of anatomical/functional domains. Segments are formed in some embryos, and each segment is determined to form either anterior or posterior regions. What term is often applied to such regions?
a. segmental fracture
b. transdetermined aspect
c. compartment
d. homeodomain
e. gap faction
c. compartment
If mating occurs solely between relatives, eventually what will happen to the population?
a. It will become polymorphic for all shared traits.
b. The individuals in the population will have more dominant alleles.
c. It will remain in equilibrium.
d. It will become completely homozygous.
e. It will become completely heterozygous.
d. It will become completely homozygous
The number of different genes influencing flower diameter in this plant is
a. 7.
b. 6.
c. 3.
d. 5.
e. 4.
c. 3.
A gene or a trait is said to be polymorphic if:
a. one form exists in the population.
b. the allele frequency is ~50:50 for each gene or trait.
c. more than one form exists in the population.
d. the allele frequency of one trait is dominant over all others.
e. one allele occurs at a frequency of less than 1%
c. more than one form exists in the population.
______________ can cause the same genotype to produce a range of potential phenotypes.
a. Epistasis
b. The inbreeding coefficient
c. Hybrid vigor
d. Heritability
e. Environmental effects
e. Environmental effects
In a tropical human population in Hardy-Weinberg equilibrium for an autosomal locus determining presence/absence of pigment in the skin, the frequency of albinism (aa) is 1 in 10,000. The frequency of heterozygotes is approximately:
a. 1 in 100
b. 1 in 75
c. 1 in 25
d. 1 in 1000
e. 1 in 50
e. 1 in 50
A major difference between Mendelian and quantitative traits is in _______________
a. there are no differences between them
b. small differences between average phenotypes compared to differences between individuals within genotypes
c. that statistical properties of quantitative traits are better understood
d. that statistical properties of Mendelian traits are better understood
e. large differences between average phenotypes compared to differences between individuals within genotypes
b. small differences between average phenotypes compared to differences between individuals within genotypes
Which of the following is the fastest way for an enzyme to respond to changing conditions in the cell?
a. altering the enzyme's activity by allostearic effectors (activators or inhibitors)
b. controlling the synthesis or degradation of the enzyme in the cell
c. covalently modifying the enzyme in the cell (by phosphorylation)
d. changing the enzyme's compartmentalization or location in the cell
a. altering the enzyme's activity by allostearic effectors (activators or inhibitors)
You are studying a single-gene locus with two alleles in a population that is in Hardy-Weinberg equilibrium. Examination of a large sample of individuals from the population reveals there are six times as many heterozygote as there are homozygote recessive individuals in this population. What is the frequency of the recessive allele?
he Hardy-Weinberg equation is p2 + 2pq + q2 = 1 (and remember that p + q = 1). The sample results from this population indicate that the ratio of heterozygotes to homozygote recessives is 6:1, respectively. Transfer this data into the relevant Hardy-Weinberg equation elements to get 2pq / q2 = 6. Therefore, 2p = 6q, 2(1 - q) = 6q; and 2 - 2q = 6q; and finally, q = 0.25.
The height of a type of bean plants is determined by five unlinked genes called A, B, C, D, and E. Each gene has two alleles: additive (uppercase letter) and nonadditive (lowercase letter).
The shortest plants are 130 cm. The tallest plants are 220 cm. Estimate how many centimeters each allele contributes to the height difference of 90 cm.
The difference between the two heights is 90 cm. There are 10 alleles total (two each for five different genes). If each additive allele contributes equally to increasing height from a baseline of 130 cm, the contribution of each is 9 cm.
Because real-life populations are, of course, not infinitely large, why is the Hardy-Weinberg condition of an "infinitely large population" usually met for natural populations?
Because most natural populations are large enough that chance factors (i.e., sampling error, random genetic drift) have negligible effects on allele frequencies.
Which is more significant in changing gene frequencies: selection against a dominant gene or selection against a recessive gene?
selection against a dominant gene
Assuming that p = 0.3 for a population, what would be the expected frequency of heterozygotes for the involved allelic pair?
0.42

q= 1-0.3 = 0.7
2pq = 2(0.3)(0.7) = 0.42
Define the term broad-sense heritability. What is implied by a relatively high value of H2? Express aspects of broad-sense heritability in equation form.
- the percentage variation due to genetic factors
- high H2 means that the variance due to genetic factors is higher than the sum of variances
- high h2 means that it will be passed on to the next generations
What is the name describing sample variability?
standard deviation
What term is given to the probability that a particular phenotype will survive and leave offspring?
fitness
What is the term given to a measure of the loss of fitness caused by inbreeding?
inbreeding depression
A "marker" in a genetic sense usually represents a site along a chromosome where a specific nucleotide sequence exists. What specific phrase is used when such markers are identified by restriction endonucleases and a particular set of DNA fragments is generated?
RAD marker
If the proportion of F2 individuals resembling either of the two most extreme phenotypes (the parental phenotypes) can be determined, what formula can be applied to determine the number of gene pairs involved?
1/4^n?
Which statement is true regarding heritability and continuous variation?
a. Heritability measures the degree to which genes determine phenotype.
b. As the number of gene loci that affect a trait increases, the proportion of extreme version of the trait also increases.
c. A heritability value of 0.8% of the total variance is due to differences in the environment.
d. A low heritability score means that genes are less influential than environment in determining phenotypic variation.
e. The total variance used to calculate heritability measures all the variance in a population.
d. A low heritability score means that genes are less influential than environment in determining phenotypic variation.
Which of the following is NOT an explanation as to why dominant disease-causing genes exist in populations?
a. Despite the genes' effects, individuals stay healthy enough to reproduce.
b. The genes are masked and therefore are passed only through carriers.
c. The genes may be the result of new mutations.
d. The genes exert their effects late in life, beyond reproductive age
b. The genes are masked and therefore are passed only through carriers.
Any change in a population from Hardy-Weinberg equilibrium can be defined as ______.
a. mutation
b. genetic equilibrium
c. evolution
d. natural selection
e. migration
c. evolution
Which of the following statistical terms is a not measure of central tendency?
a. Correlation
b. All of the above
c. The Mean
d. The Mode
e. The Median
a. Correlation
Population genetics is concerned with:
a. (b) and (c) above.
b. whether allele frequencies are changing over time.
c. how genes produce proteins.
d. how genes confer relative reproductive success on the individuals.
e. how genes interact with one another.
a. (b) and (c) above.
What is evolution? Describe four different mechanisms by which it can occur
Evolution is a change in the allele frequencies in a population.
It can occur via the following four mechanisms:
a) Genetic drift.
Conditions under which it occurs: Random change in allele frequencies due to small population size or a small founder population colonizing a new habitat.
b) Migration/gene flow.
Conditions under which it occurs: New individuals are added to a population. If their genetic makeup for any particular gene is different from that of the population they join, the overall allele frequency in the new population changes.
c) Mutation.
Conditions under which it occurs: A direct change in an allele as a result of some environmental insult and/or a problem in replication.
d) Natural selection.
Conditions under which it occurs: If there is variation for a trait, heritability for that trait, and differential reproductive success based on that trait, evolution by natural selection is occurring.
Define polymorphism.
A gene or a trait is said to be polymorphic if there is more than one form of that trait in a population.
List three statistical values often used to represent a sample.
- mean
- variance
- the measure of variability of polygenic characters
In the case of complete dominance in a population in equilibrium, we cannot tell which individuals are homozygous dominants and which are heterozygous. However, we can estimate the frequency of homozygous dominant and heterozygous genotypes if we know what?
the frequency of the homozygous recessives
Assume that in a Hardy-Weinberg population, 9% of the individuals are of the homozygous recessive phenotype.

a) What percentage of the individuals would be expected to be heterozygous?
b) What percentage of the individuals would be expected to be homozygous dominant?
a) 42%
b) 49%
Interpret the meaning of an H2 value (broad-sense heritability) that approaches 1.0.
the variance due to genetic factors is almost the same as the sum of the variances
Name two human traits that would be expected to have a very high concordance.
- blood type
- eye color
What is the name of the process of selecting a specific group of organisms from an initially heterogeneous population for future breeding purposes?
artificial selection
One of the Hardy-Weinberg assumptions states that the population is free of selective advantage. What influence might selective advantage have on a Hardy-Weinberg equilibrium?
Certain alleles will reach the next generation on a nonrandom basis, thus upsetting the equilibrium.
In a normal distribution, 99% of the measurements fall within
a) plus or minus one standard deviation of the mean.
b) 1% of the mean.
c) plus or minus three standard deviations of the mean.
d) plus or minus two standard deviations of the mean.
e) 5% of the mean.
c) plus or minus three standard deviations of the mean.
Human racial differences are produced by
a) cultural factors as well as multiple genes that affect several traits.
b) a single gene that affects skin color.
c) multiple genes that affect several traits.
d) multiple genes that affect skin color.
a) cultural factors as well as multiple genes that affect several traits.
Explain how it is that genetic variation is maintained in the population. Why is it that dominant alleles do not eventually take over?
Meiotic segregation in randomly mating populations results in an equilibrium distribution of genotypes after only one generation, so genetic variation is maintained. As long as there is random mating occurring, then the frequency of dominant and recessive alleles will remain the same.
A new kind of tulip is produced that develops only purple or pink flowers. Assume that flower color is controlled by a single-gene locus, and that the purple allele (C) is dominant to the pink allele (c). A random sample of 1000 tulips from a large cultivated field yields 847 purple flowers, and 153 pink flowers.

a. Determine the frequency of the purple and pink alleles in this field population.
b. Estimate the proportion of all purple flowering plants that are heterozygotes and homozygotes.
a. Assuming the population is in H-W equilibrium, let p = the dominant purple allele (C), and q = the recessive allele (c). Applying the H-W equation, the frequency of the pink allele = q^2 = 153/1000 = 0.153; and q = (0.153)^1/2 = 0.39. Because p + q = 1, p = 1 - q = 0.61.

b. If the population is in H-W equilibrium, p^2 + 2pq + q^2 = 1.
For the heterozygotes, 2pq = 2(0.61)(0.39) = 0.476. Therefore, 47.6%, or (0.476)(1000) = 476 of all the purple flowered plants in this population are expected to be heterozygotes (Cc), and consequently, (p^2)(1000) = (0.61)^2 (1000) = 371 plants are expected to be
homozygous dominants (CC)
According to Hardy-Weinberg, if we know the frequency of each allele in the population, what can we predict?
We can predict what genotypes and phenotypes we should see in the population.
Provide a simple definition of inbreeding.
When two individuals closely related in a pedigree mate
___________ are those genes that are involved in determining continuously varying or multiple-factor traits.
polygenes
What is meant by the symbolism p + q = 1.0?
hardy-weinberg equilbrium
What formula can be used to determine the number of categories (phenotypes) possible in the F2 results of a polygenic system?
1/4^n n=#of gene pairs involved
What term refers to the regulatory events that establish a specific pattern of gene activity and developmental fate for a given cell?
a. differentiation
b. gradient regulated
c. determination
d. lysogen
e. attenuation
c. determination
As a Drosophila larva transitions to the pupa, much of the larval body is broken down. Adult structures, such as wings and legs, are constructed from small clusters of cells called
a. syncytia
b. pole cells
c. imaginal discs
d. homeoboxes
e. homeodomain
c. imaginal discs
Huntington disease is caused by a single dominant gene and results in progressive mental and neurological damage. The disease is usually symptomatic when a person is between 30 and 50 years old and the patient usually dies within 15 years of diagnosis. Approximately 1 in 25,000 Caucasians have this disease. Huntington disease has not been associated with any other disease, now or in the past. Why might natural selection not have eliminated such a deleterious gene from the population?
Huntington's does not take effect until after reproductive age, so the selective pressure against it is either very minor or nonexistent
Assume that in the F2 of a series of crosses, 1/64 of the offspring resemble one of the parents (P). How many gene pairs are involved in producing these results?
three
Assume that four polygenic gene pairs are involved in determining phenotypes of F2. How many phenotypic classes are expected?
nine
What is the relationship between the narrow-sense heritability index (h2) and the impact of selection?
a high H2 value indicates that a trait will be highly selected for
Is genetic drift primarily associated with relatively large or small breeding populations?
relatively small breeding populations
The 9:3:3:1 ratio is typical of a dihybrid cross in which complete dominance and independent assortment occur. What is the dihybrid ratio with independent assortment of polygenes?
1:4:6:4:1
Assume that a trait is caused by the homozygous (or hemizygous) state of a gene that is recessive and X-linked. Nine percent of the females in a given population express the phenotype caused by this gene.

a. What percentage of males would be expected to express this trait?
b. What percentage of the females would be heterozygous for the gene?
a. 30
b. 42
What general genetic process is believed to account for the variety of cellular structures and functions in eukaryotic cells?
a. RNA processing
b. negative control exclusively
c. intron processing
d. maternal environmental activities
e. variable gene activity
e. variable gene activity
Provide a brief description of the variable gene activity hypothesis as it relates to development. What information is often provided in support of this hypothesis?
Since all cells apparently have the same genetic information, yet may differ structurally and functionally, the variable gene activity hypothesis suggests that differential gene transcription (genetic regulation) accounts for such cellular diversity. Evidence in support of this model includes the following: chromosome puffs, isozymes, and the presence of genes but no gene products in some tissues (hemoglobin, for example).
The genetic frequencies of two separate populations are:


AA

Aa

aa

Population 1

.36

.48

.16

Population 2

.55

.10

.35


a) What are the genotypic frequencies of the two populations?
b) What are the allele frequencies?
c) Are the populations in Hardy-Weinberg equilibrium?
a) Expected for population 1: f(AA) = 0.36; f(Aa) = 0.48; f(aa) = 0.16
Expected for population 2: same


b) Pop 1: f(A) = 0.6 = p f(a) = 1−p =0.4 = q
Pop 2 : f (A) = 0.6 f(a) = 0.4


c) Population 1 is in Hardy-Weinberg equilibrium but population 2 is not.
In a population of cattle, the following color distribution was noted: 36% red (RR), 48% roan (Rr), and 16% (rr).

a. Is this population in a Hardy-Weinberg equilibrium?
b. Will the distribution of genotypes be the same in the next generation if Hardy-Weinberg assumptions are met?
a. yes
b. yes
The Hardy-Weinberg law (equation) is a mathematical model in which allele frequencies in populations remain constant from generation to generation. Given all the conditions that must be met for the Hardy-Weinberg equation to be valid, why is this equation useful for studying population genetics?
By specifying the ideal conditions that must be met for allele frequencies to remain constant in populations, the H-W law can identify evolutionary forces that can cause changes in allele frequencies in the real world. Remember, the H-W law is a model and therefore, by definition, provides a simplistic view of reality, which serves as a starting point and basis for comparison for further examination and description of real populations.
Mutation and migration introduce new alleles into populations. What is the principal force that shifts allelic frequencies within large populations?
natural selection
The differential reproduction of genotypes, resulting from their variable fitness is called
selection
How many gene pairs are involved in generating a typical 1:4:6:4:1 ratio?
2
Inbreeding in populations that are normally outbreeding leads to which of the following?
a. More individuals affected by rare diseases
b. A higher rate of mutation
c. An increase in the frequency of heterozygotes
d. A smaller population
e. A higher rate of genetic drift
a. More individuals affected by rare diseases
In extreme cases, genetic drift may lead to the chance fixation of one allele. What happens to other alleles of that gene?
The other alleles no longer exist
Give a brief definition of the term genetic equilibrium.
Genetic equilibrium occurs when allele frequencies do not change over time
Individuals with the same genetic background and a high degree of homozygosity are said to be isogenic. Of what value are isogenic strains in genetic studies?
in an isogenic strain, all individuals are genetically identical. With this, geneticists around the world can work on genetically identical individuals
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