All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
Example Questions
Example Question #2 : Help With Hardy Weinberg
An isolated population consists of 10 males and 10 females. Two individuals are carriers of the recessive blue eye allele. Assuming all Hardy-Weinberg conditions are met. What is the frequency of the blue eye phenotype in the population?
Use the two Hardy-Weinberg equations:
Above, is the frequency of the dominant allele, and is the frequency of the recessive allele in the isolated population.
Since there are 20 people in total on the island, that means that there are 40 alleles for eye color. 2 of the 40 are for the blue allele:
We are looking for the blue eye phenotype, which can only result from two recessive alleles.
Example Question #6 : Help With Hardy Weinberg
Within his rat population, a scientist is trying to generate twice as many recessive homozygotes as heterozygotes. What allelic frequency would accomplish this?
Use the Hardy-Weinberg equations:
The equation he will need to set up is the following:
Solve for and substitute the first equation into the equation above.
Simplify.
Lastly, find .
Example Question #1 : Help With Hardy Weinberg
Assuming Hardy-Weinberg equilibrium conditions, what are the heterozygote (Bb) and homozygote recessive (bb) genotypes for a gene if the homozygote dominant (BB) genotype is 0.45?
Cannot be determined
Bb = 0.15
bb = 0.4
Bb = 0.4
bb = 0.15
Bb = 0.11
bb = 0.44
Bb = 0.44
bb = 0.11
Bb = 0.44
bb = 0.11
The correct answer is Bb = 0.44 and bb = 0.11.
Since we know BB = 0.45 and the equations for allele frequencies when Hardy-Weinberg equilibrium conditions are met:
and
We solve for B first:
Now we can solve for the homozygote recessive.
Lastly, solve for the heterozygote.
Example Question #1 : Help With Hardy Weinberg
Which of the following is not an assumption of the Hardy-Weinberg equilibrium?
No genetic drift within a population
No gene flow between populations
No natural selection within a population
Non-random mating within a population
No mutations within a population
Non-random mating within a population
Non-random mating is not an assumption of the Hardy-Weinberg equilibrium, in fact, in order to make predictions about the next generation, random mating must be assumed. Additionally, no new mutations, no gene flow, no genetic drift, and no natural selection must also occur. If any of these phenomenon are present in a population, we can not estimate allele frequencies in subsequent generations due to chance, rather selective pressures may favor one allele over another allele.
Example Question #381 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology
What are the phenotypic ratios for a given population for which the proportion of the dominant allele is 0.55 and that of the recessive allele is 0.45?
Homozygous dominant: 0.50
Heterozygous: 0.30
Homozygous recessive: 0.20
Homozygous dominant: 0.30
Heterozygous: 0.20
Homozygous recessive: 0.50
Homozygous dominant: 0.20
Heterozygous: 0.50
Homozygous recessive: 0.30
Homozygous dominant: 0.25
Heterozygous: 0.50
Homozygous recessive: 0.25
Homozygous dominant: 0.30
Heterozygous: 0.50
Homozygous recessive: 0.20
Homozygous dominant: 0.30
Heterozygous: 0.50
Homozygous recessive: 0.20
To solve this problem, assume Hardy-Weinberg equilibrium and use the associated equations to solve:
is dominant allele and is recessive allele
To find the phenotype ratios:
homozygous dominant
heterozygous
homozygous recessive
Example Question #31 : Molecular Biology And Genetics
Which of the following is not a tenet of Hardy-Weinberg equilibrium?
Genetic drift
No natural selection
Randomized mating
No migration
Large population
Genetic drift
The Hardy-Weinberg equilibrium does not account for genetic drift. The Hardy-Weinberg law states that genetic frequencies will remain constant in a population from generation to generation in the absence of evolutionary influences. Therefore, there is no migration, natural selection, nonrandom mating, or small populations in a Hardy-Weinberg population.
Example Question #1 : Help With Other Inheritance Patterns
Which of the following are examples of codominance?
I. A person with blood type AB
II. A flower that displays a red and white spotted phenotype (both colors are attributed to the same gene; homozygosity for either color makes a flower that is completely red or white)
III. A flower that displays a pink phenotype (a homozygous dominant flower is red and a homozygous recessive flower is white)
IV. An organism whose heterozygous phenotype is identical to the homozygous dominant phenotype
IV only
I, II, and III
III and IV
I and II
I and II
Codominance occurs when both phenotypes are displayed equally and independently in the phenotype (without blending). This is the case with blood type and the red and white spotted flower. A person with blood type AB expresses proteins that will recognize both type A and type B. The red and white spotted flower equally expresses the two color phenotypes.
The pink flower is an example of incomplete dominance (blended phenotype). Option IV describes a normal dominant-recessive hierarchy, where only one copy of the dominant allele is needed to display the dominant phenotype.
Example Question #2 : Help With Other Inheritance Patterns
When the expression and subsequent phenotype of one gene is dependent on the expression of another gene, this type of phenonemon is known as __________.
codominance
gene masking
epistasis
complete dominance
incomplete dominance
epistasis
The correct answer is epistasis. Complete dominance, codominance, and incomplete dominance describe the expression of only one gene (one set of alleles) that do not depend on the expression of other genes. Gene masking is not a phenomenon in genetics.
Example Question #3 : Help With Other Inheritance Patterns
Each of the listed statements about transposable genetic elements in eukaryotic genomes are true except for which one?
Found in clusters within the genome
Can introduce genetic mutations through creating inversions
Activity is repressed by small RNAs that are transcribed by RNA polymerase II and III
Converted to RNA intermediate by transposase proteins
Converted to RNA intermediate by transposase proteins
Transposable elements are divided into two categories: Type 1 (retrotransposons), which form RNA intermediates, and type 2 (transposons), which do not form RNA intermediates and directly enter a new site. Transposase proteins regulate the translocation of type 2 transposable elements, which do not require a RNA intermediate.
Example Question #4 : Help With Other Inheritance Patterns
Crossing foxes that are double heterozygotes for two genes regulating coat color yields 27 grey, 12 red and 9 black offspring. What mechanism explains the ratio of coat color observed in the offspring?
X-chromosome linked
Chromosomal linkage
Epistasis
Pleiotropy
Mendelian inheritance
Epistasis
If this were a Mendelian trait, we would expect a 9:3:3:1 ratio of offspring coat color. However, the results show a 9:4:3 ratio. Epistatic interaction between genes can be identified by one gene masking the phenotype of another gene. In this case, the double homozygote phenotype was masked by the red coat color phenotype (4 offspring, instead of seeing 3 red offspring). This suggests that the two coat color genes are epistatic.