Genetics exam test queries and
answers graded A+
1.) Which of the following indicates the correct order of these events?
A) Metaphase - Prometaphase - Prophase - Anaphase - Telophase
B) Prophase - Prometaphase - Metaphase - Anaphase - Telophase
C) Telophase - Prometaphase - Prophase - Metaphase - Anaphase
D) Anaphase - Telophase - Prophase - Prometaphase - Metaphase - ANS✅✅B) Prophase -
Prometaphase - Metaphase - Anaphase - Telophase
2.) In a dihybrid cross using Mendelian inheritance, if both parents are heterozygous for both traits,
what will be the phenotypic ratio of their offspring?
A) 3:1
B) 9:3:3:1
C) 1:1
D) 1:2:1 - ANS✅✅B) 9:3:3:1
3.) A testcross is always performed between the individual that is heterozygous for the genes to be
mapped and an individual who is ____________.
A) heterozygous for the genes
B) lacking the genes
C) homozygous dominant for the genes
D) homozygous recessive for the genes - ANS✅✅D) homozygous recessive for the genes
4.) Crossing over is more likely to occur between genes that are __________ on a chromosome
A) close together
B) far apart - ANS✅✅B) far apart
5.) You are working with fruit flies, but you forgot to write down the parents of your cross. You count
the progeny, and find you have 40 red-eyed males, 80 red-eyed females, and 40 white-eyed males.
White eyes (w) are recessive to red (w+). Assuming that all genotypes from this cross should have
equal survival rates, what are the genotypes of the parent flies?
A) X^w+ Y and X^w+ X^w
, B) X^w+ Y and X^w X^w
C) X^w Y and X^w+ X^w
D) X^w Y and X^w+ X^w+x - ANS✅✅A) X^w+ Y and X^w+ X^w
6.) The pedigree below shows the inheritance pattern of a rare genetic disorder that is inherited in
an X-linked dominant manner through one family. The filled in circles and squares show affected
individuals. What is the probability of individual III-2 being born male and affected?
A) 1/4
B) 1/2
C) 1/3
D) 0 - ANS✅✅D) 0
7.) What is the probability that an offspring will have an ssRR genotype from a cross of two SsRr
individuals?
A) 6.25%
B) 25%
C) 3.12%
D) 12.5% - ANS✅✅A) 6.25%
8.) (HAS AN IMAGE) Wild-type Drosophila have red eyes, but it is possible to isolate mutants that
have different eye colors. The chart below summarizes the results of crosses between pure-breeding
flies with different eye colors
+ = wildtype phenotype (= red eyes)
- = non-wildtype phenotype
Based on the chart, how many eye-color mutants have mutations in the SAME gene as the Garnet
mutant? (Assume that all mutant alleles are recessive.)
A) 2
B) 3
C) 0
D) 6 - ANS✅✅C) 0
9.) The physical structure that is formed when two chromatids cross over is called a(n) _______.
A) chiasma
answers graded A+
1.) Which of the following indicates the correct order of these events?
A) Metaphase - Prometaphase - Prophase - Anaphase - Telophase
B) Prophase - Prometaphase - Metaphase - Anaphase - Telophase
C) Telophase - Prometaphase - Prophase - Metaphase - Anaphase
D) Anaphase - Telophase - Prophase - Prometaphase - Metaphase - ANS✅✅B) Prophase -
Prometaphase - Metaphase - Anaphase - Telophase
2.) In a dihybrid cross using Mendelian inheritance, if both parents are heterozygous for both traits,
what will be the phenotypic ratio of their offspring?
A) 3:1
B) 9:3:3:1
C) 1:1
D) 1:2:1 - ANS✅✅B) 9:3:3:1
3.) A testcross is always performed between the individual that is heterozygous for the genes to be
mapped and an individual who is ____________.
A) heterozygous for the genes
B) lacking the genes
C) homozygous dominant for the genes
D) homozygous recessive for the genes - ANS✅✅D) homozygous recessive for the genes
4.) Crossing over is more likely to occur between genes that are __________ on a chromosome
A) close together
B) far apart - ANS✅✅B) far apart
5.) You are working with fruit flies, but you forgot to write down the parents of your cross. You count
the progeny, and find you have 40 red-eyed males, 80 red-eyed females, and 40 white-eyed males.
White eyes (w) are recessive to red (w+). Assuming that all genotypes from this cross should have
equal survival rates, what are the genotypes of the parent flies?
A) X^w+ Y and X^w+ X^w
, B) X^w+ Y and X^w X^w
C) X^w Y and X^w+ X^w
D) X^w Y and X^w+ X^w+x - ANS✅✅A) X^w+ Y and X^w+ X^w
6.) The pedigree below shows the inheritance pattern of a rare genetic disorder that is inherited in
an X-linked dominant manner through one family. The filled in circles and squares show affected
individuals. What is the probability of individual III-2 being born male and affected?
A) 1/4
B) 1/2
C) 1/3
D) 0 - ANS✅✅D) 0
7.) What is the probability that an offspring will have an ssRR genotype from a cross of two SsRr
individuals?
A) 6.25%
B) 25%
C) 3.12%
D) 12.5% - ANS✅✅A) 6.25%
8.) (HAS AN IMAGE) Wild-type Drosophila have red eyes, but it is possible to isolate mutants that
have different eye colors. The chart below summarizes the results of crosses between pure-breeding
flies with different eye colors
+ = wildtype phenotype (= red eyes)
- = non-wildtype phenotype
Based on the chart, how many eye-color mutants have mutations in the SAME gene as the Garnet
mutant? (Assume that all mutant alleles are recessive.)
A) 2
B) 3
C) 0
D) 6 - ANS✅✅C) 0
9.) The physical structure that is formed when two chromatids cross over is called a(n) _______.
A) chiasma
