Genetics Exam test queries and
answers graded A+
Based on the recombination frequency between the two genes being 20%, what are the x and y
frequencies of recombinant and non-recombinant progeny, respectively? - ANS✅✅x= 0.10 ; y=
0.40
In a testcross AaBb x aabb where the two genes are linked, but not completely (so some crossing
over still occurs but not as much as expected), what are the predicted frequencies of non-
recombinant progeny and recombinant progeny? - ANS✅✅More than 50% non-recombinant, Less
than 50% recombinant
In a hypothetical testcross, there are 10 and 10 recombinant progeny and 40 and 40 of
nonrecombinant progeny. What is the recombination frequency? - ANS✅✅20%
The __ that two genes are together, the __ the probability that a crossing over event will occur
between them. - ANS✅✅closer; less likely
___ maps estimate RELATIVE distances between genes by using recombination frequencies as a unit
of measure; while ___ maps are based on DNA sequencing and use the number of nucleotides to
determine distances between genes. - ANS✅✅Genetic; Physical
Linked genes are in the ___ configuration when each chromosome contains one wild-type and one
mutant allele. - ANS✅✅Repulsion
If one creates a library of mouse cell lines in which each cell line has a different random human
chromosome in it, and then looks for the presence of a particular human gene or protein to ascribe
it to that human chromosome, this method is called: - ANS✅✅Somatic cell hybridization
Having a single crossing over event occur between two homologous chromosomes during meiosis
causes: - ANS✅✅50% of the gametes to be recombinant
Which are true regarding Y-linked traits? Mark the three answers that are true.
a) Females do not inherit them
b) Does not skip generations
, c) Passed from a father to all of his daughters
d) Passed from a mother to all of her sons
e) Passed from a father to all of his sons - ANS✅✅a, b, e
What are two advantages of chorionic villus sampling over amniocentesis? Mark the two answers
that are correct.
a) Chorionic villus sampling is often done later than amniocentesis
b) Chorionic villus sample obtains more tissue than amniocentesis, negating the need for cell
culturing before testing
c) Chorionic villus sampling requires culturing of cells to get enough for genetic testing
d) Chorionic villus sampling is routinely done earlier in gestation compared to amniocentesis
e) None of the above - ANS✅✅b, d
The percentage of twin pairs that both have a trait is called the percent __. - ANS✅✅Concordance
In an X-linked dominant trait, which of the following are true- Mark the three answers that apply.
a) More daughters than sons are usually affected because daughters have double the chance of
inheriting at least one mutated allele compared to a son
b) All affected mothers pass the trait on to ALL of their daughters
c) Affected fathers pass the trait to ALL of their daughters
d) Skips generations
e) An affected male must have an affected mother - ANS✅✅a,c,e
What are two ways that Chromosomal rearrangements can occur? Mark the two answers that are
correct.
a. As an incorrect repair to a double stranded DNA break
b. By the deletion of an entire chromosome
c. By the duplication of an entire chromosome
d. Through errors in crossing over events
e. None of the above - ANS✅✅a,d
answers graded A+
Based on the recombination frequency between the two genes being 20%, what are the x and y
frequencies of recombinant and non-recombinant progeny, respectively? - ANS✅✅x= 0.10 ; y=
0.40
In a testcross AaBb x aabb where the two genes are linked, but not completely (so some crossing
over still occurs but not as much as expected), what are the predicted frequencies of non-
recombinant progeny and recombinant progeny? - ANS✅✅More than 50% non-recombinant, Less
than 50% recombinant
In a hypothetical testcross, there are 10 and 10 recombinant progeny and 40 and 40 of
nonrecombinant progeny. What is the recombination frequency? - ANS✅✅20%
The __ that two genes are together, the __ the probability that a crossing over event will occur
between them. - ANS✅✅closer; less likely
___ maps estimate RELATIVE distances between genes by using recombination frequencies as a unit
of measure; while ___ maps are based on DNA sequencing and use the number of nucleotides to
determine distances between genes. - ANS✅✅Genetic; Physical
Linked genes are in the ___ configuration when each chromosome contains one wild-type and one
mutant allele. - ANS✅✅Repulsion
If one creates a library of mouse cell lines in which each cell line has a different random human
chromosome in it, and then looks for the presence of a particular human gene or protein to ascribe
it to that human chromosome, this method is called: - ANS✅✅Somatic cell hybridization
Having a single crossing over event occur between two homologous chromosomes during meiosis
causes: - ANS✅✅50% of the gametes to be recombinant
Which are true regarding Y-linked traits? Mark the three answers that are true.
a) Females do not inherit them
b) Does not skip generations
, c) Passed from a father to all of his daughters
d) Passed from a mother to all of her sons
e) Passed from a father to all of his sons - ANS✅✅a, b, e
What are two advantages of chorionic villus sampling over amniocentesis? Mark the two answers
that are correct.
a) Chorionic villus sampling is often done later than amniocentesis
b) Chorionic villus sample obtains more tissue than amniocentesis, negating the need for cell
culturing before testing
c) Chorionic villus sampling requires culturing of cells to get enough for genetic testing
d) Chorionic villus sampling is routinely done earlier in gestation compared to amniocentesis
e) None of the above - ANS✅✅b, d
The percentage of twin pairs that both have a trait is called the percent __. - ANS✅✅Concordance
In an X-linked dominant trait, which of the following are true- Mark the three answers that apply.
a) More daughters than sons are usually affected because daughters have double the chance of
inheriting at least one mutated allele compared to a son
b) All affected mothers pass the trait on to ALL of their daughters
c) Affected fathers pass the trait to ALL of their daughters
d) Skips generations
e) An affected male must have an affected mother - ANS✅✅a,c,e
What are two ways that Chromosomal rearrangements can occur? Mark the two answers that are
correct.
a. As an incorrect repair to a double stranded DNA break
b. By the deletion of an entire chromosome
c. By the duplication of an entire chromosome
d. Through errors in crossing over events
e. None of the above - ANS✅✅a,d
