Mendelian Genetics REview

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Review Questions
Question 1

Homologous chromosomes move toward
opposite poles of a dividing cell during
a. mitosis
b. meiosis I
c. meiosis II
d. fertilization
Answer 1

Homologous chromosomes move toward
opposite poles of a dividing cell during
b. meiosis I
Question 2

Meiosis II is similar to mitosis in that
a. Sister chromatids separate during
anaphase.
b. DNA replicates before the division
c. The daughter cells are diploid
d. Homologous chromosomes synapse
Answer 2

Meiosis II is similar to mitosis in that
a. Sister chromatids separate during
anaphase.
b. DNA replicates before the division
c. The daughter cells are diploid
d. Homologous chromosomes synapse
Question 3

Monohybrid cross
a. Variant for a character
b. Genetic makeup of an individual
c. An alternative version of a gene
d. A cross between individuals
heterozygous for a single character
Answer 3

Monohybrid cross
a. Variant for a character
b. Genetic makeup of an individual
c. An alternative version of a gene
d. A cross between individuals
heterozygous for a single character
Question 4

Allele
a. Alternative version of a gene
b. Has no effect on phenotype in a
heterozygote
c. An organism's appearance
d. Genetic makeup of an individual
Answer 4

Allele
a. Alternative version of a gene
b. Has no effect on phenotype in a
heterozygote
c. An organism's appearance
d. Genetic makeup of an individual
Question 5

A man with type A blood marries a
woman with type B blood. Their child has
type O blood. What are the genotypes of
these individuals? What other genotypes,
and in what frequencies, would you
expect in offspring from this marriage?
Answer 5

Man IAi, Woman IBi, child ii
Other genotypes for children are ¼ IAIB,
¼ IAi, ¼, IBi
Question 6

In tigers, a recessive allele causes an
absence of fur pigmentation (white tiger)
and a cross-eyed condition. If 2
phenotypically normal tigers that are
heterozygous at this locus are mated, what
% of their offspring will be cross-eyed?
What % of cross-eyed tigers will be white?
Answer 6

25% will be cross-eyed; all of the crosseyed offspring will also be white.
Question 7

A man with hemophilia (recessive, sexlinked) has a daughter of normal
phenotype. She marries a man who is
normal for the trait. What is the
probability that a daughter of this mating
will be a hemophiliac? That a son will be a
hemophiliac? If the couple has four sons,
what is the probability that all 4 will be
born with hemophilia?
Answer 7

0; ½; 1/16
Question 8

Red-green color blindness is caused by a
sex-linked recessive allele. A color-blind
man marries a woman with normal vision
whose father was color-blind. What is the
probability that they will have a color-blind
daughter? What is the probability that their
1st son will be color-blind? (Note the
different wording of the 2 questions)
Answer 8

¼ for each daughter ( ½ chance that a
child will be female x ½ chance of a
homozygous recessive genotype); ½ for
1st son.
Question 9

A wild-type fruit fly (heterozygous for
gray body color & normal wings) is mated
with a black fly with vestigial wings. The
offspring have the following phenotypic
distribution: wild type, 778; black-vestigial,
758; black normal, 158; gray-vestigial, 162.
What is the recombination frequency
between these genes for body color & wing
size?
Answer 9

17%
Question 10

What pattern of inheritance would lead a
geneticist to suspect that an inherited
disorder of cell metabolism is due to a
defective mitochondrial gene?
Answer 10

The disorder would always be inherited
from the mother.
Question 11

Pseudohypertrophic muscular dystrophy
is an inherited disorder that causes gradual
deterioration of the muscles. It is seen
almost exclusively in boys born to
apparently normal parents & usually
results in death in the early teens. Is this
disorder caused by a dominant or a
recessive allele? Is its inheritance sexlinked or autosomal? Why?
Answer 11

Recessive, if it were dominant it would
affect at least 1 parent of a child with the
disorder. The disorder’s inheritance is sexlinked because it is seen only in boys. For a
girl to have the disorder, she would have to
inherit recessive alleles form both parents.
This would be very rare, since males with
the recessive allele on their X chromosome
die in their early teens.
Question 12

How many chromatids are in a
duplicated chromosome?
Answer 12

2
Question 13

A chicken has 78 chromosomes in its
somatic cells. How many chromosomes
did the chicken inherit from each parent?
How many chromosomes are in each of
the chicken’s gametes? How many
chromosomes will be in each somatic cell
of the chicken’s offspring?
Answer 13

39; 39; 78
Question 14

What phase are most of your body cells
in?
Answer 14

Non-dividing state called G₀.
Question 15

Each sperm of a pea plant contains 7
chromosomes. What are the haploid &
diploid numbers for peas?
Answer 15

Haploid = (n) 7
Diploid = (2n) 14
Question 16

What is the original source of all the
different alleles of a gene?
Answer 16

Mutations in a gene lead to the
different version (alleles) of that gene.
Question 17

A pea plant heterozygous for inflated
pods (Ii) is crossed with a plant
homozygous for constricted pods (ii).
Draw a Punnett square for this cross.
Assume pollen come from the ii plant.
Answer 17

i
I
Ii
i
Ii
Genotype 2:2
Phenotype 2:2
i
ii
ii
Question 18

An organism with the genotype BbDD is
mated to one with the genotype BBDd.
Assuming independent assortment of
these 2 genes, write the genotypes of all
possible offspring from this cross & use
the rules of probability to calculate the
chance of each genotype occurring.
Answer 18

¼ BBDD, ¼ BbDD, ¼ BBDd, ¼ BbDd
Question 19

Incomplete dominance & epistasis are
both terms that define genetic
relationships. What is the most basic
distinction between these terms?
Answer 19

Incomplete dominance describes the
relationship between 2 alleles of a
single gene, whereas epistasis relates to
the genetic relationship between 2
genes and the respective alleles of each.
Question 20

Andalusian chickens with the genotype
CBCB are black, those with the genotype
CWCW are white, and those with the
genotype CBCW are gray. What is the
relationship between the CB and CW
alleles?
Answer 20

The relationship between the alleles is
one of incomplete dominance.

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