General Genetics
2005
Exam 1 (60 points)
Name __________________________________
Multiple Choice. (1 point each)
_____During interphase of the cell cycle ___.
A.
B.
C.
D.
E.
DNA recombines
Sister chromatids move to opposite poles
The nuclear membrane disappears
RNA replicates
DNA content essentially doubles
_____In dihybrid crosses, the ratio 9:3:3:1 indicates ___.
A. Segregation of alleles
B. Independent assortment
C. Intermediate dominance
D. Three alleles for each trait
_____Phenotype is to protein as genotype is to
A. Genotype
B. DNA
C. Expressivity
D. RNA
E. Mutation
_____An allele is ___.
A.
B.
C.
D.
E.
one of the bases in DNA
an alternate form of a gene
another term for epistasis
present only in males and is responsible for sex determination
found in mitochondria but not in nuclei
_____Chromosomes that are matched up or paired at metaphase of meiosis I are called ___?
A.
B.
C.
D.
E.
homologous
heterologous
complementary
non-disjunctive
parallel
_____Albinism, lack of pigmentation in humans, results from an autosomal recessive gene designated a. Two
parents with normal pigmentation have an albino child. What is the probability that their next child will have
normal pigmentation? What is the probability that the next child will be an albino girl?
A.
B.
C.
D.
E.
¼; 1/8
3/4, ¼
¼; ½
3/4, 1/8
1/8; ¼
_____ The probability that all five children in a family will be males is
A.
B.
C.
D.
E.
1/32
1/16
1/2
5/16
5/32
_____What ratios typically result from crosses dealing with two genes?
A.
B.
C.
D.
E.
9:3:3:1, 1:1:1:1
1:1:1:1, 1:4:6:4:1
3:1, 1:1, 1:2:1
9:7, 12:3:1
15:1, 1:2
_____ Individuals whose genotype is represented by the alleles Aa are described genotypically as
A.
B.
C.
D.
E.
heterozygous
dihybrid
homozygous
homologous
dominant
_____ Which of the following processes occurs in meiosis but not mitosis?
A.
B.
C.
D.
Cell division
Separation of homologous chromosomes to opposite poles
Chromatic formation
Chromosome condensation (shortening)
_____ The end result of meiosis is
A.
B.
C.
D.
two cells with the exact same chromosome complement of the starting cell
two cells with half the chromosome complement of the starting cell
four cells with the exact same chromosome complement of the starting cell
four cells with half the chromosome complement of the starting cell
_____ An individual that always produces offspring with a specific phenotype is described as
A.
B.
C.
D.
true-breading
wild-type
polymorphic
boring
_____ To determine if an organism with a dominant phenotype is heterozygous, one can perform a ___.
A.
B.
C.
D.
reciprocal cross
monohybrid cross
didhybrid cross
testcross
Short Answer. (variable points)
Name one human genetic disorder that is inherited in a simple Mendelian pattern (2 points)
What is the purpose of “check points” during interphase of the cell cycle? (2 points)
Purple flower color in peas is dominant to white. Assume that Mendel conducted a series of experiments where
plants with purple flowers were crossed with plants with white flowers and the following progeny were
produced: 325 purple flowers and 350 white flowers. What is the most probable genotype of each parent? (2
points)
Describe one process that occurs during meiosis that is responsible for creating genetic diversity within a
population. (1 point)
One form of deafness in humans can be caused by a rare autosomal dominant gene. In a mating involving a
deaf man and a deaf woman, could all the children have normal hearing? Explain. (2 point)
Calculate the probability of having two girls and two boys in a family with four children. (2 point)
What is the probability of having 6 girls and two boys in a family with the following birth order: BGGGGBGG?
(1 points)
Phenylketonuria (PKU) is a recessive trait which results in toxicity due to incomplete metabolism of
phenylalanine. The PKU trait is due to the absence of an enzyme responsible for metabolism of phenylaline.
Two parents without PKU have a child with PKU. What is the probability that their next child will have PKU?
What is the probability of the couple having two additional children, both of which do not have PKU? (2 points)
Draw a Punnet square for the following cross: GgLl x GgLl and circle the genotypes that will produce
individuals who have both dominant phenotypes. (6 points)
A breed of guinea pigs can have either black and white coloration or brown and white coloration. For each of
the crosses given below, write the most probable genotype (or genotypes if more than one answer is possible)
for the PARENTS. (3 points)
Parental phenotypes
Phenotypes of Offspring
Black and white Brown and white
A) black and white x brown and white
B) black and white x brown and white
C) black and white x black and white
Cross A
12
29
19
Cross B
14
0
7
Cross C
In ReBop genetics the symbol Q is for curly tails and q is for straight tails, B is for a 3 body segments and b is
for 2 body segments. In a cross between two ReBops with Curly tails and 3 body segments and both with the
genotypes QqBb what fraction of the ReBops will have:
A) Curly tails and 2 body segments (1 point)
B) 2 body segments (1 point)
C) Straight tails and 3 body segments (1 point)
D) Curly tails (1 point)
E) Straight tails and 2 body segments (1 point)
F) Curly tails and 3 body segments (1 point)
The following diagram shows chromosomes in either anaphase of mitosis or anaphase I or II of meiosis. The
organism has a diploid number of (2n=4). In other words it has two copies of two different chromosomes (A,a
and B,b). Cross out those chromosome arrangements that are not possible (ignoring crossing over) and for
those that are possible, indicate which stage of mitosis or meiosis is represented. (4 points)
A.
.
B.
..
C.
.
D.
.
When possible (specify if it is not possible), give the stages of mitosis and meiosis I or II at which: (4 points)
Stage of Mitosis
Stage of Meiosis
Event
_______________
_______________
Homologous replicated chromosomes (sister chromatids)
move toward opposite poles of the cell
_______________
_______________
Centromeres align at the equator in diploid cells.
_______________
_______________
Homologous chromosomes pair up
_______________
_______________
Unpaired chromosomes congregate at the equator of the
spindle
Assume that a certain organism has a diploid number of 2 pairs of chromosomes (2n=4) in its body cells and
that these chromosomes may be referred to as the A, a chromosomes and the B, b chromosomes. Identify, from
the choices given below, the stage of mitotic or meiotic cell division for each diagram. (6 points)
Choices: (each may be used more than once or not at all)
A.
B.
C.
D.
E.
F.
Interphase
Anaphase of mitosis
Metaphase of mitosis
Anaphase I or meiosis
Anaphase II of meiosis
Metaphase II of meiosis
The diagram below depicts the pedigree of a family along with the molecular analysis of the gene associated
with a specific disorder with which individual II-3 was afflicted. Fill in the DNA banding pattern for
individuals II-3 and I-2. Indicate the genotypes for individuals II-1 and II-2. (4 points)
Genotype
II-1
II-2
BONUS Explain how genes on two different pairs of homologous chromosomes with different alleles (A, a and
B, b) go through the process of meiosis (you may use diagrams). (5 points)