Download Genetics Exam 3 2002

BioSc 231
General Genetics
Exam 3
Name __________________________________
Multiple Choice. (2 points each)
_____ Recombination frequencies ___
A. are the same for all genes.
B. arise from specific genetic exchange.
C. are the same for cis and trans heterozygotes.
D. decrease with distance.
_____ A plant of genotype C d/C d is crossed to c D/c D and an F1 testcrossed to c d/c d. If the genes are linked and 40 map units
apart, the percentage of C d/c d offspring will be
A. 10%
B. 20%
C. 30%
D. 40%
E. 50%
_____ When an organism gains or loses one of more chromosomes but not a complete haploid set, the conditions is known as
A. polyploidy
B. euploidy
C. aneuploidy
D. triploidy
E. trisomy
_____ When an allotetraploid is backcrossed to one of its progenitor species, a sterile progeny is produced. The genomic composition
of this sterile individual can be best represented by
A. n1 + n2
B. 2n1 + 2n2
C. 2n1
D. 2n2
E. 2n1 + n2
_____ In Drosophila, the two genes w and sn are X-linked and 25 map units apart. A female fly of genotype w+ sn+/w sn is crossed to
a male from a wild-type line. What percentage of male progeny will be w+ sn?
A. 0
B. 12.5%
C. 25%
D. 37.5%
E. 50%
_____ It was once thought that the ____ karyotype was related to criminal disposition because it led to aggressive behavior due to
excessive "maleness".
A. XO
B. XY
C. XXY
D. XYY
E. YY
_____ Polyploid plants found in nature usually have even numbers of chromosomes because organisms having odd numbers
A. exhibit altered mitosis
B. are unable to asexually reproduce
C. exhibit altered growth
D. have low fertility
E. are not viable
_____ Out of 800 progeny of a three-point testcross there were 12 double crossover recombinants, whereas 20 had been expected on
the basis of no interference. The interference is
A. 0.05
B. 0.10
C. 0.20
D. 0.30
E. 0.40
_____ In a cross of two yeast strains of genotypes c+ a+ X c a the progeny were
36 c+ a+
40 c a
11c+ a
13 c a+
The frequency of recombination is
A. 11%
B. 12%
C. 24%
D. 50%
E. 76%
_____ Two genes with a 50% recombination frequency are
A. Present on homologous chromosomes
B. Located close to each other
C. Linked
D. Far apart on a single chromosome
_____ In testcross experiments, the frequency of recombination between genes a and d is 0.3; between d and c, 0.2; between c and b,
0.1; between a and c, 0.5; and between b and d, 0.3. What is the order of the three genes?
A. c-b-d-a
B. d-c-a-b
C. a-d-c-b
D. b-a-c-d
E. a-b-c-d
_____ Euploidy is
A. a chromosome number that is not an exact multiple of the haploid number
B. an example of aneuploidy
C. a chromosome number that is an exact multiple of the haploid number
D. the addition of an extra copy of a particular chromosome
E. the absence of a particular copy of a chromosome
_____ Calico cats have a patchwork pattern of yellow and black spots. This pattern is an example of
A. somatic mutation
B. dosage compensation
C. mitotic segregation
D. all heterozygotes display this phenomenon regardless of sex
E. X-inactivation
_____ Consider a species with a diploid (2n) number of 20 chromosomes. How many chromosomes would be found in a trisomic
body cell?
A. 9
B. 10
C. 11
D. 20
E. 21
_____ The basic diploid chromosome number in Poinsettia is 16. A new species of Poinsettia is found that has four complete sets of
the chromosomes found in the 16 chromosome species (32 chromosomes total). This species is said to be
A. haploid
B. diploid
C. triploid
D. tetraploid
E. pentaploid
_____ Consider a species with a diploid (2n) number of 40 chromosomes. How many chromosomes would be found in a monoploid
body cell?
A. 10
B. 20
C. 21
D. 19
E. 40
_____ Three-point test crosses
A. Detect double crossing over events
B. Require all heterozygous gametes
C. Cannot determine gene order on a chromosome
D. Determine goodness of fit
_____ Genes ho and dp are 10 map units apart, and genes dp and da are 23 map units apart. What is the probability of a double
crossover in these regions?
A. 1.3%
B. 2.3%
C. 3.4%
D. 4.5%
E. 5.6%
_____ In Drosophila, the genes r and s are linked. Flies of genotype r+ s+/ r+ s+ and r s/ r s are crossed and an F1 obtained. The F1
allele arrangement is called
A. cis
B. trans
C. recombinant
D. complementary
_____ The Drosophila genes for white eyes (w), tan body (t) and vestigial wings (vg) lie at map positions 2, 12, and 42 respectively.
Out of 1000 progeny, 21 exhibited double crossovers. What is the degree of interference?
A. 0.10
B. 0.20
C. 0.30
D. 0.40
_____ One Drosophila genotype P m/P m is crossed with another genotype p m/p m. If the genes are closely linked
A. All progeny will be phenotypically Pm
B. All progeny will be phenotypically pm
C. 50% of the progeny will be phenotypically Pm and 50% phenotypically pm
D. None of the above
_____ A plant of genotype C D/C D is crossed to c d/c d and an F1 testcrossed to c d/c d. If the genes are unlinked, the percentage of
c d/c d recombinants will be
A. 10%
B. 25%
C. 30%
D. 40%
E. 50%
_____ How many different trisomics could be formed in a plant with a diploid number of 10?
A. 9
B. 10
C. 11
D. 20
E. 40
_____ Which of the following statements is true regarding recombination between genes on homologous chromosomes?
A. Equivalent ratios (1:1:1:1) are found in progeny from homozygous dihybrid crosses
B. Recombination frequencies are greater than 50%
C. 25% of each genotype will appear among the progeny from dihybrid crosses
D. Exchange of the middle pair of alleles occurs in double crossovers
Problems (variable points each)
Two-point testcrosses revealed the following map results:
am___________pm 17 map units
pm___________nn 11 map units
A. Draw the two possible maps for these loci. (2)
B. What cross would resolve the two possible maps and what are the possible outcomes of that cross? (1)
Consider a fully heterozygous flowering plant with normal blue flowers and round seeds. This plant, when crossed with one that has
red flowers and oval seeds, results in the following progeny:
91 blue, round
92 red, round
93 blue, oval
94 red, oval
A. What is the recombination frequency? (1)
B. Are these genes linked? (1)
What gametes are produced by an individual with the genotype k L/K l if the genes are A) linked (no crossing over) and B) unlinked?
(2)
Several testcrosses have revealed the rate of recombination for the following genes:
k-m 0.06
k-l 0.08
l-m 0.13
What is the order of the three genes? (2)
A series of two-point mapping crosses indicated the following map distances between 6 genes, A through F. (5)
A-G
C-A
A-E
B-F
D-F
C-E
C-G
D-B
20 mu
7 mu
5 mu
20 mu
10 mu
12 mu
27 mu
30 mu
Draw a map(s) for all the genes showing the correct gene sequences and map units between the loci.
5 point bonus question
An organism heterozygous for three genes AaBbCc was mated to a homozygote aabbcc, resulting in the progeny distribution below.
ABC
aBC
AbC
ABc
abC
aBc
Abc
abc
327
44
30
3
4
45
28
319
----800
Determine the gene order (1) and calculate recombination frequencies between each gene (3) and interference. (1)