13 Jun Biol 3301 – Phenotypes caused by mutations in mitochondrial genes
Question
Name:____________________
Biol 3301
PS#______________
Midterm 2
Spring 2013
Answer all questions on the scantron. Your exams will eventually be returned to you.
1. Phenotypes caused by mutations in mitochondrial genes:
a) have an inheritance pattern consistent with sex-linked dominant traits
b) have an inheritance pattern consistent with autosomal dominant traits
c) have an inheritance pattern consistent with sex-linked recessive traits
d) have an inheritance pattern consistent with autosomal recessive traits
e) have an inheritance pattern consistent with uniparental transmission
2. Deletions can be detected by:
a) reductions in fertility of deletion heterozygotes b) inviable gametes
c) genotype x environment interactions d) pseudodominance e) none of the above
In common wheat, Triticum aestivum, kernel color is determined by multiple genes, each with an R
(causing red color) and an r (causing white color) allele. Any number of R alleles will produce red
kernels, and a complete lack of R alleles will give the white phenotype. In one cross between a
homozygous red and a homozygous white line the F2 was 63/64 red and 1/64 white. (Questions 3-5)
3. How many genes for kernel color are segregating in this system?
a) two b) three
c) four
d) eight
e) you can’t tell from the data
4. If the frequency of the red allele at each locus is equal to 0.5, what is the expected frequency
of white individuals in a population?
a) 0.5
b) 0.25
c) 0.125
0.0625
e) none of the above
5. If you hypothesize that multiple genes have arisen through polyploidy, what information
would be useful for evaluating your hypothesis?
a) location of color genes in the genome
b) frequency of the red allele in the population
c) frequency of the white allele in the population
d) whether other genes also exist as multiple copies
e) all of the above
(Questions 6-8) In ornamental carp, body color is due to a single locus with two codominant
alleles: fish may be homozygous black, homozygous orange or marbled orange and black
(heterozygotes). You sample 1000 fish from a pond at the Houston Zoo and get the following
phenotype distribution:
black: 257
orange: 174
marbled:
569
6. What is the frequency of the heterozygous genotype?
a) 0.257
b) 0.174
c) 0.569
d) 2(.257)(.174)
7. What is the frequency of the black allele?
a) /0.257
b) (0.257)2
c) 1 – 0.174
e) none of the above
d) 0.257 + 0.5(0.569) e) 0.174 + 2(0.569)
8. If the population is in Hardy-Weinberg Equilibirum, then the frequncy of marbled carp would
be:
a) 2(0.257+0.5[0.569])(0.174+0.5[0.569])
b) 0.569
c) 2(0.257)(0.174)
d) 2(/0.257)(/0.174)
e) none of the above
The pedigree below is for a rare hereditary disease of the kidneys in humans. (Questions 9-10)
9. Which of the following modes of inheritance is most likely?
a) autosomal dominant
b) autosomal recessive
c) sex-linked recessive
d) sex-linked dominant
e) mitochondrial
10. Which of the following is most likely to be heteroplasmic?
a) B
b) E
c) Q
d) R
e) S
11. Which of the following statements is true? Selection will produce the greatest change in:
a) traits with the greatest phenotypic variance.
b) traits with the highest fitness.
c) traits that are determined by a single gene.
d) traits without environmental variance.
e none of the above
12. Bristle number in houseflies is controlled by three independent loci: A, B, C. The average
phenotypic effect of the three genotypes at each locus is AA or BB or CC =4; Aa or Bb or Cc =
3; and aa or bb or cc = 1. The effects of loci add to each other. Bristle number is a threshold
character; when the phenotypic value is greater than 9, an individual has 3 bristles, when it is 5 9 there are 2 bristles, and when it is less than five there is 1 bristle. How many different
genotypes will produce a fly with one bristle?
a) one
b) two
c) three
d) four
e) five
13. Narrow-sense heritability is estimated by:
a) regression of offspring phenotype on parental phenotype
b) subtracting the environmental variance from the phenotypic variance
c) subtracting the dominance variance from the genetic variance
d) regression of parental phenotype on offspring phenotype
e) subtracting the dominance variance from the total variance
The following tomato loci are on one arm of chromosome 1, in the order indicated (the distances
between them are shown in map units):
m————d——–p———o————-wo
12
6
7
16
M gives normal leaves, m gives mottled leaves
D gives tall plants, d gives dwarf plants
P gives smooth fruit, p gives peach (fuzzy) fruit
O gives round fruit, o gives oblate fruit
Wo gives woolly stems, wo gives normal stems
A plant from a standard stock that is homozygous for recessive alleles at all five loci is crossed
to a wild-type plant from Mexico that is homozygous for dominant alleles at all loci. The F1
plants express all the dominant alleles and, when backcrossed to the recessive homozygous
parent, give the following progeny phenotypes:
normal, tall, smooth, round, woolly
380
mottled, dwarf, peach, oblate, normal
379
normal, dwarf, peach, oblate, normal
30
mottled, tall, smooth, round, woolly
36
normal, tall, smooth, round, normal
75
mottled, dwarf, peach, oblate, woolly
74
normal, dwarf, peach, oblate, woolly
7
mottled, tall, smooth, round, normal
8
normal, tall, peach, round, woolly
6
mottled, dwarf, smooth, oblate, normal
5
14. The observation critical to interpreting these data is:
a) the parentals are either all dominant alleles or all recessive alleles
b) there are fewer kinds of offspring than expected
c) there are fewer progeny than expected
d) the parental plant was from a natural population
e) dwarf almost always co-segregates with peach
15. The data are most consistent with
a) a deletion of the gene for peach from the Mexican plant
b) an inversion of the genes for mottled, dwarf, peach, oblate and woolly in the Mexican plant
c) an inversion of the genes for dwarf, peach and oblate in the Mexican plant
d) a translocation of the genes for dwarf and peach in the Mexican plant
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