GTS 161 - PRACTICAL 2 – 2014
ADDITIONAL QUESTIONS NOT IN TEXTBOOK
A1. Draw 2 pairs of chromosomes (in a non-dividing cell or G1 of interphase) and indicate the
following on the diagram:
a.
homologous chromosomes
b.
non-homologous chromosomes
c.
locus
d.
alleles
e.
homozygotic alleles
f.
heterozygotic alleles
A2.
Are homologous chromosomes identical? If not, how do they differ?
TEXTBOOK QUESTIONS CHAPTER 3
Comprehension Questions 7, 9, 10 (Not present in 4th Ed)
7.
Give the genotypic ratios that may appear among the progeny of simple crosses (i.e. crosses
for a single locus with only two different alleles), and the genotypes of the parents that may
give rise to each ratio.
9.
What is the principle of independent assortment? How is it related to the principle of
segregation?
10.
In which phases of mitosis and meiosis are the principles of segregation and independent
assortment at work?
Application Questions and Problems 15, 16, 18 a, b, c, 20, 25, 28, 31, 34 b, d,
(4th Ed Q’s (no equiv of Q15) 4, 6 a, b, c, 7, 12, 15, 18, 20 b, d)
15.
Figure 1.1 (page 2) shows three girls, one of whom has albinism (recessive disorder). Could
the three girls shown in the photograph be sisters? Why or why not?
16.
JW McKay crossed a stock melon plant that produced tan seeds with a plant that produced red
seeds and obtained the following results.
Cross
F1
F2
tan ♀ x red ♂
13 tan seeds
93 tan, 24 red seeds
Explain the inheritance of tan and red seeds in this plant.
Assign symbols for the alleles in this cross and give genotypes for all the individual plants.
a.
b.
18.
a.
b.
c.
20.
In cats, blood type A results from an allele (IA) that is dominant over an allele (iB) that
produces blood type B. There is no O blood type. The blood types of male and female cats that
were mated and the blood types of their kittens follow. Give the most likely genotypes for the
parents of each litter.
Male parent
A
B
B
Female parent
B
B
A
Kittens
4 with blood type A, 3 with blood type B
6 kittens with blood type B
8 kittens with blood type A
Joe has a white cat named Sam. When Joe crosses Sam with a black cat, he obtains one-half
white kittens and one-half black kittens. When the black kittens are interbred, they produce all
black kittens. On the basis of these results, would you conclude that white or black coat colour
in cats is a recessive trait? Explain your reasoning.
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25.
a.
b.
c.
d.
What is the probability of rolling one six-sided die and obtaining the following numbers?
2
1 or 2
An even number
Any number but a 6
28.
Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents
produce a child with PKU.
What is the probability that a sperm from the father will contain the PKU allele?
What is the probability that an egg from the mother will contain the PKU allele?
What is the probability that their next child will have PKU?
What is the probability that their next child will be heterozygous for the PKU gene?
a.
b.
c.
d.
31.
a.
b.
c.
34.
b.
d.
In watermelons, bitter fruit (B) is dominant over sweet fruit (b), and yellow spots (S) are
dominant over no spots (s). The genes for these two characteristics assort independently. A
homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant
that has sweet fruit and no spots. The F1 are intercrossed to produce the F2.
What will be the phenotypic ratios in the F2?
If an F1 plant is backcrossed with the bitter, yellow-spotted parent, what phenotypes and
proportions are expected in the offspring?
If an F1 plant is backcrossed with the sweet, nonspotted parent, what phenotypes and
proportions are expected in the offspring?
The following two genotypes are crossed: AaBbCcddEe × AabbCcDdEe. What will the
proportion of the following genotypes be among the progeny of this cross?
Aa bb Cc dd ee
AA BB CC DD EE
ADDITIONAL QUESTIONS NOT IN TEXTBOOK
A3. In humans there is a dominant gene (A) for the absence of moles. The allele (a) is recessive,
and determines the presence of moles. A couple who are both heterozygous for this locus (Aa)
plan to have five children.
a.
Expand the binomial (p + q)5.
b.
What is the probability that:
(i)
The first child that is born will have moles.
(ii)
All of the children will not have moles.
(iii) The first two children will have moles and the last three will have no moles.
(iv) Of the 5 children, 3 will have no moles and 2 will have moles
c.
Assume this couple now have two children, one with moles and one without moles. What is
the probability that the child born without moles is a carrier of the a-allele (ie heterozygous)?
A4.
A sugarcane plant with wavy leaves and round pollen is crossed with a plant with wavy leaves
and elongated pollen. Seed are collected and germinated. The following results are obtained in
the progeny:
122
wavy leaves, round pollen
118
wavy leaves, elongated pollen
38
smooth leaves, round pollen
41
smooth leaves, elongated pollen
(NB Hint: When two traits are involved, it is often easier to first consider the traits separately,
convert the numbers to ratios for each locus on its own, and determine alleles, dominance and
genotypes for each trait. Then combine these to give parental genotypes and work out the cross.)
a.
Assign symbols for the alleles of both these genes, indicate the dominance interaction between
the two alleles, and give all possible genotypes and their associated phenotypes for each locus.
b.
Give the genotypes of the parents of this cross.
c.
Give the expected genotypic and phenotypic ratios of the progeny of this cross.
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