Page 136 - Genetics_From_Genes_to_Genomes_6th_FULL_Part1

128 Chapter 4 The Chromosome Theory of Inheritance

24. In humans: 28. A system of sex determination known as haplodip-
a. How many sperm develop from 100 primary loidy is found in honeybees. Females are diploid, and
spermatocytes? males (drones) are haploid. Male offspring result
b. How many sperm develop from 100 secondary from the development of unfertilized eggs. Sperm are
produced by mitosis in males and fertilize eggs in the
spermatocytes? females. Ivory eye is a recessive characteristic in
c. How many sperm develop from 100 spermatids? honeybees; wild-type eyes are brown.
d. How many ova develop from 100 primary oocytes? a. What progeny would result from an ivory-eyed
e. How many ova develop from 100 secondary queen and a brown-eyed drone? Give both geno-
oocytes? type and phenotype for progeny produced from
f. How many ova develop from 100 polar bodies? fertilized and nonfertilized eggs.
25. Women sometimes develop benign tumors called b. What would result from crossing a daughter from
ovarian teratomas or dermoid cysts in their ovaries. the mating in part (a) with a brown-eyed drone?
Such a tumor begins when a primary oocyte escapes 29. In Drosophila, the autosomal recessive brown eye
from its prophase I arrest and finishes meiosis I color mutation displays interactions with both the
within the ovary. (Normally meiosis I does not fin- X-linked recessive vermilion mutation and the au-
ish until the primary oocyte is expelled from the tosomal recessive scarlet mutation. Flies homozy-
ovary upon ovulation.) The secondary oocyte then gous for brown and simultaneously hemizygous or
develops as if it were an embryo. Development is homozygous for vermilion have white eyes. Flies
disorganized, however, and results in a tumor simultaneously homozygous for both the brown and
containing differentiated diploid tissues, including scarlet mutations also have white eyes. Predict the
teeth, hair, bone, muscle, and nerve. If a dermoid F 1 and F 2 progeny of crossing the following true-
cyst forms in a woman whose genotype is Aa, what breeding parents:
are the possible genotypes of the cyst, assuming no a. vermilion females × brown males
recombination? b. brown females × vermilion males
26. In a certain strain of turkeys, unfertilized eggs some- c. scarlet females × brown males
times develop parthenogenetically to produce diploid
offspring. (Females have ZW and males have ZZ sex d. brown females × scarlet males
chromosomes. Assume that WW cells are inviable.) 30. Barred feather pattern is a Z-linked dominant trait
What distribution of sexes would you expect to see in chickens. What offspring would you expect from
among the parthenogenetic offspring according to (a) the cross of a barred hen to a nonbarred rooster?
each of the following models for how parthenogenesis (b) the cross of an F 1 rooster from part (a) to one of
occurs? his sisters?
a. The eggs develop from oogonial cells that never 31. When Calvin Bridges observed a large number of off-
undergo meiosis. spring from a cross of white-eyed female Drosophila to
b. The eggs go all the way through meiosis and then red-eyed males, he found very rare white-eyed females
duplicate their chromosomes to become diploid. and red-eyed males among the offspring. He was able
c. The eggs go through meiosis I, and the chromatids to show that these exceptions resulted from nondisjunc-
tion, such that the white-eyed females had received two
separate to create diploidy. Xs from the egg and a Y from the sperm, while the
d. The egg goes all the way through meiosis and then red-eyed males had received no sex chromosome from
fuses at random with one of its three polar bodies the egg and an X from the sperm. What progeny would
(this scenario assumes the first polar body goes have arisen from these same kinds of nondisjunctional
through meiosis II). events if they had occurred in the male parent? What
would their eye colors have been?
Section 4.6 32. In a vial of Drosophila, a research student noticed
27. Imagine you have two pure-breeding lines of canaries, several female flies (but no male flies) with bag wings
one with yellow feathers and the other with brown each consisting of a large, liquid-filled blister instead
feathers. In crosses between these two strains, yellow of the usual smooth wing blade. When bag-winged
female × brown male gives only brown sons and females were crossed with wild-type males, 1/3 of the
daughters, while brown female × yellow male gives progeny were bag-winged females, 1/3 were normal-
only brown sons and yellow daughters. Propose a winged females, and 1/3 were normal-winged males.
hypothesis to explain these results. Explain these results.