936
UNIT SIX
2. Aneuploidy
a. Cells with the normal chromosome number
are euploid. Cells with an extra or missing
chromosome are aneuploid.
b. Aneuploidy results from nondisjunction, in which
a chromosome pair does not separate, either in
meiosis I or meiosis II, producing a gamete with
a missing or extra chromosome. At fertilization, a
monosomic or trisomic zygote results.
c. A cell with an extra chromosome is trisomic. A
cell with a missing chromosome is monosomic.
Individuals with trisomies are more likely to
survive to be born than those with monosomies.
d. Autosomal aneuploids are more severe than sex
chromosome aneuploids.
3. Prenatal tests detect chromosome abnormalities
a. Ultrasound can detect large-scale structural
abnormalities and assess growth.
b. Maternal serum marker tests indirectly detect a
small fetal liver, which can indicate a trisomy.
c. Amniocentesis samples and examines fetal
chromosomes in amniotic fl
uid.
d. Chorionic villus sampling obtains and examines
chorionic villus cells, which descend from the
fertilized egg and therefore are presumed to be
genetically identical to fetal cells.
e. Fetal cell sorting obtains and analyzes rare fetal
cells in the maternal circulation.
24.7
GENE EXPRESSION EXPLAINS ASPECTS
OF ANATOMY AND PHYSIOLOGY
(PAGE 933)
1. Gene expression patterns reveal the identities and
activities of proteins in cells (proteomics), which can
explain physiological processes.
2. DNA microarrays are used to monitor gene
expression.
3. Comparing gene expression pro±
les for the same
cell type under different conditions can provide
information on pathology.
b. Y-linked genes are considered in three functional
groups: those with counterparts on the X; those
similar to genes on the X; and genes unique to
the Y, many of which affect male fertility. Y-linked
genes pass from fathers to sons.
c. Males are hemizygous for X-linked traits; they can
have only one copy of an X-linked gene, because
they have only one X chromosome.
d. Females can be heterozygous or homozygous for
genes on the X chromosome, because they have
two copies of it.
e. A male inherits an X-linked trait from a carrier
mother. These traits are more common in males
than in females.
f. A female inherits an X-linked mutant gene from
her carrier mother and/or from her father if the
associated trait does not impair his ability to have
children.
g. Dominant X-linked traits are rarely seen because
affected males typically die before birth.
3. Gender effects on phenotype
a. Sex-limited traits affect structures or functions seen
in only one sex and may be autosomal.
b. Sex-infl
uenced traits are dominant in one sex and
recessive in the other.
c. In genomic imprinting, the severity, age of onset,
or nature of symptoms varies according to which
parent transmits the causative gene.
24.6
CHROMOSOME DISORDERS (PAGE 929)
Extra, missing, or rearranged chromosomes or parts of
them can cause syndromes, because they either cause an
imbalance of genetic material or disrupt a vital gene.
1. Polyploidy
a. Polyploidy is an extra chromosome set.
b. Polyploidy results from fertilization in which one
gamete is diploid.
c. Human polyploids do not survive beyond a few
days of birth.
24.1 Introduction
1
Which choice places the structures in order of increasing
size? (p. 917)
a. genome, chromosome, gene, DNA base
b. DNA base, gene, chromosome, genome
c. gene, DNA base, genome, chromosome
d. population, family, individual, organ, tissue, cell, DNA
2
Discuss the origin of the 23 chromosome pairs in a
diploid human cell. (p. 917)
3
Explain how a certain number of genes hold enough
information to encode a greater number of proteins.
(p. 917)
4
Explain how genes can respond to environmental factors.
(p. 918)
CHAPTER ASSESSMENTS
24.2 Modes of Inheritance
5
Which is a chromosome chart? (p. 918)
a. karyotype
b. pedigree
c. Punnett square
d. none of the above
6
Distinguish between autosome and sex chromosome,
homozygous and heterozygous, phenotype and
genotype, mutant and wild type, dominant and recessive,
and incomplete dominance and codominance. (p. 919)
7
Explain how a gene might have hundreds of alleles. (p. 919)
8
Which of the following is a mode of inheritance? (p. 920)
a. autosomal recessive
b. autosomal dominant
c. X-linked recessive
d. all of the above
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