PowerPoint PresentationCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor
From PowerPoint® Lectures for Biology: Concepts & Connections
CHAPTER 8
Modules 8.19 – 8.23
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
8.19 A karyotype is a photographic inventory of an individual’s chromosomes
To study human chromosomes microscopically, researchers stain and display them as a karyotype
A karyotype usually shows 22 pairs of autosomes and one pair of sex chromosomes
ALTERATIONS OF CHROMOSOME NUMBER AND STRUCTURE
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Preparation of a karyotype
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8.20 Connection: An extra copy of chromosome 21 causes Down syndrome
This karyotype shows three number 21 chromosomes
An extra copy of chromosome 21 causes Down syndrome
Figure 8.20A, B
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The chance of having a Down syndrome child goes up with maternal age
Figure 8.20C
8.21 Accidents during meiosis can alter chromosome number
Abnormal chromosome count is a result of nondisjunction
Either
homologous
Figure 8.21B
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Fertilization after nondisjunction in the mother results in a zygote with an extra chromosome
Figure 8.21C
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8.22 Connection: Abnormal numbers of sex chromosomes do not usually affect survival
Nondisjunction can also produce gametes with extra or missing sex chromosomes
Unusual numbers of sex chromosomes upset the genetic balance less than an unusual number of autosomes
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Table 8.22
A man with Klinefelter syndrome has an extra X chromosome
Figure 8.22A
Poor beard
Figure 8.22B
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8.23 Connection: Alterations of chromosome structure can cause birth defects and cancer
Chromosome breakage can lead to rearrangements that can produce genetic disorders or cancer
Four types of rearrangement are deletion, duplication, inversion, and translocation
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Figure 8.23A, B
Figure 8.23C
Chromosome 9
A chromosomal translocation in the bone marrow is associated with chronic myelogenous leukemia
Chromosome 22