Human Biology Sylvia S Mader Michael Windelspecht Chapter
Human Biology Sylvia S. Mader Michael Windelspecht Chapter 18 Patterns of Chromosome Inheritance Lecture Outline Part 4 Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. 1
18. 5 Comparison of Meiosis and Mitosis vs. Meiosis • Growth and repair of cells • Formation of gametes • Occurs in body cells • Occurs in sex cells • 1 division • 2 divisions • Results in 2 diploid, genetically identical cells • Results in 4 haploid, genetically different cells 2
18. 5 Comparison of Meiosis and Mitosis Comparing meiosis and mitosis Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. 2 n = 4 Prophase I Synapsis and crossing-over occur. Metaphase I Homologous pairs align independently at the equator. Anaphase I Homologous chromosomes separate and move towards the poles. MEIOSIS I 2 n =4 Prophase Metaphase Chromosomes align at the equator. Anaphase Sister chromatids separate and become daughter chromosomes. MITOSIS Figure 18. 14 A comparison of meiosis and mitosis. 3
18. 5 Comparison of Meiosis and Mitosis Comparing meiosis and mitosis Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. Telophase I Daughter cells are forming and will go on to divide again. n=2 Daughter cells Sister chromatids separate and become daughter chromosomes. n=2 MEIOSIS I cont'd Four haploid daughter cells: Their nuclei are genetically different from the parent cell. n=2 MEIOSIS II Daughter cells Telophase Daughter cells are forming. MITOSIS cont'd Two diploid daughter cells: Their nuclei are genetically identical to the parent cell. Figure 18. 14 A comparison of meiosis and mitosis. 4
18. 6 Chromosome Inheritance Changes in chromosome number • _______ occurs when both members of a homologous pair go into the same daughter cell during meiosis I, or when sister chromatids fail to separate in meiosis II. • Results of nondisjunction – _____: cell has only 1 copy of a chromosome e. g. , Turner syndrome (only 1 X chromosome) – _____: cell has 3 copies of a chromosome e. g. , Down syndrome (3 copies of chromosome 21) 5
18. 6 Chromosome Inheritance Nondisjunction Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. pair of homologous chromosomes normal meiosis II a. nondisjunction Egg will have normal Egg will have either one extra number of chromosomes. or one less chromosome. pair of homologous chromosomes nondisjunction meiosis II b. Egg will have one extra chromosome. Egg will have one less chromosome. Figure 18. 15 The consequences of nondisjunction of chromosomes during oogenesis. 6
18. 6 Chromosome Inheritance Changes in chromosome number Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. extra chromosome 21 21 Gart gene a. b. a: © Scott Wintrow/Getty Images; b (left): © CNRI/SPL/Photo Researchers Figure 18. 16 Down syndrome. 7
18. 6 Chromosome Inheritance Changes in sex chromosome number • _______ (XO) – short stature, broadshouldered, with folds of skin on the neck, underdeveloped sex organs and breasts • Klinefelter syndrome (____) – underdeveloped sex organs, breast development, large hands, and long arms and legs 8
18. 6 Chromosome Inheritance Changes in sex chromosome number • Poly-X females (XXX, XXXX) – XXX tend to be tall and thin but do not usually have mental retardation – XXXX have severe mental retardation • _______ syndrome (XYY) – tall, persistent acne, speech and reading problems 9
18. 6 Chromosome Inheritance Barr bodies and X inactivation • Females have 2 copies of X genes; males have 1. • In female embryos, 1 X chromosome becomes inactivated (Barr body) in each cell. 10
18. 6 Chromosome Inheritance Changes in chromosome structure • ______ – loss of a piece of the chromosome (e. g. , Williams syndrome) • Translocation – movement of chromosome segments from one chromosome to another nonhomologous chromosome (Alagille syndrome) • _____ – presence of a chromosome segment more than once in the same chromosome • Inversion – a segment of a chromosome is inverted 180 degrees 11
18. 6 Chromosome Inheritance Changes in chromosome structure Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. a b c b c + d d a d d e e f f f g g g a b c d d c d e e e f f f g g g a. Deletion a b b. Duplication Figure 18. 17 The various types of chromosomal mutations. c. Inversion a b c d l m n e a b c d l m n o e o f p g q q g h r r h d. Translocation 12
18. 6 Chromosome Inheritance Chromosomal inversion Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. A a B b C e D inverted segment d c E F G A a region of crossing-over C B b c homologous chromosomes Figure 18. 18 A chromosomal inversion. d e E F f g D G A g B f C c d D e b E a F G duplication and deletion in both 13
18. 6 Chromosome Inheritance Changes in chromosome structure Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. a a a s b b b t + c deletion c h c c u lost d v e u translocation d v w e w f x d d e e f f g y y g g g h z z h h Figure 18. 19 A chromosomal deletion. Figure 18. 20 A chromosomal translocation. 14
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