CHAPTER 8 The Cellular Basis of Reproduction and Inheritance

BIOLOGYCONCEPTS & CONNECTIONS

Fourth Edition

Copyright © 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 8The Cellular Basis of

Reproduction and Inheritance

Modules 8.12 – 8.18


• _____ cells of each species contain a specific number of chromosomes– Human cells have

46, making up 23 pairs of ________ chromosomes

MEIOSIS AND CROSSING OVER

8.12 Chromosomes are matched in homologous pairs

Chromosomes

Centromere

Sister chromatids Figure 8.12


Karyotype

______Cells

HaploidCells


• Cells with two sets of chromosomes are said to be ______

• Gametes are ______, with only one set of chromosomes

8.13 Gametes have a single set of chromosomes


• At fertilization, a sperm fuses with an egg, forming a diploid ______– Repeated mitotic divisions lead to the

development of a mature adult– The adult makes haploid gametes by

_____– All of these processes make up the _____

___ cycle of organisms


• The human life cycle

Figure 8.13

MEIOSIS FERTILIZATION

Haploid gametes (n = 23)

Egg cell

Sperm cell

Diploidzygote

(2n = 46)Multicellular

diploid adults (2n = 46)

Mitosis anddevelopment


• Meiosis, like mitosis, is preceded by chromosome duplication– However, in meiosis the cell divides ____

to form _____ daughter cells

8.14 Meiosis reduces the chromosome number from diploid to haploid


• In the first division, meiosis I, homologous chromosomes are _____– While they are paired, they ____ ___ and

exchange genetic information– The homologous pairs are then

separated, and two daughter cells are produced


Figure 8.14, part 1

MEIOSIS I: Homologous chromosomes separate

INTERPHASE PROPHASE I METAPHASE I ANAPHASE I

Centrosomes(withcentriolepairs)

Nuclearenvelope

Chromatin

Sites of crossing overSpindle

Sisterchromatids

Tetrad

Microtubules attached tokinetochore

Metaphaseplate

Centromere(with kinetochore)

Sister chromatidsremain attached

Homologouschromosomes separate


• Meiosis II is essentially the same as ______– The sister ______ of each chromosome

separate– The result is four haploid daughter cells


Figure 8.14, part 2

MEIOSIS II: Sister chromatids separate

TELOPHASE IAND CYTOKINESIS PROPHASE II METAPHASE II ANAPHASE II

Cleavagefurrow

Sister chromatidsseparate

TELOPHASE IIAND CYTOKINESIS

Haploiddaughter cellsforming


• For both processes, chromosomes replicate only once, during interphase

8.15 Review: A comparison of mitosis and meiosis


• Each chromosome of a homologous pair comes from a different parent– Each chromosome thus ____ at many

points from the other member of the pair– Cross-Over (Does it happen) and where

cross-over Occurs

8.16 Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring


• The large number of possible _______ of chromosome pairs at metaphase I of meiosis leads to many different combinations of chromosomes in gametes• _____ fertilization also increases variation in offspring


Figure 8.16

POSSIBILITY 1 POSSIBILITY 2

Two equally probable

arrangements of chromosomes at

metaphase I

Metaphase II

Gametes

Combination 1 Combination 2 Combination 3 Combination 4


Figure 8.18A

TetradChaisma

Centromere

CHAPTER 8 The Cellular Basis of Reproduction and Inheritance

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