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BIOLOGY

Chapter 11 MEIOSIS AND SEXUAL REPRODUCTION

CAMPBELL

BIOLOGYReece • Urry • Cain • Wasserman • Minorsky • Jackson

© 2014 Pearson Education, Inc.

TENTH

EDITION

CAMPBELL

BIOLOGYReece • Urry • Cain • Wasserman • Minorsky • Jackson

TENTH

EDITION

• Meiosis and Sexual Life Cycles

13

Semen attack unsuspecting ovum

Figure 13.1

Asexual Repro - Clones

Aspen tree = cloned

Figure 13.3b

Pair of homologousduplicated chromosomes

Centromere

Sisterchromatids

Metaphasechromosome

5 m

Karyotype

• Homologous chromosomes

• 46 or 23 prs autosomes & sex chromosomes

Human Karyotypes

Diploid Cells Contain Two Homologous Sets of Chromosomes

Section 9.2 Figure 9.4

Homologous pair:• look alike chromosomes• carry the same sequence of

genes for the same traits • ALLELES different versions

Figure 13.4

Sister chromatidsof one duplicatedchromosome

Key

Maternal set ofchromosomes (n 3)

Paternal set ofchromosomes (n 3)

Key

2n 6

Centromere

Two nonsisterchromatids ina homologous pair

Pair of homologouschromosomes (one from each set)

Homologous chromosomes

• Diploid (2n = 46)

• Haploid (1n = 23)

Figure 8.12A/11.8Haploid gametes (n 23)

Egg cell

Sperm cell

Fertilization

n

n

Meiosis

Ovary Testis

Diploidzygote

(2n 46)2n

MitosisKey

Haploid stage (n)

Diploid stage (2n)Multicellular diploid

adults (2n 46)

Figure 13.6b / 11.10

2n2n

n

MEIOSIS FERTILIZATION

Mitosis Mitosis

Mitosis

Gametes

Spores

Zygote

Haploid multi-cellular organism(gametophyte)

Diploidmulticellularorganism(sporophyte)

(b) Plants and some algae

n n nn

Haploid (n)

Diploid (2n)

Key

Alternation of generation

Meiosis Produces Human Gametes

Section 9.8 Figure 9.16

Meiosis Produces Human Gametes

Section 9.8 Figure 9.17

Meiosis Generates Variability

Section 9.5

• Identical twins: embryo splits in two• Each embryo then develops independently

Figure 9.10Identical twins: © Barbara Penoyar/Getty Images RF

Figure 13.7-1

Pair of homologouschromosomes indiploid parent cell

Duplicated pairof homologouschromosomes

Chromosomesduplicate

Sisterchromatids

Diploid cell withduplicatedchromosomes

Interphase

Meiosis Overview

Figure 13.7-2

Pair of homologouschromosomes indiploid parent cell

Duplicated pairof homologouschromosomes

Chromosomesduplicate

Sisterchromatids

Diploid cell withduplicatedchromosomes

Homologouschromosomes separate

Haploid cells withduplicated chromosomes

Meiosis I

1

InterphaseMeiosis Overview

Reduction division

• Homologous chromosome

separated

Figure 13.7-3

Pair of homologouschromosomes indiploid parent cell

Duplicated pairof homologouschromosomes

Chromosomesduplicate

Sisterchromatids

Diploid cell withduplicatedchromosomes

Homologouschromosomes separate

Haploid cells withduplicated chromosomes

Sister chromatidsseparate

Haploid cells with unduplicated chromosomes

Interphase

Meiosis I

Meiosis II

2

1

Meiosis Overview

Reduction division

• Homologous chromosome

separated

Mitotic division

• Sister chromatids

separated

Figure 13.8 /11.6 and 11.7

MEIOSIS I: Separates homologous chromosomes

Prophase I Metaphase I Anaphase ITelophase I and

Cytokinesis

Centrosome(with centriole pair)

Sisterchromatids

Chiasmata

Spindle

Homologouschromosomes

Fragmentsof nuclearenvelope

Duplicated homologouschromosomes (red and blue)pair and exchange segments;2n 6 in this example.

Centromere(with kinetochore)

Metaphaseplate

Microtubuleattached tokinetochore

Chromosomes line upby homologous pairs.

Sister chromatidsremain attached

Homologouschromosomesseparate

Each pair of homologous chromosomes separates.

Cleavagefurrow

Two haploid cellsform; each chromosomestill consists of twosister chromatids.

MEIOSIS I: Separates sister chromatids

Prophase II Metaphase II Anaphase IITelophase II and

Cytokinesis

Sister chromatidsseparate

Haploid daughtercells forming

During another round of cell division, the sister chromatids finally separate;four haploid daughter cells result, containing unduplicated chromosomes.

Meiosis

Figure 13.8a

Prophase I Metaphase I Anaphase I Telophase I andCytokinesis

Centrosome(with centriole pair)

Sisterchromatids

Chiasmata

Spindle

Homologouschromosomes

Fragmentsof nuclearenvelope

Duplicated homologouschromosomes (red and blue)pair and exchange segments;2n 6 in this example.

Centromere(with kinetochore)

Metaphaseplate

Microtubuleattached tokinetochore

Chromosomes line upby homologous pairs.

Sister chromatidsremain attached

Homologouschromosomesseparate

Each pair of homologous chromosomes separates.

Cleavagefurrow

Two haploid cells form; each chromosomestill consists of two sister chromatids.

Interphase

Prophase I• Synapsis

• Tetrad formation

• Crossing over

Figure 13.11-5Prophase Iof meiosis

Nonsister chromatidsheld togetherduring synapsis

Pair of homologs

Chiasma

Centromere

TEM

Anaphase I

Anaphase II

Daughtercells

Recombinant chromosomes

Crossing over

Figure 11.3

Crossing Over – closer look (comparison)Figure 11.3

Metaphase I

• Metaphase plate

• Pairs line up

• Independent assortment

• 2n 223 => 8 million

Figure 13.10-3 / 11.4

Possibility 1 Possibility 2

Two equally probablearrangements ofchromosomes at

metaphase I

Metaphase II

Daughtercells

Combination 1 Combination 2 Combination 3 Combination 4

Genetic variation video

Independent Assortment

Figure 11.4

Anaphase I

• Homologous chromosomes

separate

• Sister chromatids attached

Telophase I & Cytokinesis

• Cleavage furrow

• Cell Plate

• 2 cells

• Haploid

• Sister chromatids

attached

Interkinesis = Half Time

• False interphase

• Reformation of nucleus, nucleolus, etc.

• NO MORE DNA Replication!!!

• Temporary, if it occurs at all

Meiosis II - Prophase II

• Same as prophase of

mitosis

Meiosis II - Metaphase II

• Metaphase plate

• Line up single file

Meiosis II - Anaphase II

• Sister chromatids separate

Meiosis IITelophase II & Cytokinesis

• 4 cells

• haploid

• variation

Figure 11.5Prometaphase & Anaphase Comparison

Figure 13.8b

Prophase II Metaphase II Anaphase IITelophase II and

Cytokinesis

Sister chromatidsseparate

Haploid daughtercells forming

During another round of cell division, the sister chromatids finally separate;four haploid daughter cells result, containing unduplicated chromosomes.

Figure 11.6

Figure 13.9 / 11.7

Prophase

Duplicatedchromosome

MITOSIS

Chromosomeduplication

Parent cell

2n 6

Metaphase

AnaphaseTelophase

2n 2n

Daughter cellsof mitosis

MEIOSIS

MEIOSIS I

MEIOSIS II

Prophase I

Metaphase I

Anaphase ITelophase I

Haploidn 3

Chiasma

Chromosomeduplication Homologous

chromosome pair

Daughter cells of

meiosis I

Daughter cells of meiosis II

n n n n

SUMMARY

Property Mitosis Meiosis

DNAreplication

Number ofdivisions

Synapsis ofhomologouschromosomes

Number of daughter cellsand geneticcomposition

Role in the animal body

Occurs during interphase beforemitosis begins

One, including prophase, metaphase,anaphase, and telophase

Does not occur

Two, each diploid (2n) and geneticallyidentical to the parent cell

Enables multicellular adult to arise fromzygote; produces cells for growth, repair,and, in some species, asexual reproduction

Occurs during interphase before meiosis I begins

Two, each including prophase, metaphase, anaphase,and telophase

Occurs during prophase I along with crossing overbetween nonsister chromatids; resulting chiasmatahold pairs together due to sister chromatid cohesion

Four, each haploid (n), containing half as manychromosomes as the parent cell; genetically differentfrom the parent cell and from each other

Produces gametes; reduces number of chromosomesby half and introduces genetic variability among the gametes

Figure 11.7 – Meiosis & Mitosis Comparison

Spermatogenesis

• Spermatogenesis

• Puberty

• 4 potential sperm

• Acrosome cap

Oogenesis

• Oogenesis

• Prior to birth (7 month)

– Arrested: Prophase I

• Puberty

– Arrested: Metaphase II

• Fertilization

– Completion of meiosis

• Polar bodies

Ovum development

Meiosis Generates Variability

Section 9.5

• Identical twins: embryo splits in two• Each embryo then develops independently

Figure 9.10Identical twins: © Barbara Penoyar/Getty Images RF

Copyright © McGraw-Hill Education. Permission required for reproduction or display.

Meiosis I

Meiosis II

nondisjunction

pair of

homologous

chromosomes

Fertilization

Zygote

normal

pair of

homologous

chromosomes

normal

2n + 1 2n + 1 2n – 1 2n – 1

b.a.

2n 2n 2n + 1 2n – 1

nondisjunction

Nondisjunction

Anaphase I

Anaphase II

Nondisjuction & Fertilization

Downs syndrome trisomy 21

a: © Scott Wintrow/Getty Images; b: © CNRI/SPL/Science Source

Copyright © McGraw-Hill Education. Permission required for reproduction or display.

21

extra chromosome 21

Gart

gene

b.a.

Downs Syndrome & Maternal Age

Klinefelter’s Syndrome

Klinefelter’s Syndrome

XYY – Super Male

Figure 8.23A

Deletion

Duplication

Inversion

Reciprocal translocation

Homologous

chromosomes Nonhomologouschromosomes

Chromosomal Alterations

Figure 8.23B

Chromosome 9

Chromosome 22 Reciprocaltranslocation

“Philadelphia chromosome”

Activated cancer-causing gene

Chromosomal Alterations

Reciprocal translocation

Errors Also Occur Within Chromosomes

Section 9.7 Figure 9.14

Mutations in chromosome structure can have major effects on an organism.

Chromosomes: © Addenbrookes Hospital/Science Source