BIOLOGY Chapter 10: 10th Edition Meiosis & Sexual … 10: pp. 169 - 188 1 egg ... Genetic Variation...

Sylv

ia S

. Ma

der

Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display

PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor

BIOLOGY 10th Edition

Meiosis & Sexual Reproduction

Chapter 10: pp. 169 - 188

1

egg

FERTILIZATION MEIOSIS

MITOSIS

MITOSIS

sperm

n

n

2n

2n

2n

2n

zygote

haploid (n)

n = 23

2n = 46

diploid (2n)

SPERMATOGENESIS

OOGENESIS

Metamorphosis

and maturation

Primary

spermatocyte

Primary

oocyte

zygote

egg

Secondary

oocyte

Meiosis II is completed

after entry of sperm

spermatids

sperm

Secondary

spermatocytes

First

polar body

Second

polar body

fusion of sperm

nucleus and

egg nucleus

sperm nucleus

2n

2n

2n

n

n

n

n

n

n

n

n

Meiosis I

Meiosis II

Meiosis I

Fertilization

cont'd

Meiosis II

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2

Outline

Reduction in Chromosome Number Homologous Pairs

Meiosis Overview

Genetic Variation Crossing-Over

Independent Assortment

Fertilization

Phases of Meiosis Meiosis I

Meiosis II

Meiosis Compared to Mitosis

Human Life Cycle

Changes in Chromosome Number and Structure

3

Meiosis: Halves the Chromosome Number

Special type of cell division

Used only for sexual reproduction

Halves the chromosome number prior to

fertilization

Parents diploid

Meiosis produces haploid gametes

Gametes fuse in fertilization to form diploid zygote

Becomes the next diploid generation

4

Homologous Pairs of Chromosomes

In diploid body cells chromosomes occur in pairs

Humans have 23 different types of chromosomes

Diploid cells have two of each type

Chromosomes of the same type are said to be homologous

They have the same length

Their centromeres are positioned in the same place

One came from the father (the paternal homolog) the other from the mother (the maternal homolog)

When stained, they show similar banding patterns

A location on one homologue contains gene for the same trait that occurs at this locus on the other homologue

Although the genes may code for different variations of that trait

Alternate forms of a gene are called alleles

5

Homologous Chromosomes

a. sister chromatids

homologous pair chromosome chromosome

Nonsister

chromatids duplication duplication

centromere

kinetochore

paternal chromosome maternal chromosome

b.


Animation

6

Please note that due to differing

operating systems, some animations

will not appear until the presentation is

viewed in Presentation Mode (Slide

Show view). You may see blank slides

in the “Normal” or “Slide Sorter” views.

All animations will appear after viewing

in Presentation Mode and playing each

animation. Most animations will require

the latest version of the Flash Player,

which is available at

http://get.adobe.com/flashplayer.

7

Homologous Pairs of Chromosomes

Homologous chromosomes have genes controlling the same trait at the same position Each gene occurs in duplicate A maternal copy from the mother A paternal copy from the father

Many genes exist in several variant forms in a large population

Homologous copies of a gene may encode identical or differing genetic information

The variants that exist for a gene are called alleles An individual may have:

Identical alleles for a specific gene on both homologs (homozygous for the trait), or

A maternal allele that differs from the corresponding paternal allele (heterozygous for the trait)

8

Overview of Meiosis

n = 2 n = 2

2n = 4 2n = 4

MEIOSIS I

Homologous pairs

synapse and then separate.

centrioles sister chromatids synapsis

nucleolus

centromere

chromosome

duplication

MEIOSIS II

Sister chromatids separate,

becoming daughter chromosomes.

Four haploid

daughter cells


Animation













10

Phases of Meiosis I: Prophase I &

Metaphase I

Meiosis I (reductional division):

Prophase I

Each chromosome internally duplicated (consists of two identical sister chromatids)

Homologous chromosomes pair up – synapsis

Physically align themselves against each other end to end

End view would show four chromatids – Tetrad

Metaphase I

Homologous pairs arranged onto the metaphase plate

11

Phases of Meiosis I: Anaphase I &

Telophase I

Anaphase I Synapsis breaks up

Homologous chromosomes separate from one another

Homologues move towards opposite poles

Each is still an internally duplicate chromosome with two chromatids

Telophase I Daughter cells have one internally duplicate

chromosome from each homologous pair

One (internally duplicate) chromosome of each type (1n, haploid)

12

Phases of Meiosis I: Cytokinesis I &

Interkinesis

Cytokinesis I Two daughter cells

Both with one internally duplicate chromosome of each type

Haploid

Meiosis I is reductional (halves chromosome number)

Interkinesis

Similar to mitotic interphase

Usually shorter

No replication of DNA

Animation













14

Genetic Variation: Crossing Over

Meiosis brings about genetic variation in two key ways: Crossing-over between homologous chromosomes, and Independent assortment of homologous chromosomes

Crossing Over: Exchange of genetic material between nonsister chromatids

during meiosis I At synapsis, a nucleoprotein lattice (called the

synaptonemal complex) appears between homologues Holds homologues together Aligns DNA of nonsister chromatids Allows crossing-over to occur

Then homologues separate and are distributed to different daughter cells

15

Crossing Over

A

B

b B

C

c C

D

D D

A A a

b

B b

c

C c

d

d d

a a

nucleoprotein lattice sister chromatids

of a chromosome

sister chromatids

of its homologue

chiasmata of

nonsister

nhromatids

1 and 3

Bivalent

forms

b.

1 2 3 4 1 2 3 4 1 2 3 4

a. c. d.

Crossing-over

has occurred

Daughter

chromosomes


Courtesy Dr. D. Von Wettstein

Animation

16













17

Genetic Variation: Independent Assortment

Independent assortment:

When homologues align at the

metaphase plate:

They separate in a random manner

The maternal or paternal homologue may be

oriented toward either pole of mother cell

Causes random mixing of blocks of

alleles into gametes

Animation













19



20

Recombination


© American Images, Inc/Getty Images

21

Genetic Variation: Fertilization

When gametes fuse at fertilization:

Chromosomes donated by the parents are combined

In humans, (223)2 = 70,368,744,000,000

chromosomally different zygotes are possible

If crossing-over occurs only once

(423)2, or 4,951,760,200,000,000,000,000,000,000 genetically

different zygotes are possible

22

Genetic Variation: Significance

Asexual reproduction produces genetically identical clones

Sexual reproduction cause novel genetic recombinations

Asexual reproduction is advantageous when environment is stable

However, if environment changes, genetic variability introduced by sexual reproduction may be advantageous

Offspring adapt to that environment

23

Phases of Meiosis II: Similar to Mitosis

Metaphase II Overview

Unremarkable

Virtually indistinguishable from mitosis of two haploid cells

Prophase II – Chromosomes condense

Metaphase II – Chromosomes align at metaphase

plate

Anaphase II Centromere dissolves

Sister chromatids separate and become daughter

chromosomes

Telophase II and cytokinesis II Four haploid cells

All genetically unique

Animation













25

Meiosis I & II in Plant Cells (Cont.)

Prophase I

Chromosomes have duplicated.

Homologous chromosomes pair during

synapsis and crossing-over occurs.

Metaphase I

Homologous pairs align

Independently at the metaphase plate.

Anaphase I

Homologous chromosomes separate

and move toward the poles.

Prophase II

Cells have one chromosome

from each homologous pair.

Metaphase II

Chromosomes align

at the metaphase plate.

Anaphase II

Sister chromatids separate and

become daughter chromosomes.

kinetochore

MEIOSIS I

MEIOSIS II

Animal Cell

at Interphase

centrosome has

centrioles

Plant Cell

at Interphase

2n = 4

n = 2

n = 2


© Ed Reschke

26

Meiosis I & II in Plant Cells

Telophase I

Daughter cells have one chromosome

from each homologous pair.

Interkinesis

Chromosomes still

consist of two chromatids.

Telophase II

Spindle disappears, nuclei form,

and cytokinesis takes place.

Daughter cells

Meiosis results in four

haploid daughter cells.

MEIOSIS I cont'd

MEIOSIS II cont'd

n = 2

n = 2

n = 2

n = 2


© Ed Reschke

Animation

27













28

Meiosis vs. Mitosis

Meiosis Requires two nuclear

divisions

Chromosomes synapse and cross over

Centromeres survive Anaphase I

Halves chromosome number

Produces four daughter nuclei

Produces daughter cells genetically different from parent and each other

Used only for sexual reproduction

Mitosis Requires one nuclear

division

Chromosomes do not synapse nor cross over

Centromeres dissolve in mitotic anaphase

Preserves chromosome number

Produces two daughter nuclei

Produces daughter cells genetically identical to parent and to each other

Used for asexual reproduction and growth

29


Prophase I

Synapsis and

crossing-over occur.

Metaphase I

Homologous pairs align

independently at the metaphase plate.

Anaphase I

Homologous chromosomes

separate and move towards the poles.

Prophase Metaphase

Chromosomes align

at the metaphase plate.

Anaphase

Sister chromatids separate and

become daughter chromosomes.

MEIOSIS I

MITOSIS

2n = 4

2n = 4

Telophase I

Daughter cells are forming

and will go on to divide again.

Telophase

Daughter cells

are forming.

Sister chromatids

separate and become

daughter chromosomes.

Two diploid daughter cells.

Their nuclei are genetically

identical to the parent cell.

Four haploid daughter cells.

Their nuclei are genetically

different from the parent cell.

MEIOSIS I cont'd MEIOSIS II

MITOSIS cont'd

Daughter cells

Daughter cells

n = 2

n = 2

n = 2


Animation

30













31

Meiosis I Compared to Mitosis

32

Meiosis II Compared to Mitosis

33

Life Cycle Basics: Plants

Haploid multicellular “individuals” alternate with diploid multicellular “individuals”

The haploid individual: Known as the gametophyte

May be larger or smaller than the diploid individual

The diploid individual: Known as the sporophyte

May be larger or smaller than the haploid individual

Mosses are haploid most of their life cycle

Ferns & higher plants have mostly diploid life cycles

In fungi and most algae, only the zygote is diploid

In plants gametes are produced by haploid individuals Plants have both haploid and diploid phases in their life cycle

34

Life Cycle Basics: Animals

In familiar animals: “Individuals” are diploid; produce haploid

gametes Only haploid part of life cycle is the gametes The products of meiosis are always gametes Meiosis occurs only during gametogenesis

Production of sperm Spermatogenesis All four cells become sperm

Production of eggs Oogenesis Only one of four nuclei get cytoplasm

Becomes the egg or ovum Others wither away as polar bodies

35

The Human Life Cycle

Sperm and egg are produced by meiosis

A sperm and egg fuse at fertilization

Results in a zygote The one-celled stage of an individual of the next generation

Undergoes mitosis

Results in multicellular embryo that gradually takes on features determined when zygote was formed

All growth occurs as mitotic division

As a result of mitosis, each somatic cell in body Has same number of chromosomes as zygote

Has genetic makeup determined when zygote was formed

36

The Human Life Cycle

egg


MITOSIS

MITOSIS

sperm

n

n

2n

2n

2n

2n

zygote

haploid (n)

n = 23

2n = 46

diploid (2n)


SPERMATOGENESIS

OOGENESIS

Metamorphosis

and maturation

Primary

spermatocyte

Primary

oocyte

zygote

egg

Secondary

oocyte



spermatids

sperm

Secondary

spermatocytes

First

polar body

Second

polar body

fusion of sperm

nucleus and

egg nucleus

sperm nucleus

2n

2n

2n

n

n

n

n

n

n

n

n

Meiosis I

Meiosis II

Meiosis I

Fertilization

cont'd

Meiosis II


37

Gametogenesis in Mammals

38

Changes in Chromosome Number

Euploid is the correct number of

chromosomes in a species.

Aneuploid is change in the chromosome

number

Results from nondisjunction

Monosomy - only one of a particular type of

chromosome,

Trisomy - three of a particular type of chromosome

39

Changes in Chromosome

a. b.

pair of

homologous

chromosomes

2n 2n 2n + 1 2n + 1 2n + 1 2n - 1

normal

normal

pair of

homologous

chromosomes

Meiosis I

Meiosis II

Fertilization

Zygote

nondisjunction

nondisjunction


2n - 1 2n - 1

40

Trisomy

Trisome 21

Occurs when an individual has three of a particular

type of chromosome

The most common autosomal trisomy seen among

humans

Also called Down syndrome

Recognized by these characteristics:

short stature

eyelid fold

flat face

stubby finger

wide gap between first and second toes

41

Trisomy 21

a. b.

extra chromosome 21


a: © Jose Carrilo/PhotoEdit; b: © CNRI/SPL/Photo Researchers

42

Changes in Sex Chromosome

Result from inheriting too many or too few X or Y chromosomes

Nondisjunction during oogenesis or spermatogenesis Turner syndrome (XO)

Female with single X chromosome

Short, with broad chest and widely spaced nipples

Can be of normal intelligence and function with hormone therapy

Klinefelter syndrome (XXY) – a male

Male with underdeveloped testes and prostate; some breast overdevelopment

Long arms and legs; large hands

Near normal intelligence unless XXXY, XXXXY, etc.

No matter how many X chromosomes, presence of Y renders individual male

43

Changes in Sex Chromosome

a. Turner syndrome b. Klinefelter syndrome


a: Courtesy UNC Medical Illustration and Photography; b: Courtesy Stefan D. Schwarz, http://klinefeltersyndrome.org

44

Changes in Chromosome Structure

Changes in chromosome structure include:

Deletions

One or both ends of a chromosome breaks off

Two simultaneous breaks lead to loss of an internal segment

Duplications

Presence of a chromosomal segment more than once in the

same chromosome

Translocations

A segment from one chromosome moves to a non-

homologous chromosome

Follows breakage of two nonhomologous chromosomes and

improper re-assembly

Animation

45













46

Changes in Chromosome Structure

Duplication

A segment of a chromosome is repeated in the

same chromosome

Inversion

Occurs as a result of two breaks in a

chromosome

The internal segment is reversed before re-insertion

Genes occur in reverse order in inverted segment

Animation













48

Types of Chromosomal Mutation

c. Inversion d. Translocation

b. Duplication a. Deletion

+

a b c

d

e

f

g

a b c d

e

f

g

h

a b c

d

e

f

g

a b

e

f

g

l m n

o

p

q

r

a b c d

e

f

l m n

o

p

a b c

d

e

f

g

a b c

d

e

f

g

b c

d

e

f

g

g

h

q

r

d

e

a

c

d


Animation













Animation

50













51


deletion lost

a. b.

+ h

a

b

c

d

e

f

g

h

a

b

c

d

e

f

g


b: Courtesy The Williams Syndrome Association

52


translocation

a. b.

a

b

c

d

e

f

g

h

s

t

u

v

w

x

y

z

a

b

c

d

e

f

g

h

s

t

u

v

w

x

y

z


b: American Journal of Human Genetics by N. B. Spinner. Copyright 1994 by Elsevier Science & Technology Journals. Reproduced

with permission of Elsevier Science & Technology Journals in the format Textbook via Copyright Clearance Center

53

Review

Reduction in Chromosome Number Meiosis Overview

Homologous Pairs

Genetic Variation Crossing-Over


Fertilization

Phases of Meiosis Meiosis I

Meiosis II


Human Life Cycle

Changes in Chromosome Number and Structure

Sylv

ia S

. Ma

der

Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display

PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor

BIOLOGY 10th Edition

Meiosis & Sexual Reproduction

Chapter 10: pp. 169 - 188

54

egg


MITOSIS

MITOSIS

sperm

n

n

2n

2n

2n

2n

zygote

haploid (n)

n = 23

2n = 46

diploid (2n)

SPERMATOGENESIS

OOGENESIS

Metamorphosis

and maturation

Primary

spermatocyte

Primary

oocyte

zygote

egg

Secondary

oocyte



spermatids

sperm

Secondary

spermatocytes

First

polar body

Second

polar body

fusion of sperm

nucleus and

egg nucleus

sperm nucleus

2n

2n

2n

n

n

n

n

n

n

n

n

Meiosis I

Meiosis II

Meiosis I

Fertilization

cont'd

Meiosis II


Date post:	09-Apr-2018
Category:	Documents
Upload:	hanguyet
View:	226 times
Download:	2 times

BIOLOGY Chapter 10: 10th Edition Meiosis & Sexual … 10: pp. 169 - 188 1 egg ... Genetic Variation...

Documents