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Transcript of 10 Lecture Animation Ppt
Sylvia S
. Mad
er
Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
BIOLOGY10th Edition
Meiosis & Sexual Reproduction
Chapter 10: pp. 169 - 188
1
egg
FERTILIZATIONMEIOSIS
MITOSIS
MITOSIS
sperm
n
n
2n
2n
2n
2n
zygote
haploid (n)n = 23
2n = 46diploid (2n)
SPERMATOGENESIS
OOGENESIS
Metamorphosisand maturation
Primaryspermatocyte
Primaryoocyte
zygote
egg
Secondaryoocyte
Meiosis II is completedafter entry of sperm
spermatids
sperm
Secondaryspermatocytes
Firstpolar body
Secondpolar body
fusion of spermnucleus andegg nucleus
sperm nucleus
2n
2n
2n
n
n
n
n
n
n
n
n
Meiosis I
Meiosis II
Meiosis I
Fertilizationcont'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 pairchromosome chromosome
Nonsisterchromatids duplicationduplication
centromere
kinetochore
paternal chromosome maternal chromosome
b.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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 IHomologous pairs
synapse and then separate.
centrioles sister chromatidssynapsis
nucleoluscentromere
chromosomeduplication
MEIOSIS IISister chromatids separate,
becoming daughter chromosomes.
Four haploiddaughter cells
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Animation
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.
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 – synapsisPhysically align themselves against each other end
to endEnd view would show four chromatids – Tetrad
Metaphase IHomologous pairs arranged onto the metaphase
plate
11
Phases of Meiosis I: Anaphase I & Telophase I
Anaphase ISynapsis breaks upHomologous chromosomes separate from one
anotherHomologues move towards opposite polesEach is still an internally duplicate chromosome with
two chromatidsTelophase 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 ITwo daughter cellsBoth with one internally duplicate chromosome of
each typeHaploidMeiosis I is reductional (halves chromosome
number)
InterkinesisSimilar to mitotic interphaseUsually shorterNo replication of DNA
Animation
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.
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
bB
C
c C
DD D
A Aa
b
B b
c
C c
dd d
a a
nucleoprotein lattice sister chromatidsof a chromosome
sister chromatidsof its homologue
chiasmata ofnonsisternhromatids1 and 3
Bivalentforms
b.
1 2 3 4 1 2 3 4 1 2 3 4
a. c. d.
Crossing-overhas occurred
Daughterchromosomes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Courtesy Dr. D. Von Wettstein
Animation
16
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.
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
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.
19
Independent Assortment
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
20
Recombination
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© 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
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.
25
Meiosis I & II in Plant Cells (Cont.)
Prophase IChromosomes have duplicated.
Homologous chromosomes pair duringsynapsis and crossing-over occurs.
Metaphase IHomologous pairs align
Independently at the metaphase plate.
Anaphase IHomologous chromosomes separate
and move toward the poles.
Prophase IICells have one chromosomefrom each homologous pair.
Metaphase IIChromosomes align
at the metaphase plate.
Anaphase IISister chromatids separate and
become daughter chromosomes.
kinetochore
MEIOSIS I
MEIOSIS II
Animal Cellat Interphase
centrosome hascentrioles
Plant Cellat Interphase
2n = 4
n = 2
n = 2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Ed Reschke
26
Meiosis I & II in Plant Cells
Telophase IDaughter cells have one chromosome
from each homologous pair.
InterkinesisChromosomes still
consist of two chromatids.
Telophase IISpindle disappears, nuclei form,
and cytokinesis takes place.
Daughter cellsMeiosis results in fourhaploid daughter cells.
MEIOSIS I cont'd
MEIOSIS II cont'd
n = 2
n = 2
n = 2
n = 2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Ed Reschke
Animation
27
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.
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
Meiosis Compared to Mitosis
Prophase ISynapsis and
crossing-over occur.
Metaphase IHomologous pairs align
independently at the metaphase plate.
Anaphase IHomologous chromosomes
separate and move towards the poles.
Prophase MetaphaseChromosomes align
at the metaphase plate.
AnaphaseSister chromatids separate and
become daughter chromosomes.
MEIOSIS I
MITOSIS
2n = 4
2n = 4
Telophase IDaughter cells are forming
and will go on to divide again.
TelophaseDaughter cellsare forming.
Sister chromatidsseparate and become
daughter chromosomes.
Two diploid daughter cells.Their nuclei are geneticallyidentical 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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Animation
30
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.
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
gametesOnly haploid part of life cycle is the gametesThe products of meiosis are always gametesMeiosis 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
FERTILIZATIONMEIOSIS
MITOSIS
MITOSIS
sperm
n
n
2n
2n
2n
2n
zygote
haploid (n)n = 23
2n = 46diploid (2n)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
SPERMATOGENESIS
OOGENESIS
Metamorphosisand maturation
Primaryspermatocyte
Primaryoocyte
zygote
egg
Secondaryoocyte
Meiosis II is completed
after entry of sperm
spermatids
sperm
Secondaryspermatocytes
Firstpolar body
Secondpolar body
fusion of spermnucleus andegg nucleus
sperm nucleus
2n
2n
2n
n
n
n
n
n
n
n
n
Meiosis I
Meiosis II
Meiosis I
Fertilizationcont'd
Meiosis II
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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 ofhomologouschromosomes
2n 2n 2n + 1 2n + 1 2n + 1 2n - 1
normal
normal
pair ofhomologouschromosomes
Meiosis I
Meiosis II
Fertilization
Zygote
nondisjunction
nondisjunction
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
2n - 12n - 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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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
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.
46
Changes in Chromosome Structure
DuplicationA segment of a chromosome is repeated in the
same chromosomeInversion
Occurs as a result of two breaks in a chromosome
The internal segment is reversed before re-insertionGenes occur in reverse order in inverted segment
Animation
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.
48
Types of Chromosomal Mutation
c. Inversion d. Translocation
b. Duplicationa. Deletion
+
abc
d
e
f
g
abcd
e
f
g
h
abc
de
f
g
ab
e
f
g
lmn
op
q
r
abcd
e
f
lmn
op
abc
de
f
g
abc
de
f
g
bc
d
e
f
g
g
h
q
r
de
a
c
d
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Animation
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.
Animation
50
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.
51
Types of Chromosomal Mutation
deletion lost
a. b.
+ h
a
b
c
d
e
f
g
h
a
b
c
d
e
f
g
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
b: Courtesy The Williams Syndrome Association
52
Types of Chromosomal Mutation
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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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 Independent Assortment Fertilization
Phases of Meiosis Meiosis I Meiosis II
Meiosis Compared to Mitosis Human Life Cycle Changes in Chromosome Number and Structure
Sylvia S
. Mad
er
Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
BIOLOGY10th Edition
Meiosis & Sexual Reproduction
Chapter 10: pp. 169 - 188
54
egg
FERTILIZATIONMEIOSIS
MITOSIS
MITOSIS
sperm
n
n
2n
2n
2n
2n
zygote
haploid (n)n = 23
2n = 46diploid (2n)
SPERMATOGENESIS
OOGENESIS
Metamorphosisand maturation
Primaryspermatocyte
Primaryoocyte
zygote
egg
Secondaryoocyte
Meiosis II is completedafter entry of sperm
spermatids
sperm
Secondaryspermatocytes
Firstpolar body
Secondpolar body
fusion of spermnucleus andegg nucleus
sperm nucleus
2n
2n
2n
n
n
n
n
n
n
n
n
Meiosis I
Meiosis II
Meiosis I
Fertilizationcont'd
Meiosis II
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.