meiosis and sexual reproduction - linn–benton community...
TRANSCRIPT
![Page 1: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/1.jpg)
Meiosis and Sexual
Reproduction
![Page 2: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/2.jpg)
Asexual Reproduction
• Single parent produces offspring
• All offspring are genetically identical to
one another and to parent
• Produces identical somatic (body) cells
![Page 3: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/3.jpg)
Sexual Reproduction
• Chromosomes are duplicated in germ
cells (sex cells)
• Germ cells undergo meiosis and
cytoplasmic division
• Cellular descendents of germ cells
become gametes (sperm and egg)
• Gametes meet at fertilization
![Page 4: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/4.jpg)
Sperm and Egg Gametes
![Page 5: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/5.jpg)
Sexual Reproduction
• Involves:
– Meiosis
– Gamete production
– Fertilization
• Produces genetic variation among
offspring
![Page 6: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/6.jpg)
Sexual Reproduction
Shuffles Alleles
• Through sexual reproduction, offspring
inherit new combinations of alleles,
which leads to variations in traits
• This variation in traits is the basis for
evolutionary change
![Page 7: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/7.jpg)
Homologous Chromosomes
Carry Different Alleles
• Cell has two of each chromosome
• One chromosome in each pair from
mother, other from father
• Paternal and maternal chromosomes
carry different alleles
![Page 8: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/8.jpg)
Gamete Formation
• Gametes are sex cells (sperm, eggs)
• Arise from germ cells
testes
ovaries
anther ovary
![Page 9: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/9.jpg)
Chromosome Number
• Sum total of chromosomes in a cell
• Germ cells are diploid (2n)
• Gametes are haploid (n)
• Meiosis halves chromosome number
![Page 10: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/10.jpg)
Meiosis: Two Divisions
• Two consecutive nuclear divisions
– Meiosis I
– Meiosis II
• DNA is not duplicated between divisions
• Four haploid nuclei are formed
![Page 11: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/11.jpg)
Meiosis I
Each homologue in the
cell pairs with its partner,
then the partners
separate
![Page 12: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/12.jpg)
Meiosis II
• The two sister chromatids of each
duplicated chromosome are separated
from each other
one chromosome
(duplicated)
two chromosomes
(unduplicated)
![Page 13: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/13.jpg)
Stages of Meiosis
Meiosis I
• Prophase I
• Metaphase I
• Anaphase I
• Telophase I
Meiosis II
• Prophase II
• Metaphase II
• Anaphase II
• Telophase II
![Page 14: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/14.jpg)
Meiosis I - Stages
Prophase I Metaphase I Anaphase I Telophase I
![Page 15: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/15.jpg)
Prophase I
• Each duplicated, condensed
chromosome pairs with its homologue
• Homologues swap segments
• Each chromosome becomes attached
to microtubules of newly forming spindle
![Page 16: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/16.jpg)
Metaphase I
• Chromosomes are pushed and pulled into the middle of cell
• Sister chromatids of one homologue orient toward one pole, and those of other homologue toward opposite pole
• The spindle is now fully formed
![Page 17: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/17.jpg)
Anaphase I
• Homologous chromosomes segregate
from each other
• The sister chromatids of each
chromosome remain attached
![Page 18: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/18.jpg)
Telophase I
• The chromosomes arrive at opposite
poles
• The cytoplasm divides
• There are now two haploid cells
• This completes Meiosis I
![Page 19: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/19.jpg)
Meiosis II - Stages
Prophase II Metaphase II Anaphase II Telophase II
![Page 20: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/20.jpg)
Anaphase II
![Page 21: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/21.jpg)
Prophase II
• Microtubules attach to the kinetochores
of the duplicated chromosomes
• Motor proteins drive the movement of
chromosomes toward the spindle’s
equator
![Page 22: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/22.jpg)
Metaphase II
• All of the duplicated chromosomes are
lined up at the spindle equator, midway
between the poles
![Page 23: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/23.jpg)
Anaphase II
• Sister chromatids separate to become
independent chromosomes
• Motor proteins interact with
microtubules to move the separated
chromosomes to opposite poles
![Page 24: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/24.jpg)
Telophase II
• The chromosomes arrive at opposite
ends of the cell
• A nuclear envelope forms around each
set of chromosomes
• The cytoplasm divides
• There are now four haploid cells
![Page 25: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/25.jpg)
Crossing Over
• Each chromosome becomes zippered
to its homologue
• All four chromatids are closely aligned
• Non-sister chromosomes exchange segments
![Page 26: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/26.jpg)
Effect of Crossing Over
• After crossing over, each chromosome
contains both maternal and parental
segments
• Creates new allele combinations in
offspring
![Page 27: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/27.jpg)
Random Alignment
• During transition between prophase I
and metaphase I, microtubules from
spindle poles attach to kinetochores of
chromosomes
• Initial contacts between microtubules
and chromosomes are random
![Page 28: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/28.jpg)
Random Alignment
• Either the maternal or paternal member
of a homologous pair can end up at
either pole
• The chromosomes in a gamete are a
mix of chromosomes from the two
parents
![Page 29: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/29.jpg)
Possible Chromosome
Combinations
As a result of random alignment, the
number of possible combinations of
chromosomes in a gamete is:
2n
(n is number of chromosome types)
![Page 30: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/30.jpg)
Possible
Chromosome
Combinations or
or
or
1 2 3
![Page 31: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/31.jpg)
Plant Life Cycle
multicelled sporophyte
multicelled gametophytes
zygote
gametes spores
meiosis fertilization
mitosis
mitosis
Diploid
Haploid
![Page 32: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/32.jpg)
Animal Life Cycle
multicelled body
gametes
zygote
meiosis fertilization
mitosis
Diploid
Haploid
![Page 33: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/33.jpg)
Spermatogenesis
Growth Mitosis I,
Cytoplasmic division
Meiosis II,
Cytoplasmic division
spermatids (haploid)
secondary spermatocytes
(haploid)
primary spermatocyte
(diploid)
spermato- gonium
(diploid male germ cell)
![Page 34: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/34.jpg)
Oogenesis
Growth Mitosis I,
Cytoplasmic division
Meiosis II,
Cytoplasmic division
ovum (haploid)
primary oocyte (diploid)
oogonium (diploid
reproductive cell) secondary
oocyte (haploid)
first polar body
(haploid)
three polar bodies
(haploid)
![Page 35: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/35.jpg)
Fertilization
• Male and female gametes unite and
nuclei fuse
• Fusion of two haploid nuclei produces
diploid nucleus in the zygote
• Which two gametes unite is random
– Adds to variation among offspring
![Page 36: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/36.jpg)
Factors Contributing to
Variation among Offspring
• Crossing over during prophase I
• Random alignment of
chromosomes at metaphase I
• Random combination of gametes at
fertilization
![Page 37: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/37.jpg)
Mitosis
• Functions
– Asexual reproduction
– Growth, repair
• Occurs in somatic
cells
• Produces clones
• 1 nuclear division
Mitosis & Meiosis Compared
Meiosis
• Function
– Sexual reproduction
• Occurs in germ cells
• Produces variable
offspring
• Two nuclear
divisions
![Page 38: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/38.jpg)
Prophase vs. Prophase I
• Prophase (Mitosis)
– Homologous pairs do not interact with each
other
• Prophase I (Meiosis)
– Homologous pairs become zippered
together and crossing over occurs
![Page 39: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/39.jpg)
Anaphase, Anaphase I, and
Anaphase II
• Anaphase I (Meiosis)
– Homologous chromosomes are separated
from each other
• Anaphase/Anaphase II (Mitosis/Meiosis)
– Sister chromatids of a chromosome are
separated from each other
![Page 40: Meiosis and Sexual Reproduction - Linn–Benton Community …cf.linnbenton.edu/mathsci/bio/klockj/upload/Ch.9 Part B... · 2012-10-19 · Meiosis •Function –Sexual reproduction](https://reader033.vdocument.in/reader033/viewer/2022050522/5fa623f52c7c2e52823ea940/html5/thumbnails/40.jpg)
Results of Mitosis and Meiosis
• Mitosis
– Two diploid cells produced
– Each identical to parent
• Meiosis
– Four haploid cells produced
– Differ from parent and one another