11-4 meiosis meiosis chapter 11 section 4 11-4 meiosis understand that homologous chromosomes...
TRANSCRIPT
11-4 Meiosis
Meiosis
Chapter 11
Section 4
11-4 Meiosis
Understand that homologous chromosomes separate randomly during meiosis to produce haploid gametes.
COPYRIGHT PEARSON PRENTICE HALL
MT: Sexual Reproduction
11-4 Meiosis
WHAT IS HAPPENING HERE?
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
FERTILIZATION
COPYRIGHT PEARSON PRENTICE HALL
= when a male and female gamete join
11-4 Meiosis
CHROMOSOME #
Most organisms are diploid and thus want an offspring that is also diploid
So, each gamete has to be haploid so when they join they create a diploid organism
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
haploid + haploid = diploidOR
Female gamete + male gamete = offspring
OR
½ + ½ = 1
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
FIND CHROMOSOME #
DIPLOID #
Human 46 chromosomes Dog 78 chromosomes Carrot 18 chromosomes Goldfish 94 chromosomes Wheat 42 chromosomes Tobacco 48 chromosomes
COPYRIGHT PEARSON PRENTICE HALL
HAPLOID #
Human __ chromosomes Dog __ chromosomes Carrot __ chromosomes Goldfish __ chromosomes Wheat __ chromosomes Tobacco __ chromosomes
11-4 MeiosisWhat happens during the process of
meiosis?
COPYRIGHT PEARSON PRENTICE HALL
making of non-identical making of non-identical haploid gameteshaploid gametes
11-4 Meiosis
PHASES OF MEIOSIS I
Meiosis I
COPYRIGHT PEARSON PRENTICE HALL
Prophase I Metaphase I Anaphase I Telophase I and
Cytokinesis
Interphase I
Meiosis I
11-4 Meiosis
INTERPHASE 1
DNA copies itself
COPYRIGHT PEARSON PRENTICE HALL
nucleusnucleus
centriolescentrioles
11-4 Meiosis
PROPHASE INuclear membrane disappears.
Homologous chromosomes pair up to form a tetrad.Tetrad = 4 sister chromatids
Crossing over occurs
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
CROSSING OVERWhen homologous chromosomes form tetrads in meiosis I, they exchange portions of their chromatids in a process called crossing over.
Crossing-over produces new combinations of alleles.
COPYRIGHT PEARSON PRENTICE HALL
Does crossing over always occur at the Does crossing over always occur at the same allele?same allele?
NO! It is NO! It is randomrandom
11-4 Meiosis
METAPHASE 1 Homologous chromosomes line up in middle of cellSpindle fibers attach to the chromosomes.
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
ANAPHASE 1
The fibers pull the homologous chromosomes toward opposite ends of the cell.
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
TELOPHASE 1 Nuclear membranes form.
The cell separates into two cells.
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
PHASES OF MEIOSIS II
Meiosis II
COPYRIGHT PEARSON PRENTICE HALL
Telophase II and
CytokinesisProphase II
Metaphase II Anaphase IITelophase I and Cytokinesis I
Meiosis II
11-4 Meiosis
PROPHASE II
Nuclear membrane disappears.
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
METAPHASE II
Individual chromosomes line up in the middle of cell.
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
ANAPHASE II
The sister chromatids separate and move toward opposite ends of the cell.
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
TELOPHASE IIMeiosis II results in four non-identical haploid cells.
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
GAMETE FORMATIONIn male animals, meiosis results in four equal-sized gametes called sperm.
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
GAMETE FORMATIONIn many female animals, only one egg results from meiosis. The other three cells, called polar bodies, are usually not involved in reproduction.
COPYRIGHT PEARSON PRENTICE HALL
11-4 Meiosis
WEBSITES TO CHECK OUT
COPYRIGHT PEARSON PRENTICE HALL
1. http://www.cellsalive.com/meiosis.htm
2. http://www.pbs.org/wgbh/nova/baby/divi_flash.html
3. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__how_meiosis_works.html
4. http://www.youtube.com/watch?v=uh7c8YbYGqo