Sexual life cycle. Sexual life cycle. Fertilization. Sexual Reproduction and Meiosis. Made up of meiosis and fertilization Diploid cells (2n)

Size: px

Start display at page:

Download "Sexual life cycle. Sexual life cycle. Fertilization. Sexual Reproduction and Meiosis. Made up of meiosis and fertilization Diploid cells (2n)"

Gavin Blankenship
6 years ago
Views:

Sexual life cycle Sexual Reproduction and Meiosis Made up of

Somatic cells of adults have 2 sets of Haploid cells (n)

from 2 parents 2 Sexual life cycle Fertilization Alternation

1 Sexual life cycle Sexual Reproduction and Meiosis Made up of meiosis and fertilization Diploid cells (2n) Chapter 11 Somatic cells of adults have 2 sets of Haploid cells (n) Gametes have only 1 set of Offspring inherit genetic material from 2 parents 2 Sexual life cycle Fertilization Alternation of haploid and diploid stages In most animals, diploid state dominates 3 4

Features of Meiosis Meiosis includes two rounds of Meiosis I and meiosis II Each has prophase, metaphase, anaphase, and telophase stages One

poles Produces 2 haploid cells with sister chromatids still attached Meiosis II Sister chromatids separate and move to opposite poles Produces 4

Meiosis I Sister chromatids First meiotic Replication during premeiotic interphase Each chromosome now consists of two sister chromatids.

These cells have the haploid number of, but each chromosome consists of two chromatids.

2 Features of Meiosis Meiosis includes two rounds of Meiosis I and meiosis II Each has prophase, metaphase, anaphase, and telophase stages One diploid cell produces four haploid cells 5 Meiosis I Meiosis Crossing over exchanges segments of DNA between homologous Homologues move to opposite poles Produces 2 haploid cells with sister chromatids still attached Meiosis II Sister chromatids separate and move to opposite poles Produces 4 haploid cells Meiotic Divisions chromosome pair A diploid cell. Meiosis I Sister chromatids First meiotic Replication during premeiotic interphase Each chromosome now consists of two sister chromatids. Chromosome pairing during prophase I of meiosis Second meiotic may undergo crossing over by exchanging segments. separate into two cells. These cells have the haploid number of, but each chromosome consists of two chromatids. The second meiotic separates the sister chromatids, placing one in each cell. Prophase I DNA condenses into visible Synapsis (pairing of homologues) Tetrads (Fully paired homologues - 4 chromatids) Recombination (crossing over) mixes alleles across tetrads Chiasma is the site of crossing over Nuclear envelope breaks down

pair Sister Sister chromatids chromatids A A a a B B b b 1 Homologs pairs.

poles of the spindle In mitosis, homologues behave independently Orientation of each pair of homologues on the spindle

3 pair Sister Sister chromatids chromatids A A a a B B b b 1 Homologs pairs. Crossover (chiasma) Crossing Over A A a a B B b b B B b b 2 chromatids exchange segments. A a A a 3 separate at first meiotic. Meiosis I Metaphase I Paired homologues move to the metaphase plate Homologues of each pair become attached to opposite poles of the spindle In mitosis, homologues behave independently Orientation of each pair of homologues on the spindle is random Anaphase I Homologues are pulled to opposite poles f each pair of In mitosis, sister chromatids are pulled to opposite poles Independent asstment of maternal and paternal 10 Random Orientation & Independent Asstment A B C Combinations possible in gametes

First Meiotic Division First Meiotic Division Prophase I Plasma membrane Duplicated centrioles Nuclear envelope Tetrad Metaphase plate pair Interkinesis:

Synapsis come together and pair. Recombination While they are paired, the chromatids of homologous undergo recombination by exchanging segments.

Metaphase I Tetrads align along the metaphase plate between the two Anaphase I The spindle microtubules separate the two of each homologous pair and move

Second Meiotic Division Second Meiotic Division Prophase II The condense and a spindle fms. Prometaphase II The nuclear envelope breaks down.

4 First Meiotic Division First Meiotic Division Prophase I Plasma membrane Duplicated centrioles Nuclear envelope Tetrad Metaphase plate pair Interkinesis: no DNA replication between first and second meiotic To prophase II in second meiotic Condensation of At the beginning of prophase I the begin to condense. Synapsis come together and pair. Recombination While they are paired, the chromatids of homologous undergo recombination by exchanging segments. Prometaphase I In prometaphase I, the nuclear envelope breaks down. Metaphase I Tetrads align along the metaphase plate between the two Anaphase I The spindle microtubules separate the two of each homologous pair and move them to opposite Telophase I The undergo little no change except f limited decondensation unfolding in some species. Second Meiotic Division Second Meiotic Division Prophase II The condense and a spindle fms. Prometaphase II The nuclear envelope breaks down. Metaphase II Movements of the spindle microtubules align the on the metaphase plate. Anaphase II The spindle microtubules separate the two chromatids of each chromosome and deliver them to opposite Telophase II Chromosomes begin decondensing, the spindles disassemble, new nuclear envelopes fm.

gametes with missing extra Most common cause of spontaneous abtion in humans Meiosis is characterized by:

5 Errs Meiosis vs. Mitosis Nondisjunction failure of to move to opposite poles during either meiotic Aneuploid gametes gametes with missing extra Most common cause of spontaneous abtion in humans Meiosis is characterized by: 1. Synapsis and crossing over 2. Sister chromatids remain joined throughout meiosis I 3. move to opposite poles in meiosis I 4. DNA replication is suppressed between meiosis I and meiosis II

Sexual Reproduction and Meiosis. Chapter 11

Sexual Reproduction and Meiosis Chapter 11 1 Sexual life cycle Made up of meiosis and fertilization Diploid cells Somatic cells of adults have 2 sets of chromosomes Haploid cells Gametes (egg and sperm)