MEIOSIS.

Slides:



Advertisements
Similar presentations
MEIOSIS.
Advertisements

Aim: Why is meiosis important?
Sexual Reproduction and Meiosis Chapter Overview of Meiosis Meiosis is a form of cell division that leads to the production of gametes. gametes:
Mitosis, Meiosis, and Life Cycles Chapter 12. KEY TERMS DIPLOID (2N) DIPLOID (2N) The condition of having two sets of chromosomes per nucleus The condition.
Meiosis chapter 6.
Cell Division. Cell division consists of two phases: ● nuclear division ● cytokinesis = division of the cytoplasm.
Sexual Reproduction and Meiosis Chapter Overview of Meiosis Meiosis is a form of cell division that leads to the production of gametes. Gametes:
Meiosis.
Meiosis.  Meiosis is a special type of cell division that occurs only in reproductive organs. Meiosis makes reproductive cells called gametes (egg or.
Genetic Variation Meiosis reduces the number of chromosomes and produces haploid cells from diploid cells.
Unit 8- Reproduction 8a- Meiosis & Variation
Meiosis and Sexual Reproduction
Reduction of Chromosomes. Mitosis Cell duplication (or reproduction) where one cell creates two genetically identical daughter cells Cellular reproduction,
Meiosis The ability to pass on traits is called heredity. – This ability is one of the unifying themes of biology as individual units of heredity (genes)
Sexual Reproduction and Meiosis Chapter Overview of Meiosis Meiosis is a form of cell division that leads to the production of gametes. gametes:
Meiosis Day 3. Concept check on Sexual and Asexual Reproduction Yes, you may use your notes!
MEIOSIS AND SEXUAL REPRODUCTION. Meiosis Process of nuclear division that reduces the number of chromosomes in a cell by half 2 STAGES Meiosis I: Homologous.
Meiosis. Now that you know all about DNA…. How is DNA passed from parent to offspring? How is DNA passed from parent to offspring? There are two main.
3.02: Cell Types and Chromosome Number In an organism, there are somatic cells and there are sex cells. o Somatic cells are all of the body’s cells that.
Sexual Reproduction and Genetics Chapter : Meiosis MAIN IDEA: Meiosis produces haploid gametes.
Meiosis!! Chapter 10. Meiosis  Purpose: to make sex cells  Gamete: sex cell  Male gamete= sperm  Female gamete= egg (ovum)
Meiosis November Chromosome Number Diploid- 2 sets of chromosomes –In somatic (body) cells; One comes from mother and one from father –Also referred.
Meiosis and Mitosis.
Meiosis.
Do Now!!  How many chromosomes are in human non-sex cells? How about human sex cells? Where do we get those chromosomes from??
Meiosis Unit 11 continues….
DNA replication creating a tetraploid (4n) cell
Meiosis Modified by Liz LaRosa 2011.
Cell Division: Meiosis.
Meiosis SC.912.L
Meiosis.
Meiosis Modified by Liz LaRosa 2011.
Meiosis Modified by Liz LaRosa 2011.
4.2- Sexual Reproduction: Meiosis
Sexual Reproduction and Meiosis
Announcements Take out Meiosis WS to be checked from last class if you did not get it stamped Today: Meiosis Review.
Meiosis Pgs Modified by Liz LaRosa 2011.
Chromosomes and Chromosome Number
Meiosis Chapter 10.1.
Meiosis and Sexual Reproduction
Meiosis Modified by Liz LaRosa 2011.
Meiosis Modified by Liz LaRosa 2011.
Genes & Chromosomes Organisms have tens of thousands of genes that determine individual traits Genes are lined up on chromosomes A thousand or more genes.
MEIOSIS Meiosis.
Meiosis and Sexual Reproduction
Meiosis I results in 2 haploid daughter cells
Telophase I and Cytokinesis
Meiosis Modified by Liz LaRosa 2011.
Stages of Meiosis Meiosis 1 ~
Meiosis I: Reduction Division
Meiosis and Sexual Reproduction
Meiosis Chapter 10 Section 1.
Meiosis and Sexual Life Cycles
Chromosomes and Mieosis
Meiosis Notes Unit 6.
Sexual Reproduction and Meiosis
Sexual Reproduction and Meiosis
Sexual Reproduction and Meiosis
The Cellular Basis of Inheritance
Meiosis Chapter 10.1.
Genes, Alleles, and Meiosis Review
Sexual Reproduction and Meiosis
Cell division: Meiosis
Meiosis SC Standard B4.5- The student will be able to summarize the characteristics of the phases of Meiosis I and II.
Meiosis Modified by Liz LaRosa 2011 *.
Meiosis Division of Sex Cells.
Meiosis.
Zoo-352 Principles of genetics Lecture 5 Meiosis
Meiosis.
Meiosis Meiosis: Summary of process:
Presentation transcript:

MEIOSIS

Meiosis A type of nuclear division Meiosis is also called reduction division because it results in the production of daughter cells with only *1 set of chromosomes (the parent cells has 2 sets).

Meiosis - Reduction Division Eukaryotic cells are diploid (have 2n chromosomes). Mitosis (asexual reproduction) produces diploid daughter cells. Sexual reproduction involves the fusion of 2 gametes = fertilization, to produce a zygote. If the gametes each have 2n chromosomes then the zygote would have ?

Meiosis – Reduction Division Preservation of karyotype (number and physical properties of chromosomes) is essential to survival of organism. All of our cells are diploid, 2n chromosomes. Those not destined to become gametes are called somatic (body) cells, those destined to produce gametes are called germ cells.

Meiosis Meiosis is similar to mitosis but differs in 4 ways: Meiosis has 1 round of duplication of DNA; 2 rounds of nuclear division = Meiosis I and II. Homologous chromosomes are paired through metaphase of meiosis I. They are physically joined = synapsis.

Meiosis Differences from mitosis cont’d Homologous chromosomes exchange genetic material (some of father’s DNA is exchanged with mother’s DNA). This is called crossing over. Crossing over can result in recombination = production of unique chromosomes, unlike those from the mother or father.

Chromosome Replication, Synapsis, and Crossing Over A CLOSER LOOK AT THREE KEY EVENTS IN MEIOSIS Centromere during interphase. Sister chromatids are held together by proteins along the chromosome “arms” and at the centromere. Shown: early prophase of meiosis I, when chromosomes have condensed. 1. Replication, Sister chromatids Chromosomes One homolog during prophase I. Homologous chromosome are held together by proteins in the synaptonemal complex. 2. Synapsis, Synaptonemal complex Second homolog during prophase I. Complex of proteins forms where crossing over will occur. Chromosome segments are swapped between non-sister chromatids. 3. Crossing over, Non-sister chromatids Protein complex Crossing over usually occurs at least once in each non-sister chromatid, but is only shown on 1 pair here

Meiosis Sequence of Events. Chromosomes are duplicated – S phase (Interphase) Prophase I Homologous chromosomes pair and are physically joined (synapsis) until Anaphase I. *Crossing over can occur only in this phase. Nuclear membrane disappears, spindle forms.

Meiosis Sequence of events cont’d Metaphase I Homologous chromosome pairs line up at center of spindle randomly. Microtubules of the spindle attach to kinetochores. Anaphase I – homologous chromosome pairs split and migrate to opposite poles of spindle.*** Telophase I – spindle disappears and nuclear membranes reappear. Cytokinesis – separation into 2 cells, may occur.

The Phases of Meiosis PRIOR TO MEIOSIS MEIOSIS I 1. Interphase: Chromosomes replicate, forming sister chromatids. Homologous chromosomes separate. Tetrad (4 chromatids from homologous chromosomes) Nuclear envelope Chromatin Non-sister chromatids Spindle apparatus Chiasma 1. Interphase: 2. Early Prophase I: 3. Late Prophase I: Chromosomes replicate in parent cell, in uncondensed state. Chromosomes condense, nuclear envelope breaks up, spindle apparatus forms. Synapsis of homologous chromosomes. Crossing over of non-sister chromatids (often multiple cross- overs between the same chromatids).

The Phases of Meiosis MEIOSIS I 4. Metaphase I: 5. Anaphase I: Homologous chromosomes separate. 4. Metaphase I: 5. Anaphase I: Tetrads migrate to metaphase plate. Homologs separate and begin moving to opposite sides of cell. 6. Telophase I and Cytokinesis: Chromosomes move to opposite sides of cell, then cell divides.

Sequence of events cont’d Brief interphase with no DNA duplication. Prophase II: nuclear membranes disappear, spindles form in each cell. Metaphase II: chromosomes line up on spindles; sister chromatids attached to opposite poles of spindle. Anaphase II: sister chromatids split and move to opposite poles of spindle. Telophase II: nuclear membranes reappear. Cytokinesis results in 4 haploid cells, with “n” number of chromosomes.

The Phases of Meiosis: Meiosis II Sister chromatids separate. 7. Prophase II: 8. Metaphase II: 9. Anaphase II: 10. Telophase II and Cytokinesis: Spindle apparatus forms. Chromosomes line up at middle of cell (metaphase plate). Sister chromatids separate, begin moving to opposite sides of cell. Chromosomes move to opposite sides of cell, then cell divides.

Meiosis KM

Meiosis KM

Meiosis KM