Cells and nuclear division

Cytokensis?

The splitting of a cytoplasm between 2 daughter cells but not always equal

Cytokinesis in plants?

• Vesicles go to the middle of the cell

• They form a cell wall at the middle lamella

Cytokinesis in animals?

• Actin and Myosin form a Contractile ring (cleavage furrow)

• The clevage furrow pinches the cells into two

Outline unequal cytokinesis in yeast budding?

Mitosis?

The Nuclear division resulting in continuity of the chromosome number and genome

Anucleate cells?

Mature cells that lack a cell nucleus due to cytokinesis prior to nuclear division

Meiosis?

The nuclear division resulting in reduction of chromosome number and diversity between genomes

Chromatids?

One half of a replicated chromosome

Centromere?

Reigion of a cell linking sister chromatids

Kinetichore?

Protein assembled at the centromere of each sister chromatid

Where does DNA replication occur in mitosis and meiosis 1?

During interphase

Microtubules?

Cylinders that provide structural support for cell division

Kinetochore?

Specialised molecular machines that drive chromosomes along microtubules

Outline the mitosis?

• Prophase - Chromosomes condense and become visible along with spindle fibers

• Metaphase - Chromosomes align at equator and spindle fibers attach to kinetochores at centromeres

• Anaphase - Chosein connecting sister chromatids is gone and they are pulled to opposite poles by microtubules

• Telophase - Chromosomes decondence and new nuclear memebrane formed and spindle fibers dissolve decondense

• Cytokenisis

• Interphase -

Homologous?

Pairs of chromosomes in a diploid cell that share the same structural features

Diploid?

Two complete sets of chromosomes

haploid?

A single set of chromosomes

What is the haploid human cell number?

23

Non disjunction?

The failure of homologous sister chromosomes or sister chromatids to separate in cell division

Trisomy?

When a cell contains 3 copies of a specfic chromosome instead of the normal pair

Causes and symptoms of down syndrome?

Cause by an extra copy of chromosome 21 altering development and causing intellectual disability

How does meiosis lead to genetic variation in gametes?

Random orientation of bivalents and crossing over

Bivalents?

Pairs of homologous chromosomes that form during phrase 1 of meiosis

Outline the stages of meiosis

• Prophase 1 - Chromosomes condense and pair with homologous partners, then crossing over occurs

• Metaphase 1- spindle fibers attach to kinetochores at centromeres and homologous chromosomes align at the equator

• Anaphase 1- Homologous chromosomes are pulled to opposite poles while sister chromatids remain attached

• Telophase 1 - Nuclear envelope reforms

• Cytokinesis 1 - 2 haploid daughter cells with one chromosome from each homologous pair

• Prophase 2 - Nuclear envelope breaks down Chromosomes condense again and new spindle fibers form

• Metaphase 2 - Spindle fibers attach to centromeres. Chromosomes line up along equator

• Anaphase 2 - Sister chromatids separate and are pulled to opposite poles

• Telophase 2 - Nuclear envelopes reform

• Cytokinesis 2 - 4 identical haploid gametes produced

Outline unequal cytokinesis in yeast budding?

• Bud formation - Small outgrowth forms on parent cell

• DNA replication - Nucleus replicates DNA and mitosis occurs making one copy of the nucleus move into the bud

• Cytoplasmic division - Cytoplasm is distributed unequally (Bud receives les from cytoplasm)

• Cell separation - Cell wall forms between two cells and bud eventually detaches to smaller daughter cell