IB HL Bio D 2.1-2.2, & 1.3: Cell Division & Reproduction

gene knockout

technique which targets gene for deactivation or removal from an organism

purpose: lets scientists study impact of a gene on an organism

Cytokinesis

the splitting of the cytoplasm of a parent cell to form 2 daughter cells

Cytokinesis in plants vs animals

Plants: cell plate

Animals: cleavage furrow using contractile ring

The cytoplasm ________ splits equally during cytokinesis.

(Always, sometimes, or never)

sometimes

Budding

form of asexual reproduction where a small daughter cell buds off a larger cell

example of unequal division in yeast

Oogenesis

unequal division of cells during meiosis to form one large egg cell

example of unequal division in females

Mitosis is required for...

1. growth and development

2. tissue repair

3. asexual reproduction

Meiosis is required for...

the production of gametes in sexual reproduction

Meiosis produces ____ daughter cells, each with ____ the number of chromosomes in the parent cell.

4, half

What stages does DNA progress through during cell division?

1. Chromatin coils around histones to form nucleosomes

2. nucleosomes coil around each other to form chromosomes (w/ sister chromatids)

Spindle Fibers function

attach to centromeres and aid in movement of a chromosome

Stages of the Cell Cycle

interphase

prophase

metaphase

anaphase

telophase

cytokinesis

Interphase

G1: cell grows, protein synthesis occurs, allows cells to build new organelles

S: DNA replication

G2: cell grows, cell prepares for mitosis by growing/replicating organelles

Prophase

Chromatin condenses to form chromosomes (2 sister chromatids & a centromere)

nuclear envelope breaks down

spindle fibers produced

Metaphase

chromosomes line along equator of cell

Anaphase

spindle fibers separate sister chromatids & move them to opposite poles

Telophase

nuclear membrane forms around set of chromosomes @ each pole

i.e.) 2 genetically identical nuclei are produced

chromosomes uncoil back into chromatin

Purpose of Condensation of Chromosomes

segregates them during cell division

Diploid vs Haploid

diploid is two sets of chromosomes (humans have 46)

haploid is one set of chromosomes (humans have 23)

Meiosis is known as ________ division because...

reduction division

bc parent cell is diploid and daughter cell is haploid

• i.e. bc meiosis reduces # chromosomes

Purpose of 2 nuclear divisions in meiosis

Meiosis I: segregates homologous chromosomes to produce 2 haploid cells

Meiosis 2: segregates sister chromatids to produce 4 haploid cells

Prophase I in Meiosis

Chromatin condenses to chromosomes homologous chromosomes pair up and form bivalents

alleles switch

nuclear envelope breaks down

Metaphase I in Meiosis

spindle fibers move bivalents to equator in random order

Anaphase I in Meiosis

Homologous chromosomes are pulled to poles of the cell by spindle fibers

Telophase I in Meiosis

Chromosomes, at pole, uncoils

nuclear membrane forms around sister chromatids at each pole

Meiosis II

PMAT occurs again, but with sister chromatids now

@ end of Meiosis 1, cell are haploid

@ end of Meiosis 2, cells are diploid

Zygote

At fertilization, egg & sperm fuse to form a zygote

Meiosis is a source of variation. True or False?

True

Formation of bivalents and random swapping of sections of sister chromatids produce genetically different chromosomes

Cell proliferation

process of exponentially increasing cell numbers by mitotic division

ex) Plant meristems are undifferentiated & differentiate to produce plant tissue/organs

ex) Embryos grow by cell proliferation thru mitosis and cytokinesis

Cyclins

proteins which drive the cell cycle forward

bind to CDKs to be phosphorylated, trigger rxn cascade in cell cycle

tumor supressor genes

regulate/inhibit cell growth

mutations --> uncontrolled cell division

proton-oncogenes (Mutated version: oncogene)

promote normal, regulated, cell growth

mutations --> uncontrolled cell division