Biology Semester one Exam

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- Spindle fibres attach to the chromatids and help pull them apart.

- Chromatids separate at centromere and move to opposite poles of the spindle as the spindle fibres contract.

- Chromatids are now chromosomes.

Telophase:

- Chromosomes de-condense as chromatin unwinds and become less visible.

- New nuclear envelope forms.

- Nucleoli reform.

- Spindle disassembles.

Cytokinesis:

Plant Cell:

- Parts of cell wall fuse with parts of spindle during anaphase forming cell plate.

- Cellulose deposited at this site, forming a wall that divides parent cell into two daughter cells.

- Each daughter cell has a plasma membrane.

Animal Cell:

- Don’t have cell wall so they separate through process called ‘cleavage.’

- Plasma membrane around the middle of the cell draw together to from a cleavage furrow.

- Cleavage furrow continues until it meets and is then cleaved, or split.

- Two daughter cells are the result.

Binary Fission: Prokaryotic cells can’t reproduce via mitosis as they have no centromere or nucleus. [pic 4]

- Reproduce via binary fission, which includes DNA replication, chromosome segregation and cytokinesis.

Meiosis I: To produce gametes for sexual production, for genetic diversity or variation.

Prophase I:

- Chromosomes condense.

- Nucleolus disappears.

- Spindle forms with centrioles at opposite ends.

- Homologous chromosomes lie side by side, called SYNAPSIS.

- Pair of homologous chromosomes, one is maternal, one is paternal, now called BIVALENT.

Metaphase I:

- Nuclear envelope breaks down.

- Homologous pairs move together to the equator.

Anaphase I:

- Maternal and parental chromosomes move to opposite poles of the spindle.

- Separation or DISJUNTION of each homologous pairs occur independently of other homologous pairs.

Telophase I:

- Spindle breaks down.

- Cell starts to separate across its middle.

- Nuclear envelops forms around two new nuclei.

- Cytokinesis completes meiosis.

Interphase:

- DNA doesn’t replicate.

- Nothing is visible.

Meiosis II:

Prophase II:

- Spindles form at right angles to the first spindles.

Metaphase II:

- Chromosomes move to equator.

Anaphase II:

- Chromatids separate and move apart from each other.

- Chromatids become the chromosomes of daughter cells.

Telophase II:

- Spindle disappears; chromosomes de-condense to their thread-like form.

- New nuclear envelopes and nucleoli form

Mitosis

Meiosis

For growth, repair and replacement of tissues.

For producing sex cells (gametes).

Takes place in somatic cells.

Takes place in reproductive organs (ovaries and testes)

One cell division completes process.

Two cell divisions completes process.

Two cells are the outputs.

Four cells (gametes) are the outputs.

Each daughter cell contains the diploid number of chromosomes (2n).

Each daughter cell contains the haploid number of chromosomes (n).

Asexually reproducing, by mitotic division, and binary fission in prokaryotes.

Sexually reproducing, by fusion of gametes restoring the diploid number of chromosomes.

Offspring do not show variation.

Offspring do show variation.

Variation and diversity of offspring narrowed.

Variation and diversity of offspring increased.

Applications include for tissue culture such as skin grafts and cloning plants.

Applications include creating new varieties of organisms.

Budding: Form of asexual reproduction.

- Organism develops outgrowth or bud due to mitosis.

- Organism remains attached until mature, then separates.

Spore Formation: Form of asexual reproduction.

- Can develop into new individual without fusion with another reproductive cell.

- Produced by bacteria, fungi and green plants.

- They can germinate and grow under suitable conditions.

Male