Unit C: Ch 16: Cellular Reproduction

Chromatin

An active string of uncoiled DNA

(Think the tin of messy sewing supplies)

Chromatid

A coiled string of DNA; 1 strand chromosome

Two identical halves of a chromosome

Sister chromatid

The identical twin of a chromatid; 2 strand chromosome

Centrome

The identifying centre bit of a chromosome

Homologous pair

Two chromatids that are not identical, but contain the same subset of genetic instructions (X).

Can also be in reference to 2 two chromatid chromosomes (like XX), but that is typically referred to as something else

Tetrad

A group of 2 chromosomes, which are both 2 chromatid pairs. Typically in reference to what is found in early meiosis.

Karyotype

A display of the chromosomes of a person in a certain numbered configuration

Autosome

Any Chromosome that is not a sex chromosome

Germ Cell/ Stem Cell/ Gamete

AKA a sex cell

• contain half as many chromosomes as somatic cells do

• Produced through meiosis

• Haploid cells

Somatic Cell

• body cells

• Produced through mitosis

• Diploid cells

Histones

The proteins chromatid is coiled around

“-ploid” suffix and ploidy

The number of chromosomes in a cell

1. Ha-

2. Di-

3. Tri-

Etc.

Mitosis

The asexual process of cell replication

What is the order of stages in mitosis?

Interphase

Propase

Metaphase

Anaphase

Telophase

Cytokinesis

Interphase (and the 3 steps)

Initiate; growth stage

• Cells spend most their time here

• Chromatin

• G1

  • Replicate everything BUT the DNA

  • Requires lots of energy

  • Quick check everything was done right before proceeding

• S

  • Each of the 46 chromosomes is replicated

• G2

  • Double check everything was done right and there are no errors in the process

What happens if interphase is rushed or skipped?

Cells are uncontrollably replicating, and become useless bits of matter replicating and getting in the way, AKA cancer.

Prophase (mitosis)

Prepare

• Centrioles move to the poles

• Spindle fibres form

• Centromeres form between sister chromatids

• Nuclear membrane begins dissolving

Metaphase (mitosis)

Middle

• spindle fibres grab onto chromosomes

• Chromosomes get lined up

Anaphase (mitosis)

AHHHH!

• Spindle fibres pull apart and pull away

• Cell begins to stretch apart

Telophase (mitosis)

The End

• the cells begin splitting apart

  • In plants, the cell plate forms from the inside and becomes the cell wall (internal force)

  • In animals, a contractile ring in the membrane pinches inwards (external force)

• Nuclear membrane begins forming

Cytokinesis (mitosis)

Cut

• Not really a step, more the final split of the two cells that begins in anaphase

• Chromatid becomes chromatin again

• Nuclear membrane has reformed

Chromosomes

Counted by centromeres, a tightly coiled movable DNA package only visible during cell division

Meiosis

The process in which gametes are produced

• Consists of 1 DNA replication and 2 cell division processes reminiscent of mitosis

• Allows for genetic variation

• Diploid → Haploid

Prophase I

• tetrads crossover at random to create slightly different chromatids (increases genetic variation)

• Centrioles move to the poles

• Spindle fibres form

• Centromeres form between sister chromatids

• Nuclear membrane begins dissolving

Metaphase I

Middle

• spindle fibres grab onto chromosomes

• Chromosomes get lined up

• Nuclear membrane is gone

Anaphase I

AHHHH!

• Spindle fibres pull apart and pull away

• Cell begins to stretch apart

Telophase I

The End

• the cells begin splitting apart

  • In plants, the cell plate forms from the inside and becomes the cell wall (internal force)

  • In animals, a contractile ring in the membrane pinches inwards (external force)

• Nuclear membrane begins forming

Cytokinesis I

Cut

• Not really a step, more the final split of the two cells that begins in anaphase

• Chromatid becomes chromatin again

• Nuclear membrane has partially reformed, fully reformed or not reformed at all

Prophase II

Prepare

• Centrioles move to the poles

• Spindle fibres form

• Centromeres form between sister chromatids

• Nuclear membrane begins dissolving

Metaphase II

Middle

• spindle fibres grab onto chromosomes

• Chromosomes get lined up

• Nuclear membrane is gone

Anaphase II

AHHHH!

• Spindle fibres pull apart and pull away

• Cell begins to stretch apart

Telophase II

The End

• the cells begin splitting apart

  • In plants, the cell plate forms from the inside and becomes the cell wall (internal force)

  • In animals, a contractile ring in the membrane pinches inwards (external force)

• Nuclear membrane begins forming

Cytokinesis II

Cut

• Not really a step, more the final split of the two cells that begins in anaphase

• Chromatid becomes chromatin again

• Nuclear membrane has fully reformed

Non-disjunction, trisomy and monosomy

When the original chromosome pair does not split properly in meiosis I and causes an imbalance.

• Trisomy: three chromosomes where there should be two

• Monosomy: one chromosome where there should be two

Why are pregnancies in older women more likely to produce babies with genetic disorders?

The spindle fibre proteins aren’t as readily available and chromosomes aren’t pulled apart properly.

What is the technical term for down syndrome?

Trisomy 21

Spermatogenesis

The process of four haploid spermatozoa forming from one diploid spermatogonium

Oogenesis

The process by which a diploid oogonium cell becomes a single secondary oocyte by dividing and absorbing the cytoplasm of 3 discarded polar cells

Synapsis

The crossover fusion of chromosome pairs at the start of meiosis

Fraternal vs. Identical twins

Two eggs and two sperm to form two babies in utero at the same time

Vs.

One egg and one sperm that then split to create to biologically identical babies (completely random)

Asexual reproduction pros and cons

Pros

• fast

• Good if the organism is thriving in it’s surroundings

Cons

• Lack of variation

Sexual reproduction pros vs. cons

Pros

• Genetic variation = adaptability

• Diverse species

Cons

• slower

• Takes longer + more organisms

Sporophyte

Diploid generation of plants, produces haploid spores

Gametophyte

Haploid generation of plants, produces gametes that fertilize together to become diploids

Alternation of generations (describe the cycle)