cell division Flashcards
1
Q
what are the stages of the cell cycle?
A
- G1, S, G2 (interphase)
- prophase, metaphase, anaphase, telophase (mitosis)
2
Q
what is the importance of mitosis?
A
- growth
- repair of tissue
- asexual reproduction
3
Q
in what form is DNA made into for cell division?
A
- DNA coiled into chromosomes (either one or two sister chromatids that are exact copies of each other thanks to semi-conservative replication)
4
Q
what is occurring during the G1 phase?
A
- cell functions normally, growing and synthesising more organelles
5
Q
what happens during the S phase?
A
- DNA replication (DNA quantity doubles)
6
Q
what happens during the G2 phase?
A
- proteins that are needed for cell division are synthesised
7
Q
what are the differences between cells that have undergone mitosis and ones that have undergone meiosis?
A
- mitosis: diploid, complete set of chromosomes, genetically identical, in somatic cells
- meiosis: haploid, half no. of chromosomes, genetically different (due to crossing over and independent assortment)
8
Q
what happens during prophase (mitosis)?
A
- DNA condensed into chromosomes
- nuclear envelope disintegrates and nucleolus disappears
- centrioles move to poles
- spindle fibers form
9
Q
what happens in metaphase (mitosis)?
A
- chromosomes line up on the equator
- spindle fibres attach to centromeres
10
Q
what happens in anaphase (mitosis)?
A
- spindle fibres contract, pulling sister chromatids apart towards poles
- centromeres split
- sister chromatids become daughter chromosomes
11
Q
what happens in telophase (mitosis)?
A
- chromosomes unravel into chromatin
- nuclear membrane reforms
- spindle fibres disintegrate
- cytokinesis (animal cells: cytoplasm pinches in, plants: cell plate forms)
12
Q
what happens during prophase I (meiosis)?
A
- DNA breaks and reforms
- homologous chromosomes pair up (one from mother, one from father) to form a bivalent
- crossing over occurs at same point on each chromatid on each chromosome (point is called chiasmata)
13
Q
what are homologous chromosomes?
A
chromosomes with the same genes on but different alleles (different forms of same gene)
14
Q
what happens in metaphase I?
A
- bivalents line up on either side of equator in an independent assortment
- fibres attach by centromere
15
Q
what happens in prophase II that is different from prophase?
A
- no crossing over (as no bivalents)
- new spindle fibres form perpendicular to previous spindle fibres
