Cell Division Flashcards
what does each cell have?
pair of chromosomes one inherited from each parent
name of two chromosomes that carry the same genes?
Homologous chromosomes
significance of mitosis?
replacement of cells and tissue repair
what is every cell derived from?
the zygote previously formed by two gametes fused, divides until a multi cellular organism is formed
what is Asexual reproduction?
production of new species by a parent organism e.g. bacteria
what else can happen in multi cellular organisms?
new individual can bud off from parent, vegetative propagation
what must happen before mitosis?
DNA must replicate this is in Interphase, chromosomes aren’t visible , period of high metabolic activity. DNA content is doubling
stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
what happens in Prophase ? mitosis
chromosomes shorten and thicken, become visible, comprise of 2 chromatids joined at centromere. centrioles in cytoplasm move to poles, spindle fibres are made of microtubules, nucleus disappears and the nuclear membrane disintegrates
what happens in metaphase? mitosis
chromosomes arrange at equator attach to spindle fibres at centromere fibres contract and pull chromatids slightly apart.
what happens in Anaphase? mitosis
spindle fibres shorten cause 2 chromatids to separate migrate to opposite poles, energy for contraction provided by ATP
what happens in Telophase? mitosis
chromatids arrive at poles nuclear envelope forms around chromatids, uncoil become invisisble - spindle fibres disintegrate nucleolus reforms in each new nucleus
what happens in mitosis in animals?
constriction of cell as cell divides
what happens at the end of mitosis?
cell division or cytokinesis occurs
what is a haploid cell?
cell with 1 set of chromosomes
stages of meiosis?
interphase E prophase 1 M prophase 1 L prophase 1 metaphase 1 anaphase 1 telophase 1 prophase 2 metaphase 2 anaphase 2 telophase 2 cytokenisis
what happens in interphase?
DNA replicates, centrioles replicate
what happens in E prophase 1?
chromosomes shorten and become visible, made of 2 identical sister chromatids joined by centromere, nuclear envelope breaks down, centrioles move towards poles
what happens in m prophase 1?
each homologous chromosome pair come together form bivalent, called synapsis
what happens in L prophase 1?
chromatids from homologous chromosomes cross over at chiasmata, sections of chromatids are swapped
what happens in metaphase 1?
bivalents arrange on equator of spindle, independent assortment, they attach to spindle fibres by centromeres
what happens in anaphase 1?
homologous pairs of chromosomes separate and 1 of each pair, pulled by spindle fibres towards poles
what happens in telophase 1?
cells divide, the nuclear and nucleolus reform, this doesn’t occur in plants they go straight to metaphase 2
what happens in prophase 2?
nuclear envelope breaks down and disappears, centrioles replicate and move to poles. chromosomes shorten and thicken
what happens in Metaphase 2?
chromosomes arrange across the equator
what happens in anaphase 2?
centromeres divide chromatids pulled apart by spindle fibres
what happens in telophase 2?
nuclear envelope and nucleolus reform
what happens in cytokenisis?
cell division occurs, tetrad of 4 haploid cells with half the chromosome number of the parent
what is the aim of mitosis?
produce 4 unique gametes genetically different to parent cell
what is mitosis?
sexual reproduction
what are haploid cells?
one set of chromosomes, maintain chromosome number when gametes fuse
how many deaths does cancer cause?
1 in 4
what is most common cancer in men?
Lung cancer
what is most common cancer in women?
breast cancer
how does cancer arise?
uncontrolled cell division, gene mutation (oncogenes), uncontrolled mitosis tumour forms
what are carcinogens?
things that cause cancer e.g ionising radiation, tar, virus infection, hereditary predisposition
