mitosis/meiosis Flashcards
what happens in interphase- mitosis
G1-protein synthesis
S-DNA replication
G2-organelle divides
-proteins are made
-DNA copied
-cell organelles divide
-ATP produced
-cell gets bigger.
what does chromatin do to genetic material
chromatin stains genetic material.
what happens in mitosis prophase
chromatin condenses t form chromasomes.
-nucleolus disappears.
-nuclear membrane breaks down.
-centrioles move to poles.
what happens in mitosis metaphase
chromosomes line up on equator and become attached to spindle fibres by centromere.
what happens in mitosis anaphase
chromatids move to poles caused by shortening of spindle fibres.
what happens in mitosis telophase-
chromatids reach the poles.
-nucleus and nuclear membrane reforms
-chromosomes unwind.
is mitosis new cell diploid or haploid
diploid-same no of chromosomes as original.
name 3 differences between mitosis and meiosis
mitosis occurs in all organs meiosis occurs in gonads only.
-mitosis produces diploid cells, meiosis creates haploid cells.
-mitosis produces genetically identical daughter cells, meiosis creates 4 genetically non-identical daughter cells.in meiosis there is 2 divisions of chromosomes.
in meiosis chromasomes occurs in pairs what is this called
homologous -one chromasomes from maternal and one from paternal.
what is fertilisation
fusion-re-establishes the diploid no and produces a cell that has homologous pairs of chromosomes.
where does mitosis occur
all organs for gowth and aesexual reproduction
what happens during cytokenesis mitosis
Cytokinesis – during cytokinesis the parent and replicated organelles move to
opposite sides of the cell and the cytoplasm divides thus producing two daughter cells.
what happens during mitosis interphase
Interphase – during this stage the cell grows and then prepares to divide –
chromosomes and some organelles are replicated, chromosomes also begin to condense.
describe what changes occur during both divisions in meiosis
division 1-homologous chromosomes seperate forming two cells each with 1 chromosome from each homologous pair. Each chromosome is still 2 chromatids.
division 2-
chromatids seperate forming 4 cells each with example of each chromosome.
when are chromosomes visable
prophase
what happens in meiosis interphase
DNA content doubles in replication and organelles replicated.
what is independant assortment
only 1 chromosome from each pair ends up in each gamete. The way the chromosomes line up on the equator is random creatong a series of different allele combinations.
what is crossing over
homologous pairs of chromosomes are in close contact in prophase 1. At contact points chromatids can break and rejoin exchanging DNA sections. The point at which they break is called chiasma, resulting in a new combination of alleles.
what is chiasma
the point t which chromatids join and break in crossing over.
what happens in prophase 1-meiosis
chromosomes become shorted and thicker.
-each chromosome is visable with two chromatids.
-homologous chromosomes associate forming a bivalent.
-crossing over can occur.
-centriole move to poles and spindle forms.
-nuclear membrane disappears.
what happens in metaphase 1-meiosis
homologous pairs line up on equator of spindle and attach to same spindle fibre by centrioles.
-independent assortment can occur
what happens in anaphase 1-meisosis
chromosomes of each bivalent seperate and pulled to opposite poles. chromosomes are still double structures.
what happens in telophase 1-meiosis
-nuclear envelope forms around each group of chromosomes. Thw two nuclei are haploid. The cytoplasm divides and 2 cell form.
-Each chromosome is still double stranded.
what happens in cytokenesis 1
in animals cytoplasm divides and two haploid cells are formed. In plant cells meisosis 11 occurs before any cyoplasmic division due to long time to produce cell wall.
