Cell Division - cell cycle/ mitosis/ meiosis Flashcards
why does a cell divide?
need to divide to grow and repair, but also for gametes for eukaryotic cells
What are the phases in the cell cycle?
G0 (G nought, resting phase)
G1 (growth) - cell grows - transcription of enzymes - organelles replicate
S(synthesis) phase - DNA replication (becomes a single chromosome to 2 sister chromatids [chromosome as well])
G2 - cell growth
M phase (mitosis or meiosis) - nuclear division
Cytokinesis - cytoplasm and cell membrane divide
what are the checkpoints in the cell cycle?
G1/S checkpoint:
-checks if G1 operations have happened
G2/M checkpoint:
-DNA checked for damage (can it be repaired?)
-If it cannot be repaired it will trigger the cell to die, this is called apoptosis
what is involved in interphase?
phase G1,S,G2
-cell growth
-organelles replicate
-DNA replication
-transcription of enzymes
what is a mutation? example of mutations
change in the base sequence of DNA. This can cause a non-functional protein to be made (processed and packaged differently)
e.g. deletion
substitution
what/explain the phases of mitosis?
PROPHASE: the centrioles are the poles of the cells. The nuclear envelope breaks down. The chromosomes condense and become visble.
METAPHASE: there are 3 chromosomes (6 chromatids). The chromosomes line up at the equator of the cell. The spindle fibres form from the centrioles and attach to the centromere of the chromosomes.
ANAPHASE: 6 chromosomes. Centromeres divide and chromatids are pulled apart to either poles of the cell. The chromatids are now called chromosomes.
TELPHASE: The nuclear envelope reforms around each set of chromosomes. The cell has 2 identical nuclei.
Then cytokensis occurs (isn’t part of mitosis) - cytoplasm and cell membrane divide, form 2 identical daughter cells.
what are diploid cells and haploid cells, in terms of meiosis?
Diploid cell (reproductive cell)
-full set of DNA chromosomes
-contain 46 chromosomes
Haploid cell (daughter cell) x2
-half amount of of DNA/ chromosomes
-contain 23 chromosomes
(will divide again to make 4 cells in meiosis)
what are homologous paris?
contains a paternal chromosome (from father) and a maternal chromosome (from mother) - they have the same type of gene in the same location
what are the stages in the first half of meiosis? and explain them
PROPHASE 1: chromosomes condense, nuclear envelope breaks down, centrioles divide, homologous pairs form
- Can be crossing over = homologous pairs attach and overlap (that portion would swap genes over/ exchange their alleles). The crossing over point= chiasma. After they have swapped it is called bivalent (happens in anaphase). THIS IS GENETIC VARIATION.
METAPHASE 1: homologous pairs line up at the equator of the cell and line up randomly (independent assortment). Spindle fibres attach to the centromeres of the chromosome on their side and homologous pairs are split up
ANAPHASE 1: homologous chromosomes are pulled to either pole of the cell. Crossing over bivalent are created/formed (genetic variation)- when they are pulled apart.
TELOPHASE 1: nuclear envelope reforms around either group of chromosomes.
CYTOKINESIS: only happens in animal cells but in plant cells stop at Telophase and go to prophase again.
what are the stages in the second stage of meiosis? explain them
all stages happen with 2 cells
PROPASE 2: chromosomes condense nuclear envelope breaks down, centrioles divide
METAPHASE 2: chromosomes line up at the equator, spindle fibres attach to the centromeres
ANAPHASE 2: sister chromotids are pulled apart, centromeres divide
TELOPHASE 2: 4 cells are made (gametes) genetically different to each other adn the parent cell due to crossing over adn independent assortment
similarities between mitosis and meiosis
go through interphase before it goes through mitosis/meiosis
both forms of cell division
both goes through cytokensis
nuclear envelope breaks down
centrioles divide in both spindle fibres form
