Cell division, diversity and organisation Flashcards
(42 cards)
What is the order of the different sections (Gaps) of interphase in the cell cycle?
Gap 0 (waiting/resting), Gap 1, Synthesis (DNA replication and cell growth), Gap 2 (preparation for mitosis)
What are checkpoints in the cell cycle?
Processes that prevent the next stage of the cell cycle from being started unless the processes of the previous stage have occurred correctly.
What are the 3 checkpoints in the cell cycle?
G1 checkpoint, G2 checkpoint and Metaphase checkpoint.
Where is the G1 checkpoint and what does it do?
After Gap 1, before Synthesis, arrests cell if there is DNA damage.
Where is the G2 checkpoint and what does it do?
After Synthesis, before Gap 2, arrests cell if DNA replication did not occur properly.
Where is the Metaphase checkpoint and what does it do?
during Metaphase, arrests cells if chromosomes have not aligned at the mitotic plate and are under bipolar tension.
What is the purpose of mitosis?
For growth, tissue repair and asexual reproduction.
Also: (clonal expansion of lymphocytes, production of new stem cells)
What happens in prophase of mitosis?
The nuclear envelope breaks down and disappears.
DNA condenses and supercoils forming short, fat chromosomes.
Centrioles move to opposite poles.
Spindle fibres begin to form from the centrioles.
What happens in metaphase of mitosis?
Centrioles arrive at opposite poles.
Spindle fibres attach to the centromere of chromosomes.
Chromosomes line up on the mitotic plate.
Metaphase checkpoint.
What happens in anaphase of mitosis?
Spindle fibres begin to shorten, causing the two chromatids of each chromosome to separate at the centromere.
Sister chromatids are pulled towards opposite poles of the cell.
What happens in telophase of mitosis?
Chromatids reach opposite poles.
Nuclear envelopes are reformed.
The cell begins cytokinesis, the cell membrane begins to pinch at the equator forming a cleavage furrow.
What is the order of the different phases of mitosis?
PMAT
What does mitosis produce?
2 genetically identical diploid daughter cells.
What is the purpose of meiosis?
Produce 4 haploid gametes for sexual reproduction.
Meiosis is a reductive process.
What does meiosis produce?
4 genetically different haploid daughter gametes.
How is P1 of meiosis different from prophase in mitosis?
Homologous chromosomes form bivalents.
Crossing over occurs.
How is M1 different in meiosis different from metaphase in mitosis?
Bivalents become aligned along the equator of the cell in independent assortment.
How is A1 in meiosis different from anaphase in mitosis?
Homologous chromosomes move to opposite poles of the cell.
Chromosomes are NOT split at the centromere.
How is T1 in meiosis different from telophase in mitosis?
The centrioles duplicate.
How is genetic variation produced in sexual reproduction?
Crossing over and independent assortment during meiosis.
Reduction and fusion of gametes.
What is crossing over and when does it happen?
Happens during P1 of meiosis.
Non-sister chromatids (but homologous) cross over forming a chiasma (where they cross over). This results in recombinant DNA.
What is independent assortment and when does it occur?
Happens during M1 and M2 of meiosis.
The arrangement of each bivalent is random, so each of the daughter nuclei get a mix of paternal and maternal alleles.
What is the reduction and fusion of gametes?
One haploid gamete will fuse with another haploid gamete to form a diploid zygote with 50% different alleles from any one of the original parents.
How are squamous epithelial cells specialised?
Very thin (squamous) => allows rapid diffusion. Secretes basement membrane => attaches squamous epithelial cells to connective tissue.
