Cell cycle Flashcards
What is the longest phase of the cell cycle?
Interphase
What parts is interphase divided into?
G1 (cell contents replicated. Increase in size.)
S- (DNA REPLICATION)
G2 - (more cell growth)
What is the G0 stage?
A period where the cell stops replicating as there are no signals sent for division. This can be temporary or permanent and usually occurs during G1.
How many checkpoint are there during interphase?
3
What occurs at the checkpoint to allow the cycle to continue?
The proteins controlling the checkpoints are phosphorylated
What occurs if checkpoint proteins are not phosphorylated?
The cell either repairs the damage or undergoes apoptosis
When does the 4th checkpoint occur?
Before the chromosome spilt (during metaphase) to ensure the chromosomes are correctly aligned
What are the 5 stages of Mitosis?
Prophase, metaphase, anaphase, telophase and cytokinesis
What is the structure of a chromosome??
They consist of a short (p) arm and a long (q) arm and are held together by a centromere
What are the 4 chromosome structures due to centromere placement?
Metacentric, submetacentric, Acrocentric and telocentric
What occurs in prophase?
Nuclear Membrane disappears, chromosomes form
What happens in prometaphase?
Spindle fibres bind to centromeres, nuclear Membrane has completely disappeared
What happens in metaphase?
Replicated chromosomes align at the metaphase plate
What happens in anaphase?
Microtubules spindle pulls chromosomes apart to opposite poles
What happened in telophase?
Spindle disappeared, nuclear envelope reforms and a cleavage furrow forms as the cells start to be cleaved
What are homologous chromosome?
Chromosomes that have the same genes in the same loci, but different forms of the genes (alleles)
What does meiosis results in?
4 non-identical haploid cells
What stage is present in mitosis but not meiosis?
Prometaphase
What occurs in Prophase 1 of meiosis?
Synopsis occurs where the homologous chromosome pair up and crossing over occurs between non sister chromatids to form recombinant DNA
What is the importance of crossing over?
It gives genetic variation
What are the points at which crossing over occurs called?
Chiasmata
How is metaphase 1 in meiosis different?
The homologous pairs (bivalents) line up on the metaphase plate and there is independent assortment of bivalents
How is metaphase II different from metaphase I?
There is independent assortment of CHROMATIDS instead of BIVALENTS
What is the consequence of meiosis?
It allows the chromosome number to remain constant from generation to generation
What is spermatogenesis?
Cell division(meiosis) to make male gametes
What is the time length of spermatogenesis?
60 days
Outline spermatogenesis
The spermatogonium (diploid) divides by mitosis to make primary spermatocytes (diploid). These then undergo meiosis I to produce 2 secondary spermatocyte each which then undergoes meiosis II so that 4 spermatids are produced that develop into sperm cells
What is oogenesis?
Cell division by meiosis to produce female gametes
Outline oogenesis
The Oogonium divides by mitosis to produce primary oocytes. The primary oocytes undergo meiosis to produce 1 mature ovum and 3 polar bodies.
How long does oogensis take?
12-50 years
When are primary oocytes produced?
In the foetus and then the final stage of meiosis occurs after fertilisation
What is nondisjunction?
Failure to separate chromosomes properly during meiosis
What is aneuploidy?
Having not normal amounts of chromosomes
Is nondisjunction occurs in meiosis I how many of the daughter cells are affected?
All 4
If nondisjunction occurs in meiosis II how many daughter cells are affected?
Only 2
What is karyotyping?
A type of chromosome analysis
What is trisomy?
A cell which contains 3 of the same chromosomes instead of 2
What is monosomy?
When a cell contains only 1 chromosome of a pair
What is non-mosaic karyotype?
When a nondisjunction occurs in the first post-zygotes division and so all cells in the body are affected
What is mosaic karyotype?
When non-disjunction occurs in later divisions and so not all cells are affected.
What are centrosomes?
Organelles that organise microtubules in the cell cycle. There are 2 in a cell
What happens when you have more than 2 centrosomes?
There are multipolar spindles (chromosomes are pulled apart in multiple directions)
