Cell Cycle Flashcards
What shape do chromosomes have?
X-shaped
What is the short arm of the chromosome called?
p-arm
What is the long arm of the chromosome called?
q-arm
What is karyoptype?
A picture of a person’s chromosomes
What are chromatids?
2 chromatids are joined to form a chromosome and 1 chromatid will go to each daughter cell
In what kind of cells is there 1 chromosome from each parent?
Somatic cells
What are the 46 chromosomes comprised of?
22 homologous pairs and 2 sex chromosomes
What differs in the chromosomes of males and females?
Females have 2 homologous X chromosomes and males have 1 X and 1Y chromosome
What stage comes before cell division?
Interphase
What is the restriction point?
Decides if cell will continue to S phase or will enter G0
What is G1?
The first of 2 gap stages in which all cell content except genetic material is duplicated
What is G0?
G0 is cell cycle arrest and can be reversible (quiescence) or irreversible (senescence)
Why is senescence triggered?
In ageing and damaged cells to safeguard against cancer
How can arrested cells be lost?
Through apoptosis (programmed death)
How is apoptosis carried out?
Controlled by P53 protein
What can prevent apoptosis?
Mutations in P53 protein
What happens in S phase?
Chromosomes are duplicated to form sister chromatids
Why is S phase short?
To prevent interference with DNA replication
What phase follows S phase?
G2
What happens in G2 phase?
DNA replication is accuracy checked and centrioles are duplicated as they act as seed points for the formation of spindle
How is G2 regulated?
P53 protein
What phase follows G2?
M Phase
How many stages are in M phase?
5
What is the first stage of M phase?
Prophase
What happens during prophase?
Chromosomes condense and spindles begin to form. These spindles consist of an array of microtubules which grow from centrioles at either end of the cell
What stage is after Prophase?
Prometaphase
What happens in prometaphase?
The nuclear envelope breaks down and releases chromosomes. Chromosomes are organised by attaching to microtubules.
What happens after the chromosomes attach to microtubules in prometaphase?
The microtubules bind to kinetochores which are proteins on the centromere of the chromosome
What stage is after prometaphase?
Metaphase
What happens in metaphase?
Chromosomes align along the spindle equator and the kinetochores and microtubules are responsible for this alignment
What 2 stages happen after metaphase?
Anaphase and Telophase
What happens in anaphase?
The sister chromatids separate and 2 identical sets of chromosomes move to each end of the cell
What happens in telophase?
Spindle disappears and chromosomes decondense. New nuclear membranes are then formed
What happens in cytokinesis?
The cytoplasm divides and yields 2 identical daughter cells
Why does BRCA1 mutations predispose for cancer?
BRCA1 codes for correcting in errors in DNA and is a tumour suppressant. DNA can’t be checked for errors if this gene is mutated so a more erroneous method is used.
What is meiosis?
Meiosis is the formation of gametes
How many cells are produced in meiosis?
4 very different haploid cells
What is the stage before Meiosis I called?
Gametogonium
What happens in Meiosis I?
DNA is replicated and 2 sister chromatids are
generated
What happens during prophase in Meiosis I?
Chromosomes cross over and swap DNA to ensures that we do not receive a complete set of chromosomes from 1 parent
What happens during metaphase in Meiosis I?
The crossed over chromosomes move to the equator of the cell
How many chromosomes do daughter cells have after Meiosis I?
23
What is non-disjunction?
When the DNA is not divided equally amongst the cells
What can dis-junction cause?
Gametes with 1 too many or 1 too little chromosomes
What is a trisomy?
When an embryo has 3 of 1 chromosome. Most are fatal but DS is Trisomy 21 and not fatal
What happens in Meiosis 2?
Meiosis 2 is a replica of Meiosis 1 so that 4 gametes are produced
