Cell cycle & genetics Flashcards
What are cells in the cell cycle known as?
Labile cells - cells that multiply constantly throughout life.
What are cells that never enter the cell cycle known as?
Permanent cells
What are cells that are not in the cell cycle, but can enter, known as?
Stable cells
How many divisions take place during mitosis?
1
What are the stages of mitosis?
Interphase Prophase Prometaphase Metaphase Anaphase Telophase
What happens during prophase?
Chromatin condenses into chromosomes. Two centrosomes (microtubule organising centre of cell) begin recruiting microtubules and move to opposite poles of the nucleus.
What happens during prometaphase?
The nuclear membrane dissolves.
Microtubules invade the nuclear space.
Cell no longer has nucleus.
What happens during Metaphase?
Microtubules attach to kinetochores and chromosomes begin to line up in the middle of the cell.
What happens during Anaphase?
The proteins that bind the sister chromatids are cloven and they separate.
Then microtubules shorten as spindle fibres contract to pull apart the chromatids towards opposite poles.
The chromatids reach the opposite ends and are now known again as chromosomes.
What happens during Telophase?
The nuclear membrane reforms around the genetic material.
The chromosomes are unfolded back into chromatin.
What is cytokinesis?
Cell organelle become evenly distributed around each nucleus.
The cellular membrane pinches off between the separated nuclei, forming two new daughter cells.
What is a primordial (undifferentiated) germ cell?
An embryonic precursor of the gametes. They go on to produce spermatogonia (mature sperm) in males, and oogonia (immature reproductive cell) in females.
What is an oocyte?
A cell in an ovary which may undergo meiotic division to form an ovum.
Oogonium give rise to primary oocytes by mitosis.
What is spermatogenesis?
Spermatogonia undergo spermatogenesis to form mature spermatozoa in tubules of testes.
How many mitotic divisions do PGCs undergo to produce oogonia?
A) 15
B) 45
C) 30
D) 150
C) 30
At ovulation, how many divisions of meiosis does the cell complete?
Only 1 division takes place (Meiosis I) at ovulation.
Meiosis II only occurs if fertilisation occurs.
How many eggs are produced by the oocyte?
During meiosis I, the oocyte divides to produce 1 polar body, and secondary oocyte. During meiosis II, the cells divide to produce an ovum and a second polar body.
This is due to unequal division of the cytoplasm.
Define Gonadal Mosaicism.
Gonadal mosaicism is a special form of mosaicism, where some gametes (sperm or oocytes) carry a mutation, but the rest are normal. The cause is usually a mutation that occurred in an early stem cell that gave rise to all or part of the gametes.
Result of Gonadal Mosaicism
The foetus may inherit a genetic disease, whilst their parents are healthy.
What are the 3 ‘types’ of disease?
Genetic
Multifactorial
Enviromental
What does this define?:
“any chromosome other than sex chromosomes”
An autosome
Define Allelic Heterogeneity
Different mutations within the same gene result in the same clinical condition.
Define consanguinity
A reproductive union between two relatives.
What does this define?:
“Homozygosity by descent (inheritance of same altered allele through 2 branches of the same family)
Auto-zygosity
Autosomal recessive diseases…
manifest in the homozygous state (2 of affected allele)