Chromosomes and cell division. Flashcards
What is the end of the chromatids called?
The telomere.
What is telomerase and why is it required?
Telomerase in an enzyme that repairs telomeres. They require to be repaired as the ends of chromosomes cannot replicate properly, so shorten.
Which part of the chromosome connects the two sister chromatids.
Centromere
Which part of the chromosome does the spindle fibre attach too?
the centromere.
Does the euchromatin have densely packed DNA, or lightly packed DNA? How does this affect the activity of the DNA .
Lightly packed DNA, lots of activity.
Describe the DNA in heterochromatin.
Densely packed, not much activity.
Put these steps of the cell cycle in order.
G2, M, S, G1.
G1 -> S -> G2 -> M
What protein does DNA wrap itself around to become more tightly packed.
Histone.
What does DNA and histone form?
Chromatins -> Nucleosomes -> Chromosomes.
What can you see from a karyotype?
A chromosomes shape, size, the number of them.
What can you check by FISH (fluorescent in situ hybridisation)?
Chromosome number, translocation and chromosomal abnormalities.
What happens during the metaphase part of mitosis.
The chromosomes line up at the equator, spindle fibres attach to them.
what does the kinetochore protein do?
Forms on the centermere to bind to the spindle fibres.
Does meiosis form diploid cells or haploid cells?
Haploid.
Where does meiosis occur?
Ovaries and testes.
Where does cross over/recombination take place in meiosis.
Prophase 1
Where does independent assortment take place in meiosis?
Metaphase 1
What is the process of egg formation called?
Oogenesis.
what is the process of sperm formation called?
Spermatogenesis.
Does sperm formation or egg formation have more chance of mutation?
Sperm formation - it goes through many more cell divisions.
When does oogenesis occur?
early embryonic life.
When does spermatogenesis occur?
puberty .
When sperm and egg join, they form a diploid cell. What is this called?
A zygote.
Where does mitochondria and mitochondrial DNA come from?
Maternal Inheritance.
When a zygote is formed, both X chromosomes are active. However, in early embryonic development, something happens. What happens and why?
Random X inactivation. Only happens in females as males only have one X chromosome anyway. This prevents a ‘double dose’ of genes.
What is fluorescent in situ hybridisation?
fluorescent probes that only bind to specific parts of the DNA
What is centromeric prob can find?
chromosome number
telomeric probe can find?
rearrangements - can find the source of unexplained mental retardation
whole chromosome propes?
translocation and rearrangement
