Chromosomes and Cell Division Flashcards
1
Q
What is the end replication problem?
A
through multiple generations, strands will get shorter
2
Q
What is the solution to the end replication problem?
A
telomerase
3
Q
What are centromeres?
A
- Protein complexes that bind to microtubules and are required during cell division
- They are the constricted region joining sister chromatids
- site of kinetochores
- repetitive SNA sequences- satellite DNA
4
Q
Hererochromatin vs Euchromatin
A
- Heterochromatins has a condensed structure and silenced genes
- Euchromatin has an open structure and active genes
5
Q
Describe the structure of chromatin.
A
- formed of DNA packaged histones
- histones have a positive charge, DNA negative
- 146 bp DNA wrapped around core of 8 histones= nucleosome
- further wrapping of nucleosomes
- form solenoid structure
6
Q
By what factor is DNA condensed by at metaphase?
A
10,000
7
Q
What is the purpose of packaging DNA?
A
- negatively charged DNA neutralised by positive charged histone proteins
- DNA takes up less space
- Inactive DNA can be folded into inaccessible locations until required
8
Q
What is colchine?
A
- a microtubule inhibitor
- it enriches the population of cells that are visible
9
Q
Metacentric
A
p length= q length
10
Q
Submetacentric
A
p length< q length
11
Q
acrocentric
A
p length «< q length
12
Q
What does FISH stand for?
A
Fluorescent in situ hybridisation
13
Q
What types of FISH probes are there?
A
- unique sequence probes
- centromeric probes (useful for determining chromosome number)
- telomeric probes (detecting subtelomeric rearrangements, often present in children wit unexplained mental retardation)
- whole chromosome probes (cocktail of probes, used with different dyes, spectral karyotype, detecting translocation and rearrangements)
14
Q
What is meiosis?
A
- cell division in germ cells
- diploid cells (in ovaries and testes) divide to form haploid cells)
- chromosomes are passed on as re-arranged (recombinant) copies which creates genetic diversity
15
Q
What is a defining event in sexual reproduction?
A
recombination between homologues