Elements required for chromosomal maintenance

Question 1

What are centromeres?

Answer 1

Specialised chromosomal regions where kinetochores assemble and direct equal segregation of chromosomes during mitosis and meiosis

Question 2

What is the mitotic spindle?

Answer 2

Cytoskeletal structure made of microtubules (polymers of α and β tubulin subunits)
-shorten during chromosome separation

Question 3

What are kinetochores?

Answer 3

Protein complexes which recognise centromeric chromatin, bind to the centromere and to microtubules to allow segregation of chromosomes
-have a conserved Ndc80 complex, which has two domains which associate with the microtubule and one which associates with other proteins in the kinetochore

Question 4

What is a nucleosome?

Answer 4

DNA wrapped around 8 histones (2 of H2A, H2B, H3 and H4)
-histones can be post-translationally modified to change how open chromatin is (alter expression)

Question 5

What is the structure of chromatin like at centromeres in yeast?

Answer 5

Point centromere
-v. short centromere (120bp)
-containing 3 regions, the central of which is very A/T-rich

Question 6

What is the structure of chromatin like at centromeres in humans?

Answer 6

Regional chromosome
-CENP-A replaces H3
-100s/1000s kbs
-alphoid satellite DNA
-A/T-rich repetitive seqs in tandem arrays

Question 7

What is the structure of chromatin like at centromeres in C.elegans?

Answer 7

Holocentric chromosome
-whole genome is chromosome
-CenH3 histones across whole chromosome (homologues to CENP-A)