Cell Division, Diversity and Organisation - Chromosomes and Cell Cycle Flashcards
1
Q
how is each chromatid held together
A
by the centromere
2
Q
describe chromosomes during interphase
A
each DNA molecule makes a copy of itself
chromosomes are then composed of two identical chromatids
3
Q
what are homologous pairs
A
one of each pair come from the father and from the mother (same genes, but possibly different alleles)
4
Q
what are autosomes
A
the remaining chromosomes that aren’t sex chromosomes
5
Q
how many sets of chromosomes to gametes have
A
one (haploid)
6
Q
how many sets of chromosomes do body cells have
A
two (diploid)
7
Q
what are the phases of the cell cycle
A
interphase (G1, S, G2)
prophase
metaphase
anaphase
telophase
8
Q
describe interphase
A
- DNA is uncoiled and not visible during interphase
- DNA replication occurs (S) and DNA is checked for errors
- centrioles replicate (animal calls only) (G1 and G2)
- cell increases in size (more cytoplasm)
- new organelles produced
- cell is very active and large amounts of ATP required
- protein synthesis occurs
9
Q
describe prophase
A
- chromosomes become visible as they shorten and thicken
- centrioles move to opposite ends (poles) of the cell
- microtubules develop from pole to pole forming spindle fibres
- nucleolus disappears (forms part of several chromosomes)
- nuclear envelope breaks down
10
Q
describe metaphase
A
- centrioles reach the two poles
- chromosomes line up at the equator of the cell
- the spindle fibres attach to the centromere on each chromosome and pull the chromosomes to arrange them along the equator of the cell
11
Q
describe anaphase
A
- the centromeres divide
- the spindle fibres contract and shorten, pulling the chromatids apart, centromere leading, towards opposite ends of the cell
12
Q
describe telophase
A
- the chromatids have now reached the poles and can be regarded as distinct chromosomes
- the nuclear envelope reforms around each group of chromosomes
- the nucleolus reappears
- the chromosomes uncoil to form chromatin
