Mutations And Meiosis Flashcards
(10 cards)
1
Q
Gene mutations?
A
- Change in the base sequence of DNA
- Randomly occur during DNA replication - more likely if exposed to mutagenic agents
- Could result in either a base being deleted (deletion) or substituted for a different one (substitution)
2
Q
Substitution?
A
- Base changed for a different one
- May have no effect - new codon codes for same amino acid
3
Q
Deletion?
A
- Base being removed
- Results in frame shift - removal of one base changes all subsequent codons
4
Q
Chromosome mutations?
A
- Can arise spontaneously by chromosome non-disjunction during meiosis
- changes structure or number of chromosomes
- changes in whole set (polyploidy)
- changes in number (aneuploidy)
5
Q
Non-disjunction?
A
- when the chromosome or chromatids don’t split equally during anaphase
6
Q
Meiosis?
A
- produces daughter cells that are genetically different from each other
- involves two nuclear divisions and creates four haploid daughter cells from a single haploid parent cell
7
Q
Variations in meiosis?
A
- independent segregation of homologous chromosomes
- crossing over between homologous chromosomes
- both in meiosis 1 (first division)
8
Q
Independent segregation?
A
- in meiosis 1, homologous pairs of chromosomes line up opposite each other at the equator of the cell
- random which side of the equator chromosomes from each homologous pair lie
- pairs separated - each pair end up in daughter cell
- creates large number of chromosome combinations in daughter cell
9
Q
Crossing over?
A
- when homologous pairs line up at equator, chromatids can twist around each other
- puts tension on chromatids and causes breakage
- broken parts recombine with another chromatid which results in new combinations of alleles
10
Q
Meiosis Vs mitosis?
A
- meiosis - two nuclear divisions, haploid cell (one set of chromosomes), genetic variation
- mitosis - one nuclear division, diploid cells (two sets), creates genetically identical cells
