topic 4.2 Flashcards
(12 cards)
apart from mutation describe another way a genetic mutation in a species is arrived
- randomised fertilisation, new maternal and paternal combination (independent segregation).
why would offspring be sterile in meiosis?
- too many chromosomes meaning the homologous pairs can’t form -> can’t separate (non dysfunction) and then no meiosis can happen.
Define ‘gene mutation’ and explain how a gene mutation can have:
* no effect on an individual
* a positive effect on an individual.
- change in dna base sequence.
- results in new allele being formed
- genetic code is degenerate (so aa sequence may not change)
- positive effect if change in amino acid sequence positively effects eg: survival
what results in the movement of chromosomes
- independent segregation - it is randomly separated, chromosomes crossing over.
amino acid, trna molecule
se all the information and your knowledge of protein structure to suggest reasons for the differences between the effects that occur due to changes
- active site of amino acid change due to (disulphide) bonds changing
- different hydrogen bonding changing tertiary structure giving diff properties
draw structure of meiosis w chromosomes and values
- 2 chromosome, copy to 4, then divide to 2 each, then 1 each 4 cells
(b) Explain how the chromosome number is halved during meiosis
join via homologous pairs -. 1 of each goes to each cell
Describe the process of crossing over and explain how it increases genetic diversity.
crossing over occurs when homologous chromosomes pair and twist - alleles are exchanged, forming diff combination alleles in each of the 4 daughter cells.
describe how extra chromosomes are formed
in meiosis, homologous pair of chromosomes don’t separate (non - disjunction mutation) , one cell has too many chromosomes and it stays in that cell.
how does a mutation in a body cell result in all gamete cells having the same mutation
- mutation In the cell that forms the gametes
gametes are all derived from same zygote made in mitosis.
