Meiosis And Sex Flashcards
Is meiosis good?
It’s inefficient and counterintuitive
What happens during meiosis? (3)
Has two rounds
Halves number of chromosomes
Crossing over genes align so they’re not in the same plane etc which causes variation.
Why do we reproduce sexually?
Beneficial mutations and removes deleterious mutations, whereas asexual reproduction doesn’t.
What three things is sex a response to?
Parasite (or host)
Competitor species
Abiotic environment
What is Mendels first law of hereditary/ principle of segregation?
The alleles of a given locus segregate into separate gametes
What causes unequal crossing over?
Repetitive elements can align recombinantly (DNA broken and recombined to produce new combinations of alleles).
Why is unequal crossing over bad?
It can result in mutations (deletion and duplication) which are usually lethal.
Sometimes they allow divergence and create complex phenotypes however.
What are the two types of interspersed nuclear elements?
Long and short
What is exon shuffling?
It forms new genes by copying themselves as well as neighbouring DNA by SINE mobilisation. It can then add it to other genomes.
Define chiasmata
The point of contact between two non-sister chromatids of homologous chromosomes.
(Where crossing over occurs)
Define crossing over
Genetic recombination between two non-sister chromatids at chiasmata
How does independent alignment come about?
→ Terminal chiasma holds them together.
→ Microtubules attack to homologue
→ Homologues aligned randomly
→ Orientation on spindle = random
