VARIATION Flashcards
why is meiosis important in sexual reproduction?
meiosis is important in sexual reproduction because it ensures genetic variation between offspring
what is the purpose of meiosis?
to produce gametes (sperm and eggs) for sexual reproduction, halving the chromosome number so when fertilisation occurs the offspring can have the right number of chromosomes.
what needs to happen before meiosis can occur?
the DNA in the cell must replicate itself.
This ensures there are two identical copies of each chromosome in the cell,
before crossing over occurs.
what happens during crossing over?
sections of DNA are swapped between the homologous chromosomes , then the two copies of the maternal chromosome will swap sections of the DNA with the two copies of the paternal chromosome, creating new chromosomes with dif combos of alleles.
which chromosomes can cross over?
the homologous chromosomes
how does crossing over increases the genetic variation?
sections of the DNA within maternal and
paternal chromosomes are switched over to create new combinations of
chromosomes. This then creates new combinations of alleles, contributing to
genetic variation within the population
what happens during independent assortment in meiosis?
homologous chromosomes line up and are randomly separated into gametes, creating dif combos of alleles for genetic variation
how does independent assortment increases the genetic variation in the offspring?
by randomly mixing maternal and paternal chromosomes into gametes - creates dif combos of alleles
what is independent assortment?
When homologous chromosomes line up at the centre of the cell, they do so independently of all of the other pairs. This means that it is random which combination of chromosomes ends up in which cell
what is homologous chromosomes?
Pairs of maternal and paternal chromosomes
what are sister chromatids?
Two identical copies of a chromosome, created by DNA replication. The sister chromatids are stuck together by a cellular ‘glue’.
what is segregation in biology?
The chromatids that the parent has are split up randomly, so that each gamete ends up with a single allele for each trait. Which alleles it ends up with are down to chance.
define what a mutation is.
A change in the base sequence of DNA
how do mutations affect the gene pool of a population?
by adding new alleles - increasing genetic variation, beneficial mutations can be passed on and help population adapt while other mutations may be eliminated
how are new alleles produced in the gene pool?
New alleles can be produced in the gene pool through mutations occurring in
the gametes, after the process of meiosis
