AQA A Level Biology: Meiosis and Genetic Variation Flashcards
What is meiosis?
A type of cell division that produces four genetically different haploid cells from a diploid parent cell.
Where does meiosis occur in animals?
In the ovaries and testes to produce gametes.
Why is meiosis important?
It maintains the chromosome number and introduces genetic variation.
What happens in meiosis I?
Homologous chromosomes are separated, reducing the chromosome number by half.
What happens in meiosis II?
Sister chromatids are separated, producing four haploid cells.
What is crossing over and when does it occur?
The exchange of genetic material between homologous chromosomes during prophase I.
What is genetic recombination?
The production of new combinations of alleles due to crossing over during meiosis.
How does crossing over contribute to genetic recombination?
It exchanges sections of chromatids between homologous chromosomes, creating new allele combinations.
What is independent segregation?
The random alignment and separation of homologous chromosomes during metaphase I.
How does independent segregation contribute to genetic variation?
It results in different combinations of maternal and paternal chromosomes in the gametes.
What is the result of meiosis?
Four genetically unique haploid cells.
How many divisions occur in meiosis?
Two divisions: meiosis I and meiosis II.
What is a haploid cell?
A cell with half the chromosome number (n), such as gametes.
What is a diploid cell?
A cell with the full chromosome number (2n), such as body cells.
What is a homologous chromosome?
A pair of chromosomes, one from each parent, that have the same genes but may have different alleles.
What is a chiasma (plural: chiasmata)?
The point where homologous chromosomes exchange genetic material during crossing over.
What is the significance of crossing over and genetic recombination?
It increases genetic diversity by creating new allele combinations.
What is a gamete?
A haploid sex cell (sperm or egg) involved in fertilization.
What is fertilization?
The fusion of two gametes to form a diploid zygote.
What is nondisjunction?
The failure of chromosomes to separate properly during meiosis, leading to aneuploidy.
What is aneuploidy?
A condition where cells have an abnormal number of chromosomes.
How does meiosis differ from mitosis?
Meiosis produces four genetically different haploid cells, while mitosis produces two genetically identical diploid cells.
What is a zygote?
A diploid cell formed by the fusion of two gametes.
What is genetic variation?
Differences in the genetic makeup of individuals in a population, introduced by meiosis and fertilization.
How does meiosis contribute to genetic variation?
Through crossing over, independent segregation, and random fertilization.
What role does genetic recombination play in evolution?
It creates genetic diversity, which provides raw material for natural selection.
