Meiosis, Gametes, and Genetic Variation
Why Meiosis Matters
Meiosis Overview
Meiosis produces haploid gametes from diploid germ cells. It includes one round of DNA replication followed by two cell divisions, meiosis I and meiosis II.
Sources of Variation
Genetic variation arises from crossing over, independent assortment, and random fertilization. Crossing over occurs when homologous chromosomes exchange segments during prophase I.
Meiotic Events
Why Crossing Over Is Powerful
Crossing over creates new allele combinations on the same chromosome, increasing diversity beyond simple assortment.
At which stage do homologous chromosomes separate?
Homologous chromosomes separate during anaphase I.
Correct answer: Anaphase I
Why does meiosis reduce chromosome number by half?
This ensures fertilization restores the diploid number.
Correct answer: Because one DNA replication is followed by two divisions, producing haploid gametes.
Which process directly creates new combinations of alleles within a chromosome?
Crossing over exchanges DNA segments between homologous chromosomes.
Correct answer: Crossing over
Link to Inheritance
The chromosome behavior of meiosis explains why children resemble parents yet are not identical. It also explains why some traits travel together when genes are linked.
What is the difference between homologous chromosomes and sister chromatids?
They are distinct structures with different inheritance roles.
Correct answer: Homologous chromosomes are a maternal and paternal pair with the same genes; sister chromatids are identical copies of one chromosome.