Meiosis and Genetic Variation

Flashcards by , created about 6 years ago

AS Biology2 (DNA and Meiosis) Flashcards on Meiosis and Genetic Variation, created by sammi_taylor01 on 05/29/2013.

Created by sammi_taylor01 about 6 years ago
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Question Answer
What happens during: 1) meiosis one? 2) meiosis two? 1- The parent cell separates into two homologous chromosomes in different cells. 2- The chromatids move apart so four cells are formed.
In which two ways does meiosis bring about genetic variation between offspring? 1- recombination of homologous chromosomes by crossing over 2- independent segregation of homologous chromosomes
Describe the independent segregation of chromosomes. Each chromosome lines up next to its homologous partner (randomly arranged. One chromatid from each chromosome then will pass into the daughter cell.
What is the same in each member of a pair of homologous chromosomes? They have the exact same genes and therefore determine the same characteristics.
How does variation occur in genetic combinations? The haploid gametes fuse in fertilisation to become the diploid state. Each gamete has a different genetic make up and the random fusion therefore produces variety in offspring.
What happens in genetic recombination by crossing over? The chromatids of each pair become twisted round one another, tensions are created and portions of the chromatid breaks off, they rejoin with the chromatids of its homologous partner
What is produced from crossing over? new genetic combinations
What is a: 1) gene? 2) locus? 3) allele? 1) section of DNA that codes for a polypeptide 2) the position of a gene on a chromosome or DNA molecule 3) different forms of a particular gene
What does meiosis produce? Four daughter nuclei with half the genetic material (chromosomes) as the parent cell. Also known as haploid cells.
When haploid cells fuse at fertilisation, what occurs? The diploid number of chromosomes is restored.
How many nuclear divisions does meiosis have and when do they occur? Two nuclear divisions which normally occur one after the other.