Meiosis purpose

Question 1

Gametes

Answer 1

• Normal cells have 2 chromosomes of each type so they are DIPLOID.
• In sexual reproduction 2 gametes fuse to produce a fertilised egg (zygote).
• Zygote is the origin of all cells that an organism develops.
• Gametes are HAPLOID as they contain half the standard no. of chromosomes.
• Gametes are produced by meiosis as 4 daughter cells are made.
• Meiosis is known as reduction division.

Question 2

Homologous chromosomes

Answer 2

• Each characteristic of an organism is coded for by 2 copies of each gene.
• Each nucleus contains a pair of genes for each characteristic.
• So they have 2 full sets of genes.
• Therefore each nucleus contains matching sets of chromosomes called homologous chromosomes.
• Each chromosome in a homologous pair has the same genes at the same position of chromosome.

Question 3

What are alleles?

Answer 3

Different versions of the same gene.

Different alleles of a gene will all have the same locus.

Question 4

Crossing over of chromatids

Answer 4

• During prophase 1, homologous pairs of chromosomes come together and pair up.
• Chromatids twist around each other and bits of chromatids swap over.
• Chromatids still contain same genes but different combo of alleles.

Question 5

Independent assortment

Answer 5

• When homologous pairs line up in metaphase 1 and are separated in anaphase 1, it’s completely random which chromosome from each pair ends up in which daughter cell.
• So the 4 daughter cells produced have completely different combinations of maternal and paternal chromosomes.