MEIOSIS & GENETIC VARIATION

Genetic diversity

number of different alleles of genes in a population

IMPORTANCE of Genetic diversity

• Basis of:

  • biodiversity

  • natural selection

• Allows:

  • some individuals to have selective advantage

• Ensures:

  • survival of species

RANDOM FERTILISATION

Any sperm can fuse with any egg → random combination of alleles

Random fertilisation significantly increases genetic variation

KEY MECHANISM of RANDOM FERTILISATION

• Millions of sperm available:

  • ~80–300 million per ejaculation

• Thousands of eggs across lifetime

RESULT of RANDOM FERTILISATION

• Each zygote has:

  • unique genetic combination

MEIOSIS Definition

nuclear division that produces 4 haploid (n) cells from one diploid (2n) cell

MEIOSIS PURPOSE

• Produce gametes

• Halve chromosome number:

  • so fertilisation restores diploid state

MITOSIS comparison

• Produces:

  • 2 identical diploid cells

• No variation

• Used for:

  • growth & repair

MEIOSIS comaprison

• Produces:

  • 4 non-identical haploid cells

• Generates variation

HOMOLOGOUS CHROMOSOMES

Pair of chromosomes:

• one maternal

• one paternal

• Same genes

• Different alleles possible

SISTER CHROMATIDS

• Identical copies

• Joined at centromere