Sexual reproduction and Meiosis

• what happens during sexual reproduction?

  • mother and father produce gametes (sperm and egg cells)
  • gametes haploid - half chromosomes in normal cell (23 chromosomes = 23 haploid number)
  • fertilisation - male gamete fuses with female gamete forms zygote - zygote ends with full set of chromosomes
  • zygote undergoes mitosis and develops into embryo
  • embryo inherits features from both parents - received mix of chromosomes from mum and dad
  • fertilisation of gamete is random - produces genetic variation
• define sexual reproduction?

  • sexual reproduction involves the fusion of male and female gametes because there are 2 parents, offspring contains a mixture of their parent's genes
• how does meiosis take place (div 1)?

  • Before cell divides - duplicates the DNA - one arm of each x shaped chromosome is an exact copy of the other arm
  • chromosomes line up in pairs in centre of cell - one chromosome in each pair came from organism's mother and one from the father
  • pairs pulled apart - each new cell only has one copy of each chromosome - some of fathers and some of mothers chromosomes go into each new cell
  • Each new cell with a mix of the mothers and fathers chromosomes - creates genetic variation
• how does meiosis take place (div 2)

  • chromosomes line up again at centre of cell - arms of chromosomes pulled apart
  • 4 haploid gametes - each gamete only has a set of chromosomes - gametes are all genetically different