Ara bio paper 2

• Mitosis


  Cell division where one cell is copied into two identical cells
• Gametes


  Cells where the chromosomes are not paired, e.g. sperm and egg cells
• Meiosis


  Cell division that produces non-identical gametes
• Meiosis takes place in flowering plants to produce pollen and egg cells
• Sexual reproduction


  Involves the fusion of male and female gametes, mixing genetic information
• Sexual reproduction results in variation in the offspring
• Asexual reproduction


  Involves only one parent, no mixing of genetic information, produces genetically identical offspring (clones)
• Asexual reproduction does not involve gametes or meiosis, only mitosis
• Asexual reproduction in plants


  • Forming tiny buds that drop off and grow into new plants
• Meiosis


  The process by which gametes (sperm and egg cells) are produced, with half the normal number of chromosomes
• Normal human cells


  • Contain 23 pairs of chromosomes
• Gametes (sperm and egg cells)

  • Contain 23 single chromosomes
• Meiosis


  1. Chromosomes are copied

  2. Cell divides into two

  3. Cells divide one more time forming gametes
• Meiosis produces four gametes from one original cell, and each gamete is genetically different
• Fertilization


  The joining of a male gamete (sperm) and a female gamete (egg) to form a new cell with the full number of chromosomes
• Meiosis


  Halves the number of chromosomes
• Fertilization


  Restores the full number of chromosomes
• Embryo


  The clump of identical cells that forms after fertilization, which then differentiates into different cell types as the organism develops
• You'll find plenty of questions on meiosis and fertilization in the revision workbook
• Sexual reproduction


  Offspring receive a mixture of genetic information from two parents
• Sexual reproduction


  • Produces variation in the offspring
  • Gives a species survival advantage by natural selection
  • Allows for selective breeding
• Asexual reproduction


  • Only one parent is needed
  • More efficient in time and energy than sexual reproduction
  • Allows an organism to produce many genetically identical offspring rapidly
• Asexual reproduction


  • Risky because all offspring are genetically identical and could all die if conditions become unfavourable
• Organisms that can use both sexual and asexual reproduction

  • Malaria parasite
  • Fungi
  • Flowering plants (e.g. strawberry)
  • Daffodils
• Malaria parasite reproduction


  1. Asexual reproduction in human host

  2. Sexual reproduction in mosquito vector
• Fungi reproduction


  1. Asexual reproduction by producing spores

  2. Sexual reproduction producing variation
• Strawberry plant reproduction


  1. Asexual reproduction by sending out runners

  2. Sexual reproduction to produce seeds
• Daffodil reproduction


  Asexual reproduction by bulb division
• Dominant allele


  An allele that will show in the phenotype even if there is only one copy present
• Recessive allele


  An allele that will only show in the phenotype if two copies are present, with no dominant allele present
• Homozygous


  Having two copies of the same allele
• Heterozygous


  Having two different alleles
• Genotype


  The alleles present in an organism
• Phenotype


  The characteristics caused by an organism's alleles
• Normal human cells contain 23 pairs of chromosomes
• Cystic fibrosis


  An inherited disorder of cell membranes
• One chromosome in each pair comes from the father, the other from the mother
• Allele


  A version of a gene
• Cystic fibrosis


  • Controlled by a single gene
  • Has two alleles
• Normal cell membrane function allele

  Dominant, symbol capital C