Chapter 6

• Chromosomes


  Made up of DNA
• DNA


  Made up of genes
• Polymer


  2 or more molecules
• DNA is a polymer
• Mitochondrial DNA


  • Small and circular
• Human genome enables us to know cause of disease, treatment of disease and migration patterns
• Cystic fibrosis


  An inherited condition that causes sticky mucus to build up in the lungs and digestive system
• Allele


  Different version of a gene
• Genotype


  The alleles an individual has
• Homozygous


  Both alleles are the same
• Heterozygous


  One dominant and one recessive allele
• Phenotype


  The alleles that are expressed (physical appearance)
• Recessive genes only exceed in diploid cells
• Meiosis


  1. Make gametes (sex cells)

  2. Sperm and egg
• 46 chromosomes (23 each)
• Diploid parent cells


  • 2 (mitosis makes diploid cells)
• Haploid cells


  • Half the number of chromosomes
• 54 daughter cells at the end of meiosis
• Homologous chromosomes


  Chromosomes that carry the same genes in the same sequence and position
• Interphase before meiosis


  1. Chromosomes thicken and match up

  2. Crossing over to exchange genetic info
• Meiosis has 2 rounds of division, mitosis has 1
• Meiosis DNA duplicates and then divides to split each homologous pair
• Asexual reproduction doesn't involve sex cells or fertilisation
• Asexual reproduction only requires one parent
• Asexual reproduction results in genetically identical offspring (clones)
• Genes exist in different versions called alleles
• Alleles can be dominant or recessive
• Homozygous individuals have two of the same allele
• Heterozygous individuals have two different alleles
• Most characteristics are controlled by a single gene
• Gamete formation


  Meiosis makes gametes (sex cells)
• Pollination


  1. Pollen lands on stigma

  2. Bees and birds are pollinators
• Fruit


  Ovary with seeds (unfertilised ovules)
• Fertilisation


  1. Zygote

  2. Embryo

  3. Fetus

  4. Baby
• Mitosis is for growth and repair
• Gametes show variation
• Asexual reproduction has no sex cells and no fertilisation
• Mitosis is used for asexual reproduction
• Asexual reproduction has no variation