Genetics

• Meiosis

  • 4 non-identical offspring
  • used in sexual reproduction
• Mitosis

  • 2 identical offspring
  • used in assexual reproduction
• A gamete is a sex cell, eg. a sperm or an egg
• Meiosis

  1. Each cell contains a pair of chromosomes, which replicates and then splits.
  2. There are now 2 identical cells, which split again
  3. This creates 4 genetically different gametes that each have half the amount of chromosomes as the parent cell.
  4. During sexual reproduction, the male gamete fertilises the female gamete, and the fertilised cell now has the normal number of chromosomes (46)
  5. This new cell divides by mitosis, before the embryo's (new cell) cells begins to differentiate.
• Haploid cells contain only one set of chromosomes (23)
• Diploid cells contain 2 sets of chromosomes (46)
• Sexual reproduction

  • 2 parents
  • Meiosis
  • Non-identical offspring
• Assexual reproduction

  • 1 parent
  • Mitosis
  • Identical offspring
• Benefits of sexual reproduction

  • Variation = more likely to survive (adaptations)
  • artificial selection
• Benefits of asexual reproduction

  • Faster
  • No mate required
  • Lots of offspring
• A gene is a small section of DNA. They code for a specific sequence of amino acids, which combine to give a protein.
• Chromosomes are long strands of DNA
• Genome is all your genetic information.
• A nucleotide is made up of a sugar, a phosphate and a base.

  
• DNA is made up of Adenine, Thymine, Guanine and Cytosine
• Protein synthesis

  1. Each amino acid is coded for by a specific sequence of 3 bases (a Codon)
  2. The order of the bases determines the order of the combining amino acids
  3. To change the protein made, alter the base sequence
• Protein synthesis step by step

  1. A template is taken from the DNA and leaves the nucleus
  2. This template is used to guide protein synthesis on ribosomes located in the cytoplasm
  3. Specific amino acids are brought by carrier molecules to the protein chain
  4. Once added, the protein folds up to form a unique structure, which is essential for its function.
• Heterozygous = 2 different alleles (Aa)
• Homozygous = 2 of the same allele (AA) or (aa)
• Mutations are changes to the genome.

  They can be both beneficial and harmful.
• Males = XY - The Y characteristic causes male characteristics
• Females = XX - The lack of a Y characteristic causes female characteristic
• Genotype - Characteristics based of your genes

  Eg. Male or Female
• Phenotype - Physical characteristics

  Eg. Brown or blue eyes