Reproduction

• 2 types of cell division

  Mitosis

  Meiosis
• Meiosis is used in sexual reproduction
• Mitosis is used in asexual reproduction
• Gametes are sex cells
• Two gametes fuse to form a zygote
• In sexual reproduction

  2 parents needed

  Non-identical offspring

  cells divide by meiosis male and female gametes
• In Asexual reproduction

  Only 1 parent

  No gamete fusion

  Offspring are clones

  Cells divide by mitosis
• Gametes contain half of the number of chromosomes found in all body cells
• Asexual reproduction is faster and no mate is needed.
• The 4 genetically different gametes produced during sexual reproduction are called Haploid cells.
• An advantage of sexual reproduction is variation in the offspring, increasing the chances of a population being able to survive environmental change by natural selection.
• Strawberries and some fungi can reproduce both ways.
• The genome is the entire genetic material of an organism.
• Within a genome there are lots of different levels of organisation

  DNA

  Genes

  Chromosomes
• There are 23 pairs of chromosomes in the human body.
• Human genome project was in 2003.
• The genome project lead to an increased understanding of the causes of inherited disorders and in the identification of genes linked to different disorders.
• Genome sequencing helps us to identify and cure genetic diseases in the future.
• DNA is a polymer made up of 2 strands forming a double helix.
• A human body cell contains 46 chromosome pairs
• Protein Synthesis is howcour bodies make proteins
• The process of protein synthesis

  Template taken from DNA

  Template used

  Delivery of amino acids

  Unique structure created
• A mutation is a permanent change in the nucleotide sequence of DNA.
• Mutations can change the structure or shape of a protein.
• Mutations can give a undesirable change or survival advantage.
• Mutations are often disadvantageous but can bring benefits and are permanent.
• Alleles are different forms of the same gene for exp shirts are different but they are still shirts
• Alleles can be dominant ( BB or Bb) or recessive (bb)
• If 2 alleles are different we that that person is heterozygous
• If 2 alleles are the same we say that the person is homozygous
• Genotype refers to the combination of alleles an organism has
• A phenotype is an observed characteristic of an individual. Its determined by the genotype and the environment
• After the gametes have combined, the new cell divides by mitosis which increases the number of cells. As soon as the embryo reaches a threshold size, cells begin to differentiate.
• Some regions of DNA do not encode protein sequences. The term given to these sections is non-coding DNA.
• In most cases, a characteristic results from multiple genes interacting. However, sometimes, a single gene is responsible for a characteristic. such as red-green colour blindness.
• Monohybrid inheritance refers to the inheritance of one trait from one parent.
• The inheritance of certain alleles can result in the development of disorders, such as cystic fibrosis. Cystic fibrosis is a disorder of cell membranes, which can result in the build-up of thick, sticky mucus in the lungs and digestive system. It is caused by a recessive allele.