CB3 and CB4

• Which organs do meiosis take place in?


  Plants:

  Flowers, male- anther, female-ovary

  Animals
• Meiosis

  1. Begins with a single cell
  2. The cell will make a copy of each chromosome
  3. There are two divisions
  4. This makes the gametes, haploid cells
• Recombination


  Before the first division of chromosomes may recombine, which provides each daughter cell with a unique set of genes
• What is a chromosome made up of?


  -A long molecule of tightly coiled DNA

  -Coming as identical homologous pairs
• Genes


  -Sections of DNA

  -Genes code for specific characteristics e.g. eye colour

  -Genes are inherited by parents

  -They come in different forms called alleles
• DNA molecule


  Made of two strands joined by base pairs in the shape of a double helix
• Structure of DNA


  -DNA is a polymer (a repeating unit)

  -This unit is a nucleotide
• Nucleotide


  Made of:

  -Phosphate group

  -Cytosine

  -Nitrogenous base

  -Sugar

  -Backbone
• Rungs of DNA


  -Made from pairs of bases.

  -Bases carry the genetic information in DNA
• 4 types of bases


  Create a long sequence carrying instructions to make proteins

  1. Adenine
  2. Cytosine
  3. Guanine
  4. Thymine
• Rules for rungs

  • A and T
  • C and G
• Different versions of alleles


  -The chromosomes in a matching pair contain the same type of genes that code for the same characteristics
• Alleles


  Different versions of a gene, that code for different versions of a characteristics
• Homozygous


  If the matching pair are the same
• Heterozygous


  If the alleles in matching pair are different
• Dominant alleles


  Dominant alleles will always be expressed
• Representing alleles


  -Dominant alleles are represented with a capital letter

  -Recessive alleles are represented with the corresponding smaller letter
• Genotypes vs Phenotype


  Genotype-The allele pair for each characteristic

  Phenotype- The physical expression of an allele
• Cystic fibrosis


  -Inherited condition

  -Lungs+ digestive system clogged with thick mucus

  -To get CF each parent must either have CF or be a carrier of the CFTR gene mutation
• Monohybrid inheritance


  -Characterises that are determined by a single gene
• Mutation


  when something is different from the way its supposed to be
• The Human Genome Project


  -Aim of determining the base pairs that make up human DNA

  -Then mapping, identifying and sequencing these genes
• Variation


  Differences between organisms
• Inherited variation


  Differences between organism passed to offspring by their parents in reproduction
• Environmental variation


  Differences between organism by environmental factors

  ~Called acquired characteristics
• Environmental factors


  Things in the environment that can change an organism
• Continuous variation 


  Variations between individuals of a population in a trait where differences are slight e.g. height
• Discontinuous variation 


  Where individuals fall into a number of distinct classes e.g. blood group
• Theory of evolution 


  By natural selection - a gradual process where the characteristics of a species change over time
• Evidence of human evolution


  -Fossils
• Examples of fossils


  ARDI

  -4.4 million years ago

  -Leg bones shows she walked up-right

  -Big toes showed she climbed trees
• Examples of fossils


  LUCY

  -3.2 million years ago

  -Shape of hips/legs show she waked up-right

  -Strong arms for climbing trees
• Examples of fossils


  LEAKEYS

  -Found Homo erectus

  -Found in 1960

  -Feet for walking upright
• Tools


  -The complexity and variety of tools helps to tell us how evolved the species were
• Sediment


  Know how old the tools are by dating the layers of sediment
• How did evolution change us?


  -Arms became shorter

  -Increased forehead

  -Skull size increased
• Genetic variation


  Individuals in a population show differences due to mutations
• Natural selection


  Individuals that have advantageous alleles are better adapted therefore more likely to survive and reproduce
• Antibiotic resistance


  Where the bacteria are no longer killed by an antibiotic
• Flow chart to show antibiotic resistance

  1. Mutation caused by one bacterium to become resistant
  2. The bacteria survives as it is resistant
  3. It reproduces or multiplies
  4. All inherit resistance