Variation and Inhertiance

• Meiosis

  the process by which gametes are made - genetically different from parent cells
• what happens into meiosis

  chromosomes in diploid cell (23 pairs) copied > similar chromosomes pair up and genes swapped between them > cell divides to produce two diploid cells > these divide again to produce 4 haploid cells ( gametes)
• when does asexual reproduction happens

  by mitosis which means that 'daughter' / 'child' offspring's cells will be identical (cloned)
• most animals reproduce sexually while plants can reproduce by both sexual (pollen and egg) and asexual reproduction
• advantage of sexual

  offspring can become better adapted to environment
• asexual advantage

  only one organism needed to reproduce
• genome

  the entire genetic code in an organism
• DNA

  double helix polymer - stores genetic code
• gene

  portion of DNA that codes for a protein
• What does gene do

  mapping these allows us to identify causes of disorders
• Genotype


  an organism's specific genetic code
• Phenotype

  how this code is expressed in physical characteristics
• Alleles

  different versions of the same gene
• Dominant alleles

  e.g. 'B' are expressed even when genotype contains a recessive allele e.g. 'b'
• there must be no dominant allele in order for a recessive allele to be expressed in the phenotype
• BB and bb are Homozygous alleles.
• Bb is Heterozygous
• Polydactyly is caused by a dominant allele
• Cystic Fibrosis is due to a recessive one
• what is polydactyly

  when you have extra fingers or toes
• females have XX chromosomes
• male have XY chromosomes
• variation

  in offspring is a result of both genetic and environmental factor
• Darwin's Theory of Evolution

  random mutations results in variation

  some organisms better adapted to environment

  these compete ( 'survival of the fittest')

  those better adapted are more likely to survive; over time these desirable characteristics are more pronounced.
• Lamarck's Theory of Evolution

  mutations / adaptions are a result of environment affecting characteristic inherited by offspring: not random
• Antibiotic - Resistant Bacteria

  is used a s evidence for Darwinian evolution: If not all bacteria killed must resistant will reproduce. This is why you must complete the full course of antibiotics.
• species

  organisms are considered to be of the same species if they can produce fertile offspring.
• Selective Breeding

  Breeding organism that have desired characteristics to produce offspring in which they are more pronounced.
• examples of genetic engineering

  insulin - producing bacteria

  creating GM ( Genetically modified) crops e.g. golden rice which produces Vitamin A

  disease - resistant crops
• progress of Genetic Engineering

  1. desired gene is cut from another organism's DNA using enzyme.
  2. Gene inserted into a vector e.g. bacteria plasmid or virus
  3. Vector inserts gene into cells of another organism early development
  4. organism develops with desired characteristic
• fossils that look like bones are actually bones tht have been replaced by minerals
• some fossils can still have soft organic tissue if the conditions for decay are not present
• footprints that have hardened in mud are considered fossils as are other traces of organism left behind
• what is the name of a change of DNA

  mutation