inheritance

• asexual reproduction

  • one parent
  • genetically identical off spring
  • process of mitosis
• sexual reproduction

  • two organisms
  • genetically different offspring
  • gametes produced by meiosis
  • fertilisation - fusion of male and female gametes
• male gametes

  • sperm
  • pollen
• female gametes

  • egg cells
• advantages of sexual reproduction

  • variation in offspring - increases chance of survival if there is a change in the environment and some have survival advantage due to certain characteristics
  • selective breeding - speeds up natural selection and able to breed those with desirable characteristics
• asexual reproduction advantages

  • only need one parent - less energy and faster as yo do not need a mating partner
  • in favourable conditions lotsof identical offspring can be produced
• different sequences of bases = different amino acids = shape of protein = determine protein's function
• 4 different bases

  a - t

  c - g
• phosphate group and sugar molecule stay the same

  base changes
• dna is a polymer made of repeating units called nucleotides. it has two stands that twist in a double helix structure
• gene - small section of dna on a chromosome
• genome - entire genetic material of an organism
• organisms that use sexual and asexual reproduction:

  • Malarial parasites - parasite produces sexually in the mosquito and the mosquito carries the parasite onto the human. After biting, the parasite reproduces asexually in the human host
• allele - different version of a gene
• recessive allele - an allele that is expressed in the phenotype of an individual when there is two
• dominant allele - the allele that is expressed in the phenotype when the individual has one copy of that allele
• heterozygous - two different alleles
• homozygous - two of the same alleles
• monohybrid crosses - only one characteristic being studied
• genotype - expressed as an allele and has characteristics you cannot see
• phenotype - physical characteristics
• Cystic fibrosis

  • body produces thick sticky mucus in air passages and pancreas
  • carried on recessive allele
• polydactyly

  • born with extra fingers or toes
  • carried on dominant allele
• embryonic screening

  For:

  • stops people suffering
  • treating disorders cost government alot of money
  • laws to stop it going too far

  Against:

  • implies those with a genetic problem are 'undesirable'
  • everyone picks there most 'desirable' gene
  • screening is expensive
• organisms that reproduce asexually and sexually

  • Fungi - release spores and become new fungi when they land in suitable places. Spores reproduce sexually in response to an unfavourable change to avoid extinction and asexually for genetically identical offspring
  • plants - pollination to form seeds e.g strawberry plants produce runners so the stem grows away from parent plant or e.g daffodils grow from bulbs and divide of
• structure of DNA

  phosphate group, sugar molecule and base
• protein synthesis:

  mRNA, moves from the nucleus to the ribosomes

  Carrier molecules (tRNA) bring specific amino acids to add to the growing protein in the correct order.

  There are 20 different amino acids.
• 1. DNA contains genetic code proteins, cannot move out of the nucleus - too big.
  2. two strands pull apart, mRNA nucleotides match complementary base on the strand.
  3. mRNA nucleotides join together, creating mRNA strand. (template of original DNA)
  4. mRNA moves out of nucleus to cytoplasm and onto ribosomes.
  5. At ribosomes, bases on mRNA are read in threes to code for an amino acid (the first three bases code for one amino acid)
  6. corresponding amino acids are brought to the ribosomes by carrier molecules
  7. amino acids connect together - form a protein
  8. protein folds to form a unique 3D structure.
• mutations in sequences

  1. A base is inserted into the code - read in threes so changes the way it is read, it may change all the amino acids coded for after this insertion.
  2. A base is deleted from the code - they change the way it is read, it may change all the amino acids coded for after this deletion.
  3. A base is substituted - This only changes one amino acid in the sequence or it may not change the amino acid (as the new sequence can sometimes still code for the same amino acid)