W1L2 - Cells, heredity and genes

• What is a cell?

  smallest unit of living matter

  • use matter from outside the cell to perform chemical reactions
  • all cells are the same - have plasma membranes and common organelles
  • but are different - 200 cell types, different functions sizes shapes, cell fo same type may respond differently
• universal features of cells?

  1. heredity (inheritance) – passing of physical or mental characteristics genetically from one generation to another
  2. all cells replicate DNA by template polymerisation – DNA replication
  3. protein synthesis (process in all cells that uses DNA to make proteins)

  • transcription – DNA segments used to synthesise RNA, mRNA makes protein
  • translation - mRNA directs synthesis of polymers of amino acids to form proteins
• Gene – segments of DNA sequence that codes for one protein or RNA molecule, DNA in the cell is called the genome
• genetics = study of genes

  genomics = study of genome
• alleles are:

  different copies of a gene
• 2 ways cells produce:

  1. Asexual – division of the cell to form two daughter cells, containing the same genetic information as the mother cell
  2. Sexual – fusion of 2 gametes to dorm another type of cell (zygote)
• • Humans reproduces sexually (germ cells – sperm and egg)
  • Most human cells reproduces asexually (somatic cells)
• life cycle of eukaryotes:

  A) zygote

  B) fusion

  C) diploid

  D) haploid

  
• Mendelian genetics:

  • studied inheritance by breeding pea plants
  • Concept of true breeding ( more or less no mixture of alleles) same f1 and f2 generation
  • Cross breeding - have heterozygous f1 generation and different f2 generation

  
• • Homozygous - alleles are identical (RR or rr)
  • Heterozygous - alleles are different (Rr)
  • need to know of these from a medical point as they can cause several genetic diseases, for example Huntington's disease is caused by a dominant allele and cystic fibrosis is caused by recessive alleles
• Codominance:

  • both alleles are expressed (brown cow x white cow = white cow with brown spots)
  • Partial dominance - both the alleles are expressed but they are not separately shown (e.g. white flower x red flower = pink flower)
  • ABO bloody groups - A and B are dominant when paired with O, when A and B are together they are codominant