genetics

• Prokaryote

  1 chromosome
• Prokaryote DNA

  • Circular
  • Naked
  • Some have plasmids (extra loops)
• Eukaryote

  • Linear DNA molecule
  • Histone proteins
  • No plasmids
  • 2 or more chromosomes
• Genomes are the genetic info of an organism
• Chromatids

  • eukaryote are only visible during mitosis
  • in prophase they Condense and reach minimum length in metaphase
  • Sister chromatids
• homologous chromosomes

  • same genes in the same sequenc, They may not have the same alleles (different forms of a gene)
• Karyotypes are the number and type of chromosomes present in a cell or organism
• Karyograms show the chromosomes in homologous pairs of decreasing length to deduce sex and diagnose conditions
• diploid

  nucleus contains pairs of homologous chromosomes
• haploid

  I chromosome of each type- gametes like sperm and egg cell
• zygote

  2 haploid gametes fuse together to produce 1 diploid cell
• Zygote

  Has twice as many chromosomes as the gametes
• Meiosis

  Halves the number of chromosomes
• Diploid nucleus

  Divides twice to produce 4 haploid nuclei
• DNA replication


  Occurs before the first division so each chromosome consists of 2 sister chromatids
• Variation

  Gametes fuse together during fertilisation, the alleles from 2 different parents are brought together in the new individual
• Genetic variation

  • Random orientation of pairs of homologous chromosomes in metaphase
  • Crossing over during prophase 1
• Genotype

  The alleles possessed by an organism
• Phenotype

  The characteristics of an organism
• Homozygous

  Plants have 2 alleles of the gene that affects the character
• Heterozygous

  Plants have 2 different alleles of the gene that affects the character
• Cystic fibrosis is a recessive disease
• Huntington's disease is a dominant neurodegenerative disease
• Pedigree charts allow genotypes of some individuals to be deduced and can indicate whether a disease is dominant or recessive
• Individuals can be carriers of a recessive disease
• Sex-linkage

  Association of a characteristic with the sex of the individual because the controlling gene is located on a sex chromosome
• Sex-linkage is mostly due to genes on the X chromosome
• Blood groups

  • Group A
  • Group B
  • Group AB
  • Group O
• Co-dominance

  Joint effects on a heterozygous individual
• Multiple alleles


  More than two alleles of a gene
• Mutation

  Random changes to the base sequence of a genes, a source of genetic variation
• Sickle cell anemia

  Genetic disease caused by a single base substitution
• Mutagenic chemicals and high energy radiation increase the mutation rate
• alleles

  gene consists of a sequence of bases on a piece of DNA. different versions of the gene that have a small change on the bases
• A gene is a basic unit of inheritance that consists of a length of DNA and influences a specific characteristic
• Locus

  The position of a gene on homologous chromosomes
• A mutation in the HBB gene causes a single base substitution in the input coding for the 6th amino acid in the polypeptide
• Polymerase chain reaction

  Produces many copies of a DNA molecule
• Polymerase chain reaction


  1. heated to 95°C to Separate the 2 strands

  2. Reduce temperature to 53°C so primers bind to both strands next to the sequence that is copied

  3. Increase temperature to 73°C so Taq DNA polymerase replicates both strands, starting at primer, then producing 2 double-stranded copies of the original DNA
• Gel electrophoresis

  Method of separating mixtures of proteins or fragments of DNA, which are charged