The Eukaryotic Genome

Cards (39)

  • The human genome has 22 pairs of autosomes and 1 pair of sex chromosomes
  • The X chromosome is bigger than the Y chromosome
  • Eukaryotes have a huge genome, but only a small proportion of it codes for proteins
  • centromeres and telomeres have highly repetitive sequences
  • We can look at the variable number tandem repeats in a repetitive sequence through PCR
  • Most protein-coding genes only have one copy
  • Gene families come from duplication of a single gene
  • Gene families have similar sequence and function
  • the globin family is a gene family
  • DNA is wound around proteins called histones to form nucleosomes
  • Histone tails have lots of arginine and lysine, which are positively charged at physiological pH
  • histones can form electrostatic interactions with the negative phosphate backbone of DNA, independent of its sequence
  • Histones shield the negative charges of the phosphates, allowing DNA to bend and wrap
  • The ends of chromosomes contain telomeres to protect the information at the ends
  • Histone restricts transcription
  • The centromere is the region where the sister chromatids attach
  • The p arm is the short arm of the chromosome
  • The q arm is the long arm of the chromosome
  • Chromatin is the complex of DNA and proteins
  • Condensed DNA is harder for proteins such as transcription factors to access
  • Heterochromatin: More condensed, so less transcription is occurring
  • Euchromatin: Less condensed, so more transcription is occurring
  • DNA isn't always packed tightly into chromosomes
  • Modifying histone tails can remove the charge, enabling proteins to bind
  • Some proteins can recognise modifications and interact with histones
  • HATs acetylate lysine to remove the positive charge of the histone tail
  • HAT = histone acetyltransferase
  • Acetylation of histones causes DNA to be wound less tightly, meaning that is more accessible to initiate transcription
  • Some proteins can also bind to acetylated lysine
  • HDACs reverse the acetylation of histone tails, reducing transcription
  • HDAC = histone deacetylases
  • HMTs methylate lysine or arginine on the histone tail
  • HMT = histone methyltransferases
  • Some proteins can bind to these methylated residues
  • Histone demethylases remove the methyl group from the histone tail
  • In specific cells, regions of the chromosome that aren't required will be packaged tightly and not accessed
  • The packaging of chromosomes affects the expression of proteins
  • Cells only express proteins relevant to their functions
  • Induced pluripotent stem cells
    1. Modify histones
    2. Introduce transcription factors
    3. Expression of genes required for pluripotency