Biology chapter 3

• it is said to be silent mutation since the protein is synthesized so it passes unnoticed.
• nonsense mutation is a mutation results in a stop codon being read and the protein is not synthesized
• frameshift is when a nucleotide is added or deleted from the gene
• genetic polymorphism is is the variation of the alleles in a gene of a population
• genetic polymorphism is due to a mutation affecting the DNA sequence
• HLA is coded by 6 genes DP, DQ, DR, B, C, A located on chromosome 6
• HLA system in the body can distinguish between self and non self
• wild type allele is the allele that codes for the most common phenotype a population
• the origin of restriction enzyme is the bacteria
• A bacterium uses a restriction enzyme to defend itself against bacterial viruses called bacteriophages
• DNA gel electophoresis is a technique used to seperate the DNA fragments on a semi-solid gel
• The smaller the fragment, the faster it will migrate through the gel.
• The electrophoresis process involves applying an electric field across the gel which causes negatively charged molecules (like DNA) to move towards the positive end of the gel.
• The larger the fragment, the slower it will migrate through the gel.
• RFLPs are the differences among individuals in the lengths of DNA fragments cut by restriction enzyme
• RFLP can be used in order to observe whether an individual carries a mutant gene for a disease
• FISH technique is used to locate a specific DNA sequence or a gene on a chromosome
• denaturation of DNA permits to seperate the two strands of the DNA
• hybridization permits the labeled DNA probe to bind on its complementary sequence in the DNA molecule
• 1. Labelling of the DNA probe with fluorescent dye.
  2. Denaturation of the probe and DNA molecule.
  3. Hybridization of DNA probe with its complementary sequence.
  4. Washing to eleminate unbound probes.
  5. Visualization of the gene of the DNA sequence under fluorescent microscope because of the fluorescent dye attached to it.
• A genetic map is a map showing the location of genes on a chromosome.
• Jeffreys technique

  1. cut the DNA molecule into fragments with restriction enzymes
  2. seperation of DNA fragments by electrophoresis.
  3. Transfer these fragments on a nylon membrane(blotting).
  4. Denaturation of these fragments and incubation with radioactive probes.
  5. Hybridization with their complementary sequence.
  6. washing then autoradiography that gives the fingerprint.
• The aim of gene therapy is to cure a disease or help the body better fight disease
• Mutation in the gene leads to the modification in the amino acid sequence that will change the 3d structure of the protein making it non-functional, The role of that protein will not be ensured thus a disease appear.
• A mono-locus probe is specific for a given gene.
• A multi-locus probe is specific for a repetitive sequence.
• Repetitive sequence is a nucleotide sequence that occurs very frequently throughout the genome or present in multiple copies in the genome.