Human Genome Project

Question 1

Procedure

Answer 1

• enzymes split chromosomes
• clone to have unlimited supply
• exposed to chemical markers that uniquely label specific loci - not nucleotide bases – but loci which are composed of hundreds/thousands of nucleotide bases
• placed in a jell
• jell forced through a very small tube
• as going through end of tube exposed to a special light
• chemical markers show up differently and are recorded in a computer
• patterns of markers were examined to identify identical sequences which were overlapping portions of the chromosome
• loci have been identified – now attempting to identify sequence of nucleotide bases for each

Question 2

Findings of HGP

Answer 2

• The human genome contains 3.1647 billion chemical nucleotide bases (A, C, T, and G).
• The average gene consists of 3000 bases, but sizes vary greatly, with the largest known human gene being dystrophin at 2.4 million bases.
• The total number of genes is estimated at 20,000, much lower than previous estimates of 80,000 to 140,000 that had been based on extrapolations from gene-rich areas as opposed to a composite of gene-rich
  i. 1% of genes code for proteins – i.e. structural genes
• Almost all (99.9%) nucleotide bases are exactly the same in all people.
• The functions are unknown for many discovered genes.
• Scientists have identified about 1.4 million locations where single-base DNA differences occur in humans called Single Nucleotide Polymorphism (SNPs).

Question 3

3. New understandings: Epigenetic factors that influence genetic expression

Answer 3

• Nongene DNA
  a. genes make up about only 1% of human genome
  b. Rest are nongene DNA previously thought to be inactive
  c. Now known to exert control over nearby genes
• Small RNA molecules
  a. Regulate gene expression
  b. Variety of types of small RNA perform different functions
• DNA methylation and Histone remodeling
• RNA editing
  a. Small RNA and other proteins cleave or splice mRNA to form new sequence of bases
• DNA methylation and Histone remodeling
  a. Can be induced by experience: neural activity, hormonal change
  b. Can be induced by experience: neural activity, hormonal change

Question 4

4. Now clear that genetic influences include:

Answer 4

• Not only structural genes
• Interaction of many structural genes
• Influence of epigenetic factors
• Developmental timing of expression of particular genes in specific brain structures