DSA 3: Nucleic Acids, Genes & Human Genome

Question 1

Gene components

Answer 1

Genes are contiguous structures of DNA that have a minimum of a start and stop location, a promoter (RNA pol binding site), and is associated with regulation regions of the chromosome (operator, enhancer, etc). Consensus sequences are mostly conserved areas in the promoter that are recognized by σ subunit of RNA pol in prokaryotes; used for transcriptional specificity.

Question 2

exon shuffling

Answer 2

moving exons from one gene to another gene to get a new gene product; long term, evolutionary process)

Question 3

Helix-turn-helix proteins

Answer 3

two alpha helices separated by beta turn; recognition helix fits in major groove eg homeodomain proteins

Question 4

zinc finger proteins

Answer 4

contain zinc bound to Cys and His residues; used in receptors for steroid and thyroid hormones

Question 5

leucine zipper proteins

Answer 5

two alpha helices; one with DNA binding basic residues and one with regular leucine residues for dimerization. eg C/EBP (gene activator in liver) and c-myc, c-fos, and c-jun (growth regulators)

Question 6

Helix-loop-helix domain proteins

Answer 6

DNA-binding alpha helix and two dimerization helices separated by non-helical loop. eg myo D (muscle differentiation)

Question 7

Huntington’s Disease

Answer 7

Some microsatellite DNA occurs in regulatory sequences. In Huntington’s disease, a 3 NT CAG repeat normally repeated 6-34 times (codes for polyglutamine tract in protein huntingtin) is repeated >36 times, causing protein to form clusters that kill cells in the basal ganglia. The greater the expansion, the easier the onset of disease