Week 4 Flashcards
Why study DNA?
1) Essential for inheritance
2) Codes for proteins
3) Instructions for life processes
Why is DNA important?
1) Study genetics causes of disease
2) Design of gene therapies
3) Develop drugs
4) Forensic science
5) Genomic sequencing
6) Detect pathogens
7) Determine paternity
Human genome divided into:
# DNA molecules
# autosomes
# sex chromosomes
46 DNA molecules
22 autosomal pairs
2 sex chromosomes
DNA contains how many bases?
6 billion
DNA contains how many base pairs?
3 billion
How long would DNA be if unwound?
2 m long
Composition of histones
2 pairs H2A, H2B, H3, and H4
H1 resides outside as lock for DNA coiling around histone complex
Nucleosome
Histone complex with DNA wrapped 2.5 times around it; no H1 protein attached at this point
Polynucleosome
Histone complex with DNA wrapped 2.5 times around it; H1 protein attached and is tightly compacted on itself
H1 histone protein
Linker protein
Binds to entry/exit site of DNA
Needed to stabilize higher order chromatin structures
Chromatin
Collection of nucleosomes put together in a tight condensed area
Supercoiling of DNA
Allows DNA to compact even tighter around itself
Charge on histones
Positive
Charge on DNA
Negative due to phosphate groups
Euchromatin
Relaxed DNA
Transcriptionally active
Exposed to nuclease digestion
Heterochromatin
Condensed DNA
Transcriptionally LESS active
Protected from nuclease digestion
Role of topoisomerase
Change degree of supercoiling in DNA; essentially relaxes the supercoiling of DNA
Acetylation of Histones - does what?
Causes histones to become more neutral; will becomes looser and allow DNA to unwind
Transcription allowed to increase
Phosphorylation of Histones - does what?
Add negative charge
Will cause greater amount of steric hindrance between molecules - loosening DNA from histones
Transcription allowed to increase
Methylation of Cytosine - does what?
Compacts DNA even further than it was
Decreased transcription
What occurs during G1 phase of cell cycle
Protein synthesis increased
Which period of the cell cycle are cells more responsive to mitogenic GF’s and TGF-Beta?
G1
What percentage of genome is used to encode proteins?
1.5%
What percentage of genome is comprised of introns?
26%