Dr. Christopher Mayack Chromosome Flashcards
What are 3 descriptions of Bacterial and viral chromosomes
- Single nucleic acid molecule(DNA or RNA, single or double-stranded)
- Largely devoid of associated proteins
- Much smaller than eukaryotic chromosome
Describe bacterial chromosomes
Circular, double-stranded DNA in the nucleoid region
How does DNA form supercoils
Associated with HU (Histone-like proteins) and H-NS (Histone-like Nucleoid structuring) DNA binding proteins
T/F: Bacterial chromosomes are readily replicated and transcribed
TRUE!!!
Briefly describe Supercoiled DNA
- Closed circular regions
- Compact!
What is the function of Topoisomerases 1 and 2?
Help in supercoiling and uncoiling
What does Topoisomerase 1 mean? What about 2?
- Only nicks one strand.
- Topoisomerase 2 = nicks both stranded
Are puff regions more accessible for transcription?
YES!!!
What forms a nucleosome?
5 histone proteins
“Beads on a string”
Acetylation (COCH3) and Methylation (CH3) do what?
Activate a gene
Explain Acetylation
- Enzyme histone acetyltransferase (HAT), addition of acetyl group to lysine
- Gene activation
Explain Methylation
- Enzyme methyltransferase, adds methyl groups to arginine and lysine residues in histones
– Gene activation
Explain Phosphorylation
- Enzyme kinase, adds phosphate groups to hydroxyl
groups of amino acids serine and histidine - Chromatin unfolding and condensation
To allow replication and gene
expression, chromatin must do what 3 things?
▪ relax compact structure
▪ expose regions of DNA to
regulatory proteins
▪ have a reversal mechanism
for inactivity
What are features of Euchromatin
- Uncoiled and active
- Appears unstained during Interphase
What are features of Heterochromatin?
- Condensed areas are mostly inactive
- Appears stained during interphase
Explain G-banding
- Differential staining along length of each chromosome
– Digestion of mitotic chromosome by enzyme
What is Satellite DNA
– Highly repetitive and consists of short repeated sequences
– Makes up variable proportion of total DNA
– Found in heterochromatic centromeric regions of chromosomes
– NOT found in prokaryotes
EX.) CTG|CTG|CTG
Moderately repetitive DNA includes what?
– Variable number tandem repeats (VNTRs)
1. Minisatellites (10 – 100 bp)
2. Microsatellites (short tandem repeats, STRs, 1-6 bp)
What is important about the telomere caps?
These G-quartets help protect DNA from unraveling
What information is used to identify
chromosomal rearrangements?
- Size of
chromosome - Banding pattern
- Position of centromere
- Order of genes
- DNA sequence
