DNA Organization Flashcards
What is the end-to-end length of Human DNA?
1.02 m
What are the levels of DNA organization?
- Supercoiling
- Nucleosomes
- Chromatosomes
- Solenoids
- looping onto matrix
- higher order coiling
What is a virus?
non-cellular infectious particle containing a small nucleic acid genome w/ limited number of genes
What is bacteriophage?
A virus that infects bacteria
What does a non-enveloped virus contain?
Genetic material in only a protein shell (capsid)
What does an enveloped virus contain?
An envelope of host cell cytoplasmic membrane surrounding the capsid
What kind of DNA do bacterial chromosomes have?
Haploid, single chromosome, circular double stranded DNA
What is the region called that chromosomes are packed into in a bacteria?
Nucleoid. ONLY IN PROKARYOTES, NUCLEOSOME IN EUKARYOTES
What do topoisomerase do?
Maintain DNA in OPTIMAL supercoiled state. Partially unwind supercoiled DNA to relieve torsional stresses that result from supercoiling
Why does Gram- positive bacteria have such a wide genome range?
Bc there are less number of genes compared to Gram- negative. Many repeating units
What is chromatin?
DNA and associated proteins of a EUKARYOTIC chromosome
What do histone proteins do?
Tightly bind DNA
What histones are present in chromatin?
H1, H2A, H2B, H3, H4
What is the number of histone proteins present in a nucleosome?
- 2: H2A, H2B, H3, H4
- dimers –> H3-H4 & H2A-H2B tetramers –> octamers
How many base pairs of DNA can wrap around histone proteins?
146
What is the region between nucleosomes called?
Linker DNA
H1 + nucleosome =?
Chromatosome. H1 may associate with linker DNA
Euchromatin
Regions containing actively expressed genes and less condensed during interphase
Heterochromatin
remain condensed in interphase and contain fewer expressed genes. **METHYLATION
Facultative heterochromatin
Variable lengths of condensation related to levels of transcription of resident genes
Constitutive heterochromatin
Permanently condensed found in centromeres and telomeres, composed primarily of repetitive DNA sequences
What can gene expression or silencing be dictated by?
Chromatin structure
