Chapter 33: Nucleic Acids Flashcards
What is the first level of DNA packaging?
Wrapping of DNA around histones to create a nucleosome structure
What is the second level of DNA packaging?
“Beads on a string” form of chromatin
Beads = nucleosomes
String= linker DNA
_____ are the major proteins of chromatin
Histones
What are the five different histones of most eukaryotic species?
H1, H2A, H2B, H3, & H4
Histones are small basic proteins with many _____ and _____ residues
Lysine and arginine
Histones are ____ charged particles
Positively
DNA is _____ charged
Negatively
+ charge of Histone allows interaction with - charged ___
DNA
What histones make up a histone octamer?
2 each of H2A, H2B, H3, & H4
What does DNA wrap around to form a nucleosome?
Histone octamer
Histone modifications can lead to…
Gene activation or gene repression
Study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than alterations to the DNA sequence is ____
Epigenetics
Histone tails are important in
Epigenetic regulation
Epigenetic “marks” tell your genes to
switch on/off & to speak loud/soft
What does “beads on a string” consist of?
Nucleosomes connected by linker DNA
Chromatosomes are part of the ___ level
Second
What is a chromatosome?
Nucleosome (DNA wrapped around histone octamer) with one bound linker histone (H1)
H1 binds the ____ and exit/entry of the nucleosome dyad (center DNA of the nucleosome)
Linker DNA
Chromatin unfolds when treated with
Low ionic strength solution
What is the third level of packaging?
30nm fiber
With what can’t the 30nm fiber form?
H1
H1 histones from _____ bind to each other
Adjacent nucleosomes
What are the two models for the third level?
Solenoid and Zig-Zag
What is the fourth level?
Looped domains
Looped domains attached to
Chromosome scaffold
What can cause loop domains to open up?
Histone, modifying enzymes, chromatin, remodeling complexes, & RNA polymerase
In prokaryotes, DNA is ____ and there is no nucleus
Smaller
The presence of 2 ___ groups on RNA greatly affects its properties
-OH
2-OH can form hydrogen bonds. When treated with 0.1 M NaOH, what are the results?
Rapid degradation. DNA would remain stable.
Because RNA has 2-OH groups, it can participate in certain ____ and ____ reactions
Chemical and Enzyme-catalyzed
DNA is ____stable than RNA and is ____susceptible to alkaline attack
More, less
It is important for DNA to be stable because its role as the primary ____
Genetic material
What do nucleases catalyze?
Hydrolysis of phosphodiesters
Exonucleases work from the ___
Ends
5’ to 3’ or 3’ to 5’
Endonucleases work ____ the chain
Within
What are the 3 properties of restriction endonucleases?
- Recognition of short sequences on DNA and cleavage of DNA at that site
- Palindromic sequences
- Bacteria use these enzymes to destroy invading genomes by cleaving their DNA’s
What is an example of DNA recognition & cleavage?
EcoR1 Restriction Endonuclease
Palindromic means it can be read _____ forward and backward
The same.
5’-GAATTC-3’
3’-CTTAAG-5’
Bacteria can protect its own DNA from being cut by
Methylation of adenine residues which prevents EcoR1 cleavage
Restriction enzymes are important in
Molecular biology - cloning
DNA fingerprinting
DNA profiling- forensics and paternity tests
You can use restriction enzymes to
Generate fragments of a certain size
After digestion of restriction enzymes, fragments are run through a gel. The fragments travel from the ____ end to the ____ end.
Negative, positive
Which fragments travel farther in the gel? Long or short
Short
For DNA profiling, a band present in the child must be present in either their ___ or ___
Father, mother
