Chapter 5 Flashcards
Describe Griffith’s contribution to the “DNA as genetic material” debate
Dead bacteria can transfer genetic information to live bacteria
Living R strain + Dead S strain = Living S strain
Describe Avery/MacLeod/McCarty’s contribution to the “DNA as genetic material” debate
The material responsible for bacterial transformation is DNA
Fractionate S-strain cells into classes, only DNA could transform R strains
Describe Hershey/Chase’s contribution to the “DNA as genetic material” debate
Genetic material of virus is DNA
Used T2 virus, labeled DNA with 32P and protein with 35S, infected bacteria only contained 32P
What does the “denaturation” of DNA mean? How does it happen? Is it reversible?
The H-bonds between the strands of DNA will break down under high temperature or high pH
Cooler temperature or lower pH restores double helix
What is the relationship between the sequence of DNA, its length, and the denaturing temperature? What is Tm?
Longer DNA and DNA with more G/C requires higher temperature
G/C has three H-bonds, A/T has two H-bonds
TM is the temperature at which half of the DNA has denatured
What is “FISH”?
Fluorescent In Situ Hybridization, identification of sections of DNA with a probe (short piece of DNA labeled for detection with fluorescent dye or radioactivity
What is “SKY”?
Spectral KarYotyping, use probes to label each chromosome as a different color
Define karyotype
an ordered display of the full set of chromosomes of a cell arranged with respect to size, shape, and number
Define centromere. How many does each chromosome have?
Centromeres allow duplicated chromosomes to be separated during M (mitosis) phase and can be seen as the constructed region of a mitotic chromosome. There are one per chromosome.
Define replication origin. How many does each chromosome have?
The replication origin is where DNA replication is initiated. There are many per chromosome.
Define telomere. How many does each chromosome have?
Telomeres are repetitive nucleotide sequences that cap the 2 ends of linear chromosomes and counteract the tendency of the chromosome to shorten with each round of replication.
Define nucleolus
Large structure within the nucleus where ribosomal RNA is transcribed and ribosomal subunits are assembled.
Describe how DNA reaches the first level of organization
DNA Helix + 8 histone proteins → Nucleosomes with linker DNA
Define nucleosome and nucleosome core particle
Nucleosome: Nucleosome core particles + segments of linker DNA (nucleosome+linker=200bp)
Nucleosome core particle: histone octomer + 150 bp of DNA around it
How can histone interact with DNA?
It has a lot of positively charged amino acids that allow it to interact with the negative DNA
How does nuclease interact with nucleosomes?
it digests linker DNA, but DNA on histones is protected
Describe how DNA reaches the second level of organization
Nucleosomes + H1 proteins = 30 nm chromatin
Where do H1 proteins bind?
on the outside of the nucleosome core particles
Describe how DNA reaches the third step of organization
chromatin + condensin = looped DNA
How do daughter cells know what kind of cells they are?
they inherit changes in their chromatin structure
Describe the method of chromatin regulation involving proteins (as opposed to chemical groups)
Chromatin Remodeling Complexes
Local and temporary modification
Requires ATP to catalyse nucleosome sliding
Still 30 nm fiber, just changing relative position
Describe the method of chromatin regulation involving chemical groups (as opposed to proteins)
Histone Tail Modification
Covalent addition of chemical groups
Combination of histone modification is called the histone code
Define acetylation, give what catalyzes acetylation, and give what catalyzes deacetylation
Acetylation → loose packing and gene expression (overrules methylation)
histone acetyltransferases (HATs) and histone deacetylases (HDA)
Define heterochromatin
a highly condensed region of an interphase chromosome; generally gene-poor and transcriptionally inactive. (random X sequence)
