DNA Packaging and Structure Flashcards
How do prokaryotes protect their DNA/genome? What is this protection from?
methylation and supercoiling
methylation in particular protects from the bacteria’s own restriction enzymes
restriction enzymes in prokaryotes chop up __1__, restrict the __2__ of viruses (whose DNA is not methylated)
1) DNA
2) growth
What enzyme in prokaryotes responsible for supercoiling DNA?
DNA gyrase
What proteins are eukaryotic DNA wrapped around? Which type of interactions are responsible for DNA to be wrapped around these proteins?
histones
electrostatic interactions
The sugar-phosphate backbone of DNA has a slight __1__ charge, whereas the histone proteins have a __2__ charge.
1) negative
2) positive
When DNA is wrapped around an _____ of histones. This is collectively called a ______
1) octamer (a group of 8 histones)
2) nucleosome
The octamer is composed of 2 units each of the histone proteins. What are these proteins?
H2A, H2B, H3, and H4
The string between the nucleosome beads is a length of double helical DNA called linker DNA and is bound by a single linker ______
histone, called H1
Fully packed DNA is called _____
chromatin
Based on your knowledge of the interactions of macromolecules and the chemical composition of DNA, do you suppose that histones are mostly basic or mostly acidic?
They’re mostly basic, since they must be attracted to the acidic exterior of the DNA double helix. This basicity is supplied by the AA arginine and lysine, which are unusually abundant in histones
Complete the following flow to summarize the structure of DNA in the nucleus:
1) add a ___ to deoxyribose to form a nucleoside
2) add _____ to a nucleoside to form a nucleotide
3) polymerize a nucleotide by losing ______, which creates an oligonucleotide
4) continuation of polymerization creates a single-stranded _______
5) 2 complete chains ___ bond in antiparallel orientation to create a ds DNA chain
6) this ds DNA chain then coils to create a ds ____
1) base
2) 3 phosphate groups
3) 2 phosphate groups
4) polynucleotide
5) H bond
6) ds helix
When DNA is stained, darker regions of chromosomes are called __1___, whereas lighter regions of chromosomes are called __2___.
1) heterochromatin
2) euchromatin
Which regions have higher rate of transcription, heterochromatin or euchromatin?
euchromatin
what is the region that binds sister chromatids together?
centromere
what is the region that mitotic spindle fibers attach to during cell division?
centromeres
mitotic spindle fibers attach to centromeres via _____ (multiprotein complexes that act as an anchor attachment sites for the spindle fibers).
kinetochores
Centromeres are made of ____ and repetitive DNA _____
heterochromatin and repetitive DNA sequences
Chromosomes have short and long arms, and the centromere position defines the ratio between the 2. What are the 3 centromere positions called?
Metacentric: centromere is located in the center and therefore short and long arms are in 1:1 ratio
Submetacentric: ~2:3 ratio of short to long arm
Arocentric: ~1:4 ratio of short to long arm
Telocentric: centromere is located at the top to where there are only long arms of the chromatids, no short arms are present.
The ends of linear chromasomes are called _____
telomeres
Telomeres are usually rich in which nitrogenous bases?
G and C
Telomeres consist of short ___ sequences of DNA
repeated
Telomeres consist of both ___ DNA and ___ DNA
double stranded and single stranded DNA
Distinguish between transcription and translation?
transcription is the process of transcribing DNA into RNA
translation is the process of translating RNA into proteins
For a codon, how many nucleotides make up 1 AA?
3
What is the minimum amount of codons you need to synthesize all of the AA utilized in your body?
20
What’s the max amount of codons that your body can possess?
64
What is the start codon?
AUG (methionine)
What are the 3 stop codons?
UAA, UGA, UAG
these do not code for AA and therefore are also considered non sense codons
What is the only codon that codes for tryptophan?
UGG
