DNA organization Flashcards
These sequences are repeated many times within eukaryotic chromosomes
Repetitive DNA sequences
which type of DNA consists of short repeated sequences, rarely transcribed into RNA and highly repetitive
Satellite DNA
which type of DNA appears one after the other in clusters at particular regions on the chromosome
Tandem repeats
this repeating DNA sequences 15 to 100 bp long and are found within and between genes
Variable number tandem repeats (VNTRS)
these sequences are dispersed throughout genome consistsing of di,tri, tetra nucleotides
Short tandem repeats (STRs)
what type of repeats are dispersed throughout genome and constitute 1/3 of human genome
Interspersed repeats
what type of interspersed element has 300bp sequence present more than a million times
Alu, SINES (short interspersed elements)
what repeats has several thousand base pairs with remnant of transposable elements
Line 1 Long interspersed elements (LINES)
if DNA is over or under twisted, what happens
it will supercoil if the ends can’t rotate
when DNA helix is underwound by 2 turns or some coils were removed
it is underwound circular DNA
when ends 1 seal to end 20, this is called
relaxed circular DNA
when DNA helix has a conformational change and 2 supercoils form
this is supercoiled DNA
what enzyme can sever DNA and rotate ends before rejoining
Topoisomerase
Agarose gel electrophoresis seperate DNA based on
size, charge and shape
which fragment move faster on gel smaller /larger
smaller
DNA fragment move towards with pole
positive electrode
whcih runs faster on a gel supercoiled DNA/ linear DNA/ circular DNA
supercoiled DNA
which chromosomes has circular, double stranded DNA compacted into nucleoid
Bacterial chromosomes
Is nucleoid nuclei based or not
it is not
BACTERIAL chromosomes DNA are associated with what protein
HU nad H-NS (histone like-nucleoid structuring protein)
At interphase, eukaryotic chromosomes uncoil and decodnense into a form ccalled
Chromatin dispersed throughout the nucleus
Chromatin appears as
beads on a string (nucleosomes)
which chromatin is transcriptionally active and uncoiled
Euchromatin
How do chromatin become visisble chromosomes
during cell division, chromatin coils and condenses back into visible chromosomes
what are the core histones
H2A,H2B,H3,H4
Which basic protein binds very well to negatively charged DNA
Arginine Lysine (positiveky charged)
what digests of chromatin releases and further digest yielding fragment
micrococcal nuclease
what protects DNA from nuclease enzyme
DNA wrapped in histones
describe process of how nuclease attacks DNA
- A small amount of nuclease cleave the “strings fo the bead”
- release individual beads attached to about 200 bp of DNA
- more nuclease destroys all of the unprotected DNA between beads
- leaving a core of protein attached to 145-147 bp of DNA
Nucleosomes organize into
filament
which chromatin is mostly inactive and appears stained during interphase
Heterochromatin
which chromatin appears unstained in interphase
Euchromatin
which is less condensed between euchromatin/ herterochroimatin
euchromatin
To allow replication and gene expression, chromatin must do what
- relax compact structure
- expose regions of DNA to regulatory protein
- have a reversal mechanism for inactivity
what chromosomes is created by repeated round of DNA replication with no cell division
Polytene chromosome
this region is where chromosome is made less compact
chromosomal puff
chromosomal puff region is more sensitive to DNase I cleavege true/false
true
characteristics of expanded regions
active transcirption
sensitivity of DNA to digestion by DNase I is correlated with
gene expression
what enzyme is involved in histone acetylation
histone acetyltransferase
addition of what group to the positively charged amino group on side chain (lysine) changes net charge of protein
acetyl group
histone acetylation promotes
gene activity
what enzyme is involved in methylation
methyltransferase
adding of methyl group to arginine and lysine leads to
repression or activation
What enzyme is involved in phosphorylation
kinase
phosphate group adds to hydorxyl group of which amino acids
serine and histidine
what is the DNA sequence 5’-CG-3’
CpG
methylation of which group by DNA methyltransferase repress gene activity
cytosine
epigenetics changes are heritable true/false
true
