Genetics- Week 2 Vid Lectures

DNA organization

what is horizontal gene transfer

bacteria can acquire genetic material from their environment

what does supercoiling do

allows for DNA to fit inside the cell

what does supercoiling consist of

twist and writhe

what is twist

one strand crosses over the other

what is writhe

both strands cross over itself

what are the two types of supercoiling

positive and negative

what is positive supercoiling

more twists is added

when is positive supercoiling seen

ahead of transcription or replication bubbles and in thermophillic organisms

what is negative supercoiling

less twist is added (unwinding)

how are most cells in DNA supercoiled

negatively

the extent of DNA supercoiled in controlled by what enzymes

topoisomerases

what do topoisomerases do

cut DNA, introduce + or - twists, reseals DNA

what does type 1 topoisomerases do

nicks one strand

what does type 2 topoisomerase do

nicks both strands

where are linear chromosomes in eukaryotes found

nucleus

where are circular chromosomes found in eukaryotes

mitochondria and chloroplasts

in eukaryotes how is DNA wound

wound around histones (negatively supercoiled)

what is C-value

amt of haploid DNA in base pairs in an organism

what is the C-value paradox

increased C-value does not mean increased complexity

what is chromatin

DNA + associated protein in the nucleus

what does each chromosome exists as

chromatin

does it matter how each chromosome is positioned within the nucleus and why

yes it plays a role in gene expression regulation

what do histones do

help pack DNA into chromatin

are histones highly conserved

yes

function of nonhistone proteins

replicate, repair, transcript, recombination, etc

are nonhistone proteins conserved

some are highly conserved not all

during what phase is packing along the chromosome less uniform

interphase

if packed tightly and closed what is the level on transcription

low

if packed loosely and open what is the level of transcription

high

what are types of chromatin based upon

their transcriptional activity

describe euchromatin

open and accessible to the transcription machinery, expressed

describe heterchromatin

packed tight, closed and silenced

what are the two types of heterochromatin

constitutive and facultative

which type of chromatin is present n all cells at the same posiiton on the chromosome

constitutive heterochromatin

examples of constitutive heterochromatin

centromeres and telomeres

when is faculatative heterochromatin found

vary between cell type, developmental stage, between homologous chromosomes

can euchromatin become heterochromatin

yes, under certain conditions

what is a unique sequence of DNA

one or only a few copies of the sequence in the genome

what percentage does unique sequence DNA make up of a eukaroytic genome

60%

can unique sequence DNA be euchromatin or heterochromatin

yes

what are repetitive DNA sequences

repeated several to millions of times in the genome

what are repetive DNA sequences often

heterochromatin

what are transposons sometimes called

jumping genes

SINEs is what

short interspersed nuclear elements

what are LINEs

long interspersed nuclear elements

what is VNTRs

variable number tandem repeats

what is STRs

short tandem repeats

satDNA description

huge stretches of repeats, separate dif from rest of genome during centrifugation, centromere

with Chargaffs rule what has to be equal with A

T

with Chargaffs rule what has to be equal to G

C

purines amount should always equal to what

pyrimidines

any two nucelic acid fragments will spontaneously hybridize if they encounter eachother as long as they are ________ and ________

complementary, antiparallel