L2 - Eukaryotic genome

Question 1

prokaryotic vs eukaryotic key properties

Answer 1

Pro:
-single supercoiled haploid dsDNA chromosone within nucleoid = region of cytoplasm
- no histones
- non-membrane bound = no compartmentalisation
- plasmids

Euk:
- multiple highly condesned dsdNA linear chromosones in nucleus

Question 2

what does prokaryotic DNA look like

Answer 2

bottle brush
nucleoid ascociasted proteins around it = central core with loops of DNA coming out

Question 3

what type of protein is the histone core

Answer 3

octamer
- 2x H2A
- 2x H2B
- 2x H3
- 2x H4

one ‘nucleosome’ is a basic unit of chromatin

Question 4

what are the 2 states of chromatin

Answer 4

euchromatin = relaxed and open

heterochromatin = condesned and closed

Question 5

what is the C value paradox

Answer 5

a linear relationship between organism complexity and genome size does NOT exist

= unlike in bacteria, there is no correlation between size and gene number

Question 6

whats a promoter

Answer 6

non-coding region of DNA where RNA polymerase binds to initiate transcription

Question 7

what are bacterial genes organised in and how

Answer 7

Operons

cluster of co-regulared genes controlled by a single promoter and expressed as a single ‘polucistronic’ mRNA

Question 8

what are pseuodogenes and gene fragments

Answer 8

pseuodgenes = They look like normal genes, but they don’t work
- may have mutated or is a turned off duplicated version

gene fragments = incomlete pieces of genes

difference: Gene fragments are not necessarily derived from a once-functional full gene.
Pseudogenes are usually clear descendants of functional genes that just stopped working.

Question 9

percentage of non-coding DNA in human genome

Answer 9

75%

= tandem repeated sequences
= micro, mini and satellites

Question 10

what are interspersed (mobile) repeast sequnces

Answer 10

mobile genetic elements or ‘jumping genes’, DNA sequnces that can move around the genome

1. DNA transposons
2. Reterotransposons

Question 11

what are DNA transposonsand reterotransposns and how do they move

Answer 11

DNA transposons:
cut and paste
cut out of DNA and pased in new site
= no net gain or loss

Reterotransposons:
copy and paste
copied into RNA intermediate
turned int DNA from reveree transcriotase
inserted into new sites
= net gain

Question 12

what are the 2 types of reterotransposns and then 2 types of one of them

Answer 12

LTR and non-LTR
=depends on whether they have Long Terminal Repeats (LTRs) at both ends

non-LTR 2 types:
depend on whether they code for their own machinery or not

LINES:
Long INterspersed elements
can move on their own as they code for RT and integrase

SINES
short INterspersed elements
CANNOT move on their own
as they do n ot code for enzymes = rely on LINES