Lecture 11

?
  • Created by: Katherine
  • Created on: 09-02-16 15:30
What are chromosomes made of?
Chromatin
1 of 56
What is chromatin made of?
Protein and DNA
2 of 56
What is chromatin?
It is an intricate form of packaging for DNA
3 of 56
In order for transcription and replication to occur in a cell DNA must be what?
Packed in an organized manner to be accessible
4 of 56
The organisation of DNA in the cell involves association with...
specific proteins (histones) and the formation of chromatin.
5 of 56
Which is more complex, Eukaryotic chromatin or Prokaryotic?
Eukaryotic
6 of 56
Each human chromosome contains a single linear ...
DNA helix
7 of 56
Heterochromatin is...
highly condensed during interphase, it is not actively transcribed.
8 of 56
Euchromatin is...
less condensed during interphase, able to be transcribed
9 of 56
Where does packing being?
With the nucleosome - the basic unit of chromatin.
10 of 56
What are histones?
Proteins with positively charged amino acids that bind to the negatively charged DNA. They play a key role in chromatin structure.
11 of 56
During interphase, what form are most of the chromosomes in?
Euchromatin
12 of 56
What does Euchromatin look like?
Looped domains of the 30nm chromatin fibre.
13 of 56
During meiosis and mitosis, what happens to the chromatin?
It folds further (condenses)
14 of 56
The highly condensed chromatin also occurs during interphase in some regions of the chromosome. What is this called?
Heterochromatin
15 of 56
Which of Euchromatin and Heterochromatin is looser?
Euchromatin.
16 of 56
Can Heterochromatin be transcribed?
It is too tightly packed (supercoiled)
17 of 56
In both eukaroytes and prokaryotes, are genes always on?
No, they are continually be turned on and off in response to signals from their internal and external environments.
18 of 56
In multicellular eukaryotes, cellular differentiation occurs. What is this?
Long term control of gene expression
19 of 56
How many different cell types are in the human body?
>200
20 of 56
How much does a cell express of its 30,000 genes at any given time?
3-5%
21 of 56
When can regulation of gene expression occur?
At any step from gene to protein
22 of 56
How else can gene expression be adjusted?
By chemical modification of chromatin
23 of 56
What are the two types of chemical modification of chromatin?
DNA methylation and Histone acetlyation
24 of 56
What is DNA methylation?
It is when methyl groups are attached to DNA bases.
25 of 56
What does attaching methyl groups to the DNA bases do?
It triggers the formation of a compact chromatin structure
26 of 56
Is DNA methylation associated with active or inactive DNA?
Inactive
27 of 56
What does DNA methylation account for?
Genomic imprinting in mammals
28 of 56
What is Histone acetylation associated with?
Gene activation
29 of 56
What is Histone acetylation?
It is the attachment of acetyl groups (COCHE) to histones
30 of 56
Do the acetylated histones grip DNA more or less tightly?
Less
31 of 56
Acetylation is involved in the switching on or off of genes?
Switching on
32 of 56
If DNA is methylated and histones are not acetyled, is the chromatin open or closed?
It is closed.
33 of 56
If the DNA is unmethylated and histones are acetylated, is the chromatin open or closed?
It is open.
34 of 56
How many types of different RNA polyermases are in Eukaryote?
3
35 of 56
What is RNA polymerase I?
Ribosomal RNA
36 of 56
What is RNA polymerase II?
Messenger RNA
37 of 56
what is RNA polymerase III?
Small RNAs (tRNA)
38 of 56
What causes transcription to begin?
When the RNA polymerase binds to a promoter
39 of 56
What are promoters?
DNA sequences adjacent to the gene (upstream)
40 of 56
What does the promoter determine?
It determines where the transcription of the gene is initiated, and the rate of transcription
41 of 56
What is the TATA box?
A key part of the promoter, it provides the site of intial binding of the transcription initiation machinery, it is located 10-35 bp upstream of the transcription site.
42 of 56
Before transcription can start, what must form:
A pre-initiation complex
43 of 56
Can RNA polymerases bind to promoters on their own?
NO
44 of 56
In order to with with the promoter, the RNA polymerase II must bind to...
TFIIF
45 of 56
How is the rate of transcription modulated in Eukaryotes?
The interaction between the transcription initiation complex and the basal promoter is inefficient.
46 of 56
The process of transcription is regulated by what?
Specific transcription factors - activators or repressors
47 of 56
What do the activators or repressors do?
They bind to proximal control elements and distal control elements (enhancers).
48 of 56
What are the grouping of proximal control elements and distal control elements called?
Enhancers
49 of 56
How do enhancers work when they may be 1000s of base pairs from the promoter?
DNA folding occurs to bring the distal sequences into proximity with the promoter
50 of 56
What is the modular structure of specific TFs?
They have separate DNA binding and transcriptional activation domains
51 of 56
The transactivation domain is responsible for what?
For recruiting other proteins into the transcription factor complex
52 of 56
How is processing of the primary transcript in Eukaryotes done?
By capping of the 5' end, polyadenylation of 3' end, splicing to remove introns
53 of 56
How do regulatory proteins control intron-exon choices?
By binding to regulatory sequences within the primary transcript.
54 of 56
Where are Dscam proteins located?
On the surface of a growing neuron
55 of 56
What do Dscam proteins do?
They provide a cell recognition mechanism that regulated brain development.
56 of 56

Other cards in this set

Card 2

Front

What is chromatin made of?

Back

Protein and DNA

Card 3

Front

What is chromatin?

Back

Preview of the front of card 3

Card 4

Front

In order for transcription and replication to occur in a cell DNA must be what?

Back

Preview of the front of card 4

Card 5

Front

The organisation of DNA in the cell involves association with...

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Genetics resources »