25. Eukaryotic Gene Regulation

Question 1

what is chromatin?

Answer 1

DNA + histones = chromatin

the DNA double helix is packaged by proteins called histones, the protein/DNA complex is called chromatin

Question 2

define differential gene expression

Answer 2

the expression of different genes by cells with the same genome

Question 3

why is heterochromatin usually not genetically active?

Answer 3

because its highly condensed DNA, meaning RNA polymerase and other proteins needed for transcription initiation dont have access to the DNA template.

Question 4

why is euchromatin used more in transcription?

Answer 4

because its quite loosely packed DNA so its more accessible for transcription

Question 5

what is a histone protein?

Answer 5

proteins that package and order nucelosomes (DNA units). it condeneses the lenghth of DNA and helps and gene expression

Question 6

What are histone acetylations?

Answer 6

the attachement of acetyl groups (-COOH3) to the tails of histone proteins in the nuceleosome. this allows for gene expression

Question 7

what is DNA methylation?

Answer 7

attachment of methyl groups (-CH3) to bases in the DNA. highly methlylated genes are not usually expressed but REMOVAl of the methyl groups can allow transcription

Question 8

what are control elements in eukaryotic genes?

Answer 8

segments of noncoding DNA that serve as binding sites for the transcription factors (proteins). this REGULATES TRANSCRIPTION

Question 9

what are general transcription factors?

Answer 9

a transcription factor to initiate RNA polymerase to transcribe a DNA strand. a general transcription factor is one that can transcribe all protein coding genes

Question 10

where do transcription factors bind to

Answer 10

directly to the promer DNA

to each other

or RNA polymerase

Question 11

what is the promoter

Answer 11

a start point where transcription factors bind to it, usually a TATA box

must understand image!

Question 12

what are control elements? what are the two types and where are they located?

Answer 12

regulatory proteins that bind at specific DNA sequences

proximal control elements (inhibitor) - close to the promoter

distal control elemets (enhancer) - thousands of base pairs away from the promoter

Question 13

why are the control elements important for the effiecinecy of transctiption initiation?

Answer 13

because when regulatory proteins bind to the control elements, it influences binding of the general transcription factors or the activity of RNA polymerase.

Question 14

how do different cell types express diffrenent sets of genes?

Answer 14

with cell type-specific transcription. this is due to a combination of a specific type of control elements for differnent genes (eg liver and lens genes)

different cell types have different activators to bind to the transcription factors!

Question 15

how are genes with related functions coordinatley controlled within each cell?

Answer 15

its acheived with control elements. this happens when each gene has matching control elements that are recognised by a specific activator (regulatory protein).

activators promote transcription of genes no matter where their location is in the genome.

Question 16

what is alternative RNA splicing?

Answer 16

different mRNA molecules are made from the same primary transcript. depends on which RNA segments are treated as exons and introns

Question 17

what does alternative RNA splicing result in?

Answer 17

variation of forms of proteins that are made in one type of cell. one pre-mRNA can give rise to different mRNA therefore proteins that have different uses for its function

Question 18

what evidence suggests that RNA was the first genetic material in the evolution of life on earth?

Answer 18

RNA molecules have catalytic activity. its proven that modern cells use RNA catalysts called ribozymes to splice introns out of RNA molecules.

ribozymes can synthesise complimetry copies of RNA molecules

this is what proteins and DNA does.

Question 19

what would the effects by of mutations in regulatory DNA sequences?

Answer 19

mutations in the transacting protein factors in specific DNA sequences in the promoter region

causes increase or decrease in transcriptional acitivity.

can cause genetic human disease.