Topic 7.2 - Gene expression

Question 1

Gene expression?

Answer 1

When the DNA code of a gene is used to make a protein

Question 2

All cells contain genetic code (genome) for that organism.
They only need to express the genes + make protein that the specific cell type requires

Answer 2

e.g - B cells in the pancreas make insulin so the gene that codes for insulin protein will need to be expressed in that cell.

Question 3

Regulating gene expression

what 2 processes does it involve?
its an ……. expensive process.

Answer 3

• transcription + translation
• an energy expensisve proesses

Question 4

how can u make diff rotein products from a single gene?

Answer 4

• by modifying the mRNA or protein product itself

Question 5

by comparing proteins found in different types of cells, you can measure….?

Answer 5

• you can measure level of differentiation - work out which genes are expressed (on) and suppressed (off).

Question 6

What do Trancription Factors do?

Answer 6

• control gene expression by switching on and off the transcription of certain genes

Question 7

How do transcription factors work?

how do they carry out their funtion?

Answer 7

• bind to DNA in nucleus, affect process of transcribing the genetic material
• bind to the promotor region of DNA which is found just upstream of the gene (like a start codon)

Question 8

Some transcription factors bind to regions known as ……..?

Answer 8

Enhancer Sequences

Question 9

Enhancer Sequences?

Answer 9

• Regulatory DNA sequences that, when bound by specific proteins called transcription factors, enhance the transcription of an associated gene
• can be 1000s of base pairs from acc gene

Question 10

random but helpful to remember diff

Promotor vs Enhancer

Answer 10

The promoters include specific DNA motifs where transcription factors (TFs) and their complexes can access. On the other hand, enhancers are defined as DNA regions that amplify transcription initiation by directly interplaying with their target promoters

Question 11

Enhancer sequences…

What happens when transcription factors bind here?

Answer 11

• they change the structure of the chromayin (wound up DNA) making it more or less available to RNA polymerase, therefore controlling gene expression

Question 12

Transcription is the production of…

Answer 12

pre-mRNA.
- bc of introns and extrons, its editied before it leaves the nucleus

Question 13

where are transcription factors found?
what rae they and what else can act as transcription factors?

Answer 13

• found in nucleus, cytoplasm and move into nucleus to attaxch to DNA
• protein. Hormones and viruses act as T.Factors

Question 14

Trancription Factors

They’re specific. They either stimulate expression of a gene, or suppress the expression of another

Question 15

Trancription Factors

Activate meaning?
Repressor meaning?

simples, yes/no

Answer 15

Activate - Allow transcription
Repressor - Say No!

Question 16

How are genes swtiched off?

Answer 16

• in a similar way to being switched on
• when a gene is not expressed (off) the site of the transcription factor that binds to the DNA is blocked by an inhibitor molecule -> this prevents transcrition

Question 17

What are repressors and what do they do?
where are they?

Answer 17

• stop transcription
• could also block RNA polymerase binding
• sits on DNA or Transcription Factors that’s inhibitor. RNA polymerase can’t attach

Question 18

Facts abt Transcription Factors:

Answer 18

• some in all cells, some in only certain types of cells
• some present at particular stage of development
• ## Most are inactive form (inhibited) and are activated by hormones / GFs (growth factors-> plants, tell ‘em to grow)

Question 19

How hormones can turn on genes:

Answer 19

• Oestrogen can stimulate a transcriptional factor
• its a lipid soluble molecule, so it can easily enter cytoplsm.
• its a complementary shape, so changes shape of the receptor molecule -> this causes it to release the inhibitor molecule from the DNA binding site on the transcriptional factors