Regulation of transcription and translation

What is a transcription factor

Transcription factor binds to a specific target gene

At a specific DNA base sequence in the promoter region

Stimulates RNA polymerase to attach and transcribe the gene(or prevents transcription)

How would a transcription factor increase the production of a protein

The transcription factor will move from the cytoplasm to the nucleus

The transcription factor will bind to the promoter region of a gene

This will cause RNA polymerase to attach and stimulate transcription

More of the protein produced

What oestrogen

A steroid hormone

Describe how oestrogen affects gene transcription

• Oestrogen binds to the oestrogen receptor-in the cytoplasm

• This causes the oestrogen receptor to change shape

• this exposes the DNA binding site on the oestrogen receptor

• The oestrogen receptor complex moves into the nucleus via nuclear pore

• Binds to the specific base sequence in the promoter region of a gene This

• Stimulates RNA polymerase to attach and transcription to take place

What is the function of RNAi

RNA molecules inhibit gene expression by neutralising specific mRNA molecules so that translation cannot take place

Bind to complementary mRNA sequences either preventing the mRNA from attaching to the ribosome or enabling enzymes to break mRNA

Describe how RNAi functions

• Double stranded RNA is produced

• Leaves the nuckeus

• One strand of RNA is bound to (RISC) complex with proteins

• RNAi guides the enzyme to mRNA that has complementary sequence of bases

• RNAi binds by complementary base pairing

• The enzyme breaks mRNA into fragments

• mRNA is blocked from binding to a ribosome or

• Translation is prevented

What is epigenetics

The study of heritable changes in gene function that do not involve changes to their base sequences

What is DNA methylation.

The addition of methyl groups to DNA bases like cytosine

Describe and explain the effect of increased DNA methylation on gene expression

Increased methylation of DNAin the promoter region of a gene will prevent transcription factors and RNA polymerase from binding

Transcription of the gene will be inhibited

What are histones

Protein that DNA is wrapped around

What is histones Acylation

Addition of Acetyl groups to histones proteins

Describe and explain the effect of histones acetylation on gene expression

Histones acetylation causes DNA to be less condensed

Reveal promoter region of the genes

Increased binding of transcription factors and RNA polymerase to promoter regions

Can lead to transcription of the gene

-less Acylation=less transcription

What are the main characteristics of a benign tumor

A mass of dividing cells which do not break away and invade neighbouring tissues

-do not metastasise

What are the main characteristics of a malignant tumor

A mass of cells which divide uncontrollably and can metastasise invading other tissues

What does an oncogene do

Codes for a protein which stimulates cell division to take place

What is the consequence of a mutation occurring to an oncogene

Change in the base sequence of DNA

Change in primary structure of protein

Change in tertiary structure of protein (that controls cell division)

Results in uncontrollable cell division

What does a tumor suppressor gene don

Codes for a protein which prevents cell division from, taking place

What is the consequence of a mutation occurring to a tumour suppressor

Change in base sequence of dna

Change in primary structure

Change in tertiary structure

Tumour suppressor gene becomes inactivated

So uncontrollable cell division

How can abnormal methylation of a tumor suppressor gene lead to the development of a tumor

Increased/hypermethylation of DNA in the promoter region of a gene will prevent transcription factors and RNA polymerase binding

Transcription of the gene inhibited gene silenced

So less of the tumor suppressor protein produced

Mitosis no longer stopped

Uncontrollable cell division

How can abnormal methylation of an oncogene lead to the development of a tumor

Decreased methylation of a promoter region of a gene will allow transcription factors and RNA polymerase to bind

So more of the oncogene protein will be produced

Rate of mitosis increases

Uncontrollable cell division

Suggest how increased oestrogen concentration can lead to the development of some breast cancers

Oestrogen binds to oestrogen receptors

Tertiary structure of the oestrogen receptor t changes so DNA binding site exposed

Oestrogen receptor binds to the promoter region of am oncogene

Allows RNA polymerase to bind and causes transcription to occur

More of the protein produced

Uncontrollable cell division