Gene expression (complete)

Question 1

Name the types of Gene mutations

Answer 1

• Substitution
• Deletion
• Addition
• Inversion
• Translocation
• Duplication

Question 2

Describe Inversion of bases gene mutation

Answer 2

• groups of bases removed from sequence, inverted and replaced in the same place.

Question 3

Describe the duplication of bases gene mutation

Answer 3

• One or more bases are repeated, producing a frame shift to the right.

Question 4

Describe Translocation of bases gene mutation, and the effects.

Answer 4

• a group of bases become separated from the DNA sequence on one chromosome and become inserted into the DNA sequence of a different chromosome.
• can cause reduce fertility and increases development of cancer.

Question 5

Give the features of a benign tumour.

Answer 5

• grows slowly.
• can grow to large size.
• cell nucleus has normal appearance.
• cells often well specialised.
• cells produce adhesion molecules that make them stick together.
• tumour surrounded by a capsule of dense tissue to remain as compact structure.
• less-likely to be life-threatening.
• have localised effects on body.
• can usually be removed by surgery alone.
• rarely reoccur after treatment.

Question 6

Give the features of a malignant tumour.

Answer 6

• grows rapidly.
• can grow to a large size.
• call nucleus larger + darker.
• cells become unspecialised.
  -cells don’t produce adhesion molecules molecules to tend to spread to other regions of the body
• tumours not surrounded by capsule - can grow finger like projections into surrounding tissue.
• more likely to be life threatening
• often have effects on whole body
• removed using chemotherapy/radiotherapy and surgery
• more frequently reoccur after treatment

Question 7

What is an oncogene?

Answer 7

• A malfunctioning gene that can occur from the mutation of a proto-oncogene that permanently activates it, producing too much of the proteins that code for cell growth.
• They can replicate continuously, becoming out of control.
• They commonly cause cancer.

Question 8

What is a proto-oncogene?

Answer 8

• A healthy functioning gene found within a cell.
• Responsible for making a protein involved in cell division, growth etc…
• The number of them formed is regulated by cells.

Question 9

What is the function of proto-oncogenes?

Answer 9

Making the proteins responsible for:
- stimulating cell division
- inhibiting cell differentiation
- preventing apoptosis - cell death

Question 10

What do tumour suppressor genes do?

Answer 10

• slow down cell division
• repair mistakes
• stimulate apoptosis

Question 11

How can Oestrogen cause cancer?

Answer 11

• After menopause, women have increases risk of breast cancer due to higher levels of oestrogen produced by fat cells in the breast tissue.
• Oestrogen stimulates transcription factors, and if the gene is a proto-oncogene then and oncogene could form, increasing formation risk of cancer.

Question 12

Describe a pluripotent cell.

Answer 12

• Embryonic stem cells that differentiate into any cell type found in an embryo.
• Can divide in unlimited numbers and keep replacing themselves.

Question 13

What are Induced pluripotent stem cells?

Answer 13

• Can be produced from adult cells (that aren’t sperm or egg) using appropriate protein transcription factors, which can de-differentiate a cell back into its pluripotent state.

Question 14

What are multipotent adult stem cells?

Answer 14

• Adult stem cells that can divide an unlimited number of times to make a limited range of cells types.

Question 15

What are the functions for tumour suppressor genes?

Answer 15

• Stimulate apoptosis
• slow down cell division
• repair mistakes

Question 16

How can Oestrogen cause cancer?

Answer 16

• After menopause women have a higher risk for developing cancer due to increase levels of oestrogen.
• Oestrogen stimulates transcription factors, which could create proto-oncogenes, which could become oncogenes and cause cancer.

Question 17

What are pluripotent stem cells.

Answer 17

embryonic stem cells that can differentiate into any cell type found in the embryo.

Question 18

What are induced pluripotent stem cells.

Answer 18

Stem cells that have been de-differentiated from specialised cells into their original pluripotent state, done by specific protein transcription factors.

Question 19

What are Mulitpotent adult stem cells.

Answer 19

• Stem cells found in adults that can differentiate an unlimited number of times into a limited number of cell types

Question 20

What are unipotent cells?

Answer 20

• adult cells that can only differentiate into their own lineage.

Question 21

What are totipotent stem cells?

Answer 21

• stem cells that can differentiate into any type of cell

Question 22

What does cellular development involve?

Answer 22

• The specialisation of cells and arranging them into tissues and organs.
  The cells must become adapted to carry out specific functions.

Question 23

Describe how Oestrogen stimulates gene transcription.

Answer 23

• Oestrogen diffuses into the cell as it is lipid-soluble.
• It binds to a receptor site on a transcriptional factor.
• The shape of the DNA binding site on the Transcription factor changes shape, or releases inhibitor.
• The transcription factor enters the nucleus through the nuclear pores, still bound to Oestrogen
• The TF binds to a specific base sequence on DNA.
• This stimulates the transcription of the gene.

Question 24

What do Transcription factors do?

Answer 24

• Have a site on them to bind to a specific base sequence in DNA.
• They stimulate genes to code/work.

Question 25

What are the ethics behind stem cells research?

Answer 25

- Each embryo is a potential human life, so people may argue that it is unacceptable to experiment with embryos. - However some people think it’s better to end someone’s suffering than debate an embryos right to existence.

Question 26

Describe the study of epigenetics.

Answer 26

- The study of gene expression without changing the base sequence.

Question 27

What is an epigenome?

Answer 27

- The chemical tags that modify or mark the genome in a way that tells it what do to, where to do it and when to do it.

Question 28

How does the epigenome work?

Answer 28

- Environmental signal stimulates proteins to carry messages into the cell. - A series of other proteins pass this information on. - Until finally a protein binds to a specific sequence on DNA. - This has the effect of acetylation of histones and/or methylation of DNA.

Question 29

Describe the effect of Deacetylation of histones.

Answer 29

- Removing the acetyl groups from histones increases the +ve charges on histones, so increases their attractions to the phosphate groups in DNA, causing the DNA-histones complex to become more compact, therefore making the DNA inaccessible to Transcription factors, so the gene is switched off and transcription cannot occur.

Question 30

Describe the effect of methylation of DNA.

Answer 30

- The methyl groups is attached to the cytosine base in DNA, inhibiting transcription by preventing the binding of transcriptional factors to the DNA, or by attaching proteins that induce deacetylation of the histones, so making the DNA-histones complex more compact.

Question 31

How is the epigenome linked to cancer developing?

Answer 31

- Tissue samples from patients with colectroal cancer has less DNA methylation that normal tissues, so more genes are turned on. - Cancer cells can also have genes that have more methyl than normal, so are less active.

Question 32

What are some of the types of cells that are usually tuned down in cancer?

Answer 32

Cells that… - keep cell growth in check. - repair damaged DNA - initiate programmed cell death.

Question 33

How can gene expression be prevented?

Answer 33

- Using siRNA to bind to mRNA that has been transcribed from target genes that need to be silenced, the mRNA can be broken down by the protein bound to the siRNA that can break down mRNA, preventing transcription.

Question 34

How is siRNA formed?

Answer 34

- Large, double stranded molecules are cut into siRNA by enzymes. The siRNA splits into single strands that are each associated with a different enzyme.

Question 35

How does siRNA function?

Answer 35

- The siRNA leads the enzyme which cut it up to the mRNA needing to be broken down. - Once there the enzyme cuts the mRNA into small sections preventing transcription.