The Conrol of Gene Expression - Gene Expression

Question 1

State all the different types of mutation

Answer 1

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

Question 2

What is a substitution mutation

Answer 2

When one base is changed for a different base

Question 3

Does a substitution mutation result in frameshift

Answer 3

No

Question 4

What is an addition mutation

Answer 4

When one or more bases are inserted into the DNA base sequence

Question 5

Does an addition mutation result in frameshift

Answer 5

Yes

Question 6

What is a deletion mutation

Answer 6

When one or more bases are removed from the DNA base sequence

Question 7

Does a deletion mutation result in frameshift

Answer 7

Yes

Question 8

What is an inversion mutation

Answer 8

When a sequence of bases becomes separated from the DNA base sequence and rejoins at the same position but in the inverse order

Question 9

Does an inversion mutation result in frameshift

Answer 9

No

Question 10

What is a duplication mutation

Answer 10

When one or more bases are repeated

Question 11

Does a duplication mutation result in frameshift

Answer 11

Yes

Question 12

What is a translocation mutation

Answer 12

When a section of DNA from one chromosome breaks off and attaches to another chromosome

Question 13

Does a translocation mutation result in frameshift

Answer 13

No

Question 14

Describe the two features of a stem cell

Answer 14

• Undifferentiated cells
• Divide indefinitely by mitosis

Question 15

Totipotent stem cell definition

Answer 15

Can divide and differentiate into any type of body cell

Question 16

Pluripotent cell definition

Answer 16

Can divide and differentiate into most types of body cell

Question 17

Multipoint stem cell definition

Answer 17

Can divide and differentiate into a limited number of cell types

Question 18

Unipotent stem cell definition

Answer 18

Can divide and differentiate into only once cell type

Question 19

When are totipotent stem cells present in an organism’s life

Answer 19

• Early embryo
• First 4 days as an embryo

Question 20

When are pluripotent stem cells present in an organism’s life

Answer 20

Later embryo

Question 21

When are multipotent stem cells present in an organism’s life

Answer 21

Mature mammals

Question 22

Give an example of a unipotent stem cell

Answer 22

• Cardiomyocytes
• These are heart muscle cells

Question 23

How can a stem cell transplant be used in the treatment of diseases

Answer 23

Stem cells can be transplanted to divide and differentiate into the cell type required

Question 24

Advantages of adult stem cells

Answer 24

• No ethical issues
• Less chance for rejection since similar DNA is used

Question 25

Disadvantages of adult stem cells

Answer 25

- Multipotent, therefore can divide and differentiate into a limited number of cell types - Difficult to isolate

Question 26

Advantages of embryonic stem cells

Answer 26

- Pluripotent, therefore can divide and differentiate into almost all cell types - Easy to isolate since it uses embryos from IVF

Question 27

Disadvantages of embryonic stem cells

Answer 27

- Unethical - High chance of rejection

Question 28

What are iPs (Induced pluripotent stem) cells

Answer 28

Normal specialised body cells that have been reversed back into pluripotent cells

Question 29

How are iPs cells produced

Answer 29

Specialised cells are removed from a patient, and factors are added to make the cell pluripotent

Question 30

What are the Advantages of iPs cells

Answer 30

- Pluripotent, therefore can divide and differentiate into any cell type - A form of longterm treatment - No ethical issues as using own cells - Less chance of rejection

Question 31

- Describe how growth factors can be used in vitro to produce whole plants from plant tissue samples - What characteristic of plant cells allows for this process to occur

Answer 31

- Totipotent plant cells are grown in sterile conditions to produce a mass of undifferentiated plant cells (a callus) - The callus is placed in a growth medium and subjected to specific conditions - Under these conditions, the callus differentiates into specific plant tissues or tiny plantlets, which grow into whole plants - This process can occur since cells in a mature plant are all totipotent

Question 32

Describe the steps by which transcription factors control the expression of target genes

Answer 32

- Transcription factors are proteins - They move from the cytoplasm to the nucleus - They bind to a promotor on DNA - This stimulates RNA polymerase - The gene is transcribed and produces mRNA

Question 33

Describe the steps by which oestrogen initiates transcription

Answer 33

- Oestrogen is lipid soluble, so it crosses the phospholipid bilayer by diffusion - Oestrogen binds to a complementary protein receptor in the cytoplasm - The receptor-oestrogen complex acts as a transcription factor, and it binds to a promotor on DNA - This stimulates RNA polymerase to transcribe the gene and produce mRNA

Question 34

Describe the steps by which siRNA controls gene expression via RNA interference

Answer 34

- siRNA has a specific complementary base sequence to the target mRNA - The siRNA now binds to mRNA molecules by complementary base pairing - The mRNA is destroyed The mRNA can no longer be used in translation and is broken down by enzymes

Question 35

Explain why siRNA is specific to a certain mRNA

Answer 35

They have complementary base sequences

Question 36

Describe the difference between miRNA and siRNA

Answer 36

miRNA is not fully complementary and not specific to one mRNA and therefore targets more than one type of mRNA

Question 37

Define epigenetics

Answer 37

Epigenetics involves the heritable changes in gene function without changing the base sequence

Question 38

Explain how increased methylation affects the expression of genes

Answer 38

- Methyl groups are added to DNA - Transcription factors CANNOT bind to the promotor - RNA polymerase is not activated - The gene is not transcribed

Question 39

Explain how acetylation affects the expression of genes

Answer 39

- The addition of acetyl groups to histone proteins makes chromatin LESS condensed - Transcription factors CAN bind the promotor - RNA polymerase is activated - Transcription DOES occur

Question 40

What is a malignant tumour

Answer 40

- Cells can break off and spread to other parts of the body, forming a tumour elsewhere - Metastasis occurs

Question 41

What is a benign tumour

Answer 41

- Cells do not spread to other parts of the body - No metastasis occurs

Question 42

Describe the function of tumour suppressor genes

Answer 42

Codes for proteins which prevent cell division

Question 43

Describe the function of proto-oncogenes

Answer 43

Code for proteins which stimulate cell division

Question 44

Describe how a mutation in tumour suppressor genes leads to the formation of a tumour

Answer 44

- Stop the formation of proteins, which prevent mitosis - This leads to uncontrolled cell division

Question 45

Describe how a mutation in proto-oncogenes leads to the formation of a tumour

Answer 45

- Mutation of proto-oncogenes to oncogenes - Forms more proteins, which causes cell division - This leads to uncontrolled cell division