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A-Level Biology > The Conrol of Gene Expression - Gene Expression > Flashcards

The Conrol of Gene Expression - Gene Expression Flashcards

1
Q

State all the different types of mutation

A
  • Substitution
  • Addition
  • Deletion
  • Inversion
  • Duplication
  • Translocation
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2
Q

What is a substitution mutation

A

When one base is changed for a different base

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3
Q

Does a substitution mutation result in frameshift

A

No

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4
Q

What is an addition mutation

A

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

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5
Q

Does an addition mutation result in frameshift

A

Yes

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6
Q

What is a deletion mutation

A

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

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7
Q

Does a deletion mutation result in frameshift

A

Yes

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8
Q

What is an inversion mutation

A

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

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9
Q

Does an inversion mutation result in frameshift

A

No

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10
Q

What is a duplication mutation

A

When one or more bases are repeated

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11
Q

Does a duplication mutation result in frameshift

A

Yes

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12
Q

What is a translocation mutation

A

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

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13
Q

Does a translocation mutation result in frameshift

A

No

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14
Q

Describe the two features of a stem cell

A
  • Undifferentiated cells
  • Divide indefinitely by mitosis
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15
Q

Totipotent stem cell definition

A

Can divide and differentiate into any type of body cell

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16
Q

Pluripotent cell definition

A

Can divide and differentiate into most types of body cell

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17
Q

Multipoint stem cell definition

A

Can divide and differentiate into a limited number of cell types

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18
Q

Unipotent stem cell definition

A

Can divide and differentiate into only once cell type

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19
Q

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

A
  • Early embryo
  • First 4 days as an embryo
20
Q

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

A

Later embryo

21
Q

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

A

Mature mammals

22
Q

Give an example of a unipotent stem cell

A
  • Cardiomyocytes
  • These are heart muscle cells
23
Q

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

A

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

24
Q

Advantages of adult stem cells

A
  • No ethical issues
  • Less chance for rejection since similar DNA is used
25
Q

Disadvantages of adult stem cells

A
  • Multipotent, therefore can divide and differentiate into a limited number of cell types
  • Difficult to isolate
26
Q

Advantages of embryonic stem cells

A
  • Pluripotent, therefore can divide and differentiate into almost all cell types
  • Easy to isolate since it uses embryos from IVF
27
Q

Disadvantages of embryonic stem cells

A
  • Unethical
  • High chance of rejection
28
Q

What are iPs (Induced pluripotent stem) cells

A

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

29
Q

How are iPs cells produced

A

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

30
Q

What are the Advantages of iPs cells

A
  • 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
31
Q
  • 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
A
  • 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
32
Q

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

A
  • 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
33
Q

Describe the steps by which oestrogen initiates transcription

A
  • 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
34
Q

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

A
  • 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
35
Q

Explain why siRNA is specific to a certain mRNA

A

They have complementary base sequences

36
Q

Describe the difference between miRNA and siRNA

A

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

37
Q

Define epigenetics

A

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

38
Q

Explain how increased methylation affects the expression of genes

A
  • Methyl groups are added to DNA
  • Transcription factors CANNOT bind to the promotor
  • RNA polymerase is not activated
  • The gene is not transcribed
39
Q

Explain how acetylation affects the expression of genes

A
  • 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
40
Q

What is a malignant tumour

A
  • Cells can break off and spread to other parts of the body, forming a tumour elsewhere
  • Metastasis occurs
41
Q

What is a benign tumour

A
  • Cells do not spread to other parts of the body
  • No metastasis occurs
42
Q

Describe the function of tumour suppressor genes

A

Codes for proteins which prevent cell division

43
Q

Describe the function of proto-oncogenes

A

Code for proteins which stimulate cell division

44
Q

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

A
  • Stop the formation of proteins, which prevent mitosis
  • This leads to uncontrolled cell division
45
Q

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

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

A-Level Biology (23 decks)

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