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Biology - Unit 8 > Chapter 20 - Gene Expression > Flashcards

Chapter 20 - Gene Expression Flashcards

1
Q

Define mutation

A

A sudden change in the amount or the arrangement of the genetic material in a. cell

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2
Q

Define gene mutation

A

A change to one or more nucleotide bases in DNA resulting in a change in genotype which may be inherited

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3
Q

When may gene mutations arise?

A

During the replication of DNA

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4
Q

What is a substitution of base?

A

A nucleotide in a DNA molecule is replaced by another nucleotide with a different organic base

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5
Q

What are the three consequences of base substitution?

A
  • Formation of stop codon and hence protein synthesis stops
  • Formation of different codon and different acid and hence a possible nonfunctional protein
  • Formation of different codon but same amino acid so no effect
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6
Q

Define frame shift

A

Where a DNA base is deleted ands the reading frame containing each three letters is moved to the left by one

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7
Q

Define deletion of base

A

A loss of a nucleotide from a DNA sequence

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8
Q

Define and describe addition of bases

A

An extra base becomes inserted and frame shift to the right occurs unless n3 bases are inserted

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9
Q

Define and describe duplication of bases

A

Where one or more bases are repeated causing frameshift to the right

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10
Q

Define and describe inversion of bases

A

When a group of bases becomes separated and rejoins the DNA in inverse order causing a reversed effect on the amino acids

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11
Q

Define and describe translocation of bases

A

Where a group of bases become separated and inserted on a different chromosome causing abnormal phenotypes

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12
Q

Define and describe two mutagenic agents

A
  • High energy ionising radiation which disrupt the structure of DNA
  • Chemicals such as nitrogen dioxide disrupt the structure of DNA or interfere with transcription
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13
Q

Why may mutations be “good?”

A

They created genetic diversity necessary for natural selection and speciation

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14
Q

Why may mutations be “bad?”

A

They produce harmful effects and can disrupt cellular activities

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15
Q

What causes a cell to become specialised?

A

Expression of certain genes

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16
Q

Define totipotent stem cell

A

A cell derived from a fertilised egg able to differentiate into any type of cell found in the body and into embryonic cells

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17
Q

Why do cells specialise instead of expressing all genes?

A

Prevent wastage and to carry out functions more effectively

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18
Q

Give the two ways in which genes are prevented from expressing themselves

A
  • Prevention of transcription (no mRNA)

- Prevention of translation

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19
Q

How do stem cells replenish themselves?

A

Self renewal

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20
Q

Give four origins of mammalian stem cells

A
  • Embryonic stem cells
  • Umbilical cord blood stem cells
  • Placental stem cells
  • Adult stem cells
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21
Q

Define pluripotent cell

A

Cells that can differentiate into almost any type of cell but cannot form extra embryonic cells

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22
Q

Define multipotent cell

A

Cells found in adults that can differentiate into a limited number of specialised cells. Examples include adult and umbilical cord stem cells

23
Q

Define unipotent cell

A

A cell derived from multipotent cells that can differentiate into one type of cell

24
Q

What are induced pluripotent cells?

A

Pluripotent cells created from unipotent cells by expressing genes which are currently not expressed

25
What is added to embryonic stem cells to cause them to differentiate in in vitro conditions?
Differentiation factors
26
What are transcriptional factors?
Molecules that bind to a specific site on DNA to begin the process of transcription
27
Describe how oestrogen regulates transcription
- Lipid soluble so freely diffuses into the cell membrane - Binds to receptor on transcription factor and changes shape making it complementary/removes inhibitor - Transcription factor moves into nucleus and binds to DNA to start transcription
28
What is epigenetics?
Heritable changes in gene function without changes to the base sequence of DNA
29
What is the epigenome?
The second layer found in DNA created by the chemical tags on histones
30
Why is the epigenome flexible?
The chemical tags on histones can respond to environmental changes
31
Describe how the epigenome is altered
- Environmental signal stimulates proteins to carry messages - Protein passes this into nucleus - Protein attaches to DNA causing acetylation or methylation
32
What is the effect of acetylation?
Activation of gene
33
Describe the consequence of less condense DNA-histone complexes
A weak association between DNA and histones leaving DNA accessible to transcription factors
34
Describe the consequences of more condense DNA-histone complexes
A strong association between DNA and histones leaving DNA not accessible to transcription factors
35
What is acetylation?
The process whereby an acetyl group is transferred to a molecule
36
How is DNA acetylated?
- Acetylecoenzyme A donates an acetyl group to DNA
37
What is the effect of deacetylation on DNA?
- Increases positive charge of histones - Increases attraction to phosphate groups - Association stronger - Not accessible to transcription factors
38
What is methylation of DNA
Addition of methyl (CH3) to cytosine bases
39
How does methylation inhibit transcription?
- Prevention of transcription factors binding to DNA | - Attracts proteins that induce deacetylation making DNA inaccessible to transcription factors
40
How can methylation increase the chances of mutations?
- Some genes repair DNA - Increased methylation leads to genes being switched off - Protein that repairs damaged base sequences not produced - Cancer is a consequence
41
What is small interfering RNA (siRNA)?
A type of RNA that destroys mRNA before translation
42
How is siRNA produced?
- Enzyme cuts large double stranded molecules of RNA into siRNA
43
How does siRNA prevent translation?
- After siRNA is produced, it combines with an enzyme - Bases on siRNA bond with bases on mRNA - Enzyme cuts the mRNA into smaller sections - mRNA no longer capable of being translated
44
What are proto-oncogenes?
Cells that stimulate cells to divide by producing proteins that stimulate cell division
45
How do proto-oncogenes stimulate cell division?
- Produce proteins that stimulate cell division | - Activates genes that cause DNA to replicate
46
What are oncogenes?
Mutated proto-oncogenes that produce a permanently activated receptor or code for a growth factor in excessive amounts
47
What are tumour suppressor genes?
Cells that control cell division, cause the cell cycle to stop when damage occurs and programme apoptosis
48
What occurs when a tumour suppressor gene mutates?
Cell division is not regulated and cells divide rapidly and out of control
49
How does hypermethylation lead to cancer?
- Occurs in specific region of tumour suppressor genes - Tumour suppressor gene inactivated - Transcription inhibited - Hence increased cell division occurs leading to a tumour
50
How can increased oestrogen concentration cause tumour formation?
- Oestrogen binds to transcription factor - Activates genes that promote cell division - Tumour forms
51
Why are genome projects useful?
- Understand inherited disease - More understanding means more medicine and cures - More predictions on likelihood of particular disease and so can avoid risk factors - Understand evolution
52
Why is it easy to determine the proteome of a prokaryote?
- Majority of prokaryotes have one circular piece of DNA | - No noncoding portions of DNA
53
Why is it useful to know the proteome of pathogens?
So we can analyse the antigens and use this for vaccines

Biology - Unit 8 (2 decks)

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