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Biology > 3.8 The control of gene expression (A-level only) > Flashcards

3.8 The control of gene expression (A-level only) Flashcards

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1
Q

Gene mutation

A
  • change in base sequence of DNA
  • occurs during DNA replication
  • includes addition, deletion, substitution, inversion, duplication and translocation of bases
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2
Q

Mutagenic agents

A
  • chemical or radiation that
    increases mutation rate
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3
Q

Addition mutation

A
  • One extra base is added to the DNA sequence
  • causes all subsequent codons to be altered (frameshift)
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4
Q

Deletion mutation

A
  • One base is deleted in the DNA sequence.
  • causes all subsequent codons to be altered (frameshift)
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5
Q

Substitution mutation

A
  • One base in the DNA sequence is changed
  • no frameshift
  • only one codon changes
  • may have no impact due to degenerate genetic code
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6
Q

Frameshift

A
  • A change in all the codons after the point of mutation
  • each base shifts left or right one position
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7
Q

Inversion mutation

A
  • A section of bases detach from the DNA sequence and re-join inverted
  • results in different amino acids being coded for in this region
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8
Q

Duplication mutation

A
  • One base is duplicated at least once in the sequence
  • causes a frameshift to the right
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9
Q

Translocation of bases mutation

A
  • A section of bases on one chromosome detaches and attaches to a different chromosome
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10
Q

Non-functioning protein

A
  • a protein with a different primary and tertiary structure
  • therefore the shape is changed
  • it cannot carry out its function
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11
Q

Tumour

A
  • a mass of cells as a result of uncontrolled cell division
  • can be benign or malignant
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12
Q

Benign tumour

A
  • non-cancerous tumour
  • grows large but at a slow rate
  • produce adhesive and are surrounded by a capsule so they cannot spread
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13
Q

Malignant tumour

A
  • cancerous tumour
  • grows rapidly
  • can become unspecialised
  • can metastasise
  • grow projections
  • develop own blood supply
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14
Q

Cancer

A
  • Malignant tumours that form due to uncontrolled cell division
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15
Q

Metastasis

A
  • cancer cells breaking off from the tumour
  • spreading to form secondary tumours in different tissues or organs
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16
Q

Oncogene

A
  • a mutated version of a proto-oncogene
  • results in constant initiation of DNA replication and mitotic cell division
  • causes tumour formation
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17
Q

Tumour suppressor genes

A
  • genes that produce proteins to slow down cell division and cause cell death if DNA copying errors are detected
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18
Q

Epigenetics

A
  • the heritable change in gene function
  • without changing the DNA base sequence
  • caused by changes in the environment
  • can inhibit transcription
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19
Q

Hypermethylation

A
  • an increased number of methyl groups attached to a gene
  • results in the gene being deactivated
  • results in cancer if happens to a tumour suppressor gene
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20
Q

Methylation of DNA

A
  • inhibits transcription
  • methyl groups attach to the cytosine base on DNA
  • prevents transcriptional factors from binding
  • condenses the DNA-histone complex
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21
Q

How can oestrogen increase the risk of breast cancer?

A
  • Oestrogen is a steroid hormone
  • it binds to a receptor site on a transcriptional factor
  • causing a change in shape
  • so it can bind to the DNA to initiate transcription
  • can result in uncontrolled cell division
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22
Q

Stem cell

A
  • undifferentiated cells that can continually divide and become specialised
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23
Q

Totipotent stem cell

A
  • can differentiate into any body cell
  • occur for a limited time in early mammalian embryos
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24
Q

Pluripotent stem cell

A
  • can differentiate into almost any body cell
  • occur in embryos
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25
Multipotent stem cell
* can differentiate into a **limited number of cells** * found in mature mammals e.g. in **bone marrow**
26
Unipotent stem cell
* can differentiate into **one type of cell** * found in mature mammals
27
Induced pluripotent stem cell
* produced from **adult somatic cells** * using protein transcriptional factors * overcomes ethical issues of using embryonic stem cells
28
Transcriptional factor
* **proteins** that can bind to different base sequences on DNA * **initiate transcription** of genes
29
What is a vector?
* a DNA molecule used as a **vehicle** to carry a DNA fragment * e.g. **plasmids**/viruses
30
Acetylation of histones
* **Decreased** acetylation **inhibits transcription** * removing acetyl groups makes the **histones more positive** * this attracts the negative phosphate group on DNA * making it harder for the **transcriptional factors** to bind
31
RNA interference
* **inhibition of the translation** of mRNA * the **mRNA gets destroyed** so it cannot be translated
32
siRNA
* **small interfering** RNA * destroys mRNA molecules to **prevent translation**
33
Recombinant DNA technology
* combining **different organisms’ DNA** * enable scientists to manipulate and alter genes to improve **industrial processes** and **medical treatment**
34
Sequencing projects
* Reading the **full genome of organisms** * provides opportunities to screen DNA to identify potential **medical problems**
35
How can you create a DNA fragment?
* Reverse transcription with reverse transcriptase * restriction endonucleases * gene machine
36
Gene machine
* creates **DNA fragments** using a computerised machine
37
Reverse transcriptase
* An enzyme that makes **cDNA single-stranded** copies of DNA from mRNA
38
Restriction endonulceases
* Enzymes that cut up **DNA to create fragments** * cut at specific **recognition/restriction sequences** * results in **sticky ends**
39
In vivo cloning
* **Creating DNA fragments** using bacteria * involves **restriction endonulcease** enzymes
40
In vitro cloning
* Using **PCR** to create a **large number of copies** of a DNA fragment
41
Uses of PCR
* Used widely in gene technology to make **large numbers** of copies of **DNA fragments** * e.g. forensics, genotyping, cloning, paternity tests, microarrays
42
Uses of genetic fingerprinting
* Forensic science * medical diagnosis * plant/animal breeding * paternity tests
42
Describe the PCR process
* increase temperature to **95C to break hydrogen bonds** & split DNA into single strands * temperature is decreased to **55C** so **primers** can attach * **DNA polymerase** joins complementary nucleotides & makes a new strand * temperature increased to **72C** (optimum for Taq DNA polymerase)
43
What is gel electrophoresis?
* **Separation** of DNA samples using an **electrical voltage** * different lengths of DNA **VNTRs** are separated
44
Why does the DNA move in gel electrophoresis?
* DNA is **negatively charged** and moves towards the **positive end** of the gel * the **shorter the piece** of DNA, the faster and further it moves
45
What is genetic screening?
* Testing DNA to **identify the presence of alleles** that can cause/increase the risk of developing a disease
46
What is genetic counselling?
* a type of social work giving people **advice** and **information** following the **screening of disease causing alleles**
47
What is cDNA?
* Complementary, **single-stranded DNA** strands * created by **reverse transcriptase**
48
What are the advantages of using the gene machine?
* Very quick * accurate * create intron-free DNA
49
What are the advantages of using reverse transcription?
* Creates intron-free cDNA
50
What are the advantages of using restriction endonculeases?
* **Creates sticky ends** on DNA to enable the DNA fragments to join with complementary base pairs
51
Oligonucleotides
* **Short DNA molecules** * used in gene machines to create DNA fragments
52
Sticky ends
* Exposed **staggered ends** of bases * **palindromic** base sequences * created by restriction **endonuclease enzymes**
53
Palindromic sequence
* sequences of bases that read the **same forwards** as they do **backwards**
54
Blunt end
* When a restriction endonuclease cuts the DNA double-strand in the same position * there is **no overhang of bases**
55
What are the two methods to amplify DNA?
* In vivo * in vitro (PCR)
56
Promoter region
* a sequence of DNA that is the **binding site for RNA polymerase** to enable transcription to occur
57
Terminator region
* added at the end of the gene * it **causes RNA polymerase to detach** and stop transcription * to ensure one gene is copied into mRNA at a time
58
Plasmid
* a **small loop of bacterial DNA** * contains only a **few genes** * contains the genes for antibiotic resistance
59
Recombinant plasmid
* a small loop of bacterial DNA with the **DNA from another organism inserted** into it
60
Transformation
* the process of getting a plasmid to re-enter a bacterium * involves **calcium ions** and **temperature shocking**
61
How can transformed cells be identified?
* using marker genes * antibiotic resistance genes * genes coding for fluorescent proteins * genes coding for enzymes
62
What is a marker gene?
* genes on the plasmid used to **identify** which bacteria successfully took up the recombinant plasmid
63
DNA probe
* **short, single-stranded** pieces of DNA * labelled **radioactively** or **fluorescently** so that they can be identified
64
DNA hybridisation
* DNA is **heated to separate** the double helix into single strands * it is then mixed with complementary sequences of single-stranded DNA * it is then cooled so **complementary strands will anneal**
65
Personalised medicine
* screening for the presence of particular **alleles** * to select **medicines** and **personalise health** advice based on your genotype
66
VNTRs
* **variable number tandem repeats** sequences of bases in introns * unique to each person
67
How can DNA samples be collected?
* From blood, body cells or hair follicles
68
How is DNA extracted from cells so that it can be examined?
* cell fractionation and ultracentrifugation
69
How is DNA digested in genetic fingerprinting?
* **Restriction endonucleases** are added to cut the DNA into smaller fragments * enzymes that cut close to the target VNTRs are added
70
Why can the genome not be easily translated into the proteome in complex organisms?
* due to the presence of **non-coding DNA** and **regulatory genes**
71
What is the role of DNA ligase in making recombinant DNA?
* used to stick the DNA fragment to create recombinant DNA

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