Unit 8: Gene expression and DNA technology Flashcards
(95 cards)
1
Q
What is a gene mutation?
A
changes in sequence of nucleotide bases in DNA
2
Q
What genes control the rate of cell division?
A
Proto-oncgenes
Tumour suppressor genes
3
Q
What is the function of a Proto-oncogene
A
genes that code for proteins that stimulate cell division
4
Q
What is the function of Tumour suppressor genes?
A
genes code for proteins that slow cell devision
5
Q
What can happen if mutations occur in proto-oncogenes and tumour suppressor genes?
A
mutations can lead to rapid uncontrolled cell division (by mitosis) leading to the development of a tumour
6
Q
How do mutations in proto-oncogenes occur?
A
a mutated version called a oncogene stimulates cells to divide too quickly
resulting in tapid uncontrollable cell division
7
Q
How do mutations in Tumour suppressor genes occur?
A
a mutation leads to the tumour suppressor protein not being made of being non functional*
results in rapid uncontrollable cell division
8
Q
What is cancer?
A
a group of diseases caused by alterations in the genes that regulate mitosis and the cell cycle
9
Q
What is a tumour?
A
masses of dividing cells
10
Q
What are the two types if tumours
A
Benign
Malignant
11
Q
Describe a benign tumour
A
- grow slower than malignant
- non cancerous, they dont spread to other tissues bc the tumour is enclosed by fibrous tissue
- cells remain differentiated (specialised)
- nucleus has a normal appearance
12
Q
Describe a Malignant Tumour
A
- grow faster than benign
- cancerous cells break off and spread to other parts of the body bc tumour isn’t enclosed
- cells become undifferentiated (not specialised)
- nucleus is larger and darker
13
Q
What are stem cells?
A
undifferentiated cells that can divide by mitosis and differentiate into different types of cells
14
Q
What are Totipotent stem cells?
A
occur for a limited time in early manmalian embryos
can differentiate into any type of cell
15
Q
What are pluripotent stem cells?
A
- found in embryos and develop from totipotent stem cells
- can differentiate into almost any type of cell
- cant produce cells of embryonic tissue
16
Q
What ate the two embryonic stem cells
A
Totipotent
Pluripotent
17
Q
What are multi-potent stem cells?
A
adult stem cells
found in mature aminals
differentiate into few limited types of specialised cells
18
Q
What are unipotent stem cells?
A
found in mature animals
can only differentiate into one type of cell
19
Q
What are induced pluripotent stem cells (iPS)?
A
type of pluripotent cell produced from unipotent stem cells
appropriate transcription factors make the unipotent cell pluripotent
20
Q
What is the function of iPS cells?
A
develop into a wide range of different types of tissue which could be used to treat people with certain diseases
21
Q
What is the function of a transcription factors?
A
proteins that bring about expressions of some genes and inhibit other genes so that these cells differentiate a particular cell
22
Q
Describe the role of oestrogen and gene expression
A
- oestrogen is lipid soluble and diffuses across the cell membrane
- oestrogen specifically bind to a receptor protein that is part of a transcription factor
- transcription factor enters nucleus
- binding change of shape of TF and allows it to bind to promoter sequence of a gene
- allows RNA polymerase to attach to gene and catalyse transcription
- mRNA then subscribed then translated into a protein
23
Q
how can oestrogen lead to cancer?
A
In some tissues oestrogen increases the expressions of genes
so high concentrations can increase uncontrollable cell division
24
Q
How does Tamoxifen treat some breast cancer?
A
it is converted into endoxifen which is a molecule of a similar structure to oestrogen
It competes with oestrogen for biding to an oestrogen receptor
25
what is siRNA?
short double stranded sections of RNA
Usually 20 to 25 base pairs long
26
what is the function of siRNA?
Regulates gene expression by **causing mRNA to be broken down after transcription** thus **preventing translation**
27
How does siRNA prevent translation?
- double trended RNA is hydrolysed into short molecules
- RNA becomes single stranded siRNA
- siRNA binds to an enzyme that hydrolyses mRNA
- it then binds to a specific molecule of mRNA by complementary base pairing and guides to hydrolytic enzyme to a target molecule of mRNA
- The enzyme hydrolyses the mRNA this prevents the translation
28
What is epigenetics?
change in **gene function** without changes in the base sequence DNA
**heritable**
29
What causes epigenetics?
aspects if the environment
e.g stress diet
30
What are. two epigenetic changes?
increased methylation of DNA
decreased acetylation of associated histones
31
How does increased methylation occur?
- **methyl group attaches** to the DNA sequence of a gene
- attaches to CpG site
- prevents binding of transcription factors to promoter sequence so gene isn’t expressed
- thus preventing transcription
32
How does acetylation increase transcription?
histones are **more acetylated** meaning the **chromatin is less condense**
so transcription is more likely as genes are more accessible to transcription factors
33
How does acetylation decrease transcription?
histones are less acetylated so the chromatin is more condensed
This inhibits transcription as genes are not accessible to transcription factors
34
how can epigenetic changes lead to disease?
By causing abnormal activation/inhibition of genes
35
How can cancer develop from hypermethylation?
**too much** methylation of tumour suppressor genes so they are not transcribed
the proteins that slow down cell division are not produces causing rapid cell division
36
How can Hypomethylation cause cancer?
**too little** methylation of proto-oncogenes so **they’re continually transcribed**
this increases production of proteins involved in stimulating cell division causing rapid cell division and to development
37
What are the function of restriction endonucleases?
**hydrolyse phosphodiester bonds** in DNA/RNA producing smaller fragments
38
Where do restriction enzymes hydrolyse DNA/RNA?
at specific base sequences AKA **recognition sequences**
39
How are sticky ends made
when restriction enzymes hydrolyse DNA at different **locations other then the recognition sites**
40
How are blunt ends made?
When restriction enzymes hydrolyse DNA at the same position in both strands
41
What is the **function** of sticky ends?
enable DNA to be **joined or spliced** onto a different piece of DNA **more easily**
because complementary base pairing occurs between sticky ends
42
What is gel electrophoresis?
Separates DNA/RNA fragments from
- small fragments will travel faster/further thru the gel when an electric charge is applied
43
Where do fragments move in gel electrophoresis?
Negatively charged DNA fragments move **towards positively charged terminals**
44
Outline gel electrophoresis
- DNA samples placed in well at top of gel
- DNA fragments in the each sample separate according to size
- fragments are then transferred to a nylon membrane then radioactively labelled probes are added
- nylon membrane is placed on X-ray and position of radioactivity labelled fragments are revealed as dark bands **(autoradiography)**
45
What are DNA ladders?
has DNA fragments of known size and are used to calculate the size of unknown samples
46
What is a polymerase chain reaction?
enables multiple copies of identical fragments of DNA/genes to be produced from a small sample
47
outline a polymer chain reaction
- Primers and DNA are mixed and heated at 95°/ 5 minutes (breaks hydrogen bonds s)
- cool to 55°/2 minutes allows primers to anneal to specific target sequence
- free DNA nucleotide align to DNA strands by CBP
- temperature is increased to 72° (optimum for DNA polymerase) enzyme joins nucleotides to form new complementary strand
48
how do you calculate the number of molecules produced in PCR?
2^n
n= number of cycles
49
What is a DNA primer?
short single standard molecules of DNA
Provide starting sequence for DNA polymerase
- Important because DNA polymerase can’t begin at a single stranded starting point
Prevent original DNA strands joining back together
50
What is a DNA probe?
short single standard molecules of DNA that are **radioactively/fluorescently labelled**
Used to identify/locate known sequences of DNA
51
What is recombinant DNA technology?
transfer of fragments of DNA from one organism/species to another
52
What is a transgenic organism?
organism that has **received transferred DNA**
53
how can you obtain a required fragment/gene using reverse transcriptase?
- mRNA uses as a template to produce required chain/fragment of DNA
- mRNA is mixed with free nucleotides and reverse transcriptase
- free DNA nucleotides align next to
complementary bases on mRNA
- reverse transcription joints, DNA nucleotide together triple produce a fragment/gene
- DNA strand produced by this is called **complementary DNA**
- Double stranded DNA is produced from cDNA using DNA nucleotides and DNA polymerase
- No introns
54
How can you obtain a fragment using restriction enzymes?
required gene/fragment can be removed from the DNA using restriction endonuclease enzymes
-**Contains introns**
55
How can you produce fragments using a gene machine?
- doesn’t need pre-existing DNA or mRNA as a template
- **amino acid sequence of a protein** is used as a **template** to determine the sequence of DNA nucleotides for a specific gene
- **automated process** — required nucleotide sequence is programmed into the gene machine
**No introns**
56
Why must introns not be present in gene transfers?
If the source of the gene is eukaryotic and the recipient is prokaryotic introns can’t be present
57
what are promoter and terminator regions?
**sections of DNA** which must be **added to the gene/fragment** of DNA for successful transcription of the transferred genes in the recipient cells
58
What is a promoter region?
**initiate transcription** by promoting the binding of RNA polymerase
59
What is a terminator region?
**marks the end of a gene** and triggers **release of the mRNA** transcribed
60
What does it mean to amplify fragments of DNA?
Increase the number by replication
61
what is invivo?
copies are made **inside** the living organism
62
What is invitro?
copies are made **outside** a living organism
Usually by PCR
63
What are the two techniques of amplification?
in vivo
In vitro
64
What is a vector used for?
Transfers genes
65
What vector is used in bacteria?
plasmid
66
What are some other vectors?
Viruses and liposomes (phospholipid sack)
67
What is bacteria used for?
- **producing a protein** code for by a transferred gene
- **clone genes/fragments** (invivo cloning)
68
How does bacteria clone gene/fragments?
in vivo cloning
the **rapid reproduction rate** of bacteria allows a transferred gene to be **quickly copied** so a large amount of gene product can be obtained
69
How is the plasmid used to transfer a fragment/gene?
* plasma is caught using the same restriction endonuclease that cut the gene
* plasma DNA and foreign DNA join by base pairing
as they have complementary sticky ends
* **ligase** is used to form the phosphodiester bonds
* the plasma with the foreign DNA is referred to as a **recombinant plasmid**
70
What is transformation?
process in which bacteria take up the recombinant plasmid
This allows these plasma vectors to be added to a culture of bacteria
71
Why may the use of vectors not work?
- cells may not take up the vector
- Cells may take up the vector with the vector might not contain the gene
(plasma may have joined back together without the foreign DNA being taken up)
72
What is marker gene?
Allows successfully transformed bacteria/eukaryotic cells to be **detected and isolated for subsequent culturing**
73
How does GFP gene detect bacteria/eukaryotes?
GFP gene codes for the production of **green fluorescent protein**
GFP gene added to the gene being transferred
bacterial/eukaryotes can be identified as they fluorescence when viewed with **UV light** under a microscope
74
What are some humanitarian benefits of using recombinant DNA technology?
- Reducing famine and malnutrition by developing GM plants/animals which **produce high yields and are resistant to disease**
- producing vaccines and drugs
- Treating genetic diseases by gene therapy
75
what are some drawbacks of using recombinant DNA that come from environmentalists and anti globalisation activists?
- possible transfer of foreign genes to non target organisms
- An irreversible process with no certainty of economic benefits
- Ethical considerations with regard to permanently altering the genome of animals
- Long-term ecological and evolutionary consequences are unknown
76
what is gene therapy?
Uses recombinant DNA technology for the **treatment of genetic diseases**
77
How does gene therapy work?
Involves the introduction of **functional copies** of an allele into an organism which possesses **defective alleles** of the same gene
78
What are the stages of gene therapy?
• identify gene causing the disease
• obtaining and cloning copies of the functional allele
• transferring these functional values into the patient (by use of a vector)
• ensuring that the values reached the target cells and function normally
79
What is DNA sequencing?
involves technique to determine the sequence of DNA nucleotide bases (genome)
This allows the sequence of proteins (protein) to be determined
80
what are applications of DNA sequencing?
Can identify potential antigens for use vaccines
81
Why can the genome not be translated into proteom in some organisms?
these organisms are more **complex**
presence of **non coding DNA** and **regulatory genes** means the genome can’t easily be translated into the proteome
82
What is used to screen people for specific alleles
DNA probes and DNA hybridisation
83
What is the procedure before screening?
* a DNA probe is made that is complementary to the DNA sequence of the allele being investigated
* multiple copies of the DNA probe are made using PCR
* the sample of DNA is obtained from the person/organism being tested
84
Outline screening
- The DNA that’s being tested is fragmented by restriction endonucleases
- Fragments are separated by gel electrophoresis
- Fragments are treated and split into single strands
- Single strands are transferred to nylon membrane and probes are added
- Membrane is **washed** remove unattached probes
- If allele is present labelled DNA probe will bind to a complementary base on **one** of its strands
presents for as position of probe can be **identified by the radioactivity/fluorescence** it admits
85
what can patients be screened for?
- Heritable conditions
- individual drug responses
people respond differently to particular drugs due to differences in their alleles — this leads to personalised medicine
- Health risks
86
what is genetic counselling?
uses information concerning the **presence of identified mutant alleles**
87
What is genetic counselling used for?
- understand the **probability** of people developing a disease
- Advise parents who may be **carriers** of a disease causing allele
- decide the **best course** of drug treatment for genetic diseases
88
What is a variable number Tandem Repeat
many **repetitive non-coding sequences** of nucleotide bases in a genome
89
what are VNTRs used for?
Analysis of these can be used to:
- determine the relatedness between individuals
- match the identity of a DNA sample to an individual
90
Outline the procedure of genetic fingerprinting
1. PCR is used to amplify the sample DNA
2. It’s then cut into fragments using restriction endonucleases
cut DNA at sites close to, but not within the VTNRs giving a large number of DNA fragments
(some fragments will be the same length others different)
3. fragments are separated by gel electro forces.
4. Fragments are treated using alkali to form single strands
5. Singles strands are transferred to a nylon membrane
6. Radioactive probes are added that are complimentary to the repeated sequences.
Many probes are used and each bind with the VNTRs by DNA hybridisation
7. Radioactive probes allowed the position of fragments to be identified when the membrane is placed onto an x-ray film (the genetic fingerprint is obtained).
91
How can genetic fingerprints be compared?
if fingerprints have bands at the same position on the gel it means they have the same number of nucleotides and repetitive sequences
92
How is genetic fingerprint used in forensic science?
By comparing DNA samples from crime scene with DNA of suspects
93
How is genetic fingerprinting used to diagnose?
Certain diseases involve unique patterns of several areas and can be identified by fingerprinting
94
How is genetic fingerprinting used to determine genetic relationships?
it can determine genetic relationship relationships and genetic variability in a population as more closely related species have **more similar VNTRs**
95
how is genetic fingerprinting used in animal and plant breeding?
**ensuring genetic diversity is maintained** by screening organisms to **prevent inbreeding** between closely related individuals
