chapter 20 - gene expression Flashcards
(107 cards)
1
Q
What is a gene mutation
A
It is where there is a change in quantity or the structure of DNA. And if there is any change to one or more nucleotide bases, or rearrangement of bases in the DNA this is known as a gene mutation.
2
Q
What is a nonsense mutation
A
It is where there is a formation of one of the three stop codons that mark the end of a polypeptide chain. As a result the production of the polypeptide coded for by the section of DNA would be stopped. The final Protein would be significantly different then the protein cannot perform its normal function.
3
Q
what is a misense mutation
A
It is why a codon codes for a different amino acid. Meaning that the structure of a polypeptide chain produced will differ in a single amino acid therefore the protein may not function properly. For example if it’s an enzyme it’s active so it may no longer fit the substrate and therefore the reaction will not be catalyzed.
4
Q
Give an example of a misense mutation
A
Sickle cell Amenia. Where one amino acid is substituted for another.
5
Q
What is a silent Mutation
A
It is where the formation of a different codon produces the same amino acid as before. This is because the genetic code is degenerate. So most amino acids have more than one codon. The mutation has no effect on the polypeptide produced and therefore the mutation will have no effect.
6
Q
What is deletion of a base
A
Where one or more nucleotide pairs are deleted from the sequence this causes a frame shift to the left. the gene is read differently. possibly lead to the production of a non functional protein.
7
Q
how does deletion differ if The base was deleted at the start of the sequence compared to the end of the sequence
A
If the base was deleted at the start of the sequence this could alter every triplet in the sequence. Whereas if the base is deleted at the end of the sequence this is likely to have a small impact but can still have a consequence.
8
Q
What is incision/addition of a base
A
It is why one or more nucleotide pairs are inserted into the sequence. This causes a frame shift to the right.
9
Q
What is duplication of bases
A
It is where one or more bases are repeated. This produces a frame shift to the right
10
Q
What is inversion of bases
A
It is where a group of bases become separated from the DNA sequence and re-join at the same position but in the inverse order. [Back to front]. The base sequence of this portion is then reversed and this affects the amino acid sequence that follows.
11
Q
What is translocation of bases
A
It is where a group of bases become separated from the DNA sequence on one chromosome and are inserted into the DNA sequence of a different chromosome. Translocations often have a significant effects on gene expression, leading to an abnormal phenotype.
12
Q
Give some examples of the effects from translocation of basis.
A
It can include the development of certain forms of cancer and also reduce fertility.
13
Q
List two ways in which mutagenic agents can increase the likelihood of a mutation via an outside factor.
A
From high energy ionizing radiation - For example alpha and beta particles as well as short wave length radiation such as x-rays and ultraviolet lights. These forms of radiation come disrupt the structure of DNA.
Chemicals - Such as nitrogen dioxide may alter the structure of DNA or interfere with transcription. Benzopyrene, a constituent of tobacco smoke, is a powerful musician that inactivates a tumor suppressor gene leading to cancer.
14
Q
What can happen when other chemicals add groups to nucleotides.
A
Benzopyrene is a chemical found in tobacco smoke. It can add a large group to guanine that makes it unable to bind with cytisine. When DNA polymerase reaches the affected guanine it’s inserts any of the other bases.
15
Q
What can happen when certain chemicals remove groups from nucleotide bases
A
Nitrous acid come remove an email group from cytisine in DNA changing it to your cell. different bases bind coordinarily
16
Q
what type of mutation is caused by benzopyrene
A
Ionizing radiation such as x-rays come produce highly reactive agents called free radicals. These free radicals can alter the shape of the bases in DNA so DNA polymerase can no longer act on them.
17
Q
Suggest one genetic affect of DNA polymerase being unable to act on DNA
A
The replication of DNA requires DNA polymerase therefore replication cannot continue
18
Q
What is cell differentiation
A
It is where cells are specialized to perform specific functions. The process by which each cell develops into a special structure suited to the role that it will carry out is known as cell differentiation.
19
Q
Why are differentiated cells different from each other
A
This is mainly because they each produce different proteins. The proteins a cell produces are coded for by the genes it possesses [more accurately, by the genes that are expressed [switched on]].
20
Q
What is a totipotent cell
A
come from a single fertilized egg. They can mature into any type of cell. The early cells that are derived from the fertilized egg are also totipotent. These later differentiate to become specialized.
21
Q
Give two ways in which genes are prevented from expressing themselves include:
A
Preventing transcription and preventing the production of mRNA.
Preventing translation
22
Q
What are stem cells
A
in mature mammals, only a few cells retain the ability to differentiate into other cells. These are called stem cells.
Stem cells are undifferentiated dividing cells that occur in adult animal tissues and need to be constantly replaced. They have the ability to divide to form an individual copy of themselves in a process called self renewal.
23
Q
What are embryonic stem cells [mammals]
A
they Come from embryos in the early stages of development. They can differentiate into any type of cell in the initial stages of development.
24
Q
What are unbiblical cord blood stem cells [mammals]
A
They are derived from umbilical chord blood and are similar to adult stem cells.
25
What are placental stem cells [mammals]
They are found in the placenta and develop into specific types of cells
26
What are adult stem cells [Mammals]
They are found in the body tissues of the fetus through to the adults. They are specific to a particular tissue or organ within which they produce the cells to maintain and repair tissues throughout an organisms life.
27
What are totipotent stem cells
They are found in the early embryo and can differentiate into any type of cell. Since all body cells are formed from a zygote, it’s follows that the zygote is totipotent.
They can further differentiates/develop into slightly more specialized cells called pluripotent stem cells.
28
What are pluripotent stem cells
They are found in embryos and can differentiates into almost any type of cell. However they cannot differentiate into placenta cells. Examples of pluripotent stem cells are embryonic and fetal stem cells.
29
What are multipotent stem cells
They are found an adult and can differentiate into a limited number of stem cells. They usually develop into cells of a particular type for example stem cells in the bone marrow can produce any type of blood cell. examples of multipotent cells all adult stem cells and umbilical cord blood stem cells and placenta cells.
30
What are unipotent stem cells
They can only differentiate into a single type of cell. They are derived from multipotent stem cells and I made an adult tissue.
31
What is IPS [overall]
Induced pluripotent stem cells
32
What is IPS in detail
Induced pluripotent stem cells [IPS cells] are a type of pluripotent cell that is produced from Unipotent stem cells. These body cells are generally altered in a laboratory to make them acquire characteristics of embryonic stem cells [a type of pluripotent cell] to make the unipotent cell acquire new characteristics.
To make the unipotent cell acquire new characteristics this involves inducing genes and transcriptional factors within the cell to express themselves. To turn on genes that were otherwise turned off. The fact that these genes are capable of being reactivated shows that adult cells retain the same genetic information that was present in the embryo.
33
How do you IPS cells differ to embryonic stem cells
IPS cells have a feature called self renewal. This means that they can potentially divide infinitely to provide a limitless supply. This Can lead to only a single sample needed to be taken as IPS cells replicate
34
What are the advantages of IPS cells
They are very similar to embryonic cells
They do not cause destruction to an embryo
The adults giving the body cells can give permission
35
What are pluripotent cells used for
They are used to treat human disorders. The stem cells could be used to regrow damage cells in humans. Such as, replace burnt skin cells, Replace beta cells [type one diabetes],Or neurons in Parkinson’s disease.
36
What are the disadvantages of using pluripotent cells for treating human disorders
Sometimes the treatment doesn’t work [could be rejection]
Pluripotent cells can continually divide sometimes forming a tumor [cancer]
Ethically, There is a debate on whether it is right to make a therapeutic clone of yourself to obtain stem cells. as the embryo will be destroyed
37
What type of cells are found in bone marrow
adult stem cells such as bone marrow Can produce different cells to replace those in a particular Organ/tissue.
They are multipotent
38
Describe the process of in vitro culturing of human embryonic stem cells
The early embryo is cultured in a nutrient medium
The outer layer collapses on the inner layer [cell mass] is freed from the embryo.
Chemicals are added to break up the cell mass into smaller groups.
Colonies of embryonic stem cells exist and each group grows into a colony
Special differentiation factors are added to colonies in separate containers.
differentiation occurs.
Differentiated cells are transferred to damaged tissues
39
Describe growth of plant tissue cultures
Mature plants have many totipotent cells. Under the right conditions many plant cells can develop into any type of cell. For example if we take a cell from the root of a carrot, place it in a suitable nutrient medium and give it certain chemicals stimuli at the right time we can develop a completely new carrot plant.
```
root cells of carrot plant
placed in growth medium
single cell to multiple via cell division
young plant
adult plant
```
40
Give three features of plant growth factors and how they are involved in the growth and development of plants issues
They have a wide range /effect on plants tissues
The effects on a particular tissue depend upon the concentration of growth factor
The same concentration affects different tissues in different ways
41
what are the general principles involved in controlling the expression of a gene by controlling transcription
Transcription factors move from the cytoplasm into the nucleus. These molecules switch on the gene allowing transcription to begin.
Each transcription factor has a site that binds to a specific base sequence of DNA in the nucleus
When it binds it causes the region of DNA to begin the process of transcription.
Messenger RNA is produced on the information it carries is in translated into a polypeptide.
What a gene is not being expressed [switched off] the site on the transcription factor that binds to DNA is not active.
As the site is inactive it cannot cause transcription and polypeptide synthesis.
42
What does oesteogen do
it can switch on a gene. and it’s a steroid hormone. It starts transcription by combining with a receptor sites on the transcription factor. This activates the DNA binding site by causing it to change shape.
43
Describe the process of transcription and how oestrogen has a role
oestrogen Is a lipid soluble molecule so diffuses easily through the phospholipid bilayer.
Once inside the cytoplasm, oestrogen Binds with the site on a receptor molecule of the transcription factor. they bind in a complementary manner
The binding with the site, oestrogen Changes the shape of the DNA binding site on the transcriptional factor which can now bind to DNA [the transcriptional factor is activated]
The transcription factor can now enter the nucleus through a nuclear pore and bind to specific base sequences on DNA.
The combination of the transcription factor with DNA stimulates transcription of the gene that makes up the portion of DNA.
44
What is epigenetic’s
Where environmental factors can cause heritable changes in gene function, without changing the basic sequence of DNA.
45
Tell me about factors that can affect epigenetic’s
epigenetic‘s there’s a relatively new scientific field that provides explanations as to how environmental influences such as diet, stress, toxins etc. can subtly go to the genetic inheritance of an organisms offspring. It is helping to explain and maybe cure illnesses ranging from diabetics to cancer. It is even causing scientists to look again previously discredited theories Of evolution that suggested characteristics acquired during an organisms life could be passed on to future generations [lamarckism]
46
What is an epigenome
Both DNA and histones all covered in chemicals, sometimes called tags. These chemical tags form a second layer known as the Epigenome.
It also determines the shape of the DNA histone complex.
47
what is epigenetic silencing
This is where the inactive genes are packed in a tight arrangement, this ensures they cannot be read [it keeps them switched off]
This can work conversely [it unwraps active genes so that the DNA is exposed and can be easily transcribed] [switches them on].
48
Why is he a epigenome flexible
DNA code is fixed. epigenome Is flexible. This is because it’s chemical tags respond to environmental changes. Factors like diet and stress can cause the chemical tags to adjust the wrapping and unwrapping of DNA, switching genes on and off.
49
Where do epigenome signals come from
epigenome of a cell is the Accumulation of the signals it has received during its lifetime and it acts like a cellular memory.
In early development, the signals come from within. The cells of the fetus are provided by the mother, this is important in shaping the epigenome At this stage.
After birth, and throughout life, environmental factors affect the epigenome. Although signals from within the body for example hormones also influence it. These factors cause the epigenome to activate or inhibit specific sets of genes.
50
what is acetylation
Acetylation of histones leading to the activation or inhibition of a gene.
51
What is methylation
Methylation of DNA by attracting enzymes that can add or remove methyl groups
52
How can an environmental signal Determine whether a gene is activated or not
The environmental signal stimulates proteins to carry its message inside the cell from where it’s passed by a series of proteins, Into the nucleus. Here the message passes to a specific proteins which can be attached to specific sequences of bases on the DNA.
53
What happens when the DNA-his tone complex is condensed
Where the association between DNA and histones are stronger, the complex is more condensed [tightly packed]. In this condition the DNA is not accessible by transcription factors which therefore cannot initiate the production of mRNA. Then the gene is switched off.
Condensation of the DNA histone complex inhibits transcription. It can be brought about by decreased acetylation of the histones or by methylation of the DNA.
54
What happens when the DNA histone complex is weaker
Where the association of histones with DNA is weak, the DNA histone complex is less condensed [loosely packed]. In this condition the DNA is accessible by transcription factors, which can initiate production of mRNA, switching the gene on.
55
What is another word for the DNA histone complex
Chromatin
56
Describe the process of decreased acetylation of associated histones
Acetylation is the process whereby an acetyl group is transferred to a molecule. The group donating the acetyl group is acetyl-CoA. Deacytalation is where an acetyl group is removed from a molecule.
Decreasing acetylation increases the positive charges on histones and therefore increases the attraction to the phosphate groups of DNA. The association between chromatics is stronger, the DNA is not accessible to transcription factors. These transcription factors cannot initiate mRNA production to form DNA. The gene is switched off.
57
increased methylation of DNA
addition of a CH3 group to a molecule. The methyl group is added to the cytosine bases of DNA. Methylation normally inhibits the transcription of genes and two ways:
Preventing the binding of transcription factors to the DNA
By attracting proteins that condense the chromatin complex [by inducing deacetylation of histones] Making the DNA in accessible to transcription factors.
58
Tell me about epigenetic’s and inheritance
For example in humans, when a mother has a condition it increases the likelihood that the daughter will develop the condition herself.
It is thought that in the earliest stages of development a specialized cellular mechanism searches the genome and erases its epigenetic tags in order to return the cells to a genetic ‘clean state’. However a few epigenetic tags escape this process and pass unchanged from parent to offspring.
59
Tell me about epigenetic’s and disease
Epigenetic changes are a part of normal development, but they can also be responsible for certain diseases. Changing any of the epigenetic processes can cause abnormal activation or silencing of genes. Such alterations have been associated with a number of diseases including cancer. In some cases the activation of a normally inactive gene can cause cancer, and in other cases it is the inactivation of a normally active gene that gives rise to the disease.
60
How can cancer develop in the early stages [hint Methylation]
There are specific sections of the DNA [promoter regions] that have no methylation in normal cells. However in cancer cells these regions become highly methylated, causing genes that should be active to switch off. This abnormality happens in the early development of cancer.
61
Tell me about treating diseases with epigenetic therapy
As we have seen many diseases such as cancer are triggered by epigenetic changes that caused certain genes to be activated or silenced. So it is logical to try to use epigenetic treatments to contract these changes. These treatments use drugs to inhibit certain enzymes involved in either Histone acetylation Or DNA methylation. This can reactivate genes that have been silenced. However Epigenetic therapy must be specifically targeted on cancer cells. If the drugs were to affect normal cells they could trigger cancer.
62
how can epigenetic’s and disease treatment help to detect the early stages of diseases such as cancer via diagnostic tests.
Another use of epigenetic’s can disease treatment has been the development of diagnostic tests that’s helped to detect the early stages of diseases such as cancer, brain disorders and arthritis. These tests can identify the level of DNA methylation and histone acetylation At an early stage of disease. This allows those with the disease to seek early treatment and have a better chance of a cure.
63
The effect RNA interference on gene expression
In eukaryotes and some prokaryotes the translation of mRNA Produced by a gene can be Inhibited by breaking mRNA down before it’s coded information can be translated into polypeptide. One type of small RNA molecule that may be involved is small interfering RNA [siRNA). The mechanism involves small double-stranded sections of siRNA.
An enzyme cuts large double-stranded molecules of RNA into smaller sections called (siRNA)
One of the two siRNA Strands combines with an enzyme
The small interfering RNA Guides the enzyme to a mRNA molecule by pairing up at bases with a complimentary ones on the section of the mRNA molecule.
Once in position, the enzyme cuts that mRNA into smaller sections
The mRNA is no longer capable of being translated into a polypeptide
This means that the Gene has not been expressed and it has been blocked.
64
what is a single layer of chemical tags on the DNA called
epigenome. it affects the shape of the DNA histone complex. and wether DNA is tightly or loosely bound.
65
what happens if the DNA is tightly wound
transcription factors cannot bind and the epigenome inhibits transcription
66
give two examples if chemical tags
methylation
| acylation
67
what’s a heterochromatin
tightly coiled DNA
68
what’s euchromatin/chromatin
loosely coiled DNA
69
when only does transcription occur
when transcriptional factors enter the nucleus from the cytoplasm. RNA polymerase binds to DNA weakly at first at the promoter region. when transcriptional factors bind to the DNA the RNA polymerase is activated and only then can transcription occur. then mRNA can be created
70
why are transcriptional factors important
if they don’t bind to DNA, RNA polymerase isn’t activated. and the mRNA isn’t made. and the gene is inactive
71
what are transcriptional factors
proteins with receptors
72
what is oestrogen
a lipid soluble molecule. it is a steroid hormone
73
how does oestrogen initiate transcription
oestrogen diffuses through the phospholipid bilayer. oestrogen binds to a complementary receptor on the transcriptional factor. this causes a conformational change to the DNA binding site on the transcriptional factor. the transcriptional factor is now activated. this moves through the nuclear pore into the nucleus. this binds to DNA activating RNA polymerase. mRNA is made.
74
what turns genes in and off
transcriptional factors
75
why does methylation lead to heterochromatins
because DNA is negatively charged. Methyl groups are positively charged. therefore they attract, and the DNA histone complex is condensed. it’s more strongly associated.
76
why does acylation lead to euchromatins
acetyl groups are negatively charged and DNA is negatively charged. therefore the two groups repel. and the DNA histone complex is weakly associated. exposing more transcriptional factor binding sites
77
what is RNAI (RNA interference)
where the mRNA gets destroyed in the cytoplasm whilst being transcribed before leaving to the nucleus. done by a molecule called siRNA
78
how does siRNA interfere
double stranded RNA (dsRNA) is cut up. once it enters the cytoplasm it forms (small interfering RNA) (siRNA) which is single stranded. the siRNA combines with another enzyme in the cytoplasm forming a siRNA enzyme complex. mRNA with complementary base pairs to siRNA line up. the enzyme conjugated to siRNA will splice/cut up the mRNA. the mRNA sequence is no longer in tact and translation of mRNA cannot occur.
79
give an example of siRNAs
microRNAs
80
applications of siRNA
- stop genetic and inherited diseases from passing into offspring
- genetically modifying crop plants by silencing undesirable genes. (those that make toxins or allergens)
- treating human genes. cancer genes. or in antiviral therapy. eg silencing the gene for the receptor protein used by HIV
81
how does prader-willi syndrome arise
it is the result of seven genes on chromosome 15 being deleted. 
most people, only one copy of the genes (from the father) is expressed while the other copy of the genes (from the mother) is silenced through epigenetic inheritance. This means that most people have one working set and one epi-genetically silenced set of these genes. However, if a mutation on chromosome and 15 of the father deletes the relevant seven genes, any offspring produced will have one set of nonworking genes and one set of therapy genetically silenced genes. These individuals will inherit prader-willi syndrome.
82
What are the two types of tumours
benign
malignant
83
Describe in detail malignant tumours
they can grow large in size
They can grow rapidly
The nucleus is often larger and appears darker due to an abundance of DNA
Cells can become unspecialised
Cells do not produce adhesion molecules so they tend to spread to other regions of the body (Meta stasis) forming secondary tumours.
The tumours are not surrounded by a capsule therefore they can grow finger like projections into the surrounding tissue
They are more likely to be life-threatening as the abnormal tumour tissue replaces normal tissue.
The removal usually involves radiotherapy and/or chemotherapy as well as surgery
More frequently re-occur after treatment.
84
describe in detail a benign tumour 
they can grow to a large size
they can grow very slowly
The cells are often specialised (differentiated)
The cells produce adhesion molecules that make them stick together so they remain within the tissue where they arise (primary tumour)
The tumours are surrounded by a capsule of dense tissue so they remain as a compact structure
They are much less likely to be life-threatening but can disrupt functioning of a vital organ
they tend to have localised effects on the body
they can usually be removed by surgery alone
They really re-occur after treatment
85
How does a secondary tumour develop from a primary tumour
an early tumour forms
This tumour enlarges whilst developing blood and lymphatic vessels
The tumour cells squeeze into blood and lymphatic vessels
The tumour cells circulate in the blood and in the lymph
The tumour cells add here to blood vessel walls and squeeze through to form distinct meta stasis.
And meta stasis can also occur in the lymph nodes
86
What are oncogenes and proto-oncogenes
most oncogenes are mutations of Proto oncogenes. Proto-oncogenes stimulate a cell to divide when growth factors attach to a protein receptor on its cell surface membrane. The then activates the gene that cause DNA to replicate and the cell to divide. If a Proto oncogene mutates into an oncogene it can become permanently activated (switched on) for two reasons:
The receptor protein on the cell surface membrane can be permanently activated so that’s so division is switched on even in the absence of growth factors.
The oncogene may code for a growth factor that is then produced in excessive amounts, stimulating excessive cell division.
This results in cells dividing to rapidly and out of control and a tumour develops. A few cancers can be caused by mutations of Proto oncogenes however most cancer causing mutations involve oncogenes that are acquired, not inherited.
87
What are tumour suppressor genes
Tumour suppressor genes slow down cell division, and repair mistakes in the DNA they can also code for cells to die. Therefore they have the opposite role from proto-oncogenes. They maintain normal rights of cell division and prevent the formation of tumours.
88
What happens when a tumour suppressor gene becomes mutated
when a tumour suppressor gene becomes mutated, it is inactivated (switched off) so it stops inhibiting cell division and cells can grow out of control. The mutated cells that are formed are usually structurally and functionally different from normal cells. Whilst most of these die, those that survive can make clones of themselves and form tumours. There are a number of forms of tumour suppressor genes including TP53, BRCA1 and BRCA2.
89
tell me about the TP53 gene
some cancers are caused by inherited mutations of tumour suppressor genes but most are acquired, not inherited. For example more than half of human cancers display abnormalities of the TP53 gene. (Which codes for the P53 protein). Acquired mutations of the TP53 gene occur in many cancers, including lung and breast cancer. The TP53 protein is involved in the process of apoptosis (programmed cell death). This process is activated when a cell is unable to repair DNA. If the P53 is not functioning correctly, cells with damaged DNA continue to divide leading to cancer.
90
What is an important difference between oncogenes and tumour suppressor genes
oncogenes Cause cancer as a result of the activation of proto-oncogenes. Whereas tumour suppressor genes cause cancer when they are inactivated.
91
How can hyper methylation lead to cancer
hyper methylation occurs in a specific region (promoter region) of tumour suppressor genes.
This leads to the tumour suppressor gene being inactivated.
transcription of the promoter region of the tumour suppressor gene is inhibited
As a tumour suppressor gene normally slows the rate of cell division, it’s an activation leads to increased cell division and the formation of a tumour.
Abnormal methylation of this type is thought to occur in a tumour suppressor gene known as BRCA1, this leads to the development of breast cancer.
92
What is hypo methylation
Hypomethylation Is another form of abnormal methylation. (Reduction of methylation), this has been found to occur in oncogenes where it leads to the activation and hence the formation of tumours.
93
How can increased oestrogen concentrations litre breast cancer in women
oestrogen plays an important role in regulating the menstrual cycle in women. (After menopause a woman’s risk of developing breast cancer increases) this is thought to be due to increased oestrogen concentrations. The production of oestrogen from the ovaries diminishes after menopause, however the fat cells of the breasts tend to produce more oestrogen after menopause. These locally produced oestrogen is appear to trigger breast cancer in postmenopausal women. Once a tumour has developed it further increases oestrogen concentration which therefore leads to increased development of the tumour. It’s also appears that white blood cells are drawn to the tumour increase oestrogen production this leads to even greater development of the tumour.
94
How can oestrogen cause a tumour to develop
oestrogen activates a gene by binding to a receptor which promotes transcription. If the gene that oestrogen acts on is one that controls cell division and growth, then it will be activated and its continued division could produce a tumour. It is known that oestrogen causes proto-oncogenes of cells in breast tissue to develop into oncogenes. This leads to the development of a tumour (breast cancer).
95
What are specific lifestyle factors that can contribute to cancer
Smoking: those who possibly breathe tobacco smoke also have an increased risk of getting cancer
Diet: what we eat and drink affects our risk of contracting cancer. There is strong evidence that a low-fat, high fibre diet, rich in fruit and vegetables reduces the risk.
obesity: being overweight increases the risk of cancer
physical activity: people who take regular exercise are at lower risk from some cancer than those to take gl or no exercise.
some light: the most someone is exposed to sunlight or lights from some beds the greater the rest of skin cancer.

96
Give an example of a carcinogen
Tar found in cigarette smoke
97
what is the ‘two-hit ‘ hypothesis
it only takes a single mutated allele to activate proto-oncogenes but it takes a mutation of both alleles to inactivate tumour suppressor genes (two hits) as natural mutation rates are slow, it takes a considerable time for both teams suppressor alleles to mutate. This explains why the risk of many cancers increases as one gets older. It is thought that some people are born with one mutated allele. These people are at greater risk of cancer as they need only one further mutation, rather than two, to develop the disease. This explains why certain cancers carry an inherited increased risk.
98
What is bioinformatics
bioinformatics is the science of collecting and analysing complex biological data such as genetic codes. It’s uses computers to read, store, and organise biological data at a much faster rate than previously. It also utilises algorithms (mathematical formula) to analyse and interpret biological data.
99
What is whole-genome shotgun (WGS) sequencing.
This involves researchers cutting the DNA into many small easily sequenced sections and then using computer algorithms to align overlapping segments to assemble the entire genome. Sequencing methods such as these are continuously updated which, along with the increased automation of the process involved, have led to extremely rapid sequencing of whole genomes.
100
Give an example of medical advances that have been made as a result of sequencing the human Genome
for example over 1.4 million single nucleotide polymorphisms (SNPs) Have been found in the human genome. Single nucleotide polymorphisms or single base variations in the genome are associated with the with disease and disorders. Medical screening of individuals has allowed quick identification of potential medical problems and for early intervention to treat them.
101
What is the proteome
The proteome is all the proteins produced by the genome. However as a protein is only produced when a gene is switched on, and genes are not switched on all the time, a more specific definition is all the proteins produced in a given type of cell or organism at a given time under specified conditions.
102
Why is determining the proteome of prokaryotic organisms like bacteria relatively easy
The vast majority of prokaryotes have just one, circular piece of DNA that is not associated with histones.
There are none of the non-coding portions (introns) of DNA which are typical of eukaryotic cells.
103
Why is having knowledge of the proteome of organisms like bacteria important
Of those proteins that act as antigens on the surface of human pathogens, these antigens can be used in vaccines against diseases caused by these pathogens. In the case of vaccines, the antigens can be manufactured and then administered to people in appropriate doses. In response to the antigen, memory cells are produced which get a secondary response when the antigen is encountered on a second occasion.
104
When was the mapping of the human genome completed
2003
105
what is the difficulty in mapping out the human proteome
The human genome contains non-coding genes as well as coding genes. it is thought that as few as 1.5% of genes make code for proteins. There is a human proteome project currently underway to identify all of the proteins produced by humans.
106
what is apoptosis
it is programmed cell death
107
what does the TP53 gene do
it produces P53 protein which is activated when a cell cannot replace DNA
