Best Pdf Library: A2

Showing posts with label A2. Show all posts

A2 Biology Handwritten Notes 2016

Hey guys, so here are the notes I've written for A2 Biology 2016 papers 4 and 5. There are parts where I've written in pencil so it's fairly hard to read, or other places where I've condensed the words too much with symbols, so it probably isn't easy for other people to understand. But if this poses useful to you any bit at all, I'd be happy to share it :)

Click HERE to download.

A2 Chemistry Handwritten Notes 2016

shahid Mandokhail A2 , Chemistry

Download it HERE.

#165 Summary of Genetic technology

shahid Mandokhail A2 , Genetic Technology

1 Gene technology involves altering the genes in an organism, which is then said to be genetically modifi ed.

2 The usual way of genetically modifying bacteria is to insert a plasmid containing the desired gene into them.

3 The steps involved in the production of bacteria capable of synthesising human insulin are:
identifying the human insulin gene;
isolating mRNA and making cDNA using reverse transcriptase;
cloning the DNA using DNA polymerase;
inserting the DNA into a plasmid vector using restriction enzymes and DNA ligase;
inserting the plasmid vector into the host bacterium;
identifying the genetically modifi ed bacteria;
cloning the bacteria; and harvesting the human insulin.

4 The main advantage of treating diabetics with human insulin produced by gene technology is that it is chemically identical to the insulin that they would have produced had they not been diabetic. It also avoids any ethical issues that may arise from the use of insulin derived from an animal.

5 A promoter must be inserted along with the gene, because bacteria will not express a gene unless a suitable promoter is present.

6 The bacteria that have taken up the gene can be identifi ed using resistance to antibiotics or the presence of a fluorescing protein as markers.

7 Gene technology can provide benefits in, for example, agriculture, medicine and industry, but has the associated risk of the escape of the gene concerned into organisms other than the intended host. The risk is seen to be particularly high for genetically modified crops that are released into the environment to grow.

8 The social implications of gene technology are the benefi cial or otherwise effects of the technology on human societies.

9 Ethics are sets of standards by which a particular group of people agree to regulate their behaviour, distinguishing an acceptable from an unacceptable activity. Each group must decide, first, whether research into gene technology is acceptable, and then whether or not it is acceptable to adopt the successful technologies.

10 Electrophoresis is a technique that can be used to separate lengths of DNA (or RNA or proteins) of different sizes by applying an electric current to them. Small fragments move faster and therefore further than large ones, and can be made visible using radioactive labels or fluorescent compounds. Electrophoresis is used in genetic profi ling (genetic fingerprinting) and in DNA sequencing.

11 Cystic fibrosis is a genetic disease caused by a recessive allele of the gene that codes for the production of a chloride transporter protein called CFTR. People with two copies of the recessive allele produces thick, sticky mucus in their lungs, pancreas and reproductive organs.

12 Several attempts have been made to insert normal alleles of the CFTR gene into people with cystic fibrosis, a process called gene therapy. So far, there has been only limited success, because it is difficult to get the alleles into the cells. Even when this is successful, it needs to be repeated at frequent intervals because the cells have a very short natural lifespan.

13 Genetic screening involves testing people to find out if they carry any faulty alleles for genes that can cause disease. Genetic counsellors may help people who find that they have a disease-causing allele, or that their unborn child has, to make a decision about how to act on this information.

1. End-of-chapter questions

1 Different enzymes are used in the various steps involved in the production of bacteria capable of synthesising a human protein. Which step is catalysed by a restriction enzyme?

A cloning DNA
B cutting open a plasmid vector
C producing cDNA from mRNA
D reforming the DNA double helix

2 What describes a promoter?

A a length of DNA that controls the expression of a gene B a piece of RNA that binds to DNA to switch off a gene C a polypeptide that binds to DNA to switch on a gene
D a triplet code of three DNA nucleotides that codes for 'stop'

3 Which statement correctly describes the electrophoresis of DNA fragments?

A Larger fragments of DNA move more rapidly to the anode than smaller fragments.
B Positivelycharged fragments of DNA move to the anode.
C Small negatively charged fragments of DNA move rapidly to the cathode.

D Smaller fragments of DNA move more rapidly than larger fragments.

4 The table shows enzymes that are used in gene technology. Copy and complete the table to show the role of each enzyme.

5 Rearrange the statements below to produce a flow diagram showing the steps involved in producing bacteria capable of synthesising a human protein such as human growth hormone (hGH).

1. Insert the plasmid into a host bacterium.
2. Isolate mRNA for hGH.
3. Insert the DNA into a plasmid and use ligase to seal the 'nicks' in the sugar-phosphate chains.
4. Use DNA polymerase to clone the DNA.
5. Clone the modified bacteria and harvest hGH.
6. Use reverse transcriptase to produce cDNA.

7. Use a restriction enzyme to cut a plasmid vector.

6 a Genetic fingerprinting reveals the differences in variable number tandem repeats (VNTRs) in the DNA of different individuals. Explain what is meant by a VNTR. [3]
b Examine the figure, which shows diagrammatic DNA profiles of a mother, her child and a possible father of the child. Decide, giving your reasons, whether the possible father is the actual father of the child. [3]

[Total: 6]

7 a Copy and complete the table to explain the roles of primers and dideoxynucleotides in DNA sequencing.

[3]

b Explain what is meant by:
i gene therapy [1]
ii genetic screening [1]
iii genetic counselling. [1]

c Explain why it is easier to devise a gene therapy for a condition caused by a recessive allele than for one caused by a dominant allele. [5]

[Total: 11]

8 a Draw a genetic diagram to show how two heterozygous parents may produce a child with cystic fibrosis. Use the symbols A/a in your diagram. [3]

b State the probability of one of the children of these parents suffering from cystic fibrosis. [1]

[Total: 4]

The figure shows the CFTR (cystic fibrosis transmembrane conductance regulator) protein in a cell surface membrane.

a i Describe the normal function of the CFTR protein. [2] ii Use the letter E to indicate the external face of the membrane. State how you identified this face. [1]

b Cystic fibrosis is caused by a recessive allele of the CFTR gene.

i Explain the meaning of the term recessive allele. [2]

ii Explain how cystic fibrosis affects the function of the lungs. [3]

c As cystic fibrosis is caused by a recessive allele of a single gene, it is a good candidate for gene therapy. Trials were undertaken in the 1990s, attempting to deliver the normal allele of the CFTR gene into cells of the respiratory tract, using viruses or liposomes as vectors. Explain how viruses deliver the allele into cells. [2]

d In some people with cystic fibrosis, the allele has a single-base mutation which produces a 'nonsense' (stop) codon within the gene.

i Expalin how this mutation would prevent normal CFTR protein being produced. [2]

ii A new type of drug, PTCI24, enables translation to continue through the nonsense codon. Trials in mice homozygous for a CFTR allele containing the nonsense codon have found that animals treated with PTC124 produce normal CFTR protein in their cells. The drug is taken orally and is readily taken up into cells allover the body.

Using your knowledge of the progress towards successful gene therapy for cystic fibrosis, suggest why PTC124 could be a simpler and more reliable treatment for the disease. [3]

[Total: 15]

[Cambridge International AS and A Level Biology 9700/04, Question 2, October/November 2008]

2. End-of-chapter answers

1 B
2 A
3 D

Exam-style questions

6 a VNTR: a short length of highly repetitive DNA;

number of repeats and hence lengths of repeats diff er markedly in diff erent individuals; inherited: half VNTRs from father, half from mother;

only identical twins have the same VNTRs; [max. 3]

b four bands in child’s profile match four of the bands in the mother’s;

the other four bands match four bands in the father’s profile;

the possible father is the actual father; [3]

[Total: 6]

b i gene therapy: treatment of a genetic disorder by altering the patient’s genotype; [1]

ii genetic screening: determination of a person’s genotype using karyotype analysis for chromosome mutations and probes for identifying particular alleles; [1]

iii genetic counselling: a service that seeks to explain the nature of genetic disorders and probability of their transmission; [1]

c when a genetic disorder is caused by a recessive allele, the ‘normal’ allele is dominant;

adding a dominant allele allows some correct product to be made; the individual effectively becomes heterozygous;

the recessive allele may code for defective product or no product;

production of some correct product may cure the disorder;

adding a recessive allele cannot block a faulty dominant allele; [max. 5]

[Total: 11]

8 a

correct gametes; correct genotypes; correct phenotypes; [3]

b 1 in 4/0.25/25%; [1]

[Total: 4]

9 a i chloride channel; chloride moves out of cell by active transport; [2]

ii upper face because of presence of carbohydrate chains; [1]

b i allele: variant form of a gene; recessive: only aff ects phenotype when dominant allele is not present; [2]

ii thick, sticky mucus produced; mucus accumulates; reduced gas exchange; more infections; [max. 3]

c normal dominant CFTR allele added to viral DNA;

virus inserts DNA into cell; [2]

d i translation stopped at ‘stop’ codon; protein chain not completed; [2]

ii comparisons include: drug easily taken up by cells, whereas therapy is poorly taken up;

drug taken orally, whereas therapy must be inhaled into lungs;

no vector needed for drug, whereas virus vector for therapy may cause side-eff ects; [3]

[Total: 15]

#164 Social implications of GMO

shahid Mandokhail A2 , Genetic Technology

There are social implications related to using genetically modified organisms in food production.

modified crop plants become agricultural weeds and invade crop habitats
intoduced gene(s) may be transferred by pollen:

- to wild relatives --> more invasive hybrid offspring

- to unmodified plants on farms with organic certification

modified plants can be toxic and produce allergies --> fatal to humans and animals that eat it
herbicides will leave toxic residues on crops
genetically modified seeds are as expensive as herbicides --> no advantage
growers need to buy new seeds every season
loss of traditional varieties

Syllabus 2016-2018

19.3 Genetically modified organisms in agriculture

The ability to manipulate genes has many potential benefits in agriculture, but the implications of releasing genetically modified organisms (GMOs) into the environment are subject to much public debate in some countries.

a) explain the significance of genetic engineering in improving the quality and yield of crop plants and livestock in solving the demand for food in the world, e.g. Bt maize, vitamin A enhanced rice (Golden riceTM) and GM salmon

b) outline the way in which the production of crops such as maize, cotton, tobacco and oil seed rape may be increased by using varieties that are genetically modified for herbicide resistance and insect resistance

c) discuss the ethical and social implications of using genetically modified organisms (GMOs) in food production

#163 Herbicide and insect resistant crops

shahid Mandokhail A2 , Genetic Technology

Genetic technology can provide benefits in, for example, agriculture and medicine, but has the associated risk of the escape of the gene concerned into organisms other than the intended host.

Herbicide resistant crops
Fields of crops are sprayed with herbicide to kill weeds that compete for space, light, water, and ions to increase crop yield.

Oil seed rape

a source of vegetable oil and biodiesel fuel
modified oil seed rape is resistant to the herbicide glyphosphate (inhibits the synthesis of 3 amino acids: phenylamine, tyrosine, trytophan)

- glyphosphate is absorbed through leaves and is transported to growing tips

the gene transferred into crop plants come from a strain of the bacterium Agrobacterium

Tobacco

resistant to herbicides: sulfonylurea and dinitroaniline
genes taken from other plant species

Effects on the environment:

the GMed plants become agricultural weeds
pollen will transfer the gene to wild relatives, producing hybrid offspring that are invasive weeds
herbicide-resistant weeds will evolve because so much of the same herbicide is used

Insect-resistant crops

To protect crop plants against insect pests to increase crop yield

Cotton - protected against boll weevil

Bt maize - protected against corn borers

Bt toxing is - lethal to insects that eat it

- harmless to other animals

gene for Bt toxin is taken from the bacterium Agrobacterium tumefaciens
genetically modified crop plants with Bt toxin gene produce their own insectisides
Bt resistance in corn borers: recessive allele. Adult corn borers in refugees (non GM maize) supply the dominant allele to counteract the resistance when they mate with borers from the fields

Effect on environment:

evolution of resistance by insect pests
damaging effects on other insect species
transfer of added gene to other plant species

Syllabus 2016-2018

19.3 Genetically modified organisms in agriculture

c) discuss the ethical and social implications of using genetically modified organisms (GMOs) in food production

#161 Gene therapy

shahid Mandokhail A2 , Genetic Technology

Gene therapy: treatment of a genetic disorder by altering a person's genotype (insert functional alleles of genes into cells)

Common vectors:

virus: retrovirus, lentivirus, HIV, adeno-associated virus (AAV)
liposomes - small spheres of phospholipids
naked DNA

- retrovirus: inserts genes randomly into host's genome. If the gene is inserted into another gene or regulatory sequence of a gene, it could activate a nearby gene and cause cancer

- lentivirus: inserts genes randomly into host's genome, but this virus can be modified to inactivate replication e.g.: HIV

- adeno-associated virus (AAV): does not insert genes into host genome --> gene is not passed to daughter cells when a cell divides --> the virus can be used successfully with long-lived cells

Severe combined immunodeficiency (SCID)

a crippled immune system
sufferers may die at infancy due to normal infections
inability to make adenosine deaminase (ADA)

--> T-lymphocytes of sufferers are removed and normal alleles of the ADA gene are introduced into them using a virus vector. This is not a permanent cure.

They call him bubble boy.

Cystic fibrosis: genetic disorder where abnormally thick mucus is produced in the lungs and other body parts. It is caused by a recessive mutated allele of the gene for a functional transporter protein for chloride ions.

deletion mutation of 3 bases (AAA) in CFTR gene
role of CFTR: transport chloride ions across epithelial cell membranes of the pancreasm alveoli in the lungs,... ---> water follows via osmosis across membranes as water potential decreased due to the entry of chloride ions ---> membranes remain moist and runny
sufferers of cystic fibrosis: CFTR non-functional --> water is retained inside cell --> results in dry membranes and sticky mucus

Symptoms:

thick mucus accumulates in lungs --> breathing difficulties and higher risks of infections
thick mucus blocks pancreatic duct and therefore blocks off oral enzyems that help digestion
male infertility: thick mucus blocks sperm ducts

Somatic and germ cell therapy

- somatic cells = body cells

- germ cells = cells involved in sexual reproduction (alleles in the germ line are passed on through generations and generations)

Applications

electrophoresis of DNA is used in genetic profiling (fingerprinting) in forensic science
PCR is also used in forensic science to solve crimes: used to amplify DNA from small tissue samples

Syllabus 2016-2018

19.2 Genetic technology applied to medicine

a) define the term bioinformatics

b) outline the role of bioinformatics following the sequencing of genomes, such as those of humans and parasites, e.g. Plasmodium (details of methods of DNA sequencing are not required)

c) explain the advantages of producing human proteins by recombinant DNA techniques (reference should be made to some suitable examples, such as insulin, factor VIII for the treatment of haemophilia and adenosine deaminase for treating severe combined immunodeficiency (SCID))

d) outline the advantages of screening for genetic conditions (reference may be made to tests for specific genes such as those for breast cancer, BRCA1 and BRCA2, and genes for haemophilia, sickle cell anaemia, Huntington’s disease and cystic fibrosis)

e) outline how genetic diseases can be treated with gene therapy and discuss the challenges in choosing appropriate vectors, such as viruses, liposomes and naked DNA (reference may be made to SCID, inherited eye diseases and cystic fibrosis)

f) discuss the social and ethical considerations of using gene testing and gene therapy in medicine (reference should be made to genetic conditions for which treatments exist and where none exist, also to IVF, embryo biopsy and preselection and to therapeutic abortions)

g) outline the use of PCR and DNA testing in forensic medicine and criminal investigations

#162 Genetically modified organisms

shahid Mandokhail A2 , Genetic Technology

Genetic engineering is improving the quality (nutrition) and yield of crop plants and livestock --> therefore is solving the demand for food in the world

1. Golden Rice
- genetically modified rice produces large quantities of β-carotene in endosperm --> human cells convert β-carotene to Vitamin A
- Golden Rice has same yield, pest resistance and eating qualities as the original varieties
- normally:

deficiency of Vitamin A can lead to blindness and death (due to a weak immune system)
Vitamin-A is fat soluble: found in oily-fish, dairy, liver,...
Pro-vitamin A is present in the aleurone layer, not in the endosperm in rice

-genes for carotene production is taken from: and inserted into rice

daffodils
common soil bacterium Pantoea ananatis

*ethical implications?

Some organisations condemn Golden Rice: It is the wrong way to solve poverty. Solving political, cultural and economic issues will help lower poverty, as people will be given a more varied diet

From question 9a past paper of Winter 2014, paper 43

http://papers.gceguide.com/A%20Levels/Biology%20(9700)/9700_w14_qp_43.pdf
http://papers.gceguide.com/A%20Levels/Biology%20(9700)/9700_w14_ms_43.pdf

2. GM Atlantic salmon
Injected into a fertilised egg of an Atlantic salmon:

growth-hormone regulating gene from a PAcific Chinook salmon
promoter from another species of fish, an ocean pout

The salmons are able to grow all year, instead of just in sping and summer. They reach market size in 18 months as opposed to 3 years of an unmodified fish.

Syllabus 2016-2018

19.3 Genetically modified organisms in agriculture

c) discuss the ethical and social implications of using genetically modified organisms (GMOs) in food production

#160 Genetic screening

shahid Mandokhail A2 , Genetic Technology

Genetic screening: analysis of a person's DNA to check for the presence of a particular allele
* available for adults, fetus, embryo,...

- BRCA1 and BRCA2: faulty alleles that lead to breast and ovarian cancer in females and breast cancer in males ---> elective vasectomy

- pre-implantation genetic diagnosis (PGD):

carry out the IVF procedure (sperm and egg in a dish)
when it reaches the 8-cell stage, remove one cell and analyse the DNA for disease alleles

- disease allele absent: embryo chosen for implantation

- disease allele present: embryo is discarded

---> avoid pregnancies with haemophilia, sickle cell anaemia, Huntington's disease, cystic fibrosis,...

provides information about the increased risks of people having genetic conditions
people prepare for the late onset of genetic conditions like Huntington's disease
identify whether embryos from IVF will develop genetic conditions
identify a fetus that needs early treatment
helps provide early diagnosis

Ethics of genetic screening

fetus screening for genetic disease:

- amniocentesis: look for chromosomal mutations

- chorionic villus sampling (although there is an increased risk for miscarriage with this)

sex preselection: terminates pregnancy if the embryo is of the wrong sex (used PGD to select)
therapeutic abortions: terminating pregnancies for medical reasons

Syllabus 2016-2018

19.2 Genetic technology applied to medicine

a) define the term bioinformatics

b) outline the role of bioinformatics following the sequencing of genomes, such as those of humans and parasites, e.g. Plasmodium (details of methods of DNA sequencing are not required)

g) outline the use of PCR and DNA testing in forensic medicine and criminal investigations

#159 Bioinformatics

shahid Mandokhail A2 , Genetic Technology

Bioinformatics is the collecting, processing and analysis of biological information and data using computer software.

Bioinformatics build databases which hold gene sequences and sequences of complete genomes. These sequences can be matched --> calculate degrees of similarity (close similarities indicate recent common ancestry)

human genes may be found in other organisms and are used to model for investigating the way in which such genes have their effects
e.g.: Plasmodium genome: used to find new methods to control parasites

---> reading the gene sequences provides information to develope vaccines for malaria

Advantages of using human proteins produced from recombinant DNA
1. Insulin

reliable supply available for increasing demand
is not dependent on factors e.g.: meat trade
acts faster than animal insulin or slower over a long period of time

2. Factor VIII - genetically modified hamster cells produce factor VIII

Factor VIII is extracted and purified before being used to treat patients with haemophilia
avoids the risk of infection e.g.: HIV from donated blood

3. adenosine deaminase (ADA) - used to treat SCID (severe combined immunodeficiency disease)

- produced from genetically modified larvae of cabbage looper moth caterpillar

- administered to patients when:

waiting for gene therapy
gene therapy is not possible

Syllabus 2016-2018

19.2 Genetic technology applied to medicine

a) define the term bioinformatics

b) outline the role of bioinformatics following the sequencing of genomes, such as those of humans and parasites, e.g. Plasmodium (details of methods of DNA sequencing are not required)

g) outline the use of PCR and DNA testing in forensic medicine and criminal investigations

#158 Genetic markers and microarrays

shahid Mandokhail A2 , Genetic Technology

Genetic markers uses enzymes that produces fluorescent substances. There used to be antibiotic resistance gene markers, but there was the chance that they would spread the antibiotic resistance to other new strains of bacteria.

Genetic markers
Green fluorescent protein (GFP) from jellyfish:

gene inserted into plasmid --> taken up by bacteria
shine UV light --> identify genetically modified bacteria

β-glucuronidase (GUS) from E.coli:

transform into incubated with colourless/non-fluorescent substrate

---> transform into coloured/fluorescent products

---> detect activity of inserted genes

Microarray

identify genes present in an organism's genome
find out which genes are expressed within cells

---> microarrays contain thousands of gene probes

1. Genome analysis: compare genes present in two different species

DNA collected from each species, cut to fragments and denatured, labelled with fluorescent tags
DNA samples are mixed together and hybridised with DNA probes on the microarray --> inspected with UV light, causing the tags to fluoresce

- colour: DNA has hybridised with probe

- no colour: DNA not hybridised, gene not present

2. Gene expression - detecting mRNA

- to identify genes that are being transcribed to mRNA

mRNA collected --> reverse transcriptase --> cDNA
cDNA labelled with fluorescent tags, denatured, hybridised with probes on microarray
spots that fluoresce microarrays show transcribed genes

* intensity of light emitted from spots = level of activity of genes

Syllabus 2016-2018

19.1 Principles of genetic technology

Genetic engineering involves the manipulation of naturally occurring processes and enzymes.

Genome sequencing gives information about the location of genes and provides evidence for the evolutionary links between organisms.

a) define the term recombinant DNA

b) explain that genetic engineering involves the extraction of genes from one organism, or the synthesis of genes, in order to place them in another organism (of the same or another species) such that the receiving organism expresses the gene product

c) describe the principles of the polymerase chain reaction (PCR) to clone and amplify DNA (the role of Taq polymerase should be emphasised)

d) describe and explain how gel electrophoresis is used to analyse proteins and nucleic acids, and to distinguish between the alleles of a gene (limited to the separation of polypeptides and the separation of DNA fragments cut with restriction endonucleases)

e) describe the properties of plasmids that allow them to be used in gene cloning

f) explain why promoters and other control sequences may have to be transferred as well as the desired gene

g) explain the use of genes for fluorescent or easily stained substances as markers in gene technology

h) explain the roles of restriction endonucleases, reverse transcriptase and ligases in genetic engineering

i) explain, in outline, how microarrays are used in the analysis of genomes and in detecting mRNA in studies of gene expression