BY5.6 - Applications of Reproduction and Genetics Flashcards
What are clones?
Organisms that have been produced asexually and are genetically identical to the “parent” organism
What are stem cells?
Totipotent or Undifferentiated cells
From a blastocyst (3-5 day old embryo)
Capable of dividing into different types of specialised cells
Name the 2 main methods of cloning:
1) Embryo Splitting
2) Nuclear Transfer
Describe the method of embryo splitting:
1) A blastocyst produced sexually is split into separate cells
2) cells divide, forming embryos
3) Embryos are transplanted into surrogate’s uterus
Give the Advantages of embryo splitting
1) Used to conserve rare breeds
2) Farmers can increase their stock more than they would through sexual reproduction
Give the disadvantages of Embryo Splitting
No Guarantee the traits of parents will be present in the identical offspring, as they were produced sexually
Describe briefly the Method for Nuclear Transfer Cloning
1) Take the nucleus from a somatic cell of individual to be cloned
2) Insert into enucleated ovum
Describe in full the Method for Nuclear Transfer Cloning
1) A somatic cell is taken in a biopsy from the donor
2) An unfertilised ovum is taken from the recipient and enucleated
3) Donor and Recipient cells fuse
4) Cell divides by mitosis
5) Totipotent Blastocyst forms –> embryo
6) Embryo implanted into uterus of recipient
7) Offspring genetically identical to donor born
What are the Advantages of Nuclear Transfer?
1) Useful for production of genetically identically cells in quantity
- cancer cells for medical research
- monoclonal antibodies
2) Maintains genetic stocks - produces single identical line of cells
What are the disadvantages of nuclear transfer?
1) Expensive and Unreliable in Mammals
2) Can cause inadvertent selection of disadvantageous alleles
3) Progeny can cause long term unseen effects - premature ageing
What are bulbs?
Have short stems with closely packed leaves
Leaves swollen with stored food
Terminal bud produces next year’s flowering shoot
Lateral bud produces new plants
What are Corms?
1) Have short, swollen stem - stores food
2) Papery thin leaves
3) Terminal bud produces next years flowering shoot
Lateral bud produces new plants
What are suckers?
New plant grows from meristem of root or lower stem
What are the three different methods plants use for vegetive propagation?
Bulbs
Corms
Suckers
What is the technique of micropropagation based off?
Plant cells are totipotent:
- The ability of undifferentiated plant cells to give rise to all the differentiated cells of an adult plant
What parts of the plant are used in micropropagation and why are they used?
The meristems (tips of roots and shoots)
as their cells are dividing rapidly
Describe the Method of micropropagation
1) A plant with the desired characteristics is selected
2) meristem is removed from shoot with scalpel
3) meristem is cut into explants
4) explants are placed onto sterile, aerated nutrient rich agar
5) cells divide - mitosis
6) mass of undifferentiated cells - Callus - produced
7) Callus is subdivided & pieces differentiate into Plantlets
8) Plantlets transferred to sterile soil once a suitable size is reached
Define Donor DNA
A gene that is isolated for insertion
Define Plasmids
Circular loops of DNA in bacteria which acts as a vector
Define Restriction Endonucleases
Enzymes which cut DNA molecules between specific base sequences called restrictions sites
Define DNA ligases
Enzymes which join sections of DNA together (splices)
Define sticky ends
The two ends of the ‘cut’ DNA segment, which comprise of unpaired bases
Define recombinant DNA
DNA which is formed when a piece of ‘foreign’ DNA is incorporated into the plasmid from a bacterium
Define reverse transcriptase
Enzymes which use mRNA as a template for making a DNA molecule
What is Genetic Engineering?
A technique used to extract genes from one organism (the donor) to another organism (the recipient)
to produce a genetically modified organism with a new genotype
Why would donor genes be inserted into the recipient organism?
so that the gene codes for the synthesis of useful gene products e.g. bacteria producing insulin
How is a gene isolated from donor DNA in recombinant genetic technology? Use the example of human insulin as the donor gene
1) human insulin producing genes are located using a gene probe
2) the gene is isolated using restriction endonuclease enzymes
3) each specific restriction endonuclease cuts the DNA at a specific base sequence - the restriction site e.g AATT
4) the unpaired DNA bases are called sticky ends
what is used to insert the donor gene into the recipient? give an example for the case of human insulin synthesis
- a vector - a plasmid from e.Coli
what does the marker gene in the synthesis of human insulin code for?
antibiotic resistance to ampicillin
Describe the process of inserting the gene into a vector for recombinant DNA technology
*Plasmid DNA is cut using the same restriction endonucleases/ as the donor DNA
sticky ends are produced in plasmid DNA *
sticky ends on donor insulin gene and plasmids are complementary - base pairing occurs
DNA ligase enzymes join sections of DNA from donor and plasmid together
Recombinant DNA is formed
Why are marker genes used in recombinant DNA technology?
When bacteria and plasmids are mixed together only a small number of bacteria take up the recombinant plasmids.
The bacteria which contain the recombinant plasmids are identified by their marker gene
give an example of a marker gene
antibiotic resistance to ampicillin
How does the ampicillin-resistance marker gene show which bacteria contain recombinant plasmids?
1) all the bacteria are cultured on an agar plate containing ampicillin
2) the surviving bacteria must contain the ampicillin resistance gene
3) therefore the surviving bacteria must contain the recombinant plasmid, and therefore the human insulin production gene
Once the bacteria are shown to contain recombinant plasmids, what is done with them?
They are cultured in an industrial fermenter to divide and produce insulin-synthesising clones the human insulin is then extracted and purified
Why is it difficult to locate the correct gene for synthesis?
There are only 2 copies of the gene in a cell
Why is using mRNA an alternative to locating the gene itself?
there are many copies of mRNA in a cell that has been transcribed from the gene, which are complementary to the gene itself.
Give the method of synthesising recombinant DNA using mRNA
1) mRNA is extracted
2) mRNA is mixed with reverse transcriptase enzymes
3) This synthesises many copies of a single stranded DNA polynucleotide called cDNA
4) DNA polymerase enzymes are added to convert cDNA into a double stranded DNA molecule to be inserted into a plasmid
What are the advantages of recombinant DNA technology?
1) produces complex proteins or peptides in quantity which cannot be produced by other methods
2) produces higher yielding crops with superior keeping qualities
3) can be used for treating genetic diseases
What are disadvantages of Recombinant DNA technology?
1) techinically complicated - very expensive on an industrial scale
2) difficulties in identifying the genes of value in a huge genome -
3) synthesis of a required protein may require /several genes
4) treatment of human DNA with restriction enzymes produces millions of fragments of no use
5) not all eukaryote genes will express themselves in prokaryote cells
6) bacteria readily exchange genetic material - use of antibiotic resistant genes in E.coli means that genes could be accidentally transferred to human pathogens
7) Possibility of transfer of DNA with linked pathogen genes e.g. oncogenes - increase cancer risk
What allele, when mutated, expresses the non-functioning protein (of the same name) that causes cystic fibrosis?
Cystic Fibrosis Transmembrane Regulator
How does the non - functional Cystic Fibrosis transmembrane regulator protein cause cystic fibrosis?
The non functional protein cannot actively transports Cl- ions out of epithelial cells
2) Cl- and Na+ build up in the cells
3) lowers water potential in the cell
4) water moves into the cell by osmosis down the water potential gradient
5) causes the mucus to be thick and sticky
what are the problems caused by the thick mucus cystic fibrosis suffers have?
1) blocked pancreatic duct
- prevents pancreatic enzymes from being secreted into the duodenum
- > food digestion incomplete
- > limited absorption of food
2) clogged bronchioles and alveoli
- > congestion and difficulty breathing
hard to move mucus = trapped bacteria/virus
= reoccurring infections e.g. bronchitis/pneumonia
frequent daily chest physiotherapy needed to keep bronchioles open
What is the aim of gene therapy?
to treat genetic diseases by replacing the defective alleles in the patients cells with copies of the normal allele
What are the 2 types of gene therapy?
1) Somatic cell therapy
2) Germ line therapy
When in someones life would germ line therapy take place?
when they are a gamete e.g. sperm/ovum
Why would the genetic changes from somatic cell therapy not be inherited by the patients offspring?
only somatic cells are treated - gametes are not altered
Give the method for cystic fibrosis somatic cell therapy
1) identify and clone the CFTR gene by PCR
2) Insert the normal CFTR allele into liposomes
3) aerosol inhaler adds the normal allele to the lung epithelial cells
4) Liposomes fuse with phospholipid bilayer of the cell membrane
5) DNA enters the cells
6) epithelial cells with normal CFTR allele express the normal CFTR protein/
7) Symptoms are alleviated
What is germ line therapy?
When normal genes are inserted into germ line cells - e.g. sperm/ovum - enabling genetic corrections to be inherited
What biological techniques need PCR to work, and why?
1) Gene therapy:
- millions of alleles needed to have an overall effect on the body
2) Genetic fingerprinting:
- needed if little DNA is found at crime scene
What does PCR stand for?
Polymerase Chain Reaction
What is PCR?
a process which can /copy a single gene etc. many times by mimicing semi-conservative replication
What do you need for PCR?
1) PCR machine
2) Gene/DNA fragment to be copied
3) buffer solution
4) Free DNA nucleotides
5) DNA Polymerase
6) Primer
Describe the method of PCR
1) heat to 95 degrees
2) hydrogen bonds in the gene break (denature)
3) 2 template strands are formed
4) cool to 55 degrees
5) the primers attach to complementary bases on target DNA
6) heat to 70 degrees
7) DNA polymerase pairs the free nucleotide bases to the DNA
8) a identical copy of the DNA is formed
9) repeat 25 times, producing 1 million copies
What is a persons genetic fingerprint?
their DNA profile, which is unique to then
what are exons?
regions of DNA that code for proteins
What are introns?
regions of non-coding DNA
contain blocks of repeated nucleotides called /short tandem repeats (STR’s)
the number of repeats produces variation in induviduals
How is Genetic Fingerprinting used to settle paternity disputes?
1) white blood cells are taken from the mother, child, and potential dad
2) DNA taken from the cells undergo electrophoresis
3) the bands of the mother are subtracted from the child’s genetic fingerprint
4) if the man is the father, he must possess all the remaining bands in the childs fingerprint
what is a genome?
All the DNA including genes, in an organism
What are the main aims of the Human Genome Project?
1) determine the sequence of bases in all human DNA
2) Identify all the genes formed by the bases
3) Find the locus of all genes on all 23 chromosomes
4) Store this information on a database
5) consider the social, ethical and legal issues from obtaining and storing the information
what is the main benefit of the human genome project?
the information identifies which genes on particular chromosomes are responsible for different inherited diseases
What are the 2 types of genetic tests?
1) Mutated base sequences
a) DNA probes, complementary to the mutated sequence, are added to the patients blood.
b) If the mutated sequence is present, the probe will bind to it, labelling it.
2) DNA sequence comparison :
the patients DNA sequence of a gene is compared to the DNA sequence of the normal gene
Give 3 uses of genetic testing?
1) Carrier screening
- identifies unaffected parents which carry a recessive allele
for an inherited disease
which requires a homozygous recessive genotype to be expressed (cystic fibrosis)
2) pre-symptomatic testing for predicting adult onset disorders (huntington’s) disease)
3) pre-symptomatic testing for estimating the risk of developing adult onset diseases (alzheimer’s, breast cancer)
What factors is the advice in genetic counselling based on?
1) whether there is a family history of the disorder
2) whether the parents are closely related
3) The frequency of the allele in the general population
What are the tests to determine whether an embryo is affected with a disorder before it is born?
1) Blood test - cystic fibrosis
2) Amniocentesis,
which involves withdrawing some amniotic fluid, which contains embryonic cells which can be analysed using a microscope
3) Chorionic villus sampling - removing foetal tissue (8-10 weeks) where the cells are cultured and examined under the microscope
What are the Social, Ethical, and Legal concerns with gene testing/therapy?
1) Anxiety
2) Concerns that the risks of discrimination and social stigmatization could outweigh the benefits of testing
3) some believe that if prenatal tests are carried out, finding defective alleles will lead to an increase in the number of abortions
4) who should have access to personal genetic information and how it should be used e.g employers/health insurance
