Topic 7 Flashcards
What is a genome
All of an organisms DNA
What is PCR used for
Used to amplify dna by making many copies of a dna sample
What are the steps to PCR
- Reaction mixture is set up by mixing the dna sample , primers , free nucleotides and heat stable dna polymerase
- Mixture heated to 95 degs to break hydrogen bonds and separate dna strands
- Mixture cooled to 55 degs so primers can bind to strands (annealing)
- Temp increased to 70 degs, dna polymerase creates a copy of sample by complimentary base pairing using free nucleotides
- Cycle repeated many times
how can dna sequencing be used to predict the amino acid sequence of proteins
- pcr is involved in amplifying dna to produce many copies of it
- Four tubes set up containing DNA to be sequenced , dna polymerase and primers , terminator nucleotides
A diff chain terminating nucleotide is placed in each tube
DNA strands of diff lengths produced as each one terminates at a diff points
Fragments separated by gel electrophoresis
Fragments move diff distances based on size
Complim base sequence can be read from gel
how can dna sequencing be used to identify possible links to genetically determined conditions?
-some human diseases result from mutations in single genes
through dna sequencing u can identify faulty genes and see which bases have undergon mutations affecting the proteins produced.
whats a terminator base?
modified versions of the 4 nucleotide bases that halt the production of a dna molecule, as soon as theyre incoporated no more bases can be added
What are introns and exons
Introns - non coding dna , the removal of introns is splicing
Exons - coding dna
What are mini vs micro satellites
As humans we can have the same base sequences but the repeats r diff in each person
Mini-satellites are DNA regions consisting of 10–100 base pair (bp) long sequences that are repeated multiple times.
Micro-satellites are shorter DNA sequences consisting of 1–6 base pairs that are repeated.
How’s DNA profiling done
(used to identify individuals based on their unique DNA sequence. It focuses on analyzing short tandem repeats in non-coding regions of DNA)
- DNA sample extracted and multiple copies made using pcr
- restriction endonuclease enzyme produces dna fragments
- Dna samples placed into buffer solution in wells in agarose gel and an electric current is passed thru. gel electropheresis separates dna according to mass
- Southern blotting - DNA on agarose gel is transferred to nylon filter paper
- Short dna pieces with radioactive markers bind to compllim seq on dna so they can be read by computers
What are transcription factors
proteins that control the process of transcription, a gene is copied into mrna. They decide whether a gene is turned on or off by binding to specific regions of DNA.
Transcription factors bind to specific base sequences through promoter and enhancer sequences
Promoter - enables the binding of rna polymerase and promote transcription, mRNA produced and protein produced which allow cells to undifferentiate
Enhancer regions - binding sites in dna which regulate its activity by changing the structure of chromatin . They can cause dna to be more or less open to rna polymerase. Open =accessible gene available for transcription. Closed = inaccessible and not available
there are 2 ways in which the expression of a gene can be controlled: transcription factors and
splicing of pre mRNA after transcription can result..
in diff products from a single gene
how does RNA splicing work?
- Gene transcribed resulting in pre-mrna
- introns removed and some exons
- spliceosomes join exons many diff ways to produce diff strands mrna for translation
- variations in mrna = code for diff amino acids and thus diff proteins
- JOINED BY PHOSPHODIESTER BONDS
exons are joined by
enzyme complexes called spliceosomes to produce mature mrna
what is epigenetic modifications
give some examples
-changes that affect gene expression
-eg histone modification
-allows differnication / change in proteins synthesised
histone modification
methylation - addition of methyl group , can cause activation/inactivation of chromatin, linked to silencing genes
acetylation - addition of acetyl group (activates chromatin and allows transcr as it opens up the strcutre)
why are epigenetic modifications important
regulates gene expression ,they determine whether a gene is switched on or off to ensure cell differentiation, allowing cells to become specialised so they can carry out particular functions
What’s a Closed chromatin structure
Heterochromatin
How can the demethylation of dna cause the conversion of fibroblasts to fuzzy cells
A gene activated
Transcription of gene takes place producing protein that causes change in the cells
Gene switched off . Summary
Silent , heterochromatin, methylated dna , de acetylated histones
What happens in the early days of stem cells
First stage of embryonic development is cleavage
Mitosis without interphase takes place
Resulting in a small mass of identical undifferentiated cells, forming a blastocyst
Source and potency of totipotent cells
Found in Early embryos when just a few cells r present , can produce any cell type
Source and potency of pluripotent cells
Found in blastocyst stage can differentiate into any cell types except extra embryonic tissues
.source and potency of multipotenet cells
Found in adult tissues (eg Bone marrow) can differentiate into blood cells. Can differentiate into a limited range of cells
What are stomatic / adult stem cells
Undifferentiated cells found among normal differenciated cells . Can differentiate into any major cell type when needed
What can pluripotent stem cells be used for in medicine
They can be used to regenerate damaged tissues
How can totipotent stem cells in the embryo become pluripotent stem cells in the blastocysts and then become fully differentiated somatic cells in the body of an organism?
This can be achieved thru the action of transcription factors and epigentic mechanisms such as dna methylation, histone modification and ncRNAs
It’s the genes that are activated or silenced that results in the fully differentiated mature cells
what are ethical issues of using pluripotent stem cells to develop new medical advances
embryos are killed in the process of stem cell extraction, risks of rejection, cancer
what are induced pluripotent stem cells (ips)
adult stem cells that have been reprogrammed to become pluripotent again (can then turn into most cell types)
How can ips cells be produced
Fibroblasts are used
Genes are put into the cell
Using a vector
why may ips cells be less problematic than using embryonic stem cells
they come from indiv patient so no risks od rejection, no destruction of embryos which have potential to become human , religious objections
how can recombinant dna be produced
- section of dna containing genes is cut using restriction endonuclease enzyme
- same enzyme cuts open a plasmid to produce complim sticky ends
- join plasmid and gene w dna ligase to produce recombinant dna
- insert plasmid into host cell
a plasmid is used as a vector what other vectors could be used?
how can recombinant dna be inserted into other cells
gene guns - dna shot into cell at high speed
-viruses, liposome wrapping
what are gene markers
how can you identify recombinant cells in a culture
theyre used to show where a foreign gene has been inserted
antibiotic resistance and replica painting can be used as gene markers
growing bac colonies on plates, it allows the identification of colonies that can survive in the presence of a particular antibiotic
What are transgenic plants
Plants with contain genetic material from an unrelated organism
How does genetic modification using agrobacterium tumefacians occur
Agtum contains Ti plasmid and t dna , this is extracted, desired gene inserted into plasmid , the plant is infected with bacteria carrying modified plasmid . Infected cells develop into tumour called crown gall
Single cells taken from, gall and cultured forming, PLANT IS CLONED
What are the uses of plant cloning
Flood resistant rice, pesticides, changing nutrional value eg soya beans
Soya beans : linoleic acid replaced by oleic acid which oxidises less easily so doesn’t go off as quickly , healthier
What’s a knockout organism
Refers to the use of genetic engineering to inactivate or silence genes so they no longer function
What are knock out mice
What can they be used for
-Mice with one or more genes silenced by the insertion of a gene
-can be used to investigate gene function
how can dna profiles be compared?
total no. bands compared,
size of bands compared,
what are risks associated with genetically modified plants
- consequences such as resistance to pesticides
- will effect organic farmers
Why would stem cells be taken from an organisms own self rather than a diff one
- No risk of rejection
- No disease transmission
Why can stem cells be used to regenerate new tissue
- They’re totipotent
- Can differentiate into many cell types
- Cells r genetically identical
How can stem cells become specialised and differentiate into heart muscle cells
Activation of some genes , only activated genes transcribed, mrna translated and protein is made , cell differentiation
How can a fertilised egg be used as a source of pluripotent stem cells
- Let fertilised egg grow for a few days
- Inner cell mass are pluripotent
- Extraction of the cells
Why are some cells not able to become other cell types
1, already differenciated
2. Genes needed for other cell types are switched off
3. Thus cant produce proteins for other cell types
Devise a method by which black rhinos dung could be used to estimate the number of black rhinos in an area
-experts collect dung samples from all areas of the park
-DNA profiling and all the steps included
from these dung samples dna is extracted, genetic analysis will identify unique genetic profiiles corresponding to each rhino, compsrison of these genetic profiles researchers can determine which sample belongs to the same indiviual allowing a count of rhinos in the area
Give one reason as to why scientists thought Tapirus kabomani was the same species as tapirus terrestris
Both species look alike
How could distinguishing tapirus kabomani as a separate species affect the index of diversity in the area
If would increase the biodiversity , as the value for N increases in the index of diversity
Plasmids with genes for resistance to antibiotics are widely used in gene technology, these plasmids are used to create recombinant bacteria
Explain how culturing can be used to obtain recombinant bacteria
- Desired gene inserted into plasmids
- This plasmid has a marker gene for antibiotic resistance
- The recombinant bacteria will be resistant to this antibiotic
- The bacteria are grown on agar containing that antibiotic
- Only the recombinant bacteria will grow
compare and contrast the properities and uses of embryonic stem cells with those of ips
- both have potential to divide indefinitely
- both have potetnial to differnciate into a n0. cell types
- ips were adult cells but embryonic were taken from inner mass
- ips have a named gene added , embrynoic dont
- rejection issues w embryonic but not ips
what is an ethical issue of genetic engineering
some ppl see it as wrong
