✅modern genetics Flashcards
what is a genome?
the total of all the genetic material in a cell
what are exons
the coding regions which code for important proteins
what are introns?
the areas of the DNA which are non coding. they are large. and are removed from mRNA beofre it lines up on the ribsomes and is translated into proteins
what do you do in gene sequencing?
analyse individual strands of DNA, giving us patterns or bases that code for particular proteins. PCR i one of these.
what is the PCR?
when a tiny sample of DNA is increased during PCR, its been amplified.
how does PCR work?
DNA sample which is to be amplified, is mixed with the enzyme Taq, as this can uphold high temperatures, unlike human cells. also has primers, DNA Polymerase and a good supply of nucleotide bases, in a PCR machine. as well as a suitable buffer for the reaction.
what are the temperatures for PCR?
heated to 90-95 degrees which causes the strnads to separate as the hydrogen bonds break between them. mixture is them cooled to 50-55 degrees so that the primers bind to the single DNA strand. mixture then heated to 72 degrees, which is the opitmum teperature for the Taq enzyme.
what is the process of sequencing?
sequencing entire genomes or individual genes has changed.
dna chopped into smaller pieces, double strnads ae separated to give single strands, PCR is involved in replicating the DNA fragments to produce larger quantities of material for analysis.
labelled terminator bases are added to single strands of DNA.
coloured tags enable o sequence of bases to be read very rapidly by an automated machine.
what is a terminator base?
a base which stops the sequence. when incoroparted into the DNA molecule, the chain is halted as no more bases can be added.
what is massively parallel sequencing?
workd on millions of DNA at a time.
how do you predict amino acid sequences?
the universal genetic code , we recognise the start and sop condons in a gene. biologists becoming increasingly aware of the genomes and porteins available.
how does DNA sequencing link to disease management?
give us better undertanding of human disease. can identify a faulty gene. gene variants increase risk of an individual developing a specific disease such as diabetes.
what are introns an satellites?
introns are the non coding part of the DNA sequence. their function is not known. some can code for small interferring RNA molecules that interact with mRNA and prevent certain proteins. within the intrond, there are short sequences of DNA that are repeated many times to form micro-satellites and mini-satellites. the same micro and mini appear in the same position on each pair of the homologous chromosomes.
how is a DNA profile produced?
strands of DNA are cut into fragments using special enxymes known as restriction endonucleases. they cut DNA at particular points in the intron sequence. each different enzyme cuts DNA molecule into fragments are different specific base sequences known as recognition sites.
what is gel electrophoresis?
fragments need to be separated and identified. fragments places into wells in an agarose gel medium, in a buffering solution. gel contains a dye that binds to the DNA fragments in the gel. the dye will fluoresce when placed under short wave UV light, revealing a band pattern of DNA. an electric current is passed through the apparatus and the shorter chains travel the longest. goes towards a positive anode due to the negative charger on the phosphate groups.
what is southern blotting?
an alkaline buffer solution is added to the gel after electrophoresis and a nylon filer or nitrocellulose paper is placed over it. the dry absorbent material is used to draw the solution containing the DNA fragments form the gel to the filter, leaving DNA fragments as “Blots” attached to the filter. the alkaline solution also denatures the DNA fragments so the strands separate and the base sequences are exposed.
what are gene probes?
added to the filter paper after southern blotting and bind with the complementary DNA trans in a process known as hybridisation. they are short DNA sequences that are complementary to specific sequence. excess porbes are washed away.
using genes for forensic science?
application of science to the porcesses of law. to develop a DNA profile in criminal investigation, gene probes are used to pick out the short tandem repeats- which are micro-satellite regions that are widely used in DNA identification.
using genes in paternity testing?
if there is doubt about who fathered the child, an electrophoresis gel with the father genes and the child genes can show who is the father with the amount of shred genes towards both individuals. each of the childs micro-satellites would be from ither the mother of the father.
how can gene probes illuminate gene expression?
allow a particluar section of DNA and mRNA in a cell to be identified. you need a very specific probe to find a particular gene. the DNA from the cells under investgation is isolated and heated gently. this breaks down the weak H Bonds holding the 2 strands together. flourescntly labelled mRNA from the required genes is added, this is the probe. this pinpoints the gene needed when it adds to the structure.
what areas do you look at when deciding to have control over gene expression?
the expression of a gene involved 2 key stages. transcription from DNA to RNA and translation from mRNA to proteins. exerting controls at any stages of the process gives control over the expression of genes.
transcription factors and the control of gene expression
most common way is by switching on and off the transcription of certain genes. transcription factorshave DNA binding regions that enable them to bind to specific regions on the DNA: Promoter sequences.
what are transcription factors
proteins that bind to the DNA in the nucleus and affect the process of transcribing the genetic material.
what are enhancer sequences?
transcription factors bind o regions known as enhancer sequences, and regulate activity on the DNA by changing the structure of the chromatid.
what is RNA splicing?
when the spliceosomes join the same exons in a variety of ways in a process called splicing. as a result, a single gene may produce several different versions of functional mRNA.
what are the benefits of splicing?
more variation of proteins.
what are epigenetics?
studies genetic control by factors other than base sequences on the DNA. RNA splicing is a form of epigenetics, because it changes the mRNA and the proteins produced from the original code.
what are the three intracellular systems that can interact to control genes?
DN methylation
histone modification
non coding RNA
what is DNA methylation?
addition of a methyl group. the addition of the methyl group always occurs a the site where cytosine occurs next to guanine. can also modify the structure of the histones, so it can have an epigenetic effect. always silences a gene or a sequence of genes. the methyl group changes the arrangements of DNA molecules and prevents transcription.
what is DNA demethylation?
removal of a methyl group which enables genes to become active so they can be transcribed.
what is histone modification?
can be modified to affect transcription of DNA and therefore gene expression. histones are positively charged proteins. DNA helices wind around the histones to form chromatin, the DNA and protein complex.
when the chromatin is very condensed, genes aren’t available to be copied- heterochromatid. therefore active chromatin is more loose.
