22. Gene technology

Created by

Mabel smith

Cards (45)

What is step one
Obtaining DNA fragments
What are restriction endonucleases?
Enzymes that cut DNA at specific recognition sequences. They are found in bacteria.
What bonds do restriction endonuclease hydrolyse?
Phosphodiester bond in the sugar, phosphate backbone
What do the cuts at recognition sequences form?
Sticky ends
What are sticky ends?
Single stranded sections of DNA, that form an overhang
Recognition, sequences and sticky ends are palindromic. What does that mean?
The sequence on one strand is the same as the sequence on the other strand, but in reverse
How is a gene machine used?
The amino acid sequence is determined from this that mRNA codons for each amino acid are looked up. The complementary DNA triplets are worked out and the gene produced. The genes are checked using standard sequence in techniques, and those with errors are rejected.
What are the advantages of using a gene machine?
Any sequence of nucleotides can be produced in a short period of time
What is another advantage of using a gene machine?
genes are free of Intron
Where is reverse transcriptase is found
Viruses
What does reverse transcriptase do?
It can be used to convert mRNA in a cell to cDNA
What is cDNA
COMPLEMENTARY, DNA
What is step two?
Polymerase chain reaction
What is PCR?
When fragments of DNA are copied to increase the number of fragments
What is in vitro cloning?
Outside living cells
What is added to a thermal cycler during PCR?
DNA fragments, taq polymerase, free nucleotides and primers
What are primers?
Short sequences of single-stranded nucleotides
What do primers do?
Allow DNA polymerase to bind and start DNA synthesis
Why is the PCR heated to 95°?
To break hydrogen bonds and separate the strands of DNA
Why is the PCR reduced to 55°? 
Allows the primers to attach
Why is PCR raised to 72°?
Allows DNA polymerase to attach
What is gel electrophoresis?
Separates pieces of DNA on the basis of their length
What is gel electrophoresis used for?
To locate defective genes with gene probes or analyse DNA to produce genetic fingerprints
Why is an electric current passed through the gel
DNA is slightly negative so is attracted to the positive electrode. Causes the DNA to move
Which length of DNA move further in gel electrophoresis
Smaller lengths
How is the DNA made visible in electrophoresis
a stained or fluorescent chemical or radioactive labelled
What do fragments of known lengths of DNA produce
Size markers
What is genetic screening
Following gel electrophoresis gene probes can be used to identify a particular gene
What is a gene probe
Single strand short sequence of DNA nucleotides with a complementary base pair to allele being screened for
What is the use of a gene probe
It will bind to the target gene and it is usually marked with a radioactive tag
What is genetic counselling
Offered before genetic screening to advise couples - provides emotional and medical support
What is genetic fingerprinting
Used to analyse very small differences in DNA base sequences between individuals
What genetic fingerprinting focus on
Focuses on non coding DNA
What are the non coding parts of DNA
variable number tandem repeats.
What happens if there are more VNTRs
The band will be thicker as more probes bind
What are the uses of genetic fingerprinting
determine paternity
forensic science
medical diagnosis
plant breeding
personalised medication
How is genetic screening used in forensic science
Determine who was at the scene
How is genetic fingerprinting used in medical diagnosis
A sample of DNA from someone with the disease can be matched with someone else’s DNA
What is in vivo cloning
When fragments of DNA are transferred to another organism and the DNA can then be translated and cloned in living cells
What is the process of in vivo cloning
Preparing the DNA fragment for insertion
insertion of the fragments into a vector
transformation of DNA using a vector
identification of the transformed cells using marker genes
cloning of transformed cells