6.3: Manipulating genomes Flashcards
(49 cards)
What is the development of sequencing
- Sanger sequencing
- DNA sequencing machine using fluorescent dyes
- High throughput sequencing
What is the sanger technique?
5 steps
Used for gene sequencing
- Extract DNA, cut it into fragments of various lengths
- Amplify those lengths using pCR
- Sequence the DNA by adding it to 4 different solutions
DNA nucleotides
DNA polymerase
Primers
A terminator base - Add them onto an electrophoresis plate which separates out DNA based upon mass
- Read the seuqence of DNA which can be stored on a database
What is the first DNA sequencing machine and what did it do?
Based on Sanger’s method
Fluorescent dyes instead of radioactivity were used to label the terminator bases
These dyes glowed when scanned with a laser beam and the light signature was identified by computer
What is high throughput sequencing?
Fast, cheap methods to sequence genomes
What are applications of gene sequencing?
5
- The human genome project
- Comparing between species
- Variation between individuals
- Evolutionary relationships
- Predicting the amino acid sequence of proteins
What is the human genome project?
When it was launched, in 2003, it sequenced the human genome and found only 24000 genes
What does comparing the genome between the species do?
Allows us to find out what is conserved
Many of the differences between organisms are not because the organisms have totally different genes but because some stored genes have been altered and work in different ways
- Some changes to regulatory regions of DNA that do not code directly for protein have also altered the expression of the genomes
What does variation between individuals’ genomes show?
- Humans are genetically similar except for rare cases where gene has been lost by deletion of a part of a chromosome
- Same genes but different alleles
- SNPs are places on the DNA where subsitutions (mutations) can occur
- Methylation
What is methylation?
Adding a CH3 to the DNA which alters the gene expression
Prevents transcription as the alteration means RNA polymerase cannot bind to the gene
How can gene sequencing predict the amino acid sequences of proteins?
Use the genome sequence and researchers knowledge of which genes code for a specific protein
Due to their knowledge of the base triplets which code for the amino acid
They can find out the primary structure of proteins
What has sequencing allowed for?
- Synthetic biology
- Bioinformatics
- Epidemiology
- Protemics
What is synthetic biology?
Field of science that involves redesigning organsims for useful purposes by engineering them to have new abilities
To solve problems in medicine, manufacturing and agricultures
What is protemics?
Large scale study of a set of proteins produced in an organism, system or biological context
What is bioinformatics?
Software is developed to process and understand large complex data (DNA sequences) using computational biology
- Allows access to large amount of data
- Information is stored as universal
- Allows rapid comparison of sequences with newly sequenced alleles
- Amino acid sequences/protein structures held database
- Computer modelling of new protein structure from base sequences
What is epidemiology?
Bioinformatics can be used in it
The study of how often diseases occur in different groups of peole are why
- Identify source of outbreak
- Identify vulnerable populations
- Design vaccination programs to target certain individuals
What happens in DNA profiling?
7 steps
- DNA is extracted
- DNA is amplified in the process of PCR
- Cut DNA using restriction enzymes
- DNA is put into gel electrophoresis plate which separates the DNA based on the mass
- A banding pattern can be seen
- The DNA to which the individual is being compared is treated with the same restriction enzymes and also subjected to electrophoresis
- The banding patterns of the DNA samples can then be compared
What types of DNA is used in DNA profiling?
Short tandem repeats (STR) - small regiion 2-4bp repated 5-15 times
Variable number tandem repeates (VNTR) - 20-50bp repeated 50-several 100 times
Why are introns used in genetic profiles?
- In most people genome is very similar
- Using coding sequences of DNA would not provide a unique profile
- Non - coding DNA contains VNTR/STR/repeating sequencing
What are uses of DNA profiling?
- Paternity test to discover the father of a child
- Suspects at a crime scene
- Searching for genes that can trigger diseases
What is PCR (polymerase chain reaction)?
DNA is obtained from a crime scene from a criminal and it is amplified enabling it ot be analysed
What does PCR rely on?
3x
- DNA is made of two antiparallel backbone strands
- Each strand has a 5’ end and a 3’ end (only grows from the 3’ end)
- Base pairs pair up according to complementary base pairings
How does PCR differ from DNA replication?
- Only short sequences of up to 10,000 base pairs of DNA can be replicated (not entire chromosomes)
- Requires the addition of primer molecules to make the process start
- A cycle of heating and cooling is needed to separate the DNA strands, bind primers to the strands and for the DNA strands to replicated
What is the process of PCR?
8 steps
- The sample of DNA is mixed with DNA nucleotides, primers, magnesium ions and the enzyme Taq polymerase
- Mixture is heated to around 94-96 to break hydrogen bonds between base pairs - denaturing double stranded DNA
- Mixture is cooled to 68 so primers can anneal to one end of each single stranded DNA. Gives a small section of double-stranded DNA at the end of each
- Taq polymerase enzyme molecules can now bind to the end where there is double stranded DNA
- Temp raised to 72 which keeps the DNA as single strands
- Taq polymerase catalyses the addition of nucleotides to the single stranded DNA molecules starting at the end with the primer and going in 5’ to 3’
- Taq reaches end of the DNA molecule, then a new DNA has been generated
- Whole porcess begins again and is repeated for many cycles
What is electrophoresis?
Used to separate different sized fragments of DNA for identification and analysis