topic 7 Flashcards
1
Q
genome
A
all the genetic information within a cell
2
Q
PCR - what is it
A
- makes large number of copies of DNA fragments - amplifying DNA
3
Q
how does PCR work
A
- reactants are mixed and placed in the PCR machine
- DNA sample
- DNA primers
- 4 nucleotide bases
- taq DNA polymerase
- pH buffer - heated at 90-95C for 30 seconds - DNA strand separates
- DNA unzips due to breakage of hydrogen bonds - 50-55C for 20 seconds - primers bind to DNA strands (annealing)
- 72C for 1 minute minimum - DNA polymerase builds up complementary strands of DNA
- DNA polymerase creates a copy of the sample by complementary base pairing (elongation) - repeated 30 times - 1 billion copies made in 3 hrs
4
Q
taq DNA polymerase - why is it added?
A
- when heated to 90C to unzip the DNA, DNA polymerase gets denatured and DNA can’t replicate
- taq polymerase is able to withstand high temperatures (as it is made from bacteria which live in hot conditions) so won’t denature
5
Q
using DNA sequences
A
- predicting amino acid sequences
- uses genetic code - not all DNA sequences are translated so it is not certain
- particular sequences linked to disease or increased likelihood of disease can be identified in individuals
6
Q
gene sequencing process
A
- DNA strands are chopped into smaller pieces
- double strands are separated into single strands
- PCR is involved in replicating the DNA fragments to produce large quantities of materials for analysis
- labelled terminator bases are added to the single strands of DNA
- coloured tags enable the sequence of bases to be read rapidly by an automatic system
7
Q
what are terminator bases
A
- modified version of one of the four nucleotide bases
- when a terminator base is incorporated, the chain is halted and no more bases can be added
8
Q
DNA profiling
A
- identifies individuals or relationships
- uses the fact that restriction enzymes cut an individual DNA into fragments in a way that is unique
- fragments are separated by electrophoresis
- gives a pattern/profile that can be compared with forensic samples or relatives
9
Q
gel electrophoresis
A
- fragments placed in wells in gel
- dyed with ethidium bromide - to become visible under UV light
- current applied to the gel
- DNA is negative so fragments of different sizes move at different speeds
10
Q
what are transcription factors
A
- proteins that bind to DNA
- either stimulate or prevent transcription of DNA
11
Q
what is meant by gene expression
A
- when the protein coded for by a gene is produced / synthesised (via transcription & translation)
12
Q
how are genes expressed
A
- when mRNA is actively produced using the gene’s base sequence in transcription
- mRNA then carries the code to produce a specific sequence of amino acids in a polypeptide
13
Q
what are polypeptides used for
A
- used to produce proteins, some of which control cellular activity
14
Q
why do cells differ from eachother
A
- each cell type expresses a different group of genes
15
Q
what is differentiation
A
- the process by which certain groups of genes are activated to produce a particular cell type
