6.1.3 Manipulating Genomes

Question 1

genome

Answer 1

all the genetic information in an organism

Question 2

explain what is meant by the term: DNA is degenerate

Answer 2

multiple codons code for the same amino acid

Question 3

explain what is meant by the term: DNA is non-overlapping

Answer 3

DNA read in sequences of 3 bases

Question 4

explain what is meant by the term: complementary base pairing

Answer 4

certain bases only pair with their complementary base
hydrogen bonding

Question 5

compare the structure and functions of mRNA and tRNA

Answer 5

similarities: sequences of nucleotide bases joined by phosphodiester bonds
join to a ribosome
differences: tRNA - 3 bases only, mRNA - more than 3 bases
tRNA - carries an amino acid, mRNA - no amino acid
tRNA - not a copy of DNA template, mRNA - copy of DNA template

Question 6

introns

Answer 6

non-coding regions of DNA that are removed from mRNA and made into polypeptide chains

Question 7

exons

Answer 7

coding regions of DNA

Question 8

requirements for PCR

Answer 8

DNA sample
excess triphosphates of the 4 bases - DNTP (deoxynucleotidetriphosphates)
enzyme DNA polymerase - Taq polymerase (thermophillic bacterium)
PCR machine thermal cylcer - cycles between different temperatures
primers - short sequences of bases, provides site of attatchment for Taq polymerase to bind
Mg 2+ - cofactor for DNA polymerase, enables tight binding between active site and substrate

Question 9

stages of the PCR

Answer 9

1. 90-95°C denaturation of double stranded DNA, H bonds broken between 2 strands
2. 55-68°C annealing of primers - allows Taq polymerase to bind, primers bind by H bonds to 3’ end of DNA
3. 71-75°C (optimum temp. for DNA polymerase) Taq polymerase moves from a 5’ to 3’ direction, forming phosphodiester bonds betweens nucleotides

Question 10

purpose of PCR

Answer 10

to amplify DNA

Question 11

basic procedure to separate DNA fragments

Answer 11

1. DNA samples treated with restiction enzymes to cut them into fragments
2. DNA samples placed in wells cut in cathode
3. gel plate is emmersed in tank of buffer solution
4. electric current passed through solution for fixed time period
5. DNA is negatively charged (phosphate back) - attracted to positive electrode
6. DNA fragments diffuse through gel towards anode
7. shorter lengths move faster in the fixed time period
8. position of fragments shown by using DNA stains