D DNA genomics

Question 1

how can the banding pattern of alleles can be produced and visualised?

Answer 1

1. DNA sample is digested by EcoRI; @ restriction enzymes
2. Carry out gel electrophoresis - DNA fragments are separated through a gel in an electrical field where rate of migration is inversely proportional to their molecular size;
3. Southern Blotting: DNA is transferred from gel to nitrocellulose membrane via capillary action in an alkaline buffer which denatures double-stranded DNA into single- stranded DNA;
4. Nucleic acid hybridisation can be carried out using the gene probe which would hybridise with DNA sequence of interest on the nitrocellulose paper via complementary base pairing;
5. Autoradiography is then carried out. DNA fragments bound to the radioactive probe will show up on the film / image;

Question 2

advantage of introns ie function of non-coding region

Answer 2

allows alternative splicing to occur -> when pre-mRNAs are processed by joining exons in different combinations, different mature mRNA are produced from the same pre-mRNA -> to a single gene being able to code for more than one polypeptide, increasing number and variety of proteins in the cell without increasing genome size

Question 3

genetic code

Answer 3

1. each codon consists of 3 RNA nucleotide bases coding for one amino acid
2. a single amino acid can be coded for by more than one codon
3. 4.

Question 4

why is lagging synthesis required?

Answer 4

double stranded DNA is ANTI PARALLEL, one strand runs from 5’ to 3’ while the other complementary strand runs from 3’ to 5’, DNA polymerase can only add nucleotides to 3’ end of a growing DNA strand therefore only synthesising DAUGHTER STRAND from 5’ to 3’