• Submitted By: hortcr
  • Date Submitted: 11/25/2015 2:01 AM
  • Category: Science
  • Words: 15522
  • Page: 63

1. (a)
Location of receptors
Islets of Langerhans/bcells/pancreas;

(Increase) take up of glucose from blood/conversion of glucose to glycogen;

(b) Answer to include elements -
triggers effects which return to set level; 1

2. (a) Gene is a (length) of DNA;
Gene is a sequence of bases/chain of nucleotides;
Triplet (base) code/read in three’s;
On sense/coding strand;
Triplet coding for amino acid;
Degenerate code; non-overlapping; start/stop code;
Sequence of triplets/bases code for protein; max 4

(b) Restriction enzymes;
Cut DNA; at specific base sequences;
Same (restriction) enzyme also cuts DNA; into which gene is
(DNA) ligase;
Joins two pieces of DNA together/forms recombinant DNA;
Vector needed to insert DNA into host/plasmid enters host/second
Correct ref. to sticky ends; Reverse transcriptase; mRNA ® DNA; max 6

(c) Unwinding/unzipping of DNA;
involving breaking of hydrogen bonds;
Assembly of mRNA nucleotides;
Complementary base pairing/example;
Role of polymerase enzymes;
mRNA enters ribosomes;
Specific tRNA molecule associated with specific amino acid;
Codon - anticodon relationship;
Formation of peptide bonds;
Specific role of ATP/energy; Reference to gene switched on; max 7

Quality of language
Aspect of work
Grammar, punctuation and spelling of an acceptable standard 1
Material presented in an appropriate scientific style with due regard to correct use
of technical terms 1
Argument clearly and logically presented 1

3. (a) (i) Cells of islets of Langerhans / pancreas / a cells; 1
(ii) High glucagon because –
eg stimulated by low glucose/
glycogen must be converted to glucose;
Low glucagon because –
e.g. body has absorbed glucose; 2

(b) Clear understanding that a change from the set level initiates mechanism
returning it;
low glucose® secretion of glucagon ® glucose level increases/...