Suggest why this mutation reduces the effectiveness of salmeterol.
(mutation) change in (DNA) nucleotide/ base, sequence ;
(mutation causes) change in,
amino acid sequence / primary structure
(of protein) ;
change in , tertiary structure/ 3D shape / binding site , of
salmeterol unable to bind ;
idea that no response triggered in cell /
no second messenger system activated ;
After one year, the children taking montelukast had better control of their asthma and were able to reduce their use of montelukast. Suggest why these children responded better to montelukast than to salmeterol.
(mutation resulted in) receptor having complementary shape to montelukast ; montelukast able to bind ; (whereas) salmeterol cannot ; montelukast may have a different receptor ;
State the number of DNA nucleotide bases that code for a single amino acid.
There is a maximum of 64 different base combinations in DNA that could each code for an amino acid.How is this number of combinations calculated?
Twenty different amino acids are commonly used for protein synthesis. In theory, this would need only 20 different base combinations.
Explain the uses of the remaining 44 combinations.
Several, triplet(s) / codon(s) , code for one amino acid ; (some are used as) start / stop / termination ; idea that mutation may , not result in change in amino acid / have a neutral effect / result in silent mutation ;
Describe how a nucleotide base sequence in a gene is used to synthesise a polypeptide.
1 DNA / gene , copied / transcribed , into mRNA ;
2 free / activated ,
(RNA) nucleotides / (RNA) nucleoside triphosphates ;
3 (line up by) complementary base-pairing / described ;
4 (to) one / template / reference / sense , (DNA) strand ;
5 (catalysed by) RNA polymerase ;
6 (mRNA moves to) ribosomes ;
7 tRNA (molecules) bind to mRNA ;
8 anticodon(s) , match / pair with / bind to , codons ;
9 specific / correct , amino acid attached to tRNA ;
10 formation of peptide bond between amino acids;
Meiosis is used in many organisms for the production of gametes.
Explain why meiosis needs to have twice as many stages as mitosis.
to, halve chromosome number / reduce from 2n to n ;
to separate homologous pairs (of chromosomes)
and sister chromatids ;
because, DNA (previously) replicated /
chromosomes are two chromatids at start ;
What feature of the DNA molecule is changed as a result of mutation?
sequence / order, of bases / nucleotides ;
Discuss the possible effects that mutation can have on the structure and function of a protein.
different, primary / secondary / tertiary, structure ;
(protein ) shorter due to, deletion / stop codon OR
longer due to, insertion / duplication ;
(protein) unchanged due to, silent mutation /
non-coding DNA altered ;
(function is) lost / worse / better ;
Explain why dwarfism can be described as a genetic condition.
inherited / passed to offspring /
passed (down) from parents ;
(caused by) mutation / allele ;
Describe one other example of genes being switched on or being switched off by a molecule that binds directly to DNA.
1 (lac) repressor protein ;
2 (repressor protein) changes shape when bound to
3 (with lactose) lifts off operator allowing,
transcription / gene expression /
binding of RNA polymerase to promoter ; ORA
4 β-galactosidase / enzyme(s) / structural gene(s) ;
5 homeotic / homeobox / hox (genes) ;
6 gene product / protein / transcription factor,
binds to DNA ;
7 gene product / protein, starts transcription / is a
transcription factor ;
8 many genes affected / controls body plan ;
Outline the events that lead to genetic variation in gametes and in the plants grown from seed.
1 mutation ; 2 meiosis ; 3 cross(ing)-over ; 4 between non-sister chromatids ; 5 (in) prophase I ; 6 independent / random , assortment / segregation ; 7 (in) metaphase ; 8 idea of random , fertilisation / fusion of gametes ;
Suggest two ways in which the varieties may differ from one another biochemically to account for the difference in the length of the cold period required by each.
they have different (qualitatively or quantitatively)
1 genes / DNA / alleles / genotypes ;
2 repressor proteins ;
3 enzymes ;
4 protein folding / tertiary structure / thermostability ;
5 (plant) growth regulators / hormones ;
RNA polymerase and DNA polymerase are both enzymes. RNA polymerase is involved in the action of some control elements, whereas DNA polymerase is not.
Describe and explain the difference between the functions of these two enzymes.
(m / messenger / t / transfer / r / ribosomal) RNA ;
2 transcription ;
3 one strand (DNA) used / short section used /
one strand formed ;
4 DNA replication ;
5 semi-conservative / both strands used /
whole length used / 2 strands formed ;
6 before , nuclear / cell , division ;
The panda crystallin protein obtained was 175 amino acids long, corresponding to a 528 base pair cDNA gene.
Explain why a protein that is 175 amino acids long is coded for by 528 base pairs of DNA.
triplet code or 3 bases = 1 amino acid ;
3 bases are , stop / (chain) termination , codon ;
State what is meant by a homeobox gene.
homeotic / regulatory, (gene) ;
contains, 180 bp / homeobox, sequence ;
that codes for homeodomain (on protein) ;
(gene product) binds to DNA ;
initiates transcription / switch genes, on / off ;
control of, development / body plan ;
Homeobox genes show ‘astonishing similarity across widely different species of animal’.Explain why there has been very little change by mutation in these genes.
these genes very important ;
mutation would, have big effects / alter body plan ;
many other genes would be affected / knock-on effects ;
mutation likely to be, lethal / selected against ;
List two cellular processes that must occur during the development of a tadpole into a frog.
protein synthesis / transcription and translation ; respiration ; DNA replication ; mitosis ; cytokinesis ; apoptosis ; differentiation / gene switching ;
Name another kingdom of organisms, other than animals, that have similar homeotic genes.
fungi / plants ;
State the name of the stage of protein synthesis and name the organelle in the cell where this takes place.
ribosome / rough ER / RER ;
State what is meant by gene mutation.
idea of change to , DNA / base(s) / nucleotide(s) ;
Distinguish between the terms ‘regulatory gene’ and ‘structural gene’.
idea that makes , repressor protein / transcription factor
idea that product switches (structural / another) gene ,
on / off ;
idea that makes , enzyme / polypeptide / protein ;
relationship between the 2
idea that regulatory gene , controls / affects ,
the expression of structural gene ;
Describe how genes lacZ and lacY are switched on in bacteria that are moved to a nutrient medium that contains lactose.
lactose binds to repressor protein ;
changes , shape / structure (of protein) ;
removes it from / stops it binding to , operator ;
RNA polymerase binds to promoter ;
idea that (so that Z and Y) are ,
transcribed / mRNA made ;
Name the type of gene which, if mutated, gives rise to dramatic changes in body plan.
homeotic / homeobox / hox ;
) Describe how the information coded on genes is used to synthesise polypeptides and how these polypeptides control the physical development of an organism.
synthesis DNA, copied into / , mRNA or described ; transcription / transcribed ; one strand copied ; complementary base-pairing ; triplet code / code read in threes / codon is 3 bases ; base sequence determines amino acid sequence ; translation ; ribosomes ; role of tRNA described ; roles of polypeptides (named) structural protein ; enzymes / catalyse reactions / control metabolism ; hormones / growth factors ; receptor proteins ; adenyl cyclase / cAMP ; idea of switching genes, on / off ; homeotic / homeobox, genes or homeodomain proteins ; idea of master switch gene / one gene turns on/off whole set of other genes / cascades of gene switching ; apoptosis
Three alleles of DRD4 have the following alterations: • a single base-pair substitution• a 21 base-pair deletion • a 13 base-pair deletion.Suggest which of the three mutations will have the most serious consequences for the structure of the protein receptor. Give a reason for your choice.
13 b-p deletion (has most serious consequences) ;
frameshift / alter reading frame ;
genetic code is triplet / read in groups of 3 bases ;
alters all amino acids (coded for) after the mutation ;
21 b-p deletion causes 7 amino acids to be lost ;
substitution changes, one / no, amino acids