pmt q Flashcards
Describe how a gene is a code for the production of a polypeptide. Do not
include information about transcription or translation in your answer.
- (In) triplet(s)
-(Because) base/nucleotide sequence; - (Determines) order/sequence of amino acid sequence/primary structure (in polypeptide);
Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule
1)Condensation (reaction)/loss of water;
2. (Between) phosphate and deoxyribose;
3. (Catalysed by) DNA polymerase;
Define ‘non-coding base sequences’ and describe where the non-coding multiple repeats are positioned in the genome
DNA that does not code for protein/polypeptides
(Positioned) between genes;
Give three ways in which the DNA in a chloroplast is different from DNA in the nucleus
- DNA shorter;
Accept smaller - Fewer genes;
- DNA circular not linear;
Accept DNA in a loop not linear
Accept no chromosomes (in chloroplast) unlike nucleus - Not associated with protein/histones, unlike nuclear DNA;
- Introns absent but present in nuclear DNA
Compare and contrast the DNA in eukaryotic cells with the DNA in prokaryotic cells.
- Nucleotides joined by phosphodiester bond;
- Nucleotide structure is identical;
- Eukaryotic DNA contain introns, prokaryotic DNA does not;
- Eukaryotic DNA is linear, prokaryotic DNA is circular;
- Eukaryotic DNA is associated with / bound to protein / histones, prokaryotic DNA is not;
Describe how one amino acid is added to a polypeptide that is being
formed at a ribosome during translation.
1.tRNA brings specific amino acid
2. Anticodon (on tRNA) binds to codon (on mRNA);
3. Amino acids join by condensation reaction (using ATP)
Describe how mRNA is produced from an exposed template strand of DNA.
Do not include DNA helicase or splicing in your answer.
1.
2. Phosphodiester bonds form;
(Free RNA) nucleotides form complementary base pairs;
Accept A-U, G-C OR combination of those pairs Accept linkages for ‘bonds’
3. By (action of) RNA polymerase;
Describe how mRNA is formed by transcription in eukaryotes.
-Hydrogen bonds (between DNA bases) break
-(Only) one DNA strand acts as a template;
-(Free) RNA nucleotides align by complementary base pairing
-(In RNA) Uracil base pairs with adenine (on DNA)
- RNA polymerase joins (adjacent RNA) nucleotides;
-(By) phosphodiester bonds (between adjacent nucleotides);
-Pre-mRNA is spliced (to form mRNA)
Describe how a polypeptide is formed by translation of mRNA.
(mRNA attaches) to ribosomes
(tRNA) anticodons (bind to) complementary (mRNA) codons;
tRNA brings a specific amino acid
Amino acids join by peptide bonds;
(Amino acids join together) with the use of ATP;
tRNA released (after amino acid joined to polypeptide);
The ribosome moves along the mRNA to form the polypeptide
Starting with mRNA in the cytoplasm, describe how translation leads to the production of a polypeptide
mRNA associates with a ribosome / ribosome attaches to mRNA;
Ribosome moves to / finds the start codon / AUG
tRNA brings / carries (appropriate / specific) amino acid
Anticodon (on tRNA complementary) to codon (on mRNA);
Ribosome moves along to next codon;
(Process repeated and) amino acids join by peptide bonds / condensation reaction (to form polypeptide);
The genetic code is described as degenerate.
What is meant by this?
More than one codon codes for a single amino acid;
Genetic variation within a species is increased during meiosis by crossing over and the independent segregation of homologous chromosomes.
Apart from mutation, explain one other way genetic variation within a species is increased.
Random fusion of gametes
(Produces) new allele combinations
(c) Define ‘gene mutation’ and explain how a gene mutation can have:
* no effect on an individual
* a positive effect on an individual.
- Change in the base/nucleotide (sequence of chromosomes/DNA
- Results in the formation of new allele;
- Genetic code is degenerate (so amino acid sequence may not change);
May result in increased reproductive success
A student used a dilution series to investigate the number of cells present in a liquid culture of bacteria.
Describe how he made a 1 in 10 dilution and then used this to make a 1 in 1000 dilution of the original liquid culture of bacteria
.
Add 1 part (bacteria) culture to 9 parts (sterile) liquid (to make 10–1 dilution)
Mix (well);
Repeat using 9 parts fresh (sterile) liquid and 1 part of 10–1 and 10–2 dilutions to make 10–3 dilution
Suggest and explain one reason why bacteria resistant to tetracycline are more common than bacteria resistant to streptomycin in these farm animals.
1.Tetracycline used more often / in higher doses;
2. Resistant bacteria more likely to (survive and reproduce and) pass on allele/gene for (tetracycline) resistance
(e) In recent years, these farm animals have not been given tetracycline in their food. Despite this, the percentage of bacteria resistant to tetracycline has remained constant.
Suggest one reason why.
No selection against resistant bacteria / resistance gene/allele;
OR
Bacteria pass on (resistance) gene / allele when they reproduce;
OR
One hypothesis for LP in humans suggests that the selective pressure was related to some human populations farming cattle as a source of milk.
Describe how farming cattle as a source of milk could have led to an increase in LP.
LP due to mutation
Milk provides named nutrient
Individuals with LP more likely to survive and reproduce
4. Directional selection;
5. Frequency of allele increases (in the offspring/next generation);
Lactase persistence is caused by a mutation in DNA. This mutation does not occur in the gene coding for lactase.
Suggest and explain how this mutation causes LP.
Mutation in gene for transcription factor;
Lactase gene continues to be transcribed/active;
Figure 1 shows a hierarchy. Explain how.
(It shows) smaller groups within larger groups / larger groups containing smaller groups;\
With no overlap (between groups);
(e)
Some populations of animals that have never been hunted show very low levels of genetic diversity.
Other than hunting, suggest two reasons why populations might show very low levels of genetic diversity.
- Population might have started with small number of individuals /
by one pregnant female / founder effect; 3. Inbreeding.
Population might have been very small / genetic bottleneck;
Describe how breeding experiments could determine whether the two populations are from the same species
Breed the two mice together;
(Same species) produce fertile offspring.
(a) There are many different species of field mouse in Europe. Using a phylogenetic classification, all of these species have names that start with Apodemus.
What information does this give about field mice?
Same genus;
Same evolutionary origin / common ancestor.
