OCR A-Level Biology Module 6 Genetics, evolution and ecosystems overview quiz quiz

Binds the promoter region and recruits RNA polymerase to begin active transcription

Catalyses the hydrolysis of lactose into glucose and galactose subunits

Binds the operator and blocks RNA polymerase, preventing transcription

Switches on the structural genes by binding the operator

A substitution always shifts the reading frame, scrambling every codon downstream

Substitution mutations cannot occur within the coding region of any gene

It always introduces a premature stop codon that truncates the protein

The genetic code is degenerate, so the new codon may code for the same amino acid

They code for transcription factors that control the body plan during development

They code for the respiratory enzymes embedded in the inner mitochondrial membrane

They code for the enzyme that hydrolyses lactose into glucose and galactose

They trigger programmed cell death (apoptosis) and nothing else

3:1

9:3:3:1

1:1:1:1

1:2:1

Reject the null hypothesis, because the difference between observed and expected is significant

Conclude the experiment has failed and the data must be discarded entirely

Accept the null hypothesis; the difference is not significant (data fit the ratio)

Double the degrees of freedom and read the critical value again

0.09

0.3

0.7

0.81

Strong directional selection acting on a small, isolated breeding population

Frequent migration between populations combined with strongly non-random mating

A high mutation rate driving rapid allele frequency change each generation

No mutation, no selection, no migration, random mating and a large population

Begins with geographical separation of populations

Occurs without any physical, geographical or reproductive isolation

Only occurs in prokaryotes such as bacteria and never in animals

Always requires a polyploidy event to occur first

Denaturation (about 95 degrees Celsius)

Extension (about 72 degrees Celsius)

Annealing (about 55 degrees Celsius)

Ligation

DNA carries a net positive charge from its nitrogenous bases

The agarose gel matrix physically pushes the fragments along

Smaller fragments carry a positive charge while larger ones stay neutral

DNA is negatively charged due to its phosphate groups

So they have complementary sticky ends that can base-pair and be joined by ligase

To break the plasmid into many small pieces so that the gene cannot ever reinsert itself

To cut the gene into shorter fragments that fit more easily inside the host cell

To remove the promoter so the gene cannot be expressed in the host bacterium

They contaminate the product and so must be filtered out at extra cost each time

They are easily recovered and reused, and are more stable to temperature and pH

They cannot be recovered or reused once a reaction is complete

They denature far more easily than free enzymes when the temperature rises

The total chemical energy fixed by producers before any respiration occurs

The energy that is lost from the ecosystem as heat during respiration

Gross primary productivity minus respiratory losses

The energy stored in the biomass of the top trophic level only

Nitrogen fixation

Ammonification

Denitrification

Nitrification