OCR Biology F251 - cellular control exam questions

questions and answers you should know

  • Created by: sophie
  • Created on: 08-04-12 09:58

State 2 processes that occur in the cell during in

DNA replication

protein synthesis

membrane synthesis



organelle synthesis

1 of 7

Explain how distinct phenotype differences between

Populations geologically isolated

mutations occur

new alleles arise

no mixing of the popukations

adaptation to location - different selection pressures eg coat colour for camoflage

beneficial alleles increase frequency

ii) suggest why the populations are classed as subspecies rather than different species

they are geographically isolated but are still able to interbreed freely with fertile offspring. they have similar behavioural/biological/biochemical features

2 of 7

State 3 practical precautions that must be taken b

male sterility gene/emasculation

anthers removed before maturity

flowers isolated

pollen transfered by hand

3 of 7

The Chi^2 result was very large. explain the discr

Genes are linked/on same chromasome

no random assortment

large number of parental types

small number of recombinants

crossing over during Metaphase 1

between non-sister chromatids of homologous chromasome

number of recombinants depends on closeness of genes

4 of 7

State the functions of the lac operon

Operator region - length of DNA that switches off/on structural genes

Promoter region - length of DNA where the enzyme RNA polyperase binds to begin transcription of structural genes

Repressor molecule - prevents RNA polyperase binding with promoter

Beta Galactase - breaks down lactose

Lactose Permease - increases uptake of lactose

5 of 7

Explain how Beta Galactosidase and lactose permeas

Regulator gene produced repressor protein

Protein binds to the oerator region

it prevents RNA polyperase binding

so no transcription/translation of genes

saves energy

saves amino acids/resources

6 of 7

Describe the events that occur in E Coli when lact

lactose bind to the repressor molecule

via abd allosteric site

this alters the shape of the molecule

so its unable to bind to the operon

RNA polymerase can bind to promoter

transcription of genes

translation/peotein synthesis

increased uptake of lactose

breakdown of lactose from glucose to galactose

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Genius :)

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