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Control, Genome and Environment
Cellular Control

(a) state that genes code for polypeptides, including enzymes

(b) explain the meaning of the term genetic code
The sequence of the bases on a gene is a code with instructions for the construction of proteins. It
has a number of characteristics:
It is…

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(h) explain genetic control of protein production in a prokaryote using the lac operon
This involves both regulatory and structural genes.
Regulatory genes make a repressor protein which is a transcription factor that switches a
structural gene on or off
Structural genes make enzymes, polypeptides or proteins
So the regulatory…

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Meiosis and Variation

(a) describe, with the aid of diagrams and photographs, the behaviour of chromosomes during meiosis, and the
associated behaviour of the nuclear envelope, cell membrane and centrioles. (Names of the main stages are expected,
but not the subdivisions of prophase)
Meiosis I
Prophase I
1. The chromatin…

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The combination of alleles possessed by organism
Characteristic in which the allele responsible is expressed in the phenotype, even in those
with heterozygous genotypes
A characteristic where both alleles contribute to the phenotype

Characteristic in which the allele responsible is only expressed in the phenotype is there…

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unless the alleles A or B are not present

(f) describe the interactions between loci (epistasis). (Production of genetic diagrams is not required)
Epistasis is the interaction of different gene loci so that one gene locus makes or suppresses the
expression of another gene locus.
The gene products are usually…

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(k) explain that both genotype and environment contribute to phenotypic variation. (No calculations of
heritability will be expected)
While an organism may have the genetic potential to achieve a certain characteristic, e.g. length of
corn cob, the environment also has an influence. The corn cob may have the genetic potential…

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Seasonal barriers e.g. climate change throughout the year
Reproductive mechanisms e.g. their genitals, breeding seasons or courtship rituals may
be different

Isolating mechanisms involved in dogs evolving from wolves are
geographic wolves avoid human settlements but dogs are confined by humans
behavioural ­ dogs and wolves have different courtship rituals…

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large udders or the correct udder shape (for milking machine)
resistance to disease (eg mastitis) or effective immune system
calm temperament
Process of selection
Each cow's milk yield is measured and recorded
The progeny of bulls is tested to find out which bulls have produced daughters with high
milk yields…

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Biotechnology and Gene Technologies
Cloning in Plants and Animals

(a) outline the differences between reproductive and nonreproductive cloning
Reproductive cloning is the production of offspring which are genetically identical to either the
mother (nuclear transfer), or the other offspring (splitting embryos)
Nonreproductive cloning is the use of stem cells in…

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(d) discuss the advantages and disadvantages of plant cloning in agriculture
1 quick
2 diseasefree stock is created
3 uniform plants are created
4 it is possible to reproduce infertile plants
5 it is possible to reproduce plants that are hard to grow from seed
6 it is possible…


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