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F215 Module 1: Cellular Control and Variation
5.1.2 Meiosis and Variation

(a) describe, with aid of diagrams and photographs, the behaviour of the nuclear envelope, cell membrane
and centrioles (name of the main stages are expected but not the subdivisions of prophase)
Meiosis ­ is a reduction division. The resulting…

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F215 Module 1: Cellular Control and Variation

(b) explain the terms:
Allele A version of a gene there may be a difference in the base sequence that is
expressed as a slightly different polypeptide.
Locus The position of a gene on a chromosome. Alleles of a gene are found at…

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F215 Module 1: Cellular Control and Variation
Random mutation DNA mutation may occur during interphase when DNA replicates.
1. Insertion/deletion mutations ­one of more nucleotide pairs are inserted or
deleted from a length of DNA, causing a frameshift ­ the amino acid sequence
is altered after the insertion/deletion point.
2.…

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F215 Module 1: Cellular Control and Variation
W
Heterozygous individuals with genotype CR C have red and white hairs ­ roan coat.
(f) describe the interactions between loci (epistasis)
(g) predict phenotypic ratios in problems involving epistasis
Epistasis ­ the interaction of different gene loci so that one gene locus…

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F215 Module 1: Cellular Control and Variation
The gene loci must complement each other ­ if one gene codes for an intermediate colourless
pigment and the second locus codes for an enzyme that converts the intermediate compound
to the final purple pigment.


(h) use the chisquared (x2 ) test to…

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F215 Module 1: Cellular Control and Variation
Genetic variation is caused by spontaneous mutation, due to sexual reproduction.
The selection pressure causes some individuals to have a selective advantage over the others.
They are more likely to survive and pass on their allele to their offspring, causing an increase in…

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F215 Module 1: Cellular Control and Variation
predators or parasites, disease and space for plants to grow, or for animals to defend a feeding territory and to
rear young).

Over a period of time, the population size will fluctuate around the carrying capacity. If environmental resistance
is great enough, the…

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F215 Module 1: Cellular Control and Variation
A large population of organisms may be split into subgroups by various isolating mechanisms. This leaves two
subpopulations, isolated from each other. In each case different alleles will be eliminated or increased within
subpopulation. Eventually the subpopulations will not be able to interbreed…

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F215 Module 1: Cellular Control and Variation

Natural Selection Artificial Selection
Natural selection is a mechanism for evolution. In artificial selection:
Genetic variation is caused by spontaneous Humans select the organisms with useful
mutation, due to sexual reproduction. characteristics.
The selection pressure causes some individuals to Humans allow those with…

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F215 Module 1: Cellular Control and Variation
Each year, in the UK, the Camden and Chorleywood Food Research Association (C&CFRA), formerly The Flour
Milling and Baking Research Association, surveys the wheat varieties grown in the UK and classifies them
according to their suitability for making bread or biscuits or for…

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Mona

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Thank you! This is really helpful 

Mona

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Thank you! This is really helpful 

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