Genetic Variation

  • Created by: Esme.B
  • Created on: 13-01-18 14:03
A section of DNA that codes for one (or more) polypeptide(s)
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A variation of a gene. (Still codes for a polypeptide)
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How do different Alleles arise?
By the process of Mutation
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The genetic make up of an organism.
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Visible characteristics of an organism. Determined by Genotype and enviroment
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Causes of phenotypic variation? (list 4 factors)
Sexual reproduction, environmental factors, chromosomes mutations and gene mutations
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List 3 physical agents which increase the risk of Mutation?
x-rays, Gamma rays, UV light
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List 4 chemical agents which increase the risk of mutation?
Benzopyrene (found in tobacco smoke), Mustard gas, nitrous acid and aromatic amines in some synthetic dyes.
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List 3 Biological agents which increase the risk of mutation?
Some viruses, Transposons (Jumping gene) and food contaminations, i.e- mycotoxins from fungi.
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Definition of a Persistent mutation and random mutation?
Persistent mutation= transmitted through many generations without change. Random mutation= not directed by a need on part of the organism in which they occur.
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Chromosome mutation occur during meiosis which cause variation , list the 5 different chromosome mutations?
1). Deletion-lost chromosome 2).Inversion-section turns 180 and then not properly expressed.3).Translocation-piece of 1 chromosome becomes attached to another chromosome.4)Duplication-piece of chromosome =over expressed 5)non-disjunction- pair of
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Chromosome number not multiple of haploid number, sometimes caused by non-disjunction of chromosomes/chromatids.
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Example of Aneuploidy?
Trisomy 21 (Downs syndrome)
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When there is more than 2 sets of chromosomes. i.e - diploid gamete fertilises a haploid gamete the end zygote will be triploid.
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What are the 2 different types of Polyploid
1). Autopolyploidy=possessing more than 2 sets of chromosomes,where all sets come from the SAME SPECIES. 2). Allopolyploidy = possessing more than 2 sets of chromosomes,where sets/chromosomes come from TWO CLOSELY RELATED SPECIES.
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Why is variation important?
Evolve in responses to enviroment (natural) or human (artificial) selection pressures. NATURAL SELECTION!
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List 3 factors needed for a population of organisms to evolve?
Variation-difference between individuals in a population, Heredity- differences between organisms must be heritable and Means of selection- mechanism or pressure that selects some variable for next generation.
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How Meiosis and Fertilisation leads to genetic variation, list 5 main factors?
Crossing Over, Reassortment of Chromosomes ,Reassortment of Chromatids,Fertilisation and mutation
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chromosome mutation?
1. Inversion. 2. Deletion. 3. Translocation 4. Non-disjunction
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What is a mutagen?
An agent that causes/increases the chances of mutation
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When, during the cell cycle, is a mutation to the DNA most likely to occur?
During interphase/when DNA is replicating/during S phase
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A variation of a gene. (Still codes for a polypeptide)

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How do different Alleles arise?


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