Introduction to Inheritance (5.1.2)

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What is a gene?
A length of DNA which codes for a specific polypeptide.
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What is an allele?
A version of a gene- different alleles of the same gene have slightly different DNA structures, so code for different versions of the polypeptide.
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What is a locus?
The specific position on a chromosome where a particular gene is found.
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What is crossing over?
Where sections of DNA from non-sister chromatids swap and rejoin, creating new allele combinations.
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What is a genotype?
The genetic makeup of an organism in terms of the alleles it contains.
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What is a phenotype?
The physical characteristics that are expressed in an organism. It is determined by the genotype and sometimes the environment as well.
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What is a dominant allele?
An allele which is always expressed in the phenotype, regardless of any other alleles present with it.
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What is a recessive allele?
An allele that is only expressed in the phenotype when there are two present together, and in the absence of a dominant allele.
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What is co-dominance?
When two alleles of a gene are equally dominant. When both are present, both are expressed in the phenotype.
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What are linked genes?
When two or more genes are located on the same chromosome and so are usually inherited together.
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What does a faulty version of the CFTR protein cause?
Cystic fibrosis.
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What does the CFTR protein do?
The protein sits in the plasma membrane of lung cells and other organs. Each protein molecule forms a channel which allows chlorine ions out. This results in thin watery mucus, as water leaves the cell by osmosis.
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How should you set out a genetic diagram?
Key of alleles. Parent phenotypes. Parent genotypes. Possible gametes. Genetic cross. Expected ratio.
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Card 2

Front

What is an allele?

Back

A version of a gene- different alleles of the same gene have slightly different DNA structures, so code for different versions of the polypeptide.

Card 3

Front

What is a locus?

Back

Preview of the front of card 3

Card 4

Front

What is crossing over?

Back

Preview of the front of card 4

Card 5

Front

What is a genotype?

Back

Preview of the front of card 5
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