Human Biology Unit 2 - set 2

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Pedigree Charts
analyse patterns of inheritance in genetic screening and counselling
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Pattern of Inheritance
revealed by collecting information about a specific characteristic from family members and the information is used to construct a family tree
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Autosomal Inheritance
genes carried by normal body cells
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Recessive
a gene whose effect does not show if paired with a dominant allele too, a recessive characteristic is only shown if there are two recessive genes, traditionally shown by lowercase letters
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Dominant
a gene whose effect is always shown, normally represented by uppercase letters
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Autosomal Recessive - example
Cystic Fibrosis - all sufferers are homozygous recessive
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Homozygous
both genes for a particular characteristic are the same
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Heterozygous
both genes are different - one dominant, one recessive
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Autosomal dominant Inheritance - occurrence
Appears in every generation
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Autosomal dominant - example
Huntington's Disease
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Autosomal Incomplete Dominance
recessive gene still has effect and there is an intermediate phenotype- a heterozygous person will still suffer from a milder form of the condition
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Autosomal Incomplete Dominance - example
sickle cell anaemia
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Sex Linked Recessive - example
haemophilia
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sex linked genetic problems
only the X chromosomes carry an effective gene, females have 2 X chromosomes (less likely to develop the condition themselves) males only have 1 X so have nothing to cancel out the recessive gene so will have the condition
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Carrier females
as males receive the Y chromosome from their father and the X from their mother if the mother is heterozygous she can pass the gene to her sons
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Carriers - example
if a normal male and normal but carrier female have children they might expect half their daughters tone normal and half to be carriers and half their sons to be normal and half their sons to be affected
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Other cards in this set

Card 2

Front

revealed by collecting information about a specific characteristic from family members and the information is used to construct a family tree

Back

Pattern of Inheritance

Card 3

Front

genes carried by normal body cells

Back

Preview of the back of card 3

Card 4

Front

a gene whose effect does not show if paired with a dominant allele too, a recessive characteristic is only shown if there are two recessive genes, traditionally shown by lowercase letters

Back

Preview of the back of card 4

Card 5

Front

a gene whose effect is always shown, normally represented by uppercase letters

Back

Preview of the back of card 5
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