A set of one maternal and one paternal chromosome that pair up with each other inside a cell during meiosis.
Corresponding but not identical genetic information
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What is formed when two haploids (n) gametes fuse in fertilisation?
Zygote (2n)
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What happens in meiosis?
Two nuclear divisions
DNA replicated only once
Reduces the number of chromosomes to n
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What are errors in meiosis called?
Nondisjunction
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What is the term for loss of genetic material?
Aneuploidy
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What is the term for a gain of genetic material?
Polyploidy
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What is Down Syndrome?
Failure of chromosome 21 to separate
Impaired intelligence
Abnormalities of hands, tongue and eyelids
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What is the term for when part of a chromosome attaches to another?
Translocation
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Who discovered mendelian genetics?
Gregor Johann Mendel
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What did Gregor Mendel do?
Cultivated and tested 28000 pea plants
He found that the plants' offspring retained traits of the parents
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Why did Gregor Mendel use pea plants?
Can be grown in large quantities
Produce large numbers of offspring (seeds)
Short generation times
Have male and female reproductive organs: self-fertilisation
Easy to control which individuals mate
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What was Mendel's experiment procedure?
Mendel hand-pollinated flowers using a paintbrush
He snipped the stamens to prevent self-pollination
Covered each flower with a cloth bag
He traced traits through several generations
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How did Mendel produce pure strains?
Allowed the plants to self-pollinate for several generations
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What is the term for the offspring from the cross of the first parents?
First filial generation (F1)
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What does a test cross determine?
Whether an individual with a dominant trait is homozygous or heterozygous
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How is a test cross carried out?
S- x **
If ** x ** (homozygous) then all seeds will be ** so all smooth
If ** x ** (heterozygous) then 50% will be ** smooth and 50% will be ** wrinkled
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What happens in incomplete dominance?
F1 hybrids have an appearance in between the phenotypes of the parental varieties
e.g. R=red r=white Rr=pink
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What is codominance?
Two alleles are expressed (multiple alleles) in heterozygous individuals
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What is an example of codominance?
Blood type
type A = IAIA or IAi
type B = IBIB or IBi
type AB = IAIB
type O = ii
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What is formed when two haploids (n) gametes fuse in fertilisation?
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