Variation and inheritance

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What is chlorosis?
A condition where the leaves of a plant appear yellow or discoloured
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Why does chlorosis occur?
Lack of light- if certain section has no light, turns off chlorophyll production there to save resources, Mineral deficiencies- cannot make chlorophyll without certain minerals (e.g. magnesium), Virus infection- preventing production of chlorophyl
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Is body mass due to environmental or genetic factors?
Both: Environmental- extreme cases with amount and quality of food and quantity of exercise, Genetic- occasionally obesity can be due to genetic makeup, e.g. it has been found that mutation in a gene that controls fat deposit causes obesity
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How is variation created during meiosis?
Independent assortment of chromosomes in metaphase 1 and 2, crossing over in anaphase 1
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What is a genotype?
The combination of alleles an organism inherits
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What is a phenotype?
The observable characteristics of an organism
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What is a dominant allele?
A version of a gene that will always be expressed if present in an organism
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What is a recessive allele?
A form of a gene that will only be expressed if 2 copies of this allele is present in the organism
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What is a homozygous pair of alleles?
2 identical alleles for a certain characteristic, e.g. homozygous dominant (2 dominant alleles) or homozygous recessive (2 recessive alleles)
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What is a heterozygous pair of alleles?
2 different alleles for a certain characteristic, in this case the dominant allele will always be expressed
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Describe continuous variation
Characteristics that can take any value within a range (e.g. height, mass), caused by both genetic and environmental, the type of genetic control is polygenes (a number of genes controlling it)
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Describe discontinuous variation
A characteristic that can only appear in specific critical values, e.g. blood group, tongue rolling, caused by genetics (mostly), controlled by either 1 or 2 genes
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Other cards in this set

Card 2

Front

Why does chlorosis occur?

Back

Lack of light- if certain section has no light, turns off chlorophyll production there to save resources, Mineral deficiencies- cannot make chlorophyll without certain minerals (e.g. magnesium), Virus infection- preventing production of chlorophyl

Card 3

Front

Is body mass due to environmental or genetic factors?

Back

Preview of the front of card 3

Card 4

Front

How is variation created during meiosis?

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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