B1h: Variation and Inheritance

This item looks at the causes of variation and how we can use our knwledge of inheritance to help predict the characteristics of children.

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What are body mass, intelligence and height determined by?
Environment and genes.
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Where are chromosomes found and what do they carry information in the form of?
They are found in the nucleus and carry information in the form of genes.
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What do genes control?
Inherited characteristics.
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Body cells contain chromosomes in what?
Matched pairs.
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If body cells have 46 chromosomes, how many do gametes have?
23 chromosomes.
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Name three inherited disorders.
Red-green colour blindness, cystic fibrosis and sickle cell anaemia.
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What two types of inherited characteristics are there?
Dominant and recessive.
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List three causes of genetic variation.
Mutations, gamete formation and fertilisation.
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Describe mutations - linked to variation.
A gene may mutate (change) creating new characteristics, increasing variation.
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Describe gamete formation- linked to variation.
Gametes are sperm and egg cells. Body cells are made from 23 pairs of chromosomes, one inherited from mum, and one from dad. When the body cell split to form gametes, chromosomes are too. The shuffling of chromosomes leads to variation.
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Describe fertilisation - linked to variation.
Fertilisation is when the sperm and egg join to form a new cell with the full 46 chromosomes. Firtilisation is random, and it is unknown which two gametes are going to join together - variation.
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Does everyone have 23 pairs of chromosomes in body cells?
No, humans do, but most other species don't.
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What are alleles?
Different versions of the same gene.
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What is the female sex chromosome?
XX
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What is the male sex chromosome?
XY
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What are inherited disorders caused by?
Faulty genes.
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What are the issues raised by knowledge of inherited disorders in a family?
-Should all family members be tested? -Is it right to have children if there is a risk of passing on a genetic condition? Is it fair to tell them not too? - Is it right to terminate pregnancy if there is a chance?
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Debate to do with health, over lifestyle and genes.
Some people are more limey to get certain diseases because of genes, but other factors such as smoking and eating junk food increase the risk.
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Debate to do with intelligence, over lifestyle and genes.
Maximum IQ might be determined by genes, however upbringing and education also contributes.
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Debate to do with sporting ability, over lifestyle and genes.
Genes determine potential, but training is just as important.
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When are dominant alleles expressed?
If they are present.
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When are recessive alleles expressed?
When dominant alleles are absent.
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Explain a monohybrid cross.
The lines show all possible ways the parent alleles could combine. One possibility will happen for one offspring. From this you can work out the chance.
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What does homozygous mean?
Two identical alleles.
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What does heterozygous mean?
Two different alleles.
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What does genotype mean?
The genetic makeup.
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What does phenotype mean?
The characteristics expressed.
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Are most fault alleles dominant or recessive?
Recessive.
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Other cards in this set

Card 2

Front

Where are chromosomes found and what do they carry information in the form of?

Back

They are found in the nucleus and carry information in the form of genes.

Card 3

Front

What do genes control?

Back

Preview of the front of card 3

Card 4

Front

Body cells contain chromosomes in what?

Back

Preview of the front of card 4

Card 5

Front

If body cells have 46 chromosomes, how many do gametes have?

Back

Preview of the front of card 5
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