B1 OCR 21st Century Flashcards

Where are genes found in the cell?
Genes are found on the chromosomes in the nucleus of the cell.
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Briefly describe how a gene works.
Each gene is a chemical code that instructs the cell how to make a particular protein.
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What are the different forms of genes called?
The different forms of gene are called alleles.
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When will an individual show a recessive characteristic?
An individual will only show a recessive characteristic if they have both recessive alleles.
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What are the differences in characteristics within a species called?
The differences in characteristics within a species are called variation.
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Give two causes of variation.
Two causes of variation are the environment and genes.
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Give two examples of characteristics that are determined only by genes.
Characteristics that are determined by genes include: blood group, eye colour, facial features and certain inherited disorders such as cystic fibrosis and haemophilia.
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What determines the sex of a baby?
Egg cells always contain an X chromosome but sperm cells are produced in equal amounts with either an X chromosome or Y Chromosome. The sex of a baby depends on which type of sperm cell fertilises the egg.
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What is meant by the term Phenotype. (Higher)
The characteristics of an organism due to its alleles are its phenotype. (Higher)
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If two parents were carriers of cystic fibrosis, what's the probability of their children suffering from the condition?
If two parents are carriers of cystic fibrosis there is a 25% chance of their child suffering from the condition.
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Why is Huntington's disease unusual in how it is inherited?
Most faulty alleles are recessive but Huntington's disease is unusual because it is caused by inheriting one faulty dominant allele instead of the normal recessive allele.
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What is genetic screening?
Genetic screening can be used to detect faulty alleles in cells.
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Why might couples expecting to have a baby wish to have their embryo screened?
Couples expecting a baby might wish to have their embryo screened if they know they are carriers of a condition such as cystic fibrosis.
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When testing for genetic disorders what is meant by a false positive and a false negative?
When testing for genetic disorders a false positive is when a test shows a genetic disorder for a healthy person. A false negative is when a test shows a person is healthy when they actually have a genetic disorder.
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What are clones?
Clones are genetically identical individuals.
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Explain how an adult body cell can be used to form embryo cells.
The nucleus is extracted from an unfertilised cell. The nucleus from an adult body cell (like a skin cell) is then inserted into the egg cell. An electric shock causes the egg to begin to divide to form embryo cells.
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What are stem cells?
Stem cells are unspecialised cells that can develop into other types of cell.
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Where are embryonic stem cells obtained from?
Embryonic stem cells can be obtained from spare embryos from fertility treatment or from the umbilical cords of newborn babies.
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What might embryonic stem cells be used for in the future?
Embryonic stem cells can be used to grow new replacement cells for people with illnesses. This technique might be used in the future to cure conditions such as heart disease, paralysis due to spinal damage, arthritis and Parkinson's disease.
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Other cards in this set

Card 2

Front

Briefly describe how a gene works.

Back

Each gene is a chemical code that instructs the cell how to make a particular protein.

Card 3

Front

What are the different forms of genes called?

Back

Preview of the front of card 3

Card 4

Front

When will an individual show a recessive characteristic?

Back

Preview of the front of card 4

Card 5

Front

What are the differences in characteristics within a species called?

Back

Preview of the front of card 5
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