B1: You and Your Genes key terms and definitions

For OCR 21st Century B1, just some definitions and key words. Hope this helps and give feedback if you spot any mistakes :)

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B1 Key terms and definitions
Term Definition
Gene A short length of DNA in a chromosome
Chromosome A strand of DNA
Allele A different copy of the same gene
Genotype The genetic coding for a characteristic
Example: blue eyes (bb)
Phenotype The physical appearance of a characteristic
Example: the phenotype of bb would be blue eyes.
Recessive The characteristic that will only appear if the alleles are
homozygous
Example: blue eyes (bb)
Dominant The characteristic that will appear if the alleles are either
heterozygous or homozygous dominant
Example: Huntingtons can occur with either (HH) or (Hh)
Homozygous A combination of alleles that are the same. This can either
be dominant or recessive.
Example: Cystic fibrosis (cc)
Huntingtons (HH)
Heterozygous A combination of alleles that are different. If the alleles are
heterozygous the dominant characteristic will occur.
Example: Brown eyes (Bb)
Embryonic stem cells A type of cell which is unspecialised and can become any
type if cell.
Adult stem cells A type of cell which is unspecialised but is limited in the
type of cell it can become.
Genetic testing Screening done for genetic disorders, this can be done on
anyone.
Amniocentesis A form of genetic testing performed on a foetus where cells
are collected from the amniotic sac.
Chronic villus Another form of genetic testing performed by taking cells
sampling from the placenta.
False positive When a healthy person is told they have a genetic disease
False negative When a person who has a genetic disease is told they are
healthy
Clones Individuals that are genetically identical
Asexual reproduction A type of reproduction that produces clones, it is most
common in plants. (remember this as natural cloning)

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Artificial cloning Where a donor egg cell has the nucleus removed and a
donor adult cell is implanted in its place, this means the
egg has a full set of genes without reproduction.…read more

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