What is a gene?
A section of DNA found in chromosomes that contains instructions for a specific protein.
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What is an allele?
Genes that come in different versions.
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What does dominant mean in an allele?
An allele that always affects the phenotype, despite the other allele.
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What does recessive mean in an allele?
An allele that only affects the phenotype if both of the two alleles are the same. It has no affect if the other allele is dominant.
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What does heterozygous mean?
Heterozygous is when the two alleles in a gene are both different to each other.
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What does homozygous mean?
Homozygous is when the two alleles in a gene are the same.
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What is a genotype?
A genotype is the alleles for a certain characteristic that is found in an organism.
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What is a gamete?
A gamete is a haploid cell produced by meiosis, used for sexual reproduction.
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What is a phenotype?
The physical characteristics produced by a certain set of alleles. e.g: eye colour.
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What is a zygote?
A fertilised egg cell.
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Explain what genetic diagrams are.
Genetic diagrams show the different possible combinations of alleles when 2 organisms breed.
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Explain what punnett squares are.
Punnett squares are a way to demonstrate inheritance. They are used to work out the probability of offspring inheriting certain genotypes.
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Explain what family pedigrees are.
Family pedigrees show how genotypes and their resulting phenotypes are inherited in families.
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How is the gender of offspring decided at fertilisation?
There are 2 types of chromosomes: X and Y. Females have 2 X chromosomes and males have 1 X and 1 Y chromosme. A woman's gamete always contain an X whereas a male's either contain an X or Y. ** means it is female. XY means it is male.
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Are phenotypic features made up of only one set of genes?
No, most human characteristics are controlled by many genes, not just one. Usually, most of the variation is caused by one gene.
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What are mutations?
Mutations are a change in a gene that creates a new allele. They happen when there is a mistake in copying DNA during cell division. Mutations can cause variation if an allele is produced that causes a big change in the protein. Most mutations have n
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How can environmental variation influence a phenotype?
Climate, diet, physical accidents, culture and lifestyle can all affect a phenotype. Genes determine what characteristics we inherit however environmental factors affect how the characteristics develop.
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Discuss the outcome of the Human Genome Project.
The human genome project produced a map of 3.3 billion complementary base pairs in a set of 46 chromosomes. Other human genomes have been mapped, which show that there is variation between people but 99% of the bases are the same in different people.
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How could the human genome project be used in medicine?
Mapping a person's genome can show their risk of developing diseases that are caused by different alleles of genes. Can be used to see which medicines would work best to treat an illness, because the alleles we have affect how well medicines work.
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What affect do mutation have on the phenotype?
Most mutations have no affect on the phenotype, some mutations can cause a slight change to the phenotype and very rarely, a single mutation will significantly affect the phenotype.
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Card 2


What is an allele?


Genes that come in different versions.

Card 3


What does dominant mean in an allele?


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Card 4


What does recessive mean in an allele?


Preview of the front of card 4

Card 5


What does heterozygous mean?


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