Flashcards · Biology · Inheritance
Genes, the Genome and Phenotype
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What is a gene?
A section of DNA that codes for a protein.
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What is an allele?
A different version of the same gene, also called a variant.
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What does homozygous mean?
Two identical alleles of a gene.
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What does heterozygous mean?
Two different alleles of a gene.
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What is a dominant allele?
One that shows in the phenotype even if only one copy is present.
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What is a recessive allele?
One that only shows when there are two copies.
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What is a genotype?
The combination of alleles of a gene, such as Tt.
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What is a phenotype?
The feature that the organism shows.
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What is the genome?
The entire genetic material of an organism.
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How many pairs of chromosomes are in a human body cell?
23.
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About how many genes are in the human genome?
About 20 000.
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What two things influence the phenotype?
The genome and its interaction with the environment.
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Are most features controlled by one gene?
No, most are controlled by many genes.
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Give an example of a single gene feature.
Cystic fibrosis, or the flower colour of a pea plant.
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Can Tt and TT have the same phenotype?
Yes, both are tall, but they have different genotypes.
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Common mistake about dominance?
Saying that a dominant allele is the more common one. It only means that it shows when one copy is present.