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Flashcards · Biology · Genetic Inheritance

Genes, Alleles and Genetic Terms

16 cards

  1. What is an allele?

    A different form of the same gene.

  2. Where are the two alleles of a gene found?

    On the two chromosomes of a pair, at the same position.

  3. How many alleles of a gene does a gamete carry?

    One.

  4. What is a dominant allele?

    One that is always expressed, even if only one copy is present.

  5. When is a recessive allele expressed?

    Only when two copies are present, so there is no dominant allele.

  6. How are dominant and recessive alleles written?

    A capital letter for dominant and the lower case of the same letter for recessive.

  7. What does homozygous mean?

    Both alleles of the gene are the same.

  8. What does heterozygous mean?

    The two alleles of the gene are different.

  9. What is a genotype?

    The alleles an organism has, such as Bb.

  10. What is a phenotype?

    The characteristic that shows, such as brown fur.

  11. Which genotype gives a recessive phenotype?

    Only the homozygous recessive genotype, such as bb.

  12. Do BB and Bb have the same phenotype?

    Yes, if B is dominant, but they are different genotypes.

  13. Give two examples of single gene characteristics.

    Fur colour in mice and red-green colour blindness in humans.

  14. Are most characteristics controlled by one gene?

    No. Most are controlled by many genes interacting.

  15. What is a common mistake about dominant alleles?

    Thinking they are stronger or more common. They are only expressed when present.

  16. Three pairs of chromosomes with coloured bands marking the alleles, with no labels. Describe the three pairs of chromosomes, using the words homozygous, heterozygous, dominant and recessive.

    Panel 1 is homozygous dominant (BB), panel 2 is heterozygous (Bb) and panel 3 is homozygous recessive (bb). Panels 1 and 2 show the dominant phenotype. Only panel 3 shows the recessive phenotype.