genetic diagrams

what is a dominant allele?

• B (capitalised)

• overrules recessive allele

for the characteristic for the dominant allele to be displayed…

at least one dominant allele must be present

what is a recessive allele?

• b (lowercase)

for the characteristic for the recessive allele to be displayed…

both alleles must be recessive

what does homozygous mean?

alleles are both identical

• BB or bb

what does heterozygous mean?

alleles are both different

• Bb

what is a homozygote?

an individual who has identical alleles for a particular gene

what is a heterozygote?

an individual who has different alleles for a particular gene

what is a genotype?

• combination of alleles

• BB, Bb, bb

what is a phenotype?

the physical characteristics of an organism

what do genes control?

characteristics you develop

• some are controlled by a single gene

  • mouse fur colour, red-green colour blindness

• most characteristics are controlled by several genes interacting

how many versions (alleles) of every gene are in the body?

two (one on each chromosome in a pair)