Edexcel IGCSE Biology 3.20 Genetic terminology
Practise using inheritance vocabulary to interpret allele expression, genotypes and phenotypes in family or breeding contexts.
- Syllabus
- First assessment 2019
- Course
- Biology 4BI1
Exam points
- state when dominant and recessive alleles appear in the phenotype
- use homozygous and heterozygous genotypes to explain visible characteristics
- explain why hidden recessive alleles can persist in breeding populations
3.20 Genetic terminology question 1
[Maximum number: 2]
Fur colour in rats is controlled by a gene with two alleles.
One allele codes for black fur colour. The other allele codes for agouti fur colour.
Several female rats with agouti coloured fur are mated with several male rats with black coloured fur.
All of the offspring have agouti coloured fur.
Explain which allele is dominant.
agouti
- all offspring are agouti / no offspring are black / as allele always expressed / shown / visible in all phenotype / expressed in heterozygous / black allele not expressed / /eq
ignore passed on as black allele also passed on
otherwise, all the black
parents
would need to be
heterozygous
and even then only 0.5
probability
that each is black / eq
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