Genetics Answers

What would the genotypic ratio look like if aa was crossed with aa

A herpetologist finds an anuran which has a green hue. This is the dominant

colour trait and therefore the genotype for colour can be either homozygous

(GG) or heterozygous (Gg). In this species of frog body colour that is brown

suggests a recessive phenotype and therefore this genotype would have to be

homozygous for the recessive allele (gg). G represents the dominant allele and g represents the

recessive allele. Using selective breeding techniques, how would the researcher determine the

genotype of the original green anuran? Explain how the results of this would help the researcher

identify the genotype or the original green anuran.

10 marks

There are three alleles for the gene that determines the ABO blood grouping system in

humans namely IA

, IB and IO. IA and IB are co-dominant and both are dominant over IO.

Two babies were born in a hospital on the same day (these were the only babies born

in the hospital on that day). One set of parents suspected that the babies were

swopped in the hospital nursery and immediately ordered blood tests to determine their blood

groups. Of the parents, Mr Suspicious was blood group A and Mrs Suspicious was blood group B.

The baby given to them was blood group O. Mr Convinced was blood group A and Mrs Convinced

blood group AB. The baby given to them was blood group B.

Did a mix-up occur? (Give a reason for your answer) What are the genotypes of the parents and

their babies? Show all the possible genotypes and phenotypes of children that can be produced by

Mr and Mrs Suspicious, and the expected ratios in which they will occur (include a Punnett Square)

10 marks

A researcher has two pure breeding strains of fruit flies: strain A and strain B.

Strain A produces only enzyme A and strain B only enzyme B. The alleles

coding for enzyme A and enzyme B are the only alleles involved here and occur at the

same locus. The researcher crossed a fly from strain A with one from strain B and found

that all the offspring (F1 generation) could produce both enzyme A and enzyme B. When he

crossed two of the F1 generation flies, he found the following in the offspring:

658 produced enzyme A, 1364 produced enzyme A and B, 581 produced enzyme B

What type of inheritance can produce these results? Using appropriate symbols, show the

researcher’s cross (up to the F2 generation) What would the expected result be if one of the

offspring that can produce both enzyme A and enzyme B were crossed with one that can only

produce enzyme A (include a Punnett Square)?

10 Marks

A herpetologist finds an anuran which has a green hue. This is the dominant

colour trait and therefore the genotype for colour can be either homozygous

(GG) or heterozygous (Gg). In this species of frog body colour that is brown

suggests a recessive phenotype and therefore this genotype would have to be

homozygous for the recessive allele (gg). G represents the dominant allele and g represents the

recessive allele. Using selective breeding techniques, how would the researcher determine the

genotype of the original green anuran? Explain how the results of this would help the researcher

identify the genotype or the original green anuran.

how does DNA replicate?

what is your opinion on genetic engineering? support with facts and include the issue of biosafety

The female cat has black fur. The male cat has black fur. Figure out the phenotypes and genotypes of their possible kittens by using a Punnett Square.

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Q3. The following is a pedigree for a rare human trait: (10 Marks)

a.    What is the most probable mode of inheritance for the trait indicate above? Give reasons. (3 Marks)

b.    If individuals III-3 and III-8 marry, what is the probability of them having a child with the trait? (3.5 Marks)

c.    If individuals IV-1 and IV-10, what is the probability of them having a child who expresses the trait? (3.5 marks)