Homework Answers

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

What possible genotypes and phenotypes can be produced in the offspring of Mr and Mrs Suspicious, and what are the expected Mendelian Genetics ratios of these? You can use a Punnett Square to determine your answer. You will indicate the possible genotypes and phenotypes by entering in the expected ratios produced of these

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

2.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? Use a Punnett Square to demonstrate the expected outcome using appropriate symbols.

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.

Complete the following Punnet Squares and likely phenotype and genotype numbers representing the above cross scenarios, assuming that there were 100 offspring produced in the F1 generation of both crosses (i.e. for the genotypes and phenotypes, write the expected number/ratio). [4]

Following a mutagenesis experiment to identify novel genes affecting the circadian clock in Drosophila melanogaster you discover several mutants. You start considering two of those mutants that you call c and d. The two homozygous c/c and d/d are arrhythmic (arrhythmic is the definition of their phenotype), whereas the two heterozygous C/c and D/d are rhythmic (rhythmic is the definition of their phenotype) with a 24h period. You make two true-breeding stocks: stock 3 homozygous for c and stock 4 homozygous for d. You cross them in both directions and in both cases you observe complementation with no difference between males and females. Then you take the progeny of one cross, for instance the F1 of Females 3 x Males 4, and you perform a Testcross. Out of 1000 flies resulting from the Testcross only 125 are rhythmic.

What is the genotype of Females 3 ? Select only one answer.