Questions
a. Information is stored in DNA as a genetic code. Genes, composed of DNA, specify proteins. Summarise in your own words how the information stored in a gene is used to produce a functional protein. (Word count:150–200 words)
b. The guppy (Poecilia reticulata) shows contrasting phenotypic characters for body colour: black and non-black. These are a result of the fish carrying certain combinations of the two alleles of the melanin gene. In a genetic crossing experiment, the following mating crosses were carriedout:
Cross 1:
A male parent fish that was homozygous for one melanin allele and had a black body was mated with a female parent fish that was homozygous for the second melanin allele and had a nonblack body colour. The offspring of this cross (the F1 generation) were all black-bodied.
Cross 2:
A male and a female fish from the F1 generation were selected and mated with each other. The offspring of this cross (the F2 generation) contained black-bodied fish and non-black-bodied fish.
i. Based on this information, allocate a suitable abbreviation for each allele of the melanin gene, stating whether it is dominant or recessive.
ii. Draw two Punnett squares: one for Cross 1 and one for Cross 2, showing the individual gametes of each parent and the combination in their resulting offspring.
iii. Referring to the Punnett squares in (ii) above, explain how the genotype of the parents determines the phenotype of the offspring in each cross. (word count: 170 words)
iv. In this experiment, the total number of offspring in the F2 generation was 560 fish. The ratio of non-black fish to the total number of fish was 1:4. How many non-black fish were present? (Show your calculations.)
v. What is the ratio of non-black fish to black fish?
vi. What is the probability that a gamete produced by an individual in the F1 generation will contain the recessive allele?

Questions a. Information is stored in DNA as a genetic code. Genes...