A researcher found a new species of butterfly. Some of the individuals had short bodies, while others had long bodies. First he bred the butterflies to get true-breeding strains for short or long bodies.
1. What does this statement mean? (1p)
Once he had true-breeding strains, he crossed a short-bodied individual with a long-bodied individual.
2. If the body length is determined by a single gene, exhibiting normal dominant-recessive inheritance, what are the expected F1 and F2 if short bodies are recessive? (8p)
In observing the butterflies he also noticed variation in body colour. Most individuals were black, while some were grey.
3. Determine the F1 and F2 of the cross of the following true-breeding individuals, if all Mendel's rules and laws apply:
grey, long bodied x black, short bodied (8p)
The researcher was curious about other characteristics, so he crossed an individual with curly mouthparts with another with rounded mouthparts. He noticed that all the offspring had curly mouthparts. He then crossed two F1 individuals.
4. Indicate the genotypes of the parents and the F1. What do you predict the genotypes and phenotypes of the F2 to be. Show your work in a Punnett square. (6p)
The butterflies had lovely wing patterns and colours. The researcher noted that some butterflies had red spots on black wings, while others had orange on black and yet others had yellow on black. When he crossed a red with a yellow all the offspring were orange, but when he crossed two orange individuals, he saw red and yellow reappear in their offspring.
5. How can this inheritance be explained? What are the ratios of the different colours in the F2? (5p)
The coloured spots were arranged on the upper wings in either a clover-leaf pattern or a heart-shaped pattern. When he crossed an individual with heart-shaped patterns with an individual with clover-leaf patterns, half of the offspring had the heart-shaped pattern and half had the clover-leaf pattern, but when he crossed two individuals with heart-shaped patterns, he saw a ratio of 2/3 heart-shaped patterns to 1/3 clover-leaf patterns in their offspring.
6. How can these ratios be explained? (1p)
The researcher noted a range in overall wing size that didn't have 2 distinct phenotypes, but rather showed continuous variation, with the majority of individuals in the intermediate range, but only a few that were very large or very small.
7. What might explain this type of phenotype? (1p)
When the researcher crossed two black-bodied, long-antennaed butterflies and when the eggs hatched and the caterpillars metamorphosed, he counted the following offspring:
86 individuals that were black with long antennae
34 individuals were black with short antennae
27 individuals were grey with long antennae
8 individuals were grey with short antennae
8. Explain the inheritance and the genotypes of the parents and offspring. Use a Punnett Square. (8p)
No comments:
Post a Comment