Question

1. You identify a mutation in roses for the red pigment molecule; the pigment molecule is encoded by the gene RED.

The mutation you identified creates a much smaller, non-functional protein. You know the RED gene is haplosufficient.  

Is the mutation a loss-of-function or gain-of-function?

Is a heterozygote for the RED mutation (one wild type allele, one mutant allele) likely to look wildtype in phenotype (red colour) or have a mutant

phenotype (not red)? Explain your answer.

2. In a population of sneetches there are three body shapes: diamond, triangular and skinny. Body shape is controlled by two genes.

You breed a true-breeding diamond sneetch to a true-breeding triangular sneetch and all the offspring are diamond shaped.  

You then intercross the diamond F₁ and out of 64 offspring: 36 are diamond, 24 are triangular and 4 are skinny shaped. What best explains the inheritance pattern of sneetch shape? Explain your answer.

3.

A female cat heterozygous for genes A, B and C mates with a male cat homozygous recessive for all three genes.  Genes A and B are on the same chromosome and are 10 map units apart while gene C is on a different chromosome from A and B.  What is the probability of offspring that are homozygous recessive at all three genes (the cross is shown below)? Show your work (either by typing in an explanation/calculations or by attaching an image of your work.

AB/ab; C/c       X          ab/ab; c/c

4.

In the Deep Sea Kraken tentacle colour is determined by the presence of two pigment molecules. The pigment molecule/tentacle colour is normally controlled in the tentacle cells as follows:

• Precursor pigment molecule 1 is a colourless molecule. It is normally converted by Enzyme 1 into a blue pigment molecule.
• Precursor pigment molecule 2 is a colourless molecule. It is normally converted by Enzyme 2 into a yellow pigment molecule.   
• If both blue and yellow pigment molecules are present in the tentacle, the tentacle appears green.

A. One true-breeding Kraken line  (line A) has a mutation in the core promoter of the gene for precursor molecule 1 (mutated allele -> p^1A).  The mutation prevents transcription.  Presuming everything else about the line is normal what colour would you predict the Crake eyes to be in this line (line A)?  Explain your answer.

B. Another true-breeding Kraken line (line B) has a mutation in the gene for enzyme 2 (mutated allele -> e^2B). The mutation prevents conversion of the precursor molecule into the yellow pigment (only the colourless precursor is present).  If you crossed line A (from the question above) with line B what colour(s) would you find amongst the offsprings's eyes? Explain your answer.

5.

You are a dragon breeder and have discovered that some of your dragons have a rare disorder that causes them to suffer progressive neurodegeneration leading to an early death. Unfortunately the disorder does not become apparent until after they have reached reproductive age.  This means that some of your healthy looking dragons may soon succumb to the neurodegenerative disease. It also means that “healthy” is not a good criteria to use when setting up future breeding because dragons who are “healthy” upon reaching breeding age may still develop the disease later.

Luckily there is a microsatellite marker that is located very close (on the chromosome) to the gene that when mutated causes the neurodegenerative disease. Below is the pedigree and microsatellite typing for one dragon family.  As the neurodegenerative disease allele is extremely rare you can assume anyone outside the family does not have the disease allele.

You have affected information for generation I and II (symbol filled in = affected = neurodegenerative disease) however the individuals in generation III are too young to show the condition (regardless of whether they have the affected genotype). Letters on the pedigree refer to the microsatellite alleles shown in the gel on the upper right. The chromosome region is also shown for your information.

A . What is the most likely inheritance pattern of the neurodegenerative disease? Explain your answer.

B . You type generation III for the microsatellite alleles A, B, C and D and find that III-1 inherited microsatellite allele B from her mother.  Given the inheritance pattern, and distance between the microsatellite allele and the gene of interest, what is the likelihood III-1 will have the neurodegenerative disease? For full marks you must show your work or explain your answer.

To show your work you may type in a description or attach an image.

Answer 1

1). Mutation is loss of function as because it creates much smaller non functional protein .

Since RED gene is haplosufficient. Therefore, heterozygote for the RED mutation (one wild type allele, one mutant allele) likely to look wildtype in phenotype (red colour)...

Haplosufficiency occurs in situations where a single copy of a functional gene is enough to maintain normal function. Heterozygote carriers of recessive alleles usually exhibit haplosufficiency, which is the main reason why they remain unaffected even though their cells are making some dysfunctional proteins.

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