Unformatted text preview: Bios 101, Problem Set 2 These questions are due in discussion. Please type or print neatly on separate sheets of paper. It is imperative that no portion of your answers be copied directly from another student or from an online source. 1. (1 point) A man with redgreen color blindness marries a woman with normal vision. Their first child, a boy, has normal vision. i) Diagram the cross above. ii) The couple have a second child, a girl, with normal vision. This girl grows up and becomes pregnant with a child she knows to be a boy. The father of this child has normal vision. What is the probability that this child will have redgreen color blindness? Diagram the cross. 2. (3 points) A snapdragon from a truebreeding line with white flowers and small leaves (line A) is crossed to a snapdragon from a truebreeding line with red flowers and large leaves (line B). The resulting offspring, the F1, are all pink flowered, with mediumsized leaves. i) Based on the information above, is it possible to determine how many loci involved in this cross?___No____ Suppose an individual from the F1 is crossed to an individual from line A. The resulting offspring are as follows: 50% white flowers and small leaves, 50% pink flowers and medium leaves. What type of allelic interaction is this, and how many loci are involved? Diagram the cross. What is the term for when one locus affects two or more traits? ii) From the cross above, how many types of gametes can the F1 plants make?_____2___________ iii) Imagine instead that instead of the results above, the offspring are as follows....25% small leaves and white flowers, 25% medium leaves and pink flowers, 25% small leaves and pink flowers, 25% medium leaves and white flowers. How many loci would be involved in the cross? What sort of allelic interaction would it be? Diagram the cross. cross above, how many types of gametes can the F1 plants make?_____4___________ v) Now imagine that the exact same cross is performed, and instead of the results above, the results are as follows; 45% small leaves and white flowers, 45% medium leaves and pink flowers, 5% small leaves and pink flowers, 5% medium leaves and white flowers. How many loci would be involved in the cross? What sort of allelic interaction would it be? Are the loci on the same chromosome? If so, which genotypes are recombinants? Diagram the cross. 3. (2 points) In Primulas, such as Primula versis, there are three loci that code for flower and pollen morphology. The dominant, G allele codes for short style (the female part of the flower), which reaches to the middle of the corolla tube, the recessive, g allele codes for a longer style, which reaches to the lip of the corolla. The dominant, A allele codes for long anthers (the male part of the flower), which reaches to the edge of the corolla tube, the recessive, a allele codes for short anthers, which reach to the middle of the corolla tube. The dominant P, allele codes for "thrum" pollen, the recessive, p allele codes for "pin" pollen, which is much smaller. The genotype ggaapp gives rise to the "pin" phenotype, which has long styles, short anthers, and pin pollen. The genotype GgAaPp gives rise to the "thrum" phenotype, which has short styles, long anthers, and thrum pollen. Thrum x thrum crosses are impossible, because thrum pollen cannot grow down a short style. Pin x pin crosses are possible, but very rare. a) A pin plant crosses with a pin plant. Diagram the cross. What is/are the expected phenotype(s) of the offspring? b) A pin plant crosses with a thrum plant. Diagram the cross. Assuming no linkage, what are the expected phenotypes of the offspring? c) The cross above is done (it happens in nature 99% of the time). If 1000 offpring are grown to maturity from seeds produced from this cross, predict the phenotypic composition of the offspring. d) The following offspring result from the cross: Short Style, Long Anther, Thrum Pollen (the thrum phenotype) 500 Short Style, Long Anther, Pin Pollen 1 Short Style, Short Anther, Thrum Pollen 0 Long Style, Short Anther, Thrum Pollen 1 Short style, Short Anther, Pin Pollen 0 Long Style, Long Anther, Pin Pollen 0 Short Style, Short Anther, Pin Pollen 0 Long style, Short Anther, Pin Pollen (the pin phenotype) 500 i) What can you say about the three loci? ii) What are the approximate map distances between the three alleles, or is it possible to even tell? e) Homozygous dominant genotypes, eg., GGAAPP, GGAAPp, GGAaPP, GgAAPP, GGAaPp, GgAAPp, GgAaPP, are absent in nature. In light of the cross above, and the fact that thrum can only cross with pin, can you explain why? 5. (2 points) A line of Drosophila melanogaster with ebony body and sepia eyes (line A) is crossed to a line with tan body and red eyes (line B). The F1 are all tan bodied, redeyed. What proportion of gametes produced by line A have the dominant allele for both loci?______0_______ What proportion of the gametes produced by the F1 have the dominant allele for both loci?____.25_________ An F1 female is crossed to a male from line A. If 1000 offspring were scored for both characters, what number of offspring would be expected to have each of the four phenotypes (assuming no linkage)? List them below. Now imagine that the following data were actually collected from the cross above: Body Eyes Tan normal 411 Tan sepia 89 Ebony normal 87 Ebony sepia 413 Are the loci linked? _________yes_________ If so, how many map units are they apart ? Do a 2 test and show your work below: 6. (2 points) Go online, and look up four hereditary illnesses that are caused by having two copies of an autosomal recessive allele. Next, find two hereditary illnesses that are caused by having a single copy of a dominant allele. Next, find four hereditary illnesses that are sexlinked. i) List your results ii) In which case is the condition mostoften observed in males? iii) In which case is the condition very often observed in parents of the afflicted offspring? iv) In which cases is it sometimes believed that the condition "skips a generation" and why? ...
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- Fall '08
- white flowers, Small leaves, Thrum Pollen, short style, pin pollen