Homework 2 Basic Genetics Mexican columnar cacti Stenocereus queretaroensis consist of several vertical cacti stems that rise out of a short central trunk These stems can sometimes reach meters tall Cactus in this group produce flowers that are typically pollinated by bats however the flowers can be pollinated by other pollinators such as birds and insects Flowers attract different pollinators based on the color of the flower in the daytime and the ability to absorb UV light which is visible at night to bats Bees and birds are attracted by bright colors like pinks and greens while bats are attracted by strong UV absorbance which is usually found in white flowers The Stenocereus are diploid with 11 chromosomes 2n 22 The columnar cacti are becoming a popular addition in landscaping around the world however they are native to Mexico For this particular species of cacti the different color plants can all be interbred in greenhouses however these different color plants typically do not breed in their natural environment because different insects and birds are responsible for pollinating each color Remember that pollination is essential to flowers for reproduction Without their pollinators helping the plants would not be able to produce seed A majority of this case study is taken from Ibarra Cerde a C I iguez D valos L and S nchez Cordero V 2005 Pollination ecology of Stenocereus queretaroensis Cactaceae a chiropterophilous columnar cactus in a tropical dry forest of Mexico Journal of Botany 99 3 503 509 DOI 10 3732 ajb 92 3 503 Table 1 Flower color UV Absorbance Level and Primary Pollinator for Three Colors of Columnar Cacti Flower Color Ability To Absorb UV Light Primary Pollinator Pink White Green Minimal High Minimal Bees Bats Hummingbirds Researchers are interested in whether the differences in flower color are controlled primarily by genetic factors OR in response to environmental factors One group of researchers led by S nchez Cordero proposed that a plant can change flower color and its ability to absorb UV light during its lifetime based on the availability of different pollinators in the area Another group of researchers led by Ibarra Cerde a hypothesized that a single gene controls both flower color and UV absorption and the plants cannot change their flower color during their lifetime regardless of pollinators species composition in the environment 1 In 2 3 sentences briefly explain how you would design an experiment that would test S nchez Cordero s proposal that plants can change their flower color based on pollinator species composition to increase pollination 2 What is the null statistical hypothesis for the experiment to test S nchez Cordero s idea 3 What is an alternative statistical hypothesis for the experiment to test S nchez Cordero s idea 4 Based on your experiment in question 1 what are your independent and dependent variables For the upcoming summer season Patriotic Plant Company PPC wants to create a cactus that produces plants with extra large red white or blue flowers The researchers at PPC have found a species of Cacti with a single gene for petal color The petal color gene is located on chromosome 4 The allele R produces red flowers in the homozygous form and the allele W produces white flowers in the homozygous form In addition the gene for petal color shows co dominance in the heterozygous form Researchers have located a gene in the Blue Sea Star Linckia laevigata called BSS The B allele at this locus produces a blue protein called linckiacyanin Zagalsky et al 1989 They have successfully inserted the BSS gene on chromosome 5 of this species of cacti When expressed in cacti the B allele produces Blue flowers in either the heterozygous and homozygous dominant forms and these plants suppress expression of alleles at the petal color gene on chromosome 4 Plants that are homozygous for the alternate b allele do not produce blue pigment and fail to suppress alleles at the petal color gene Pollinator Type Bat Finally on chromosome 6 is a gene that controls size of the flowers in the plants The G1 allele produces extra large flowers and is dominant to both the G2 medium flowers and G3 small flowers alleles G2 is dominant to G3 Fill in the table below to help you keep track of the genes Chromosome Number Alleles R or W Genotypes RR RW WW Phenotypes Red pink white 4 5 Chromosome Number Alleles Genotypes Phenotypes 6 Q5 In the main office at PPC there is a cactus plant that has all medium flowers let s assume it is homozygous for the flower size gene Its flowers are red in color Draw a nucleus of this plant in phase G1 of the cell cycle Show chromosomes 4 5 and 6 Label an example centromere sister chromatids and or homologous pairs if appropriate Q6 Is the DNA in the cell drawn in Question 6 replicated or unreplicated Q7 Is the cell drawn in Question 6 diploid or haploid Q8 What is the n for the cell in Question 6 Q9 Draw a nucleus of this plant at metaphase of mitosis Show chromosomes 4 5 and 6 Be sure to include centromeres in your chromosomes Label an example centromere sister chromatids and or homologous pairs if appropriate Reminder Have you lined up your chromosomes properly so that when the cell divides you will end up with the correct products Q10 Is the DNA in the cell drawn in Question 10 replicated or unreplicated Q11 Is the cell drawn in Question 10 diploid or haploid Q12 What is the n for the cell in Question 10 Q13 Draw the product s at the end of mitosis Label an example centromere sister chromatids and or homologous pairs if appropriate Q14 Is the DNA in the cell drawn in Question 14 replicated or unreplicated Q15 Is the cell s drawn in Question 14 diploid or haploid Q16 What is the n for the cell in Question 14 Part II As discussed in class heights of students vary over a wide range We have collected R B2 B2 f f f data for several independent variables that potentially influence student heights Your task is to choose one of these variables and test whether we have evidence that it influences the student height Possible factor choices include A Dad s height B Mid parent height average height of both parents C Student shoe size D Number of servings of vegetables each week E Number of servings of protein each week F Number of candy bars each week Choose a factor that may influence student height which was not discussed in class Develop a null and alternative hypotheses for that factor Note You may separate the sexes when analyzing your variable 17