SDSU Population Genetics GH Hardy and W Weinberg Theories Lab Report

SDSU Population Genetics GH Hardy and W Weinberg Theories Lab Report# SDSU Population Genetics GH Hardy and W Weinberg Theories Lab Report Population Genetics, BIOLOGY LAB, I ATTACHED THE worksheet below, all you need to do, is reading it, and fill out the last page ( the table) . population_genetics Laboratory Extra: Population Genetics INTRODUCTION G.H Hardy and W. Weinberg developed a theory that evolution could be described as a change of the frequency of alleles in an entire population. In a diploid organism with a gene that is following Mendelian patterns of inheritance, in a simple case, the dominant allele is called A and the recessive allele is called a. The letter p represents the frequency of A in a population. The letter q represents the frequency of the a. An example: in a population of 100 organisms, if 45% of the alleles are A then the frequency (or p) is 0.45. The remaining alleles would be 55% or 0.55. This is the allele frequency. An equation called the Hardy Weinberg equation for the allele frequencies of a population is: p2+ 2pq+ q2 = 1 p+q=1 Hardy and Weinberg also gave five conditions that would ensure the allele frequencies of a population would remain constant: A. The breeding population is large. The effect of a change in allele frequencies is reduced. B. Mating is random. Organisms show no mating preference for a particular genotype. C. There is no net mutation of the alleles. D. There is no migration or emigration of organisms. E. There is no natural selection. Every organism has an equal chance for passing on their genotypes. If these conditions are met then no change in the frequency of alleles or genotypes will take place. Activity 1: What is your combination of traits? A simple class experiment will take place to serve as model of the evolutionary process in a stimulated population. This experiment is great in order to test a few of the basic parts of population genetics. In the experiment the class will place a piece of paper in their mouth to see if they can taste the chemical PTC which is phenythiocarbamide (YOU CANNOT DO THIS SEMESTER –LEAVE BLANK) People with the alleles AA, which is homozygous, and Aa, which is heterozygous, will be able to taste the PTC. People that can’t taste PTC are aa. Fill out Table 1 with visible traits. The trait descriptions are below. We are (falsely) assuming that these traits follow simple Mendelian patterns of inheritance. Other Human Traits Following is a series of easily determined human phenotypic characters that are believed to be inherited as simple autosomal traits. You and your lab partner will catalog your phenotypes and record them. You may find that even dominant traits are not all expressed to the same degree in every individual.SDSU Population Genetics GH Hardy and W Weinberg Theories Lab Report ORDER NOW FOR CUSTOMIZED AND ORIGINAL NURSING PAPERS When this is the case, the trait is said to exhibit variable expressivity. Variable expressivity can be caused by interactions with other gene loci, as well as by environmental influences during development or at any stage of the life cycle. See Figure 4 for illustrations of a few autosomal human traits. Determine your phenotype and possible genotypes for each, and enter the data in Table 1. 1. Hairy digits: The presence or absence of hair on the backs of the fingers between the first and second joints is determined by a simple autosomal trait in humans. Examine your fingers to ascertain your phenotype (“hairy” or “hairless” digits). The presence of even a single hair indicates the presence of at least one dominant “hairy” allele. This trait does exhibit variable expressivity, so you might have to really look for those hairs in some individuals. 2. Widow’s Peak: A Widow’s Peak is the term applied to a hair margin that forms a point, vampire-like, over the center of the forehead. The gene for this character is dominant over the gene expressing a straight or curved hairline. Which do you have? How sharp are your canines? Do you sparkle annoyingly when you play baseball? 3. Tongue rolling: Determine whether or not you have the ability to roll your tongue into a longitudinal U-shaped trough, running from the tip to the rear of your tongue. (Other weird permutations of which you might be capable do not count, but you can entertain your lab partner with them, anyway.) You must be able to accomplish this mighty feat without the aid of your teeth, fingers or other appendages. (No one wants to see that.) If you carry the dominant allele (“roller”), you will be able to roll your tongue with little difficulty. If you are homozygous recessive, no amount of facial contortion, bodily twisting or prayer will allow you to roll your tongue. Once you have finished humiliating yourself, enter your phenotype on Table 1. 4. Ear Lobe Morphology: Although the extent to which ear lobes hang free varies (the trait is probably controlled by more than one gene locus, and is thus polygenic), the pendulous lobe is thought to be dominant over the lobe type that is attached all the way to the ear’s base at the neck. Unless you have a mirror (or stalked eyes), you may have to rely on your lab partner’s judgment to determine which phenotype you express. 5. Freckles: Freckles are localized masses of pigment occurring in relatively high density on the skin, between areas of normal pigmentation. Anyone can have freckles, as long as they have the dominant allele of the MC1R (melanocortin-1 receptor) gene. Sunlight (specifically, ultraviolet-B radiation) triggers pigmentcontaining cells known as melanocytes to increase production of the brown pigment, melanin. Although freckles are not considered a pathology (disease or disorder), people expressing freckles usually have less ability to produce protective melanin than people without copious freckles, and are thus more susceptible to DNA damage in the skin due to ultraviolet radiation in sunlight. So if you express a lot of freckles, slap on that SPF 100, and keep yourself covered. Note that freckles are not the same as “moles,” which are dark areas of pigment, often slightly raised above the rest of the skin. 6. Hitch-hiker’s Thumb: “Distal hyperextensibility of the thumb” can be determined by bending the joint of the thumb back as far as possible. If the top segment of thumb bends backward, you have a very useful “hitch-hiker’s thumb.” This capacity is the result of a recessive gene, and you should never use it on a deserted road at night. 7. Cleft Chin: The mandible (lower jaw) of a mammal fetus starts out right and left halves, fusing during development. If the jawbones fail to completely fuse to the tip of the chin, this bone structure is reflected on the outer tissues, as well. The resulting phenotype is called a cleft chin (“cleft” means “split”). The trait is usually more obvious in males than in females, but in both sexes, the cleft is the result of a dominant allele’s action. Not everyone who has a cleft chin has a very distinct one, and there are different morphologies of the cleft chin, from the classic Y-shaped split (sometimes called “butt chin” by those who don’t have one and are jealous) to a circular dimple. Such variation suggests that there may be more than one gene involved in the final phenotypic product. The full development of cleft chin phenotype is yet to be fully understood. 8. Interlocking fingers: Quickly! Before even thinking about what you’re doing, fold your hands together, fingers interlocking. Now look down at your thumbs. If the left thumb is riding on top of the right thumb, you are expressing a dominant allele. If the right thumb is riding on top of the left thumb, you are a recessive mutant. Although the eight traits discussed above are considered monogenic, most are more complex than that. There can be slight variability in the expression of each of these traits, suggesting that other genes as well as environmental influence during development can influence the final phenotype. Many human traits you may have been told are monogenic are turning out to be far more complex. Activity 1: What traits do you have? Table 1. A personal record of your phenotypes and possible genotypes. As you ascertain your phenotypic expression of each trait, circle (or fill in, if necessary) the appropriate choices. Save this for yourself and all of your descendants. Class Data: Digital hair Tongue rolling Vampire hairline Ear lobe Elfin ear Freckles Class number dominant phenotype Class number recessive phenotype Class total Activity 2: Determine Phenotypic Proportions of Different Traits and the Corresponding Frequencies of the Determining Alleles Digital hair Frequency of recessive genotype (q2) Frequency of recessive allele (q) Frequency of dominant allele (p) Frequency of homozygous dominant genotype (p2) Frequency of heterozygous genotype (2pq) Tongue rolling Vampire hairline Ear lobe Elfin ear Freckles … Get a 10 % discount on an order above $ 100 Use the following coupon code : NURSING10