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Biology 4415 NAME:__________________________________ Evolution
Exam I
To the intelligent man or woman, life appears infinitely mysterious. But the stupid have an answer for every question. —Edward Abbey
1. Fill in the blanks! Use one letter per blank, and don’t skip any blanks. When you’re done, the first letters of each word , read downwards, will give you the answer to this question: In 1860, “Darwin’s Bulldog”, Thomas Henry Huxley, locked horns in public debate with a well-known Anglican bishop, one of the best public speakers of his time, who was opposed to the idea of evolution. What was his name? (20 pts.) S M I T H Economist who proposed laissez-faire capitalism (and influenced Darwin) A L L E L E S Different forms of a gene at one locus M O R G A N Scientist who first mapped genes onto chromosomes, using fruit flies U C A Football team with a decent chance of upsetting Tulsa this weekend, which would make us 5-0 going into Southland Conference play. Go Bears! E P I S T A S I S Interaction between genes at several loci L Y E L L “Father of Modern Geology” and deviser of uniformitarianism W E I S M A N N 19 th century scientist who theorized about “germ plasm” and “intracellular pangenes” I M M I G R A T I O N One of the factors that will knock a population out of Hardy-Weinberg equilibrium L A M A R C K First person to come up with a theory of how evolution might happen
B E A G L E Charles Darwin sailed on the ship _HMS . E U G E N I C S The idea that humans should apply artificial selection to themselves R A N D O M M A T I N G One of the criteria for the Hardy-Weinberg equilibrium F I T Z R O Y Captain of the ship Darwin sailed on O R I G I N Darwin’s most famous book, ___ of Species. R E C E S S I V E Allele whose presence may be masked by the presence of another allele of the same gene C O D O N A group of three nucleotide bases that codes for one amino acid E R A S M U S First name of Charles Darwin’s grandfather, the poet, inventor, and evolutionary theorizer
... and the name of the infamous bishop, nicknamed “Soapy Sam” for his legendary slipperiness in debate, was Bishop
“S A M U E L W I L B E R F O R C E”
2. For each of the following case studies or examples below, write a couple of sentences explaining the general concept or principle that is illustrated. (5 pts. each; 20 pts. total) a. On Tuesday, Sept. 23, 2008, the New Orleans Times-Picayune reported that Louisiana state legislator John LaBruzzo (R–Metairie) had a plan to pay poor women to be surgically sterilized. LaBruzzo was also working on a plan to offer tax breaks and/or other financial incentives for college-educated, high-income people to have more children. (I’m not saying that this is a good idea, and you may not approve either. Just explain what concept, mentioned in lectures, this is an example of.) This is an example of eugenics; LaBruzzo is applying artificial selection to humans by trying to keep those with presumably poor genes from breeding and encouraging those with presumably good genes to breed. [This assumes that poverty, education, etc. are governed by genes in the first place, which they probably aren’t, at least not in any simple and straightforward way. I didn’t say LaBruzzo’s plan was a good idea -- or that it would work as he probably intends.. .]
3. There is evidence for a human gene that affects the blood’s ability to carry oxygen. There are two alleles; persons that are homozygous or heterozygous for the autosomal dominant allele (call these the BB and Bb genotypes) average 6-10% higher oxygen saturation than persons that are homozygous recessive ( bb ). In a sample of 698 Tibetan women living at high altitudes (about 13,000 feet / 4000 meters), women with the BB genotype had, on average, 3.79 children that survived to adulthood. Women with the Bb genotype averaged 3.58 surviving children, and women with the bb genotype averaged 1.69 surviving children.^1 This difference is entirely due to differences in infant mortality; a woman’s genotype had no effect on how many children she gave birth to. a. In one village, there are 37 BB individuals, 21 Bb individuals, and 22 bb individuals. Estimate the allele and the genotype frequencies after one generation. (10 pts.) starting frequency of BB = 37/80 = 0. starting frequency of Bb = 21/80 = 0. starting frequency of bb = 22/80 = 0. frequency of B=[(37 x 2) + 21] / 160 = 0.594. Call this p. frequency of b=[(22 x 2) + 21] / 160 = 0.406. Call this q. wBB = 3.79/3.79 = 1. wBb = 3.58/3.79 = 0. wbb = 1.69/3.79 = 0. To predict the effect of selection, first calculate w-bar: p^2 wBB + 2pqwBb + q^2 wbb = w-bar. Plug in the numbers, and you get w-bar = 0.352 + 0.456 + 0.0735 = 0.882. Now divide all terms through by w-bar, and you get: new frequency of BB = p^2 wBB / w-bar = 0. new frequency of Bb = 2pqwBb / w-bar = 0. new frequency of bb = q^2 wbb / w-bar = 0. BIG DIFFERENCE between starting and new, right? (^1) Beall, C. M., Song, K., Elston, R. C., and Goldstein, M. C. 2004. Higher offspring survival among Tibetan women with high oxygen saturation genotypes residing at 4, m. Proceedings of the National Academy of Sciences of the USA 101 : 14300-14304.
b. Estimate the allele and the genotype frequencies after another generation. (10 pts.) You have to recalculate p and q to do this -- because p and q will have changed because of natural selection. Which is really the point... So from the previous problem, you know that: frequency of BB = p^2 wBB / w-bar = 0. frequency of Bb = 2pqwBb / w-bar = 0. frequency of bb = q^2 wbb / w-bar = 0. new frequency of B = 0.399 + (0.517/2) = 0.658. Call it p. new frequency of b = 0.0833 + (0.517/2) = 0.342. Call it q. wBB = 3.79/3.79 = 1. wBb = 3.58/3.79 = 0. wbb = 1.69/3.79 = 0. To predict the effect of selection, first calculate w-bar, and you get: w-bar = 0.432 + 0.425 + 0.0522 = 0. Now divide all terms through by w-bar, and you get: new frequency of BB = p^2 wBB / w-bar = 0. new frequency of Bb = 2pqwBb / w-bar = 0. new frequency of bb = q^2 wbb / w-bar = 0.
5. The young Charles Darwin was a great admirer of the writings of Rev. William Paley, writing later in life that at one time he almost had one of his books memorized. Darwin’s actual views came to be very different from Paley’s, and yet we can still measure Paley’s influence on Darwin’s work. What was Paley noted for, why did it influence Darwin— and how is it that Darwin’s own conclusions came to be so different from Paley’s? Paley was noted for his presentation of natural theology -- the idea that the complexity of living things proved the existence of a God who designed them, and so that you could learn about God by studying the complex things God created. First, this gave religiously devout people a reason to study nature -- it’s ultimately the reason why Darwin as a college student, studying for the ministry, could take so many courses in science. Secondly, Paley drew attention to the complex adaptations that animals and plants have to their surroundings. Darwin was very impressed by the adaptations, but showed that they can be explained in other ways than a single Designer.
6. Imagine you’re studying the genetics of a population of some organism, which has one gene with two alleles... and you find that the population consists of 63% heterozygotes. Is the population in Hardy-Weinberg equilibrium? Show all work. Any equation of the form ax^2 + bx + c = 0 may be solved by using the quadratic formula,
x = - b ± √(b
2
- 4ac)
2a
If a population is in H-W, then the frequency of heterozygotes (for any gene with two alleles) is equal to 2pq. So if this population is in H-W, then 2pq = 0. 63 Since q = 1-p, then 2p(1-p) = 0. which you can expand and rearrange into a quadratic equation,
- 2p^2 + 2p – 0.63 = 0 Plug the numbers into the quadratic formula, which I gave you, and the roots are: p = {-25.166, 1.2517} But since it’s a p must fall between 0 and 1 -- it can’t be negative, and it can’t be 1.25, because that would mean that 125% of the alleles were p, which isn’t possible. So the population cannot be in H-W equilibrium.
