{"id":6109,"date":"2013-07-16T09:48:26","date_gmt":"2013-07-16T09:48:26","guid":{"rendered":"https:\/\/schooltutoring.com\/help\/?p=6109"},"modified":"2014-12-02T08:26:59","modified_gmt":"2014-12-02T08:26:59","slug":"biology-review-of-genetics-and-probability","status":"publish","type":"post","link":"https:\/\/schooltutoring.com\/help\/biology-review-of-genetics-and-probability\/","title":{"rendered":"Biology Review of Genetics and Probability"},"content":{"rendered":"

Overview:\u00a0 Chance and Probability<\/strong>
\nGeneticists use the principles of chance\u00a0 and probability to express the results of genetic experiments with pea plants, as well as other plants and animals.\u00a0 In mathematical terms, probability refers to the fraction (or percentage, in decimals) of times an event can occur.\u00a0 According to the product rule for independent events. the probability of events occurring together is the product of the probabilities for each event multiplied.\u00a0 For example, the probability of a girl being born is 50 % , but the probability for two girls being born in the same family is 50% x 50% =25%.\u00a0 This does not necessarily mean that a specific family will have a girl if another family has a boy at the same time, just that the overall probability, in a sample of many, will be 50%.<\/p>\n

Predicting Genetic Crosses<\/strong>
\nIn Mendel’s experiments, seven simple genetic factors were manipulated, such as whether the seed is round or wrinkled, the pod is green or yellow, and so on.\u00a0 At the time those experiments were formed, the way that alleles separate during meiosis and other details of cellular reproduction were not known.\u00a0 Geneticists assume that alleles segregate during meiosis in a 1:1 ratio, and that gametes combine randomly.\u00a0 Suppose the dominant gene for round seeds is called R and the recessive form ( for wrinkled seeds) is called r.\u00a0 One heterozygous parent with phenotype Rr mated with another heterozygous parent with phenotype Rr will have offspring with the probability (1\/2 R +1\/2 r)(1\/2 R + 1\/2r) or 1 RR, 2 Rr, 1rr for genotypes, and 3 with round seeds and 1 with wrinkled seeds.\u00a0 Geneticists often use thousands of trials to produce as many offspring as they can to use the rules of probability,<\/p>\n

Punnett Squares and Testcrosses<\/strong>
\nThe range of probable genetic crosses can be demonstrated by drawing a simple grid with all the alleles contributed by one parent on one side and the other parent on the other, then showing each possibility in each square of the grid.\u00a0 That way, all the possibilities can be accounted for.\u00a0 https:\/\/schooltutoring.com\/wp-content\/uploads\/sites\/2\/2013\/07\/punnett-square-green-peas.jpg<\/a><\/p>\n

Both parents, in this case, contribute G and g.\u00a0 In addition, biologists can perform a testcross if they have the phenotype to discover the genotype.\u00a0 In the example above of the green pods, the genotype could be GG or Gg.\u00a0 By crossing it with a plant with yellow pods (gg), if the genotype is GG, all the offspring will have genotype Gg and have green pods.\u00a0 If the genotype is Gg, half the offspring will have genotype Gg, with green pods.\u00a0 The other half will have genotype gg with yellow pods.<\/p>\n

Monohybrids and Dihybrids<\/strong>
\nSome hybrids have only one trait, involving one pair of alleles, and others involve separate pairs of alleles and two separate traits.\u00a0 When only one trait is involves, the possibilities are simple, and the Punnett square is a simple 2 X 2 grid.\u00a0 A relatively simple trait in humans is whether earlobes are free (dominant) or attached (recessive).\u00a0 If two individuals are heterozygous for the trait, their offspring might have the following genotypes:\u00a0 EE, Ee, Ee, and ee.\u00a0 If two separate traits are involved, the Punnett square will be larger because of the many different possibilities.\u00a0 For watermelons, solid color green (G) is dominant over striped green (g), and short length (S) is dominant over long (s).\u00a0 If a green , short watermelon (GGSS) is crossed with a striped, long watermelon (ggss), the grid grows to 4 X 4, with 16 different genotypes in the second generation.<\/p>\n

Incomplete Dominance<\/strong>
\nNot all alleles are dominant or recessive, however.\u00a0 Sometimes, both alleles are expressed.\u00a0 For example, short tailed cats have one gene for no tail(TN<\/sup>) and one gene for long tail (TL<\/sup>).\u00a0 If two short tailed cats are crossed, the Punnett square has a simple 2 X 2 grid, and the offspring probabilities include 25% long tail (TL<\/sup>TL<\/sup>), 50% short tail (TN<\/sup>TL<\/sup>), and 25% no tail (TN<\/sup>TN<\/sup>).\u00a0 The roan (reddish-brown) color of some cattle also results from incomplete dominance, as well as many other features of plants and animals.<\/p>\n

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Overview:\u00a0 Chance and Probability Geneticists use the principles of chance\u00a0 and probability to express the results of genetic experiments with pea plants, as well as other plants and animals.\u00a0 In mathematical terms, probability refers to the fraction (or percentage, in decimals) of times an event can occur.\u00a0 According to the product rule for independent events. […]<\/p>\n","protected":false},"author":22,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[3,15],"tags":[501,728,897,922,1144,3822,1447],"class_list":["post-6109","post","type-post","status-publish","format-standard","hentry","category-biology","category-probability","tag-dihybrids","tag-genetics","tag-hybrids","tag-incomplete-dominance","tag-monohybrids","tag-probability","tag-punnett-square"],"acf":[],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/schooltutoring.com\/help\/wp-json\/wp\/v2\/posts\/6109","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/schooltutoring.com\/help\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/schooltutoring.com\/help\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/schooltutoring.com\/help\/wp-json\/wp\/v2\/users\/22"}],"replies":[{"embeddable":true,"href":"https:\/\/schooltutoring.com\/help\/wp-json\/wp\/v2\/comments?post=6109"}],"version-history":[{"count":0,"href":"https:\/\/schooltutoring.com\/help\/wp-json\/wp\/v2\/posts\/6109\/revisions"}],"wp:attachment":[{"href":"https:\/\/schooltutoring.com\/help\/wp-json\/wp\/v2\/media?parent=6109"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/schooltutoring.com\/help\/wp-json\/wp\/v2\/categories?post=6109"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/schooltutoring.com\/help\/wp-json\/wp\/v2\/tags?post=6109"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}