Mendelian Genetics PDF

Mendelian Genetics FISH 147 (FISH GENETICS) https://www.google.com/url?sa=i&url=https %3A%2F%2Fwww.expii.com%2Ft%2Fmendelian-genetics Introduction Heredity is responsible for the specific characteristics passed on from parents to offspring...

Mendelian Genetics FISH 147 (FISH GENETICS) https://www.google.com/url?sa=i&url=https %3A%2F%2Fwww.expii.com%2Ft%2Fmendelian-genetics Introduction Heredity is responsible for the specific characteristics passed on from parents to offspring Basic tenet of genetics These traits are “embedded” in genes, and genes are in chromosomes Introduction Concept Checkpoint Which of the following factors did not contribute to Mendel’s success in his study of heredity? A. His use of the pea plant B. His study of plant chromosomes C. His adoption of an experimental approach D. His use of mathematics Concept Checkpoint Which of the following factors did not contribute to Mendel’s success in his study of heredity? A. His use of the pea plant B. His study of plant chromosomes C. His adoption of an experimental approach D. His use of mathematics Mendelian Genetics Mendel used the pea plant Pisum sativum in his studies of heredity. He examined seven characteristics that appeared in the seeds and in plants grown from the seeds. Mendelian Genetics Mendelian Genetics Genetic Crosses Monohybrid Dihybrid Genetic Crosses Predicting the Outcome The Punnett square was developed by English geneticist Reginald Punnett Constructed by drawing a grid, putting the gametes produced by one parent along the upper edge and the gametes produced by the other parent down the left side Each block within the Punnett square contains an allele from each of the corresponding gametes, generating the genotype of the progeny produced by fusion of those gametes Concept Checkpoint 1. What is the genotypic ratio of a cross between a homozygous dominant red-tailed guppy with a guppy heterozygous for caudal fin color? 2. In swordtails, black eye color is dominant over the red one while orange body color is dominant over having a white streak of body coloration. A male, red-eyed swordtail with white streak body coloration is mated with a female heterozygous for both traits. What are the phenotypic and genotypic ratio of their offspring? Genetic Crosses Predicting the Outcome Two rules of probability are useful for predicting the ratios of offspring produced in genetic crosses The first is the multiplication rule, which states that the probability of two or more independent events occurring together is calculated by multiplying their independent probabilities For the multiplication rule to be valid, the events whose joint probability is being calculated must be independent Genetic Crosses Predicting the Outcome Two rules of probability are useful for predicting the ratios of offspring produced in genetic crosses The second is the addition rule, which states that the probability of any one of two or more mutually exclusive events is calculated by adding the probabilities of these events For the addition rule to be valid, the events whose probability is being calculated must be mutually exclusive Concept Checkpoint 1. If the probability of red-colored caudal fin in guppies is 1/8 and the probability of having an anal fin is 1/2, what is the probability of having a red- colored caudal fin and anal fin in guppies? 2. If the probability of red-colored caudal fin in guppies is 1/8 and the probability of having a blue-colored caudal fin in guppies is 1/4, what is the probability of having either red or blue-colored caudal fin in guppies? 3. If we cross RrYyTtSs x RrYyTtSs, what is the probability of obtaining the genotype RRYyTtss? The Goodness-of-Fit Chi-Square Test When two individual organisms of known genotype are crossed, we expect certain ratio of genotypes and phenotypes in the progeny These expected ratios are based on the Mendelian principles The ratios of genotypes and phenotypes actually observed among the progeny, however, may deviate from these expectations For instance, if you expected a 1 : 1 ratio of red and blue guppies but the cross produced 22 red and 18 blue, you probably wouldn’t be too surprised even though it wasn’t a perfect 1 : 1 ratio. But, if you observed 25 red and 15 blue, would the ratio still be 1 : 1? Clearly, we need some means of evaluating how likely it is that chance is responsible for the deviation between the observed and the expected numbers. The Goodness-of-Fit Chi-Square Test To evaluate the role of chance in producing deviations between observed and expected values, a statistical test called the goodness-of-fit chi-square test is used Provides information about how well observed values fit expected values The Goodness-of-Fit Chi-Square Test To evaluate the role of chance in producing deviations between observed and expected values, a statistical test called the goodness-of-fit chi-square test is used Provides information about how well observed values fit expected values Concept Checkpoint Concept Checkpoint Cyclops sp., an aquatic copepod, has antennae that is either barbed or smooth. The allele for barbed antennae (B) is dominant over smooth (b). In the same organism, non-resistance to pesticides (N) is dominant over resistance to pesticides (n). When two Cyclops sp. heterozygous for both traits mated a numbers of times, the phenotype of their nine hundred sixty (960) offspring were as follows: Phenotype Number of offspring Barbed antennae; Non-resistant to pesticide 498 Barbed antennae; Resistant to pesticide 198 Smooth antennae; Non-resistant to pesticide 213 Smooth antennae; Resistant to pesticide 51 Using Chi-square analysis, determine if the data above follows a Mendelian distribution at 95% confidence interval. Practice Word Problems 1. In pea plants, tall stems (T) are dominant over short stems (t), and round seeds (R) are dominant over wrinkled seeds (r). A dihybrid cross is performed between two pea plants that are heterozygous for both traits. Their offspring are counted and categorized based on their phenotypes. The results of the cross are as follows: Tall plants with round seeds: 315 Tall plants with wrinkled seeds: 101 Short plants with round seeds: 108 Short plants with wrinkled seeds: 32 Use a Chi-Square test to determine if the observed data fits the expected Mendelian ratio at a 95% confidence level. Practice Word Problems 2. In fruit flies, red eyes (R) are dominant to sepia eyes (r), and normal wings (N) are dominant to vestigial wings (n). Two flies heterozygous for both traits are crossed, and their offspring are classified based on their phenotypes. The data collected from the cross are as follows: Red eyes, normal wings: 560 Red eyes, vestigial wings: 185 Sepia eyes, normal wings: 190 Sepia eyes, vestigial wings: 65 Using Chi-Square analysis, determine if the observed results adhere to a Mendelian pattern of inheritance at a significance level of 0.05. Testcross Tool for analyzing genetic crosses One individual of unknown genotype is crossed with another individual with a homozygous recessive genotype for the trait in question A testcross tests, or reveals, the genotype of the first individual For example, because tallness is a dominant trait in peas, your plant could be either homozygous (TT) or heterozygous (Tt) Testcross A testcross is used to determine the genotype of a female mouse with big ear phenotype, which is a dominant trait. The mouse produces a litter of 12 mice. Four of these mice exhibit the big ear phenotype while eight mice have ears of normal size. What is the genotype of the mouse? Binomial Expansion and Probability When probability is used, it is important to recognize that there may be several different ways in which a set of events can occur Consider two parents who are both heterozygous for albinism, a recessive condition in humans that causes reduced pigmentation in the skin, hair, and eyes When two parents heterozygous for albinism mate (Aa x Aa), the probability of their having a child with albinism (aa) is ¼ and the probability of having a child with normal pigmentation (AA or Aa) is ¾ Binomial Expansion and Probability Consider two parents who are both heterozygous for albinism. A. What is the probability of this couple having three children, one with albinism and two with normal pigmentation? B. What is the probability of this couple having five children, two with albinism and three with normal pigmentation? In hypothetical Fish X, black body coloration (B) is dominant over white (b). Two heterozygous black Fish X are mated. A. What is the probability of this pair having seven offspring with three black and four white? B. What is the probability of this pair having nine offspring with three black and six white?