BIOL102 University of Maryland Classical Genetics Lab Report




explore the concept of probability as it relates to genetics. I uploaded the assingment

Name: BIOL 102-001L Laboratory Laboratory 5: Who Am I? (Classical Genetics) Experiment 1 – Pennies and Probability: Exploring Genetics with Money Purpose The purpose of this lab is to explore the concept of probability as it relates to genetics. In addition, students will be introduced to Punnett Squares, and will begin to use them to predict results of monohybrid crosses. Materials and Resources: Pennies (2) Pen/pencil to record results Procedure In this lab, your pennies will represent gametes an offspring receives from its mother (one coin) and its father (the second coin). The parents’ genotypes are Bb and Bb. Heads presents the Dominant trait: Brown hair (B) Tails represents the Recessive trait: Blond hair (b) 1. Before starting the lab, read the procedure completely and make your hypothesis in the space provided. 2. Acquire 2 coins. 3. Flip both coins at the same time, and record the results below for a total of 50 times. a. For Heads, Heads, make a tally mark in the “BB” column b. For Heads, Tails, make a tally mark in the “Bb” column c. For Tails, Tails, make a tally mark in the “bb” column 4. Total your tallies. 5. Answer the questions. Hypothesis (State here – 3 points) Name: Data Collection (8 points) BB Bb bb Tally for 50 tosses Total for 50 trials Questions 1. Based on your data, what is the probability of producing an offspring that has: (2 points) a. Brown hair? b. Blond hair? 2. What is the ratio of genotypes produced from this particular genetic cross? (1 point) 3. Create a Punnett Square for the cross between two pea plants that are both heterozygous (Tt) for the plant height trait (the Tall allele is Dominant). (3 points) a. What is the probability that these plants will produce tall offspring? (1 point) b. What is the probability that they will produce an offspring with the genotype “tt”? (1 point) c. What is the ratio of the all possible genotypes (TT:Tt:tt)? (1 point) Experiment 2: Human Monogenetic Traits Purpose The purpose of this lesson is to explore how humans inherit monogenetic traits. Monohybrid crosses will be used to predict the probability of creating offspring with monogenetic traits. Procedure In this experiment, you will collect data on the expression of monogenetic human traits from 5 individuals, including yourself. Individuals may include parents, siblings, neighbors, or friends. Construct a table for data collection, and indicate presence or absence of each trait for each individual. Name: NOTE: In this activity, you will collect data from individuals outside of your class. You should be polite as you approach people during the data collections of your investigation, and inform individuals that you are collecting data for a genetics lesson in your Biology class. Monogenetic Traits Monogenetic traits are traits due to alleles of a single gene. They are genetically inherited on the same locus of homologous chromosomes. Due to the single gene nature of monogenetic traits, trait expression occurs in an “on/off” fashion. You will investigate these 5 human monogenetic traits: o Free or Attached earlobes: (L/l). In most people, earlobes hang free and detached. When a person is homozygous for a recessive gene (l), the earlobes are attached directly to the side of the head. Other genes affect the size and appearance of the lobes, look only for the presence or absence of lobes. o Presence or absence of Widow’s peak: (W/w). In some people the hairline drops downward and forms a distinct peak. This is from the action of a dominant gene, W. Look for a continuous hairline or for a widow’s peak. Note that a gene for baldness may prevent detection of the widow’s peak. o Tongue rolling ability or inability: (R/r). The ability to roll the tongue into a distinct U-shape when it is extended from the mouth is due to a dominant gene R. o Presence or absence of eye pigment: (P/p). When a person is homozygous for a recessive gene, p, no pigment is deposited in the front part of the eye and a blue layer at the back of the iris shows through. Therefore, individuals with blue eyes are homozygous recessive for the eye pigment trait. A dominant gene, P, allows pigment to be deposited which masks the blue color. Other genes are responsible for the type and amount of this pigment leading to various shades of brown, hazel, green and other colors. Determine if your eyes either have pigment or lack it. o Absence or Presence of Hitchhiker’s thumb: (H/h). The ability to hyperextend the last joint of the thumb is due to a recessive gene, h, although there appears to be some variability in expressivity (i.e. it is occasionally seen for one thumb but not the other). Bend the thumb back as if you were hitchhiking and look to see if the thumb is extended to an almost 90-degree angle or is straight. Data Collection (8 points) Construct a table of the data you collected to include a total number of each phenotype. Remember you are collecting data from yourself plus four other individuals regarding the above 5 traits. Please note specifically if you collect data from family members. Name: Questions 4. For each of the monogenetic traits you collected data for, how do your results reflect the gene as being dominant or recessive? Why or why not? (4 points) 5. A man is heterozygous and can roll his tongue (Rr). His wife is homozygous recessive for tongue rolling (rr). a. Draw the Punnett square for this cross: x (3 points) b. What would the genotypic ratio be of this genetic cross? (1 point) c. What phenotypes could a child from these parents possibly have? (1 point) d. What is the likelihood of the child having each of these phenotypes? (1 point) 6. A woman with detached earlobes and a man who also has detached earlobes have a child with attached earlobes. a. What are the genotypes of the parents in this cross? Draw a Punnett square. (4 points) . b. What is the probability that they will have another child with attached earlobes. (1 point) c. Is it possible for these parents to have a child that is homozygous dominant for earlobes? Explain. (2 points)

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