Lab 5: Dihybrid Cross in Corn
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Questions and Answers

Which of the following factors contributes to changes in allele frequencies?

  • Mutation
  • Natural selection
  • Genetic drift
  • All of the above (correct)

    • Tongue rolling has a clear anatomical advantage for individuals who can do it.

    False

    What is the genotype of an individual who is able to roll their tongue?

    Dominant

    ___________ is the study of distribution and change in frequency of alleles within a population.

    <p>Population genetics</p> Signup and view all the answers

    Match the following traits with their description:

    <p>Tongue rolling = Ability to roll the tongue upward from the sides Allele frequency = Proportion of different alleles in a population Mutation = Change in DNA sequence Genetic drift = Random changes in allele frequencies</p> Signup and view all the answers

    What does the presence of hair on the middle joint of a finger indicate?

    <p>Dominant phenotype represented by H</p> Signup and view all the answers

    Natural selection is one of the conditions necessary for a population to be in Hardy-Weinberg Equilibrium.

    <p>False</p> Signup and view all the answers

    Name one of the five conditions that must be met for a population to be considered in Hardy-Weinberg Equilibrium.

    <p>No gene mutations or Random mating or No migration or No genetic drift or No natural selection</p> Signup and view all the answers

    The ___ phenotype is represented by the genotype hh.

    <p>recessive</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Dominant phenotype = Presence of a trait even if only one allele is present Recessive phenotype = Absence of a trait when both alleles are recessive Hardy-Weinberg Equilibrium = State of allele frequencies remaining constant over time Random mating = Mating that occurs by chance among individuals</p> Signup and view all the answers

    What is the genetic trait associated with a hairline that forms a downward (V) shape at the center of the forehead?

    <p>Widow's peak</p> Signup and view all the answers

    The left thumb on top when clasping hands is a dominant trait.

    <p>True</p> Signup and view all the answers

    What type of earlobe is considered dominant?

    <p>Unattached</p> Signup and view all the answers

    If your earlobe hangs free, it is considered __________.

    <p>detached</p> Signup and view all the answers

    Match the following traits with their descriptions:

    <p>Widow's peak = V-shaped hairline Left thumb on top = Dominant hand clasping trait Detached earlobes = Free hanging earlobes Attached earlobes = Connected directly to the head</p> Signup and view all the answers

    What is the function of the Beta-lactamase gene in the pGLO plasmid?

    <p>It allows transformed bacteria to survive on plates with ampicillin.</p> Signup and view all the answers

    The AraC protein acts as a switch that turns the GFP gene ON and OFF depending on the presence of arabinose.

    <p>True</p> Signup and view all the answers

    What is the formula for calculating transformation efficiency?

    <p>(Number of Colonies on Plate / Amount of DNA plated (µg))</p> Signup and view all the answers

    What is the primary purpose of analyzing the results in this genetics lab?

    <p>To determine the allele frequency for a common genetic trait</p> Signup and view all the answers

    Transformed bacteria can be used to generate __________ libraries.

    <p>cDNA</p> Signup and view all the answers

    The Hardy-Weinberg equation can be used to predict genetic variation in a population.

    <p>True</p> Signup and view all the answers

    What should students prepare to score the numbers of students according to their traits?

    <p>A table</p> Signup and view all the answers

    Match the applications of transformation with their descriptions:

    <p>To make multiple copies of DNA = Used in PCR and cloning In cloning procedures = Creates recombinant DNA for various applications To express large amounts of proteins and enzymes = Produces proteins for research or pharmaceuticals In DNA linkage studies = Analyzes genetic relationships and mapping</p> Signup and view all the answers

    In the experiment, the total number of students is expected to represent the contribution of different _____ groups in the country.

    <p>ethnic</p> Signup and view all the answers

    Match the following steps with their descriptions:

    <p>Step 1 = Count the students by sex. Step 2 = Prepare a table for scoring traits. Step 3 = Analyze results using Hardy-Weinberg equation. Step 4 = Take total class size for genetic traits.</p> Signup and view all the answers

    What is the purpose of shining UV light on the UV plate?

    <p>To cause mutations in the bacterial DNA</p> Signup and view all the answers

    Students should add tobacco extract to the water plate.

    <p>False</p> Signup and view all the answers

    What should be done to the plates after adding bacteria?

    <p>Let them dry for ~10 minutes.</p> Signup and view all the answers

    Students filter the extract through __________ into a bottle.

    <p>cheesecloth</p> Signup and view all the answers

    Match the step in the lab with its action:

    <p>Step 1 = Making tobacco extracts Step 2 = Adding extracts to the plates Step 3 = Adding bacteria and using UV light</p> Signup and view all the answers

    What law states that alleles for separate traits are passed independently of one another?

    <p>Law of Independent Assortment</p> Signup and view all the answers

    All kernels from the F1 generation are purple and round.

    <p>True</p> Signup and view all the answers

    In the F2 generation, what was the ratio of yellow to green kernels?

    <p>3:1</p> Signup and view all the answers

    Kernels that have a wrinkled shape are categorized as __________.

    <p>sweet</p> Signup and view all the answers

    Match the following traits of corn kernels with their characteristics:

    <p>Purple kernels = Have anthocyanin pigment Yellow kernels = Colorless aleurone affects endosperm Starchy kernels = Round shape with low water content Sweet kernels = Wrinkled shape due to high water content</p> Signup and view all the answers

    Which trait is dominant in corn kernels?

    <p>Yellow color</p> Signup and view all the answers

    The round shape of kernels is associated with high concentrations of starch.

    <p>True</p> Signup and view all the answers

    What enzyme is defective in yellow kernels?

    <p>Pigment manufacture enzyme</p> Signup and view all the answers

    What is the first organism in which transformation was reported?

    <p>Streptococcus pneumoniae</p> Signup and view all the answers

    All bacteria are capable of taking up foreign DNA from the environment.

    <p>False</p> Signup and view all the answers

    What two key components are involved in the heat shock transformation method?

    <p>Calcium chloride and heat shock</p> Signup and view all the answers

    The gene for GFP can be turned on in transformed cells by adding __________ to the cell's nutrient medium.

    <p>arabinose</p> Signup and view all the answers

    Match the following terms with their correct definitions:

    <p>Competent cells = Cells that can take up foreign DNA pGLO plasmid = Contains the gene for GFP and antibiotic resistance GFP = Protein that causes fluorescence in jellyfish Heat shock = Method to induce DNA uptake by creating pores</p> Signup and view all the answers

    What color do transformed cells appear when grown on plates not containing arabinose?

    <p>White</p> Signup and view all the answers

    The GFP gene comes from a non-biological source.

    <p>False</p> Signup and view all the answers

    What is the main purpose of the transformation procedure in this lab?

    <p>To introduce the GFP gene into <em>Escherichia coli</em></p> Signup and view all the answers

    What is one major effect of chemicals in tobacco on DNA?

    <p>They cause DNA damage and mutations</p> Signup and view all the answers

    Tobacco smoke contains fewer than 4,000 different chemicals.

    <p>False</p> Signup and view all the answers

    What visible change occurs in Serratia marcescens when exposed to UV light?

    <p>It grows white.</p> Signup and view all the answers

    Cigarette smoke can lead to serious diseases including ______ and ______.

    <p>cancer, heart disease</p> Signup and view all the answers

    Match the following effects with their corresponding causes:

    <p>DNA damage = Free radicals from tobacco Visible change in bacteria = Exposure to UV light Cancer = Tobacco exposure Weak immune system = Smoking</p> Signup and view all the answers

    What is the primary purpose of the Ames Test?

    <p>To determine if substances can cause mutations</p> Signup and view all the answers

    The Ames Test was developed at Harvard University.

    <p>False</p> Signup and view all the answers

    What type of bacteria is primarily used in the Ames Test?

    <p><em>Salmonella typhimurium</em></p> Signup and view all the answers

    The Ames Test uses a strain of Salmonella typhimurium that cannot synthesize the essential amino acid __________.

    <p>histidine</p> Signup and view all the answers

    If a test substance causes mutations in the bacteria, what is likely to happen?

    <p>Colony growth will occur on histidine-deficient media</p> Signup and view all the answers

    Match the materials used in the Ames Test with their descriptions:

    <p>Agar plates = Used for growing bacteria Sterile saline solution = Used to dissolve test chemicals Histidine-free media = Media that lacks an essential nutrient Sterile filter paper discs = Used to apply test substances</p> Signup and view all the answers

    The number of bacterial colonies that grow indicates how non-mutagenic the test substance is.

    <p>False</p> Signup and view all the answers

    At what temperature is the Ames Test typically incubated?

    <p>37°C</p> Signup and view all the answers

    Study Notes

    Dihybrid Cross in Corn and Mendel's Laws

    • Investigation of Mendel's law of independent assortment with traits of corn kernels: color (yellow/green) and shape (round/wrinkled).
    • Yellow is dominant over green, and round is dominant over wrinkled.
    • F1 generation from yellow round seeds crossed with green wrinkled seeds produced all yellow and round seeds.
    • F2 generation ratios: 9/16 yellow round, 3/16 yellow wrinkled, 3/16 green round, 1/16 green wrinkled.
    • Color trait ratio in F2: 3/4 yellow and 1/4 green; shape trait ratio: 3/4 round and 1/4 wrinkled, reflecting independent inheritance.
    • Corn kernels with high starch content are round; those with high sugar content are wrinkled due to water loss.

    Population Genetics

    • Studies allele distribution and changes within populations over time.
    • General objectives: assess allele frequency changes, influence of mutation, migration, selection, genetic drift.
    • Human population traits analyzed, including tongue rolling, hairline shape, hand clasping, earlobe attachment, and mid-digital hair.
    • Traits are impacted by dominant and recessive alleles; e.g., tongue rolling is a dominant trait.

    Hardy-Weinberg Equilibrium

    • Used to assess allele frequencies over time; requires five conditions: no mutation, no migration, random mating, no genetic drift, and no natural selection.
    • Key in determining population genetic structure and evolution.

    Bacterial Transformation

    • Bacterial cells can uptake foreign DNA, creating competent cells, primarily using the heat shock method.
    • Transformation process includes calcium-rich environments and sudden temperature shifts to introduce plasmid DNA.
    • Plasmid pGLO contains the gene for GFP and a resistance gene for ampicillin.
    • Selection for transformed cells occurs by growth on antibiotic plates, revealing fluorescence in the presence of arabinose.

    Tobacco-Induced Mutations

    • Cigarette smoke contains numerous chemicals, which can generate free radicals and DNA damage, leading to mutations.
    • Experiment with Serratia marcescens to investigate the mutagenic effects of tobacco extracts within two days.
    • Procedure involves creating tobacco extracts, applying them to agar plates, and exposing the plates to UV light for mutation.

    Ames Test

    • A method developed by Dr. Bruce Ames to determine the mutagenic potential of substances using Salmonella typhimurium.
    • Test uses bacteria that cannot synthesize histidine; growth on histidine-deficient media indicates mutagenicity.
    • Connection between test substance and DNA alteration, resulting in colony growth, used to assess health risks of chemicals.

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    Description

    This lab explores Mendel's law of independent assortment through a dihybrid cross involving corn traits, specifically color and shape. Students will apply statistical analysis to the results, drawing conclusions about inheritance patterns. Engage with the principles of genetics and learn how traits are passed on from generation to generation.

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