Download Intro to Punnett Squares

Intro to Punnett Squares­ annotated.notebook
November 03, 2016
Introduction to Punnett Squares Example 1 pea plants. Using Punnett Squares, you can predict the genotypes and phenotypes of the offspring of a cross between a homozygous (purebred) tall pea plant and a homozygous (purebred) short pea plant. In pea plants (which Gregor Mendel studied), tall pea plants are dominant over short genotype ­the visual (dominant) and hidden (recessive) traits that an organism has and can pass on to its offspring. For example: a pea plant may be tall, but its genotype may be TT or Tt. In humans, curly hair is dominant over straight hair. A woman heterozygous for hair curl marries a man with straight hair (homozygous). Predict the possible genotypes and phenotypes of their children. phenotype ­ the visual, or dominant, traits that an organism has. It is the genetic trait that is observable. For example, if a plant is tall but has a hidden trait for short (Tt), its phenotype will be the trait that is dominant, tall. This is observable. recessive allele ­ an allele that is part of a pair of traits that is passed on to offspring, but not observable. It can be hidden by a dominant allele and can be passed from generation to generation. A recessive allele is "overpowered" by a dominant allel that represents the same trait. dominant allele ­ an allele that is part of a pair of traits that is passed on to offspring and usually observable. A dominant allele is not hidden as is it passed from generation to generation. It "overpowers" a recessive allele representing the same trait. homozygous ­ a genotype containing two of the same allele. For example, the genotype TT (phenotype ­ tall) or tt (phenotype ­ short) heterozygous ­ a genotype containing two different alleles. For example, the genotype Tt (phenotype ­tall) What are the possible genotype(s) of a tall plant? What are the possible genotype(s) of a short plant? What would be the phenotype of TT? What would be the phenotype of tt? Steps to Complete a Punnett Square 1. Write the phenotype of each parent 2. Determine the genotype of each parent 3. State which allele is dominant and which is recessive by creating a legend 4. Determine the possible gametes that may be formed for each parent 5. Determine the possible genotype combinations after fertilization using a Punnett Square 6. Answer the question that is asked in sentence form Example 3 Example 2 A homozygous, dominant individual for long eyelashes is crossed with a heterozygous individual. What is the probability that they will produce offspring without long eyelashes? Long lashes is dominant; short lashes is recessive. Free ear lobes are dominant to attached ear lobes in humans. If a homozygous, recessive male marries a homozygous dominant female, determine the possible genotypes and phenotypes of their future children. Example 5 Albinism (lack of pigment) in humans is caused by a recessive gene. Two pigmented parents have an albino child. Determine the possible genotypes and phenotypes of their Example 4 future children. The ability to roll the tongue is dominant over the inability to do so in humans. If two heterozygous tongue­rollers have children, what genotypes could their children have? 1
Intro to Punnett Squares­ annotated.notebook
November 03, 2016
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