Genotypes, Phenotypes, Genetics, Oh my! GEMS ... Teacher Guide Genotypes, Phenotypes, Genetics, Oh my!

  • View
    0

  • Download
    0

Embed Size (px)

Text of Genotypes, Phenotypes, Genetics, Oh my! GEMS ... Teacher Guide Genotypes, Phenotypes, Genetics, Oh...

  • Teacher Guide

    Genotypes, Phenotypes, Genetics, Oh my!

    GEMS 11/04/2017

    Standards

    SC.7.L.16.2 Determine the probabilities for genotype and phenotype combinations using Punnett Squares and

    pedigrees.

    SC.912.L.15.15 Describe how mutation and genetic recombination increase genetic variation.

    Objectives

    Introduce how some traits are inherited by Mendelian genetics

    Predict genotype and phenotype using Punnett squares

    What are Traits?

    Traits are characteristics you inherit from your parents. Ask students to identify traits in the 3 individuals in the figure

    below (eye color, skin color, height, freckles).

    You should mention that not all traits are visible. A useful video can be found at

    http://learn.genetics.utah.edu/content/basics/traits/

    http://learn.genetics.utah.edu/content/basics/traits/

  • Tasting trait

    Have students determine what their trait (bitter or not) is for tasting PTC (phenylthiocarbamide). Tasting strips are

    available at Amazon.com https://www.amazon.com/Nasco-PTC-Paper-Strips-Vial/dp/B001D7FF5E

    To explore more about PTC tasting http://learn.genetics.utah.edu/content/basics/ptc/

    Genetics

    A gene carries the information (DNA) that determines traits. In the field of genetics, we can predict some of the traits

    a child will have if we know the parents’ genes. [For more information on genes & DNA,

    http://learn.genetics.utah.edu/content/basics/dna/]

    Show the following video to introduce Mendelian genetics: https://www.youtube.com/watch?v=Mehz7tCxjSE

    Review all of the definitions in the video before practicing Punnett squares:

    1. Traits are characteristics you inherit from your parents.

    2. A gene carries information (DNA) that determines your traits.

    3. Alleles are different variations of a gene. There are 2 alleles for every gene.

    4. The 2 alleles for a gene that represents a specific trait are called genotype.

    Ex) The genotype Bb represents hair color

    5. Homozygous: the alleles are the same for a particular trait

    Ex) BB, bb

    6. Heterozygous: the alleles are different for a particular trait

    Ex) Bb

    7. Phenotype is the observable characteristic of a specific trait resulting from its

    genotype.

    Ex) Blonde hair is the phenotype observed determined by genotype Bb

    8. A dominant trait “hides” the recessive trait in the phenotype of an individual. A capital letter represents

    the dominant form in an allele.

    9. A recessive trait describes a trait that is covered over (or dominated) by another form of that trait and

    seems to disappear. A lowercase letter represents the recessive form in an allele.

    https://www.amazon.com/Nasco-PTC-Paper-Strips-Vial/dp/B001D7FF5E http://learn.genetics.utah.edu/content/basics/ptc/ http://learn.genetics.utah.edu/content/basics/dna/ https://www.youtube.com/watch?v=Mehz7tCxjSE

  • Punnett squares

    The Punnett square is a way of working out the possible genotypes and phenotypes of offspring.

    We use two letters to represent the genotype. A capital letter

    represents the dominant allele and a lowercase letter is the

    abbreviation for the recessive allele.

    In the example on the left, B=dominant, blue and b= recessive

    red.

    Have students practice the definitions using the Punnett square above.

    1. What is the trait?

    color

    2. What are the alleles?

    B and b

    3. What are the 3 different genotypes of the offspring?

    Bb, BB, bb

    4. Which genotypes are homozygous?

    BB and bb

    5. Which genotypes are heterozygous?

    Bb

    6. What are the phenotypes of each offspring?

    Bb=blue; BB=blue; bb=red

  • How to generate a Punnett square:

    Walk students through constructing a Punnett square using the PTC tasting gene. This demonstrates to students that

    by knowing the parents’ genotypes for the PTC tasting gene, we can predict their kids’ ability to taste PTC.

    Ask students if the kids of these parents will be able to taste PTC.

    Answer: Yes, since the all genotypes have the dominant allele “T”.

    TT

    T

    T

    t t

    Tt

    Tt

    Tt

    Tt Genotype=TT Phenotype=can taste PTC Homozygous Dominant

    Genotype= Phenotype=cannot taste PTC Homozygous Recessive

    heterozygous

    heterozygous heterozygous

    heterozygous

    1. Put one letter (allele) above/ next to each box. It does not

    matter which parent’s genotype goes on the top/side.

    2. Fill in the boxes by copying the column & row letters down and

    across

    Fill in the boxes by copying the column & row le ers down & across into the empty spaces.

  • Practice filling in a Punnett square

    Fill in the Punnett square below and use the results to answer the questions below.

    Questions:

    1. What are the phenotypes of each kid?

    2. Which kids will be able to taste PTC?

    3. Which kids will NOT be able to taste PTC?

    Tt

    Genotype=Tt Phenotype=can taste PTC Heterozygous Dominant

    Genotype= Phenotype=cannot taste PTC Homozygous Recessive

  • Mutations

    Sometimes mutations can occur in the DNA of specific genes that changes the phenotype. Most mutations are not

    bad but just different.

    A useful video for mutations http://learn.genetics.utah.edu/content/basics/mutation/

    Tt

    T

    t

    t t

    ANSWERS

    Genotype=Tt Phenotype=can taste PTC Heterozygous Dominant

    Genotype= Phenotype=cannot taste PTC Homozygous Recessive

    Tt Tt

    heterozygous heterozygous

    homozygous homozygous

    Can taste Can taste

    CanNOT taste CanNOT taste

    http://learn.genetics.utah.edu/content/basics/mutation/

  • Use Punnett squares to design a unicorn suncatcher

    In groups, students will be assigned genotypes of unicorn “parents” for various traits and create Punnett squares.

    Possible traits and genotypes are listed below. The trait “4 or 2 legs” refers to unicorns standing on four or two legs

    (https://www.amazon.com/Plastic-Unicorn-Suncatchers-24-Pack/dp/B01KU3AAA6). Students will put the resulting

    individual squares into cups labeled with each trait. Students will pick a random square from each trait and use that

    phenotype to design their suncatcher. An example of the parent traits and one pair of genotypes is shown below.

    The Punnett squares for each trait for Group 1 parent unicorns can be found at the end of this document. You can

    include a mutation square in the cup and indicate the phenotype.

    Student directions:

    1. With a partner, pick one piece of paper from the cup labeled “TRAITS”. Write down the trait you picked.

    TRAIT: ______________________________________

    2. With your partner, create a Punnett square for the trait you selected. Use the piece of paper from your TA

    and follow the directions on it.

    Trait Dominant Allele Recessive Allele

    4 or 2 legs L l

    Body Color B= silver b= pink

    Hoof Color H= blue h= purple

    Tail Color T= purple t= yellow

    Horn Color W= pink w= black

    Mane Color M= green m= blue

    Group 4 or 2 legs Body color Hoof color Tail color Horn color Mane color 1 (father) LL Bb Hh TT ww Mm 1 (mother) ll Bb HH TT Ww mm

    2(f) 2(m)

    3(f) 3(m)

    4(f) 4(m) 5(f)

    5(m) 6(f) 6(m)

    https://www.amazon.com/Plastic-Unicorn-Suncatchers-24-Pack/dp/B01KU3AAA6

  • 3. Once your table has created all the Punnett squares and put each individual square in the appropriate trait

    cup, pick one square from each trait cup and write down the genotype and phenotype below.

    PUT THE PAPER BACK IN THE CUP SO THE NEXT PERSON CAN PICK!!!

    4. Once you’ve finished selecting all traits, use the markers to create your unicorn suncatcher. Make sure your

    unicorn matches the phenotype!!!

    5. Choose a piece of string so you can hang your suncatcher up!

    Trait Genotype Phenotype

    Standing on 4 or 2 legs

    Body color

    Hoof color

    Tail color

    Horn color

    Mane color