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Understanding Genetics: Homozygous, Heterozygous, and Punnett Squares, Slides of Ecology and Environment

An introduction to genetics concepts, including genotype and phenotype, homozygous and heterozygous genotypes, and the use of punnett squares to predict the genotypic and phenotypic ratios of offspring from a cross between two individuals. Students will learn the definitions of key terms and how to apply this knowledge to complete a punnett square.

Typology: Slides

2012/2013

Uploaded on 01/22/2013

ashwini
ashwini 🇮🇳

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Inheritance of single traits
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Download Understanding Genetics: Homozygous, Heterozygous, and Punnett Squares and more Slides Ecology and Environment in PDF only on Docsity!

Inheritance of single traits

GENETIC TERMS

  • Genotype
  • Phenotype
    • The particular set of genes an organism contains (represented by letters, ex. Bb)
    • The physical expression of the genes (ex. Brown hair)

Punnett Square

  • A Punnett square helps geneticists organize the results of a cross involving the sex cells of two individuals.

Now try to complete these crosses…

RR X Rr Rr X rr Rr X Rr

RR X Rr Sex cells formed R, R X R, r Fertilization R r R RR Rr R RR Rr

To complete a Punnett square there are five steps. Here is an example of a question and the right answer.

Q. Two heterozygous green pod plants are crossed with each other. What ratios would you expect in the F1 generation?

Step 3. Give the gametes (sex cells) of the parents.

G , g X G, g

Step 4. Draw the Punnett Square G g G GG Gg g Gg gg

Step 5. Write out the phenotypic and genotypic ratios.

Genotypic ratio: 1GG:2Gg:1gg

Phenotypic Ratio: 3 green pod plants: 1 yellow pod plant