Standard 9

7Sb.5: Summarize how genetic information is passed from parent to offspring by using the terms genes, chromosomes, inherited traits, genotype, phenotype, dominant traits, and recessive traits.

Lesson on Phenotypes and Genotypes- what you carry versus what you show!

Group Activity

1)    The students will work in groups of 4 to create a human being.

2)     There will be 23 envelopes on each desk for each group of 4. They will be marked with a phenotype- physical trait: eye color, height, hair color, etc.

3)     The students will pull out the Genotype- either a dominant gene (brown eyes) or a recessive gene (blue eyes). Once they have pulled out and written down all 23 genotypes (genetic trait) they will then go “hook up” with another group, creating a whole human. The group with the dominant gene will be the phenotype (physical trait) shown

http://www.diffen.com/difference/Genotype_vs_Phenotype

CLASS DEMONSTRATION

       The teacher will pull out of the Eye envelope-small b, meaning blue eyes. Next, walk over to another group who has a capital B- brown eyes. She will explain even the “new” human shows brown eyes (phenotype), they carry the genotype for both brown and blue (Bb-genotype)

Question 1-

Why do humans have two genotypes for every physical trait?

          Because we inherit one from mom (23 chromosomes) and one allele from dad (23 chromosomes), giving us 46 total

Question 2-

  Can a person who has brown eyes have an offspring with blue eyes?

Yes- only if they carry the b/recessive trait gene and have an offspring with someone else who has the b/recessive trait gene but they only have a ¼ chance of passing it on if both parents have brown eyes but carry the blue.

References

Anderson, Paul (2011, August 4).  033-Genotypes and Phenotypes.  Retrieved from http://www.youtube.com/watch?v=OaovnS7BAoc

http://www.diffen.com/difference/Genotype_vs_Phenotype