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5.06 Genotypes and Phenotypes
Important VOCABULARY to know:
Alleles - Alleles are pairs of genes on the chromosomes. Together, alleles determine the genotype of an individual.
Ex: Gg GG Alleles = Genes
Genotype - The Genotype describes the specific genetic makeup of an individual. A person’s genotype tells us exactly
what Alleles/Genes they have. You cannot see someone’s genotype.
So – gene/allele/genotype =same thing! (Genotypes are written as letters; aa Aa TT Tt….. they can be dominant or
recessive.
Dominant = uppercase
ex: TT or Tt = dominant alleles
Recessive = lowercase
ex: tt = recessive alleles
Dominant ALWAYS takes over recessive. If there is a dominant gene present, it’s like the recessive one isn’t even
there – the dominant trait will show.
Phenotype - Phenotypes are the observable or physical traits of an individual which the individual’s genes (alleles)
have expressed. So -Traits you actually see on someone = phenotype for physical
5.06 Questions
AA or Aa
aa
Dominant
Recessive
1.
Both parents have attached earlobes. What is their genotype? ___________ (you should have letters
here)
aa
aa
aa
Based on the parents’ genotype for earlobes can you eliminate any of the people claiming to be the
heir? Explain why or why not. Well if both parents have attached earlobes then they both have the recessive
genes aa. Can they possibly produce a child with detached earlobes (AA, Aa)? Why? So can we eliminate
someone?
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2.
DD or Dd
dd
Dominant
Recessive
3.
The father has a genotype of Dd. What is his phenotype? _________________________ (Remember
phenotype refers to the traits that show on the outside of a person. Does dad have dimples or no dimples?)
4.
Both parents have dimples. What are their possible genotypes? ___ or ____ (You should have two
possible genotypes here. Dominant genes can be expressed two ways)
DD or Dd
DD or Dd
**Genius Question -Both the parents have Dimples. This means that they must have at least one Dominant
Gene in their Genotype. Both Mom and Dad could have a DD or a Dd as their Genotype. What does this mean
for the offspring? Is it possible for these parents to have offspring without dimples? Why?
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WW or Ww
Dominant
ww
ww
Recessive
ww
5. If a claimant has a genotype of Ww can they be a possible heir? Neither Mom nor Dad has a widow’s peak.
They have the recessive gene for widow’s peak (ww). Can the parents possibly produce a child with a widow’s
peak? Is there anyone we can eliminate? Explain why or why not.
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