Genetics

Gene = Eye Color

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Allele = Blue Eyes

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Allele = Brown Eyes​

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​Allele = a variant form of a gene

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Open Ended

Every person has TWO alleles. WHY?

Multiple Choice

Only one allele is needed for a recessive trait to be expressed.

• TRUE

• FALSE

​We use letters to show if the allele is dominant or recessive.

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Dominant alleles only need one to show: AA or Aa

Recessive alleles need two to show: aa​

Multiple Choice

Brown eyes (B) is dominant over blue eyes (b).

BB would show which trait?

• Brown Eyes

• Blue Eyes

Multiple Choice

Brown eyes (B) is dominant over blue eyes (b).

bb would show which trait?

• Brown Eyes

• Blue Eyes

Multiple Choice

Brown eyes (B) is dominant over blue eyes (b).

Bb would show which trait?

• Brown Eyes

• Blue Eyes

Match

Match the following

• Homozygous Dominant

• Heterozygous

• Homozygous Recessive

BB

Bb

bb

• BB

• Bb

• bb

Multiple Choice

Which of the following is not a phenotype?

• Red Hair

• Freckles

• GG

• Purple Flowers

Multiple Choice

Which of the following represents a genotype?

• Green Eyes

• Ff

• G

• Dimples

​Used to predict all possible allele combinations and their frequencies in offspring.

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​Punnett Squares

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Draw

In dogs, a long tail (T) is dominant to a short tail (t). TT breeds with Tt. What are the chances of offspring having a long tail? Short tail?

Draw

A tall, heterozygous pea plant is crossed with another tall, heterozygous pea plant. What is the probability that an offspring will be tall? Short?

Draw

In humans, dimples are a dominant trait. Predict the percentage of children that will have dimples if one parent is heterozygous for dimples and the other parent does not have dimples.

​These examples we have just looked at traits that are controlled by only two alleles

• Long tail or short tail

• Tall plant or short plant

• Green or yellow peas in plants

• Red or white flowers

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​Mendelian pattern of inheritance = traits only have two possible alleles with one dominant and one recessive AKA complete dominance

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Non-mendelian inheritance is controlled by multiple alleles​

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Neither allele is dominant.

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The heterozygous genotype will show a third phenotype = blend of the other two​

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​Incomplete Dominance

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Occurs when both alleles are expressed equally

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​Codominance

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​Roaning occurs when the coat of the animal has white hairs and the hairs of any other colored mixed in together.

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Codominance can also create spots/stripes​

Draw

A man with type AB blood is crossed with a woman with type O blood. What are the resulting percentages for each blood type?

Traits that are determined by multiple genes

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Hundreds of genes acan be involved

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​Polygenic Traits

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A single gene affects multiple phenotypes

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Marfan syndrome: genetic disease that affects the development of connective tissue during fetal development, so it has a wide range of effects throughout the body​

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​Elongated arms, legs fingers; joints could be extra flexible; affects eyesight; increases likelihood of cardiovascular issues

​Pleiotropy

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