Allele

Traits and Alleles

Write down all of the notes that are in color throughout the presentation.

Traits

Traits are characteristics belonging to a person. Your environment can affect your traits.

Investigation of Our Traits

Answer the following questions about your traits.

Poll

Do you have a widow's peak or a straight hairline? Click the image.

Poll

Do you have attached or detached earlobes?

Poll

Can you roll your tongue?

• Yes

• No

Poll

Do you have a smooth or cleft chin?

Poll

Do you have freckles?

• Yes

• No

Review

• A gene is a segment of DNA

• Our DNA is bundled up to make up our chromosomes

• We have 46 chromosomes; we get 23 from each of our parents

Alleles

• Alleles are different forms of the same gene.

• Ex: There are genes that code for eyes, and alleles determine the color of our eyes

• Ex: There are genes that code for earlobes, and the alleles determine if our earlobes are attached or not.

Alleles

• Organisms of the same species have alleles in the same places on their chromosomes.

• We inherit two alleles for each gene; one from each parent.

Multiple Choice

How do we get our alleles?

• We get both pair of alleles from one parent.

• We get one allele from each parent.

• We get a mixed version of both parents' alleles.

Multiple Choice

All humans have alleles that are in the same place on each of our ______________?

• cells

• chromosomes

• membranes

• traits

Alleles

• Although we receive an allele from each of our parents, we only express one.

• In most allele pairs, one is allele is dominant and the other is recessive.

• We use letters to represent allele combinations.

Alleles

• Dominant alleles are uppercase, and recessive alleles are lowercase.

• Dominant alleles mask recessive alleles

• The allele for freckles (F) is dominant to the allele for no freckles (f), so this person will have freckles.

Multiple Choice

For eye color, (B) is the allele for brown eyes, and (b) is the allele for blue eyes. Which is the recessive trait?

• brown eyes

• blue eyes

Genotypes

• Each allele combination is called a genotype. Genotypes are listed below.

Genotypes

Homozygous Dominant - both alleles are dominant

The dominant trait will be expressed.

Genotypes

Homozygous Recessive- both alleles are recessive

The recessive trait will be expressed.

Genotypes

Heterozygous - one allele is dominant and the other is recessive

The dominant trait will be expressed.

Multiple Select

Select all of the heterozygous genotypes.

• Hh

• Zz

• NN

• bb

• Ss

Multiple Select

Select all of the homozygous recessive genotypes.

• aa

• Bb

• ee

• LL

• Pp

The trait expressed with the genotype is called the phenotype.

• BB (two dominant alleles) produce a purple phenotype.

• Bb (one dominant and one recessive allele) produce a purple phenotype

• bb (two recessive alleles produce a white phenotype

Multiple Select

Sandra Bullock has a cleft chin. If cleft chin is a recessive trait, how would you describe her genotype? Select all that apply.

• homozygous dominant

• heterozygous

• homozygous recessive

Multiple Select

Unattached earlobes (E) is dominant over the attached earlobes trait (e). If Justin Bieber's earlobes are unattached, what could his genotype be? Select all that apply.

• heterozygous

• Ee

• EE

• homozygous recessive

Incomplete Dominance

• With incomplete dominance, the dominant allele does not completely mask a recessive allele

• Appearance is usually a blend of both alleles

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