Genetics!The study of heredity

• Heredity: The passing of traits from parents to offspring

• Traits: Characteristics that are inherited– Hair color, eye color, height…

• Alleles: Different forms of a gene• You have two alleles for every gene.

Genetics Vocab• Homozygous: Two alleles are the same– Also known as purebreeds– Ex: AA or aa

• Heterozygous: Two alleles are different – Also called hybrids or carriers– Ex: Aa

Genetics Vocab

• The presence of an allele does not mean it will be expressed

• In a heterozygote (Aa), the dominant trait is seen and the recessive trait is hidden

• The recessive trait can only be seen when an organism has 2 copies of the recessive allele (aa)– Dominant Allele: Capital letter– Recessive Allele: Lowercase letter

What does it mean to be Dominant or Recessive?

How many of you have 6 fingers on each hand?

• 6 fingers are dominant

How many of you have a widow’s peak?

• Widow’s peak is dominant

How many of you have attached ear lobes?

• Attached earlobes are recessive

How many of you have the ability to roll your tongue?

• Rolling your tongue is dominant

How many of you have a straight thumb?

• Straight thumb is recessive

How many of you have blue eyes?

• Blue eyes are recessive

How many of you have freckles?

• Having freckles are dominant

How many of you have a cleft chin?

• Having a cleft chin is recessive

How many of you have a second toe longer than your big toe?

• Having a longer second toe is dominant

Which way do your thumbs cross each other when you are clasping your hands together?

• Left thumb on top is dominant

How many of you have an immunity to poison ivy?

• Poison ivy immunity is dominant

So….

•The dominant trait is not always more

common than the recessive trait!

Genetics Vocab• Phenotype: The way an organism looks

physically• Genotype: The gene combination an organism

has– Homozygous dominant: AA– Homozygous recessive: aa– Heterozygous: Aa

• You can’t always tell an organism’s genotype by looking at its phenotype

Try some practice!

Gregor MendelThe father of genetics

Gregor Mendel used pea plants to study the inheritance of traits

Mendelian Vocabulary

• Parental Generation (P1): The first two pea plants crossed

• The offspring of the P1 generation are called the F1 generation

• If we cross plants from the F1 generation we get the F2 generation and so on…

Mendel’s Laws• 1. Law of Dominance

In a heterozygous individual, the dominant allele will be expressed and the recessive allele will be hidden

2. Law of Segregation: During meiosis, homologous pairs are separated

and each gamete only receives one allele3. Law of Independent Assortment

During meiosis, homologous pairs separate RANDOMLY and INDEPENDENTLY of each other