Mendel's Laws

Mendel's Laws

Three Laws of Inheritance based on observations made in pea plants.

Law of Dominance

• The seven traits Mendel tracked all showed a complete dominance pattern of inheritance.

• Complete dominance = dominant allele masks, or hides, the recessive allele

• You only see the recessive phenotype if the genotype is homozygous recessive (aa)

• AA or Aa both show the dominant phenotype

Multiple Choice

Phenotype refers to the ______________________ of an individual.

• genetic makeup

• actual physical appearance

• recessive alleles

Multiple Choice

Which of the following genotypes is homozygous recessive?

• Tt

• tt

• TT

• T

Multiple Choice

What does heterozygous mean?

• An organism that has the same alleles for a trait (TT or tt)

• An organism that has different alleles for a trait (Tt)

• When neither allele is fully dominant; offspring is a mixture of both

• the different forms of a trait (hair color--> brown, blonde, red

Law of segregation

• Two copies of each gene on homologous chromosomes.

• Individual copies are called alleles.

• Alleles separate during meiosis.

• Each parent gives only 1 allele for each gene to offspring

Law of independent assortment

• For each gene the alleles separate independently during meiosis

• Result of random assortment of homologous pairs and crossing over during meiosis I

Dihybrid Cross

• Independent assortment of Pea Color and Pea shape

• Yellow is dominant to green

• Round is dominant to wrinkled

• Phenotype Ratio: 9 Yellow & Round: 3 Yellow & Wrinkled: 3 Green & Round: 1 Green & Wrinkled

Multiple Choice

Physical characteristic or trait

• phenotype

• genotype

Multiple Choice

Law which states that different traits are inherited independently of each other

• Law of independent assortment

• Genetics law

Multiple Choice

Law states that 1 allele is more dominant than the other. Recessive allele is only expressed when dominant is not present

• Law of dominance

• Law of inheritance

Multiple Choice

If your genotype is Bb, then you can only pass a B or b to your child but you can't pass both.

• Law of Dominance

• Law of Segregation

• Law of Independent Assortment

Multiple Choice

An organism is a hybrid genotype (Tt) but is appears tall instead of short.

• Law of Dominance

• Law of Segregation

• Law of Independent Assortment

Multiple Choice

If a heterozygous parent and a homozygous recessive parent mate, what percentage of their offspring will be dominant?

• 25%

• 50%

• 75%

• 100%

Multiple Choice

What allele combination should go in the missing box?

• AA
• Aa
• aa
• none of these

Multiple Choice

What is the probability of heterozygous offspring?

• 25%
• 50%
• 0%
• 100%

Multiple Choice

B = brown fur b = white fur

In the punnett square, what is the probability for white fur?

• 0%

• 25%

• 50%

• 75%

Multiple Choice

T - tall and t = short

In the punnett square below, what belongs in the missing square

• tt

• Tt

• Bb

• TT