Introduction to Punnett Squares

Intro to Genetics

​HS-LS3-1. Ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring.

Open Ended

Who is the "Father of Modern Genetics"?

Multiple Choice

Eye color, hair color, and freckles are examples of...

• traits

• alleles

Multiple Choice

One possible version of one specific gene, represented by letters is a...

• trait

• allele

Multiple Choice

Type of allele that may mask the effect of others, represented by capital letters

• dominant

• recessive

Multiple Choice

Type of allele that may be masked by others, represented by lowercase letters

• dominant

• recessive

Multiple Choice

Two alleles of the same type are present; BB, bb

• homozygous

• heterozygous

Multiple Choice

Two different alleles are present; Bb

• homozygous

• heterozygous

Multiple Choice

Physical appearance of trait

• phenotype

• genotype

Multiple Choice

Genetic makeup (alleles) of a trait

• phenotype

• genotype

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

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

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

How to draw a Punnett Square...

• Find the genotype for each parent.

• Draw a 2 x 2 square

• The male parent goes at the top.

• The female parent goes along the left side.

• Bring the male letters down.

• Bring the female letters across.

Multiple Choice

What allele combination should go in the missing box?

• AA
• Aa
• aa
• none of these

Multiple Choice

T - tall and t = short
In the punnett square below, what belongs in the missing square

• tt
• Tt
• Bb
• TT

Multiple Choice

What is the probability of heterozygous offspring?

• 25%
• 50%
• 0%
• 100%

Multiple Choice

How is the Punnett Square set up?

• Parents genotypes on the inside and offspring is on the outside

• The genotypes of each parent are on the sides and the offspring is in the boxes

• Grandparents genotypes on the sides and offspring in the box

Multiple Choice

In a certain species of plant, the color purple (P) is dominant to the color white (p).
According to the Punnett Square, what is the probability of an offspring being purple?

• 25%
• 0%
• 100%
• 50%