Who is Gregor Mendel?

Science Fact of the Day:Sheep, goats, and the octopus have almost

rectangular-oval pupils in their eyes.

Content Objective: I will understand and predict genetic

outcomes using a Punnett Square

Language Objective: I willwrite notes. I will answer questions by writing Punnett Squares with a

partner.

Homework: Due Friday

“A Beginner’s Guide to Punnett Squares”

Watch the video and complete the worksheet.

There will be consequences for those who do not complete this homework by Friday.

Who is Gregor Mendel?

A trait is a specific characteristic that varies from one individual to another. Example…

Biological inheritance is determined by factors that

are passed from one generation to the next.

The chemical factors that determine traits are called

genes.

The different forms of a gene are called alleles.

The principle of dominance states that

some alleles are dominant while others

are recessive.

The dominant allele will always be expressed.

A capital letter is used to represent a dominant

allele.

The recessive allele will only be expressed (phenotype) when the dominant allele for the trait is not present.

A lower case letter is used to represent a recessive

allele.

A phenotype is an organism’s physical

characteristics.

A genotype is an organism’s genetic

makeup.

Two organisms can have the same phenotype but

different genotypes.

Example…

Organisms that have two of the same alleles for a trait are

homozygous.

Organisms that have two different alleles for a trait are

heterozygous.

Homozygous organisms are true-breeding for a trait.

Heterozygous organisms are hybrid for a trait.

The way in which alleles separate during meiosis is completely random. This is also known as the principle of independent

assortment.

The results of genetic crosses can be explained by probability.

Probability is the likelihood that a

particular event will occur.

The gene combinations that might result from a

genetic cross can be determined by drawing a

diagram known as a Punnett square.

The letters in the Punnett square represent alleles.

Punnett squares are used to predict and compare the genetic variations that will result from a

cross.

Punnett Square practice…1. What would be the possible outcomes for the offspring of a

cross between pink flower (PP) and a white flower (pp)?

2. Long fingers are dominant (F) to short fingers (f). Complete the Punnett square for a homozygous recessive

mom and a heterozygous dominant dad.

3. In a plant, long stems are dominant (L) to short stems (l). If a homozygous dominant flower and a homozygous recessive plant

are crossed, what would be the phenotypic ratio of their offspring?

4. Straight hair (C) is dominant to curly hair (c). What would be the probability that a child would have curly

hair if both parents are heterozygous dominant?

5. Having a hitchhiker's thumb is a dominant trait. If a woman with a straight thumb has a child with a man

who is heterozygous for the trait, what are the chances their child will have a hitchhiker's thumb?

6. What would the phenotypic and genotypic ratios be for two purple (Pp) flowers that were bred together?

7. If being right handed is a dominant trait, then how many right handed children would two left handed

parents have?

Summary: In 35 words summarize your understanding of genetics. Be sure to use the words allele, dominant, phenotype