Punnett Squares Gregor Mendel 1822 1884 Genotype v

Genotype v. Phenotype �Genotype = the genes of an organism. For one specific trait

Genotype v. Phenotype Practice �Complete � 1. 1 � 1. 2 now (1. 1

Probability � Probability is the likelihood that something will occur. Probabilities are expressed by

Probability Practice �Complete � 2. 1 � 2. 2 now (2. 1 and 2.

Punnett Squares �A Punnett square is a tool used to determine the probability of

Step 1 �Determine parents �Example: the genotypes of the ◦ Parent #1: Tt ◦

Step 2 �Draw a Punnett square (a square divided into four smaller squares)

Step 3 �“Split” the letters of the genotype for each parent and put them

Step 4 �Determine the possible genotypes of the offspring by “crossing” the alleles of

Step 5 �Summarize the results by writing the probability for each genotype & phenotype

Important Notes ◦ Each box in the Punnett square is worth 25% of the

Practice � Complete practice problems 3. 1 and 3. 2 with your partner. �

Review � Which are genotypes and which are phenotypes? Aa Brown Oval rr Short

Slides: 17

Download presentation

Punnett Squares

Gregor Mendel 1822 -1884

Genotype v. Phenotype �Genotype = the genes of an organism. For one specific trait we use two letters (alleles) to represent the genotype. Examples: Ee, GG, yy �Phenotype=the physical appearance of a trait in an organism (remember, phenotype and physical). The phenotype depends on the genotype.

Genotype v. Phenotype Practice �Complete � 1. 1 � 1. 2 now (1. 1 and 1. 2) AA Aa aa KK=white Kk=white Homozygous Heterozygous kk=black homozygous

Probability and Punnett Squares

Probability � Probability is the likelihood that something will occur. Probabilities are expressed by a number (fractions, %, or ratios). ◦ Example 1: The likelihood of flipping a coin and it landing heads up is 1 out of 2 ( ½ or 50%). ◦ Example 2: If 4 names are in a hat, one of which is yours, the likelihood of your name being drawn is 1 out of 4 ( 1/4 or 25%).

Probability Practice �Complete � 2. 1 � 2. 2 now (2. 1 and 2. 2) Fraction: ¼ Percent: 25% 1/ 4 = 25% 2/ 4 = 1/2 = 50% 3/ 4 = 75% 4/4= 100%

Punnett Squares �A Punnett square is a tool used to determine the probability of an offspring having a particular genotype. �To solve a Punnett square, the following steps must be followed:

Step 1 �Determine parents �Example: the genotypes of the ◦ Parent #1: Tt ◦ Parent #2: tt (“T”=tall and “t”=short)

Step 2 �Draw a Punnett square (a square divided into four smaller squares)

Step 3 �“Split” the letters of the genotype for each parent and put them "outside" the square

Step 4 �Determine the possible genotypes of the offspring by “crossing” the alleles of both parents

Step 5 �Summarize the results by writing the probability for each genotype & phenotype of the offspring � Genotypes: 50% Tt & 50% tt � Phenotypes: 50% tall & 50% short

Important Notes ◦ Each box in the Punnett square is worth 25% of the whole (1 out of 4). ◦ Also, uppercase letters are always written before lowercase (incorrect example: t. T)

Video

Practice � Complete practice problems 3. 1 and 3. 2 with your partner. � When you are done, have me check your work.

Review � Which are genotypes and which are phenotypes? Aa Brown Oval rr Short Which Punnett square is incorrect? Hh