1. Essential Question: Pgs. 420-425
Genetics and DNA: The Science of Heredity
Ms. De Los Rios
7th Grade
12.3 Probability and Heredity
Essential Question:
Why Don’t Offspring always look like their Parents?
How is Probability Related to Inheritance?
What Are Phenotype and Genotype?
Pgs

2. Probability and Heredity – Vocabulary
Probability – A number that describes how likely it is that a particular event will occur Punnett square – A chart that shows all the possible combinations of alleles that can result from a genetic cross Pedigree – A chart that shows the presence or absence of a trait according to the relationships within a family across several generations Phenotype – An organism’s physical appearance, or visible traits Genotype – An organism’s genetic makeup, or allele combinations Homozygous – Having two identical alleles for a particular gene Heterozygous – Having two different alleles for a particular gene

3. Have you ever watched a hurricane form?
My Planet Diary p.420
Storm on the Way?
Have you ever watched a hurricane form?
Weather forecasters at the National Hurricane Center (NHC) in Miami, Florida, have. From May 15 to November 30, the NHC Operations Area is staffed around the clock with forecasters. They study data from aircraft, ocean buoys, and satellites to develop computer models. These models predict the probable paths of a storm. If the probability of a certain path is high, the NHC issues a warning that helps save lives and reduce damage.

4. Probability and Heredity – My Planet Diary p.420
Storm on the way? Local weather forecasters often talk about the percent chance for rainfall. What do you think they mean? _________________________________________________

5. What is probability? Pg.421 Do the math!
Probability is a number that describes how likely it is that an event will occur
Ex: probability that a tossed coin will land on heads = 50%
The laws of probability predict what is likely to occur, not what will occur
The more trials you do, the closer your actual results will be to those predicted by probability
When tossing a coin, one toss does not affect the result of the next toss – each event occurs independently
Do the math!
Step 1: write the comparison as a fraction 3 out of 5 = 3/5
Step 2: Calculate the number value of the fraction 3/5 = 0.6
Step 3: multiply this number by 100% 0.6 x 100% = 60%

6. Punnett Squares and Pedigrees P.422-423
A Punnett square is a chart that shows all the possible ways alleles can combine in a genetic cross
In a genetic cross, the combination of alleles that parents can pass on to an offspring is based on probability
The boxes in the Punnett square show the possible combinations of alleles that the offspring can inherit
A pedigree is a chart or “family tree” that shows the presence or absence of a trait according to the relationships within a family across several generations
Doctors us pedigrees to trace and diagnose genetic disorders

7. Probability and Heredity – Figure 1 p. 422-423
Determine the probability that an offspring will have wrinkled seeds.
____________________________________
2. Determine the probability that an offspring will have round seeds.

8. Assess Your Understanding pg. 423
1a. Review- What is probability?__________________________ ___________________________________________________ b. Apply Concepts- What is the probability that a cross between a hybrid pea plant with round seeds and one with wrinkled seeds will produce offspring with wrinkled seeds? (Draw a punnett square on another paper to find the answer) I get it! Now I know that the combination of alleles parents can pass to offspring ___________________________________

9. What are Phenotype and Genotype p.424
An organism’s phenotype is its physical appearance or, visible traits
An organism’s genotype is its genetic makeup or allele
Identical Alleles
SS or ss
Homozygous
Different alleles Ss
Heterozygous
An organism that has two identical alleles for a trait is said to be homozygous for that trait.
An organism that has two different alleles for a trait is said to be heterozygous for that trait. Ss
Recall that Mendel used the term hybrid to describe heterozygous

10. What are Phenotype and Genotype p.424
The allele for smooth pea pods (S) is dominant. Therefore those with the phenotype of smooth pods can have two genotypes, SS or Ss
The plants with a phenotype of pinched pods would only only have one genotype, ss

11. Apply it! p. 425 Mendel’s principles apply to many other organisms.
Example: In guinea pigs, black fur color (B) is
Dominant over white fur color (b). Suppose a pair
Of black guinea pigs produces several litters of
Pups during their lifetimes. The graph shows the
Phenotypes of the pups. Write a title for the graph.
How many black pups were produced? How
many white pups?
______________________________________
2. What are the possible genotypes of the offspring?
____________________________
3. What can you conclude about the genotypes of the parent guinea pigs? Explain your answer.
____________________________________________________________________________________________________________________________________________

12. Assess Your Understanding pg. 425
2a. Relate Cause and Effect- Explain how two organisms can have the same phenotype but different genotypes. ____________________________________________________________________________________________________ b. Challenge- In their lifetime, two guinea pigs produce 40 black pups and 40 white pups. On a separate sheet of paper, make a Punnett square and find the likely genotypes of these parents. __________________________________________ ___________________________________________________ I get it, Now I know that phenotype and genotype are terms that describe __________________________________________