Probability of Inheritance Lesson 1Mrs. Anna WardSeventh Grade ScienceRidge Road Middle School

Do Now!!! Please write each of the following statements. Use the following word bank to complete each sentence:

1. We note dominant alleles by using _________________.

2. We note recessive alleles by using _________________.

3. The _____________ are the traits that can be observed or seen.

4. The _____________ are the actual genetic traits that an organism has.

UPPER CASE LETTERS LOWER CASE LETTERSPHENOTYPE GENOTYPE

Announcements• Welcome Back!

• Progress Reports

Agenda for today…• Review vocabulary from Genetics• Phenotype, Genotype, Dominant, and Recessive• Check for Understanding

• Add two new vocabulary terms• Homozygous• Heterozygous• Check for Understanding

• Create Vocab Comparison Cards for our Genetics Terms• Attach into Science Notebook

Phenotype/Genotype REVIEW

• Phenotype: The characteristics you can observe/see or the organism has

• EXAMPLE: My phenotype is Brown Hair.

• Genotype: The actual genetic make-up of the organism

• EXAMPLE: My genotype is Bb.

Check for understanding…• Which of the following is a genotype? • Brown Hair• Bb• Green Eyes• Huntington’s Disease• Xx• White Flowers• Curly Hair• cc Gg

Which of the following is a phenotype?• Blue Eyes• ff• Tall Plant• Gg• Wrinkled Peas• Dark Skin• Aa• RR• Attached Earlobes

Dominant & Recessive• Traits can be either DOMINANT or RECESSIVE.

• DOMINANT TRAITS ALWAYS COVER UP RECESSIVE TRAITS.

• DOMINANT = Big Letter (B)• RECESSIVE = Little Letter (b)

Practice• Mark which of the following are dominant:

1. D 2. d 3. F 4. f 5. r 6. G 7. g 8. y

DOMINANT

DOMINANT

DOMINANT

RECESSIVE

RECESSIVERECESSIVE

RECESSIVERECESSIVE

So, to practice….Consider the if a person can have the Alleles…

B—Brown Hair or b—Blonde Hair

What are the possible Genotypes and Phenotype…• BB – 2 DOMINANT Alleles

• Phenotype--BROWN HAIR• Bb – 1 DOMINANT Allele & 1 RECESSIVE Allele

• Phenotype--BROWN HAIR• Bb – 2 RECESSIVE Alleles

• Phenotype--BLONDE HAIR

• Because blonde is recessive, you can not have any dominant “B” traits to mask the trait

Your Turn…• There are TWO possible alleles for seed shape in

pea plants, WRINKLED or ROUND.• Round Peas are Dominant -- W• Wrinkled peas are recessive – w

• If a pea plant has the following genotype, would it have round or wrinkled peas?1. WW? 2. Ww?3. ww?

ROUNDROUND

WRINKLED

One more try…• In cats, the allele for LONG tails (L) is dominant

over the allele for SHORT tails (l). What would be the phenotype for the following genotypes?

• LL? • Ll?• ll?

LONG TAILLONG TAIL

SHORT TAIL

Homozygous Means….• Homozygous means that the alleles in

the genotype are the same, either both dominant (LARGE letters) or recessive (SMALL letters).

• Examples:

• RR—HOMOZYGOUS DOMINANT• rr—HOMOZYGOUS RECESSIVE• AA—HOMOZYGOUS DOMINANT• aa—HOMOZYGOUS RECESSIVE

Heterozygous means…• Heterozygous means that the alleles

in the genotype are different, with both a dominant & recessive allele.

• Examples:

• Rr—HETEROZYGOUS• Aa—HETEROZYGOUS• Bb—HETEROZYGOUS

Check for Understanding…• In your notebook, write down whether each of the

following is Homozygous (HO) or Heterozygous (HE).

1. AA 2. Ff 3. rr 4. Gg 5. HH 6. Bb

HO

HO

HO

HEHEHE

Vocabulary Comparison CardsVocabulary Term Is: The opposite would

be: How? (Sketch or explain)

GenotypeThe actual genetic make-up of an organism

Phenotype Write with two lettersAa, Rr, RR, aa, BB, etc.

 Phenotype 

  

 

 Dominant 

  

 

 Recessive 

  

 

  Homozygous 

  

 

 Heterozygous  

  

 

After you have attached the Comparison Cards, Complete the Exit Ticket:1. In a Goddess Flower Plant, White Flowers (P) are dominant to purple flowers (p). What would the phenotype be if the plant had the following genotypes?a. Pp?b. pp? c. PP?

2. How do we write a heterozygous genotype?

3. Would a heterozygous genotype show characteristics of the recessive or dominant allele?