Plan for the Day

Seating Chart & Group Cards

Notes: Introduction Genetics

Activity: Class Trait Variation

Exit Ticket: In class assessment

Homework = Bring Your Text book.

How does an organism pass

its characteristic

s on to its offspring?

Chapter 11

Learning Targets

• I can describe where an organism gets its unique characteristics.

• I can describe how the different forms of a gene are distributed to offspring.

Genetics• The scientific study of heredity

Section 11- 1 How it all began

Gregor Mendel (1822-1884)• Known as the father of

genetics• Worked with pea plants

Mendel’s Pea Plants

He observed 2 traits for each part of the plant.

Mendel’s Pea Plants

He came up with the concept of alleles.He noticed that alleles are hereditary, and that you can predict the probability of the offspring having certain alleles.

Mendel’s Pea PlantsHe observed that some traits dominated over others

For instance, if you “crossed” a round seed-pod plant with a wrinkled seed-pod plant you generally get a round seed-pod plant.

Mendel Video

Mendel’s Pea Plants

Mendel’s Pea PlantsWhat does “crossing” the pea plants mean?It means to mate a plant with another plant by pollination.

Garden peas are both self-fertilizing and cross-fertilizing.self-fertilizing – a plant’s pollen grains fertilize its own egg cells in the ovary.cross-fertilizing – a plant’s pollen grains fertilize another plant’s egg cells in the ovary.

Genes and Dominance• The offspring of crosses between

parents with different traits are called Hybrids

• When Mendel crossed plants with different traits he expected them to blend, but that’s not what happened at all.

• All of the offspring had the character of only one of the parents

Mendel drew two conclusions

1. Inheritance is determined by factors that are passed from generation to generation – today we call these factors genes

Alleles (uh LEELZ)

• Different forms of a gene• Plant Height

–One form produced tall plants–Another form produced short plants.

Mendel’s 2nd conclusion

2. The Principal of Dominance• Some alleles are dominant and

some are recessive

dominant• Covers up the recessive form

Ex.) T = tall

recessive• Gets covered up in the presence

of a dominant allele

Ex.) t = short

Quick Lab Period 6

Trait Survey

FeatureDominant

TraitNumber

Recessive Trait

Number Total

AFree ear

lobes29 Attached

ear lobes5 34

BHair on fingers

22No hair on

fingers12 34

CWidow’s

peak7

No widow’s peak

27 34

D Curly hair 17Straight

hair16 34

E Cleft chin 2Smooth

chin32 34

1. Copy the data table into your notebook.

2. Write a prediction.

3. We will collect our data together starting with Trait A.

4. Those with free ear lobes move to the left side and those with attached to the right.

5. Count the number in each group and record.

6. Repeat for B to E.

Quick LabPeriod 4

Trait Survey

FeatureDominant

TraitNumber

Recessive Trait

Number Total

AFree ear

lobes32

100%Attached ear lobes

0 32

BHair on fingers

2681%

No hair on fingers

619%

32

CWidow’s

peak10

31%No widow’s

peak22

69%

D Curly hair16

50%Straight

hair16

50%32

E Cleft chin4

13%Smooth

chin28

87%32

1. Copy the data table into your notebook.

2. Write a prediction.

3. We will collect our data together starting with Trait A.

4. Those with free ear lobes move to the left side and those with attached to the right.

5. Count the number in each group and record.

6. Repeat for B to E.

Segregation• Mendel wanted to answer another

question

Q: Had the recessive alleles disappeared? Or where they still present in the F1 plants?

• To answer this he allowed the F1 plants to produce an F2 generation by self pollination

P1 Parental

Tall Short All Tall

F1 F2

3 tall : 1 short

75% tall

25% short

The F1 Cross• The recessive traits reappeared!• Roughly 1/4 of the F2 plants

showed a recessive trait

Explanation of the F1 Cross• The reappearance indicated that at some point

the allele for shortness had been separated from the allele for tallness

• Mendel suggested that the alleles for tallness and shortness in the F1 plants were segregated from each other during the formation of sex cells or gametes

• When each F1 plant flowers, the two alleles segregate from each other so that each gamete carries only a single copy of each gene. Therefore, each F1 plant produces two types of gametes – those with the allele for tallness and those with the allele for shortness

Segregation• Segregation is the process of

alleles separating from one another during gamete formation.

In Your Notebooks:1a. What did Mendel conclude determines biological inheritance?

1b. What are dominant and recessive alleles?

1c. Why were true-breeding pea plants important for Mendel’s experiment?

2a. What is segregation?

2b. What happens to alleles between the P generation and the F2 generation?

2c. What evidence did Mendel use to explain how segregation occurs?