Topic: GeneticsAim: How do we use pedigree charts to

follow a trait through generations of a family?

Do Now: next slide

HW: Genetic Engineering Reading notes due tomorrow!

T = tall t = shortCross two heterozygous plants.

T tT

t

T

T

T

t

T t

t t

Tt x Tt

T tT

t

T

T

T

t

T t

t t

Phenotype %:75% tall25% short

Genotype %:25% homozygous

dominant50% heterozygous

25% homozygous recessive

Humans have 46 chromosomes in EVERY somatic cell in the body.

Out the 46 chromosomes, 2 of them are sex chromosomes that determine gender.

The other 44 chromosomes are called autosomes.

1. Identify the sex chromosomes found in males.

•XY

•XX2. Identify the sex chromosomes found in females.

3. Study Figure 8 on p.138. How do the X and Y chromosome differ in shape.

•X chromosome is larger than the Y chromosome

How is the sex of an individual determined?

• Eggs = X• Sperm = X or Y

Female chromosomes Male chromosomes

The X chromosome carries a couple of thousand genes but few, if any, of these have anything to do directly with sex determination. The X chromosome likely contains genes that provide instructions for making proteins. These proteins perform a variety of different roles in the body.

The Y chromosome likely contains genes that provide instructions for making proteins. The genes on this chromosome tend to be involved in male sex determination and development. Sex is determined by the SRY gene, which is responsible for the development of a fetus into a male. Other genes on the Y chromosome are important for male fertility.

4. Explain what a pedigree chart is used for.

•To follow a trait through generations of a family

5. Identify how each of the following is represented in a pedigree chart.a.Maleb.Femalec.A male with the traitd.A female with the traite.A carrierf.A normal male (does not have the trait)

a.A normal female (does not have the trait)

SquareCircle

Completely filled squareCompletely filled circle

Half colored circle or square

Empty square

Empty cirlce

9. What does the horizontal line between the male and female represent?

They have children with each other

10. What do the vertical lines represent?

Offspring

11. How many offspring did the first generation have?

4

12. How many offspring from the first generation were born with the trait?

None

13. One of the females in the 2nd generation had children with a male with the trait.

a.How many children were born with the trait?

2

b.What is the genotype of the children with the trait?

homozygous recessive

14. What is the mom’s genotype?

heterozygous

6. How many offspring did the 1st generation have?

3

7. How many offspring from the 1st generation were born with the trait?

1

8. Individual 3 had children with individual 4.

male

a. How many children did 3 and 4 have?

2

b. Which child was born with the trait?

c. What were the genotypes of individuals 3 and 4? heterozygous

9. What is the genotype of individual 2?

No

Tt

10. If individual 2 had children with a normal female (without the trait), can they have children with the trait?

Let’s Review:1. What are “regular” chromosomes called?2. Explain the difference between sex

chromosomes in a male and sex chromosomes in a female.

3. Put the following terms in order from smallest to largest:

chromosomes, nucleus, DNA, genes4. Put the following terms in order from largest

number to smallest number: chromosomes, nucleus, DNA, geneshttp://www.brainpop.com/science/cellularlifeandgenetics/heredity/

1 2

34

56 7 8 9 10 11 12 13

14 15 16 17 18 19 2021

22 2324

25

1. Identify the genotypes of 1 and 2. 2. How many offspring did 1 and 2 have?3. Identify the genotype of 3.

1. Identify the genotype of the father.

2. Identify the genotype of the mother.

RR

rr

G = green g = yellowCross a pure green plant with a

hybrid plant.G G

G

g

G

G

G

G

G G

g g

GG X Gg

Phenotype percentages:100% green

Genotype percentages:50% heterozygous50% homozygous dominant

G GG

g

G

G

G

G

G G

g g