Chapter 26 genetics
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Chapter 26: Genetics. Genes and chromosomes. Eye color. Hair color. Skin color. Nose size. Nose shape. Genes. Eye shape. hair texture. Ear size. widow’s peak. Ear lobes. Chromosome. Types of Chromosomes. Sex Cell. Body Cell. Chromosomes NOT paired.

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Genes and chromosomes
Genes and chromosomes

Eye color

Hair color

Skin color

Nose size

Nose shape

Genes

Eye shape

hair texture

Ear size

widow’s peak

Ear lobes

Chromosome


Types of chromosomes
Types of Chromosomes.

Sex Cell

Body Cell

Chromosomes NOT paired

Chromosomes are paired and therefore have two genes for every trait


A body cell has ___________ genes for every trait.

two

One

Sex cells only have ________ gene for every trait


egg

sperm

Fertilized egg


B =

Brown eyed Dad

b =

Blue eyed Mom

b

B

Child has a gene for BLUE eyes and a gene for BROWN eyes…

????

B b


What happens when you have a gene for Brown eyes AND a gene for Blue eyes??

A gene that will SHOW the trait

Dominant

B B = ___________________

B b = ___________________

Brown eyes

Brown eyes

A gene that will NOT show the trait if a dominant gene is present.

Recessive

b b =

Blue eyes


Terminology: for Blue eyes??

GENOTYPE – a person’s genesPHENOTYPE (physical appearance)

B B

Brown eyes

= HOMOZYGOUS Dominant

(pure dominant)

B b

= HETEROZYGOUS

(hybrid)

Brown eyes

b b

= HOMOZYGOUS recessive

(pure recessive)

Blue eyes


Possible Sperm for Blue eyes??

Possible Eggs

B

B

b

b

What are the possible

outcomes for the child?


Dad is B b for Blue eyes??

Mom is B b

Possible Sperm

Possible Eggs

B B = brown eyes

B

B

B b = brown eyes

b

B b = brown eyes

b

b b = blue eyes


Punnett square
Punnett Square for Blue eyes??

A method for predicting the possible outcomes (offspring) of a genetic cross

Mother’s Genes

B

b

B

B

B

B

b

Father’s

Genes

B

b

b

b

b


Sperm for Blue eyes??

Sperm

offspring

egg

offspring

egg

offspring

offspring


B for Blue eyes??

B

b

B b

B b

b

B b

B b

B B

b b

X

B b

B b

B b

B b


B for Blue eyes??

b

b

B b

b b

b

B b

b b

B b

b b

X

B b

B b

b b

b b


B for Blue eyes??

b

B

B B

B b

b

B b

b b

B b

B b

X

B B

B b

B b

b b


Gregor mendel 1865
Gregor Mendel: 1865 for Blue eyes??

  • Austrian monk

  • Father of genetics

  • Botanist

  • Worked with pea plants.

  • Discovered recessive and dominant genes using mathematics

  • Genetics – study of how traits are passed from parent to offspring


Mendel s experiments
Mendel’s experiments: for Blue eyes??

GG

gg

G G

Gg

Gg

g

P1

All green

* yellow trait “disappeared”??

Gg

Gg

g

F1

G g

G

GG

Gg

3 green

1 yellow

Gg

gg

g

F2

yellow

green

green

green

*yellow trait “re-appeared”


Mendel repeated this for all the traits of a pea plant. Since the results were the same, he concluded:

TT x TT = all tall

TT x Tt = all tall

TT x tt = all tall

Tt x Tt = ¾ tall, ¼ short

Tt x tt = ½ tall, ½ short

tt x tt = all short

Mendel used statistics and punnett squares to accurately predict the outcomes of all his possible genetic crosses.


Proving mendel s work
Proving Mendel’s work Since the results were the same, he concluded:

T

T

T

T

T

T

T

t

T T

T T

T

T T

T T

T t

T t

T

T T

T T

T t

T t

T t

t

T t

t

4 tall

4 tall

4 tall

T

t

T

t

t

t

T t

T t

T

T T

T t

t

t

t t

t t

T t

t t

t

t t

t t

t

t t

t t

t

3 tall, 1 short

All short

2 tall, 2 short


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