Quiz Wednesday

probability of cards, dice, coins, spinner, tree diagrams

4.4 Probability & Genetics

ProbabilityIf you roll one die, If you roll one die, what’s the what’s the probability of probability of rolling a 6?rolling a 6?

If you pull one card If you pull one card from the deck, what’s from the deck, what’s the probability of the probability of getting the ace of getting the ace of hearts?hearts? If you flip a coin, If you flip a coin,

what’s the what’s the probability of probability of landing on heads?landing on heads?

1/6

(1 out of 6)

1/52

(1 out of 52)

1/2

(1 out of 2)

A Genetic Cross

Gregor Mendel (1865) discovered that probability could be used to predict the results of a genetic cross (mating)

If you know parent genotypes, you can predict offspring genotypes

Genotype ( 유전형 )

A genotype is an individual's collection of genes.

The word 'genotype' is usually used when talking about the genetics of a particular trait (like eye color).

Examples of genotype are the genes responsible for:

eye color hair color height how your voice sounds certain diseases certain behaviors a person’s shoe size

Phenotype ( 표현형 )

Phenotype is the observable physical or biochemical characteristics of an individual organism, determined by both genetic make-up and environmental influences, for example, height, weight and skin color.

Phenotypes are the actual visible characteristcs including:

Eye color Hair color Height Sound of your voice Certain types of disease Certain behaviors An individual’s shoe size

Definitions

Homozygous – means both parts (alleles) of the genes are the same.

Heterozygous -means both parts (alleles) of the genes are the different.

두벌이 다 다르면 이형접합자 , 같으면 동형접합자 , 한벌만 있으면 반접합자 , 다 없으면 무접합자이다

More Definitions

Alleles can be either DOMINANT (우성유전자 ) or Recessive ( 열성유전자 )

When the two alleles are different, the dominant one determines the traits.

Shape of face Oval dominant, square recessive

Cleft in chin No cleft dominant, cleft recessive

Hairline Widow peak dominant, straight hairline recessive

Eyebrow size Broad dominant, slender recessive

Eyebrow shape Separated dominant, joined recessive

Eyelash length Long dominant, short recessive

Dimples Dimples dominant, no dimples recessive

Earlobes Free lobe dominant, attached recessive

Eye shape  Almond dominant, round recessive

Freckles  Freckles dominant, no freckles recessive

Tongue rolling  Roller dominant, nonroller recessive

Tongue folding  Inability dominant, ability recessive

Bent little finger Bent dominant, straight recessive

Hair on back of hand Hair dominant, no hair recessive

A Genetic Cross If you know parent genotypes, you can

predict offspring genotypes

Example: Brown hair (B) is

dominant to blond hair (b). What are the possible

genotypes for their offspring?

bb Bb

♀ Bb x ♂ bb

Bb, Bb, bb, bb

A Genetic Cross If you know parent genotypes, you can

predict offspring genotypes

Example: Brown hair (B) is

dominant to blond hair (b). What is the probability that

the Incredibles’ next child will have brown hair?

bb Bb

♀ Bb x ♂ bb

Bb, Bb, bb, bb

2/4 (50%) chance of brown hair

A Genetic Cross If you know offspring genotypes,

you can predict parent genotypes

Example: Brown eyes (B) are

dominant to blue eyes (b). If Dash’s genotype is bb,

what are his parents’ genotypes?

bb

? ? bb Bb

Practice In pea plants, smooth peas (S) are

dominant to wrinkled peas (s). A homozygous smooth pea is

crossed with a wrinkled pea.

♀ _____ x ♂ _____

Practice In pea plants, smooth peas (S) are

dominant to wrinkled peas (s). A homozygous smooth

pea is crossed with a wrinkled pea.

Determine the possible offspring genotypes & phenotypes.

♀ SS x ♂ ss

Ss, Ss, Ss, Ss

100% chance of smooth peas

Punnett Squares Created by Reginald Punnett (1900) to

make predicting the outcome of genetic crosses easier

show all the possible

outcomes of a genetic

cross show the probability

of each outcome

25% 25%

25% 25%

Punnett Squares show all the possible outcomes of a genetic cross show the probability of each outcome

Example: In dogs, short

hair (S) is

dominant to

long hair (s). Determine the possible

offspring phenotypes.

25% 25%

25% 25%

♀

Ss

♂ SS

S

s

S S

100% chance of short hair

SS

Ss

SS

Ss

Why Use a Punnett Square?

Most scientists study MANY traits at one time

It gets VERY confusing without a Punnett Square!

Practice In humans,

straight toes (S) is dominant to curled toes (s).

Determine the possible results for a cross between a recessive male & heterozygous female.

25% 25%

25% 25%

♀

Ss

♂ ss

50% chance of straight toes

50% chance of curled toes

S

s

s s

Ss Ss

ss ss

Practice In pea plants, yellow color (Y) is

dominant to green (y).

Determine the possible

results for a cross of

2 heterozygous

plants.

25% 25%

25% 25%

♀ S

s

♂ Ss

S s

S

s

SS Ss

Ss ss

75% chance of yellow peas

25% chance of green peas

Bikini Bottom Genetics

1) Heterozygous(hybrid) (He) – capital and small letter

Homozygous(purebred) (Ho) – both capital or both small

2) Dominant gene is capital – if there is one capital – the phenotype is the dominant trait.

3) What mixtures of letters are possible

4-8) Make a Punnett square and answer the questions

Homework

• Spongebob Genetics Worksheet