Class Padlet

(1)

Ch 14: Genetics: Pile Driver of

Knowledge

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Mendel’s Laws

• _{Law of Segregation:}_Two

alleles are packed into separate gametes.

• _Dominance • _Recessive

• _{A or a} • _{T or t}

• _{Law of Independent}

Assortment:

Each pair of

(4)

Punnett Square Review

• _Monohybrid • _Dihybrid

• _{Phenotypic Ratios?} • _{Genotypic Ratios?}

(5)

Probability Rules

• _{Rule of Multiplication:}_The

probability that

independent events will occur simultaneously is the product of their individual probabilities.

Question: Cross plants that are heterozygous for flower color. What is probability of them being homozygous recessive?

Answer:

Probability that egg will get a p: ½ Probability that sperm will get a p: ½ Solve: ½ x ½ = ¼

Pp female Pp male Formation of eggs Formation of sperm

1_/ 2 1_/ 2 1_/ 2 1_/

2 1/4

1_/

4 1/4

(6)

• _{Dihybrid answer}

–

_{YyRr x YyRr}

–

_{Probability of YYRR}

–

_{Egg have Y and R}

• _{½ x ½ = ¼}

–

_{Sperm have Y and R}

• _{½ x ½ = ¼}

- Chance that egg and sperm will pass Y and R at the same time:

(7)

Probability Rules

• _{Rule of Addition:}_{The probability of an event that can occur}

in two or more independent ways is the sum of the separate probabilities of the different ways.

Question: Cross two Heterozygous for flower color. What is the probability that the offspring is heterozygous?

Answer:

Two ways to be heterozygous:

(1) Dom Egg with Rec Sperm (2) Dom Sperm with Rec Egg

½ x ½ = ¼ ½ x ½ = ¼

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Beyond Simple Inheritance

• _{Incomplete Dominance:}_{results in “blending” when neither}

allele is completely dominant over the other

(9)

• _Codominance:_{when both alleles affect the phenotype, so you}

see both at the same time. Ex: MN blood groups

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O

A

B

AB

ii

IA _IA

or

IA _i

IB _IB

or

IB _i

IA _IB

• _{Multiple Allele Traits:}_{when a gene is determined by}

multiple alleles (3 or more) but an individual only gets two out of the possible alleles.

Ex: ABO Blood Group

Blood Group

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• _{Polygenic inheritance:}_{an additive effect of two or more}

genes on a single phenotype.

– _{Quantitative characters: vary in the population in gradations}

Ex. Skin color or height

– _{AABBCC: dark}

– _{AaBbCc: intermediate}

– _{Aabbcc: light}

(12)

Nature Vs. Nurture

• _{Environmental impact on}

phenotype

• _{Altitude on blood etc…} • _behavior

• _{Phenotype integrates the}

(13)

Pedigree Chart Review

• _{Review various pedigrees to determine}

- _Dominant - _Recessive

• _{Consanguinity: relationship by descent from common}

ancestor

- _Autosomal - _{Sex linked}

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• _{Fetal Testing}

• _{Amniocentesis:}http://www.doctoroz.com/videos/amniocentesis-animation

• _{Chorionic Villus sampling:}http://www.muschealth.com/video/Default.aspx?videoId=10068&cId=34&type=rel • _Ultrasound

• _Fetoscopy

• _{Newborn screening}

• _PKU:PKU is an inherited disease in which the body cannot metabolize a protein called phenylalanine. It is estimated that one baby in 25,000 is born with PKU in the US. Without treatment, PKU can cause mental retardation. Newborn screening for PKU is required in all 50 states.

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–

_{Cystic fibrosis}

• _{Is the most common lethal genetic disease in the United}

States

• _{Is caused by a recessive allele carried by about one in 25}

people of European ancestry

–

_{Prolonged geographic isolation of certain populations}

can lead to

inbreeding

, the mating of close relatives.

• _{Inbreeding increases the chance of offspring that are}

homozygous for a harmful recessive trait.

(20)

–

_{Some human genetic disorders are dominant.}

• _{Huntington’s disease}_{, which leads to degeneration of the}

nervous system, does not begin until middle age.

• _{Achondroplasia}_{is a form of dwarfism.}

– _{The homozygous dominant genotype causes death of the embryo.}

– _{Thus, only heterozygotes have this disorder.}