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Inheritance: Mendelian Genetics. I. Gregor Mendel (1865) A. Before Mendel B. Mendel’s experimental approach II. Genetic terms 1. genes 2. gene pair 3. alleles 4. homozygous/heterozygous 5. dominant/recessive 6. homozygous dominant and recessive/heterozygous

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inheritance mendelian genetics
Inheritance: Mendelian Genetics

I. Gregor Mendel (1865)

A. Before Mendel

B. Mendel’s experimental approach

II. Genetic terms

1. genes

2. gene pair

3. alleles

4. homozygous/heterozygous

5. dominant/recessive

6. homozygous dominant and recessive/heterozygous

7. genotype/phenotype

III. Genetic crosses

A. Monohybrid crosses

B. Dihybrid crosses

IV. Mendel's discoveries

A. Principle of segregation

B. Principle of independent assortment

C. Genes are particles

a before mendel
Darwin and MendelA. Before Mendel

The blending theory (paradigm)

Inheritance of acquired characteristics

  • statistics
  • amateur
  • inductive leap
b mendel s experimental approach
B. Mendel’s experimental approach

Hermaphrodite

Perfect flowers

Genetic barriers

pollen

egg

slide6
Why was Mendel’s experimental findings ignored during
  • his lifetime?
  • He was an amateur
  • There was a problem with inductive leaps
  • The dominant paradigm was opposed to his findings
  • He used statistics
  • All of the above
ii genetic terms
II. Genetic terms

1. genes/ loci

2. gene pair = homologues

3. alleles

4. homozygous/heterozygous

5. dominant/recessive

6. homozygous dominant and recessive/heterozygous

7. genotype/phenotype

human traits
Human traits

Hand folding

iii genetic crosses
III. Genetic crosses

Punnett Square

slide11
Red coat in foxes is a dominant trait; white is the

recessive trait. If a red fox whose mother had a

white coat is bred to a white fox, what will be the

probable percentage of red kits (baby foxes)?

a. 25% b. 50% c. 75% d. 100%

slide14
Tay-Sachs is a lethal disorder resulting in death by the
  • age of 4. A couple who are normal have a child with Tay-
  • Sachs. Which of the following is true of the parents?
  • One parent is homozygous dominant and the other is
  • homozygous recessive
  • b. both parents are heterozygous
  • c. both parents are homozygous dominant
  • d. both parents are homozygous recessive
sickle cell trait recessive disorder16
Sickle cell trait: recessive disorder

Homozygous dominant = normal, not malaria resistant

Heterozygous = malaria resistant

Homozygous recessive = sickle cell anemia

huntington s disease dominant disorder
Huntington’s disease: dominant disorder

CAGCAGCAG

Normal, 26 times

HD, 40 to >100 times

Manifests after age 40

Why is dominant lethality less common than recessive?

dwarfism dominant trait
Dwarfism: dominant trait

Homozygous dominant = lethal

Heterozygous = dwarf

Homozygous recessive = normal height

Hardy-Weinburg rule

slide19
If two achondroplasic dwarfs have children, what fraction of the children would be expected to be dwarfs like their parents?

a. 1/4 b. 1/2 c. 2/3 d. 3/4

  • What determines how common a trait is in a population?
  • it’s frequency
  • Dominance
  • Selection
  • Chance
b dihybrid crosses human traits
B. Dihybrid crosses: Human traits

Dark hair dominant to light hair

Curly hair incompletely dominant to straight hair

Brown eyes dominant to blue

Dimples dominant to no dimples

slide21
In humans, a widow's peak is dominant and a straight hairline is

recessive. Dimples are dominant and no dimples are recessive. A male

who is heterozygous for both widow's peak and dimples has a child with

a woman who has a straight hairline and no dimples.

What is the phenotype ratio of children can they produce?

a. 3: 1 b. 2:2 c. 1:1:1:1 d. 4:0

iv mendel s discoveries
IV. Mendel’s discoveries

A. Principle of segregation

Sexually reproducing diploid

organisms have 2 alleles of

each gene.

These 2 alleles segregate from

each other to form gametes

that contain only 1 allele of

each gene.

b principle of independent assortment
B. Principle of independent assortment

Different genes on different chromosomes segregate into gametes independently of each other.

v eugenics
V. Eugenics

Social Darwinism

Francis Galton

Positive Eugenics

eugenics today
Eugenics today?

IVF/ PGD

Gene “therapy”

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