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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 l.jpg
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 l.jpg

Darwin and Mendel

A. Before Mendel

The blending theory (paradigm)

Inheritance of acquired characteristics

  • statistics

  • amateur

  • inductive leap


B mendel s experimental approach l.jpg
B. Mendel’s experimental approach

Hermaphrodite

Perfect flowers

Genetic barriers

pollen

egg




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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 l.jpg
Human traits

Hand folding


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III. Genetic crosses

Punnett Square



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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%


Monohybrid cross genetic disorders and lethal genes l.jpg
Monohybrid cross: genetic disorders and lethal genes


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  • 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 l.jpg
Sickle cell trait: recessive disorder

Homozygous dominant = normal, not malaria resistant

Heterozygous = malaria resistant

Homozygous recessive = sickle cell anemia


Huntington s disease dominant disorder l.jpg
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 l.jpg
Dwarfism: dominant trait

Homozygous dominant = lethal

Heterozygous = dwarf

Homozygous recessive = normal height

Hardy-Weinburg rule


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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 l.jpg
B. Dihybrid crosses: Human traits the children would be expected to be dwarfs like their parents?

Dark hair dominant to light hair

Curly hair incompletely dominant to straight hair

Brown eyes dominant to blue

Dimples dominant to no dimples


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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 l.jpg
IV. Mendel’s discoveries hairline is

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 l.jpg
B. Principle of independent assortment hairline is

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



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V. Eugenics hairline is

Social Darwinism

Francis Galton

Positive Eugenics


Eugenics l.jpg
Eugenics hairline is


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Eugenics hairline is


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Eugenics today? hairline is

IVF/ PGD

Gene “therapy”


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The end hairline is


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