Will I need therapy after this class?

Lecture 14 - Genetics

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Mendel Founder of modern genetics called

classical genetics or Mendelian genetics

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Mendel’s garden in Austria

Mendel (Genetics) vs (?) Darwin (Evolution)

Worked in mid 1800s

Saw work of the other as contradictory to their own work

Mendel’s work now explains Darwin’s work

Mendel studied inheritance of garden pea anatomy and described meiosis without

knowing anything about meiosis

........such as shape, color and texture of

pea seeds.

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Morgan advanced Mendel’s ideas using fruit flies.

Next………………………………

Some genetics terms and concepts

Gene = that section of DNA responsible for trait (seed color, eye color, skin color, etc.)

Chromatin

Gene

GenesGenes make protein products

Alleles are alternate forms of gene for same trait

Hemoglobin normal gene = H

Hemoglobin sickle cell gene = h (allele)

GenotypeGenotype is combination of genes responsible for

traits or products.

Three possibilities for genes H and h:

HH and hh and Hh

HH and hh = Homozygous Genotypes

Homo = same zygous = union;

Hh = Heterozygous Genotype

Hetero = other zygous = union

H

h

Normal zygote

zygote with sickel cell

Normal zygote

Heterozygous genotype

spermEgg

Hh

h h

hh

H

H

HH Homozygous genotypes

Phenotype

Physical, chemical, physiological, behavioral appearance of organism

Review - Gene, Genotype & Phenotype

GENOTYPES = HH or

Hh

GENEOTYPE = hh

PHENOTYPE = normal

hemoglobin

PHENOTYPE = abnormal hemoglobin

Phenotype = normal red blood cell

Phenotype = sickled red blood cell

H = normal hemoglobin GENE

h = abnormal hemoglobin GENE

Types of genetic interactions following amphimixis:

Dominance / recessiveness

Incomplete Dominance

Codominance

Pleiotropy

Atavism

Multiple Alleles at the same loci

Dominant / Recessive Alleles

Dominant allele - homozygous or heterozygous genotype = same phenotype

Recessive allele – phenotype only shows up in homozygous genotype

Alleles Genotypes Phenotypes

T (tall plant) TT Tall Plant

t (short plant) Tt Tall Plant

tt Short Plant

G = allele for green seed pods is dominant g = allele for yellow pods is recessive

gg GG or Gg

PP or Pp

Polydactyly due to dominant gene (P); normal is due to recessive allele (p)

PP or Pp genotype

pp is normal

syndactyly

Genotypes ff FF or Ff

Phenotypes attached Free

Attached and Free earlobes

Several types of interactions:

Dominance / recessiveness

Incomplete Dominance

Codominance

Pleiotropy

Atavism

Multiple Alleles at the same loci

Incomplete Dominance

neither allele is completely expressed when the other allele is present.

Genes Genotypes Phenotypes

R (red flower) RR Red

W (white flower) WW White

RW Pink

WW RW RR

Several types of interactions:

Dominance / recessiveness

Incomplete Dominance

Codominance

Pleiotropy

Atavism

Multiple Alleles at the same loci

Codominance

equal expression of two alleles that occur at the same loci on homologous chromosomes

Genes Genotypes Phenotypes

IA IAIA Blood type A IB IBIB Blood type B i ii Blood type O

IAIB Blood type AB IAi Blood type A IBi Blood type B

IA and IB are codominant to each other, but dominant to i

Type A blood is IAIA or IAi

Type B blood is IBIB or IBi

Type AB blood is IAIB

Type O blood is ii

Type “A” protein in membrane

Type “B” protein in membrane

Type “A” and type “B” proteins

in membrane

Neiter Type “A” or type “B” proteins in membrane

Several types of interactions:

Dominance / recessiveness

Incomplete Dominance

Codominance

Pleiotropy

Atavism

Multiple Alleles at the same loci

Pleiotropy = single gene has have multiple effects

Bad hemoglobin protein = bad cells

Bad cells = bad physiology

Bad physiology = organ failures and “bad” life

Key word is ……BAD

Several types of interactions:

Dominance / recessiveness

Incomplete Dominance

Codominance

Pleiotropy

Atavism

Multiple Alleles at the same loci

AtavismTraits similar to ancestral

evolutionary traits.

Examples include:

human tail, mammary line, human gill slits

May be due to:

ancient genes

mutations resulting in traits that resemble ancient traits

Normal allele is N

atavistic allele is W and rare

NN = normal

NW = normal

WW = atavism

Human gene pool

N

N

N

N

N

N

N

N

N

N

N

N

W

W

W

Human Tail is an example of Atavism or a form similar to an ancestral form

Mammary line - atavistic trait resulting in

multiple mammary glands in humans; as is found in other

more primitive mammals

There have been some documented cases of humans born with gill slits in neck without gills – very controversial little agreement on origin.

Several types of interactions:

Dominance / recessiveness

Incomplete Dominance

Codominance

Lethal Alleles

Pleiotropy

Multiple Alleles at the same loci

S Si Sp Sw

S – solid black

Si – Black with some white

Sp – white with some black

Sw = all white

Alleles

Genotypes

and

Phenotype

Order of dominance

Black and white coat color in dogs.

Multiple Alleles at the same loci.

3 or more alleles at same loci within a population.

least

S S

or

S Si

or

S Sp

or

S Sw

phenotype

genotypes

S – solid black

Si – Black with some white

Sp – white with some black

Sw = all white

Si Si

or

Si Sp

or

Si Sw

S – solid black

Si – Black with some white

Sp – white with some black

Sw = all white

Phenotype = Black with some white

genotypes

Sp Sp

or

Sp Sw

S – solid black

Si – Black with some white

Sp – white with some black

Sw = all white

genotypes

Phenotype = White with some black

Sw Sw

S – solid black

Si – Black with some white

Sp – white with some black

Sw = all white