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
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