Transcript N.S. 100 Lecture 14 - PPT Genetics Spring 2009 Assignment Page

Lecture 14 - Genetics
Will I need
therapy after
this class?
MENDLE
Founder of modern genetics
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Mendel’s garden as it
appears today in Austria
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Mendel studied
inheritance of
garden peas with
no knowledge of
meiosis
........such as shape,
color and texture of
pea seeds.
Morgan advanced Mendel’s
ideas using fruit flies.
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Fruit fly genetics is most well known of any animal
Next………………………………
Some genetics terms and concepts
Review
Gene = that section of DNA responsible for protein (or
trait) such as seed color, eye color, skin color, etc.)
Chromatin
Gene
Genes
Genes make protein products
Alleles are alternate forms of gene for same trait
Hemoglobin
normal gene
=H
Hemoglobin
sickle cell gene
= h (allele)
Genotype
GENOTYPE 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
Egg
sperm
H
H
h
h
HH
Homozygous
genotypes
hh
Normal zygote
h
H
Heterozygous
genotype
zygote with
sickel cell
Hh
Normal zygote
Phenotype
Physical, chemical, physiological,
behavioral appearance of organism
Review - Gene, Genotype & Phenotype
PHENOTYPE
= normal
hemoglobin
Phenotype =
normal red
blood cell
GENOTYPES
= HH or Hh
H = normal hemoglobin GENE
h = abnormal hemoglobin GENE
GENEOTYPE
= hh
PHENOTYPE
= abnormal
hemoglobin
Phenotype =
sickled red
blood cell
Types of genetic interactions following amphimixis:
Dominance / recessiveness
Incomplete Dominance
Codominance
Pleiotropy
Atavism
Multiple Alleles at the same loci
Dominant / Recessive Alleles (genes)
DOMINANT allele - homozygous or
heterozygous genotype = same phenotype
RECESSIVE allele – phenotype only shows up
in homozygous genotype
Alleles (genes)
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
Polydactyly due to dominant gene (P);
normal is due to recessive allele (p)
PP or Pp
genotype
syndactyly
pp is
normal
PP or Pp
Attached and Free earlobes
Genotypes
Phenotypes
ff
attached
FF or Ff
Free
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
IB
i
IA IA
IB IB
ii
IAIB
IAi
IB i
Blood type A
Blood type B
Blood type O
Blood type AB
Blood type A
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
…. More pleitropy
Sickle cell
hemoglobin protein =
Sickle cells
…. More pleitropy
Sickle cells =
reduced blood flow
…. More pleitropy
Reduced blood flow
= organ failures
Several types of interactions:
Dominance / recessiveness
Incomplete Dominance
Codominance
Pleiotropy
Atavism
Multiple Alleles at the same loci
Atavism
Traits similar to ancestral
evolutionary traits.
Examples include:
human tail, mammary line, dolphin
hind limb
May be due to:
ancient genes
mutations resulting in traits that
resemble ancient traits
Human gene pool
Normal allele is N
atavistic allele is
W and rare
N
W N
N
W
NN = normal
N
N
N
N
N
W
N
N
N
N
NW = normal
WW = atavism
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
Dolphin hind limb bud (atavism)
degenerates by week 5
abnormal
Normal
Several types of interactions:
Dominance / recessiveness
Incomplete Dominance
Codominance
Lethal Alleles
Pleiotropy
Multiple Alleles at the same loci
Si
S
Sp
Sw
least
Order of dominance
S – solid black
Si – Black with some white
Sp – white with some black
Alleles
Sw = all white
Black and white coat color in dogs.
Multiple Alleles at the same loci.
Genotypes
and
3 or more alleles at same loci within a population.
Phenotype
genotypes
SS
Phenotype = Black
or
S Si
or
S Sp
S – solid black
or
Si – Black with some white
S Sw
Sp – white with some black
Sw = all white
genotypes
Phenotype =
Black with some 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
genotypes
Sp Sp
or
Sp Sw
S – solid black
Si – Black with some white
Sp – white with some black
Sw = all white
Phenotype =
White with some black
S – solid black
Si – Black with some white
Sp – white with some black
Sw = all white
Sw Sw