Transcript Free sample makeup

Homunculus
A long time ago…
How is heredity passed on?
Spermist
Spermist
conception of a
human sperm
Mendelian Genetics
Mendel’s Three Principles
• Dominance
• Segregation
(1822-1884)
• Independent Assortment
The
The foundation
foundation of
of “classical” genetics
We call him the “Father of Genetics”
Dominance according to Mendel
• Traits of both parents are
inherited, but one trait is
expressed (shows) over the other
Dominance
• Two alleles (a version of a gene) are
carried for each trait
• In pure-breed individuals, both alleles
are the same (homozygous)
• Hybrids, on the other hand, have one
of each kind of allele (heterozygous)
• One allele is dominant, the other trait
is recessive
Segregation
• Each gamete (egg and sperm)
will carry half the genetic
information
• Half the traits of one parent and
half the traits for the other parent
23n
23n
Independent Assortment
Each parent has two alleles for a trait
During meiosis (remember?) the alleles for
that trait will be inherited independently of
one another during gamete formation
Example: eye, hair or skin color
Difference between Meiosis and Mitosis
Remember…
99.9% of your
DNA is found in
your nucleus…
So, the nucleus
directs which
proteins are
made to give
you the traits
that you have!
Genetic Definitions
• Genes- genetic material (DNA)
on a chromosome that codes
for a specific trait
• Genotype- the genetic makeup
of the organism
• Phenotype- the expressed trait
(physical appearance)
• Allele- an alternative form of a
gene
Genetic Information
Genes code for traits
“Eye color”
Widow’s peak
Lactose Intolerance
Genes direct the production
of proteins which make
YOU…YOU!
Homologous Chromosomes
gene: location
allele: specific trait
Allele Examples
appearance
B
B
eye color:
homozygous
Allele Examples
appearance
B
b
eye color:
heterozygous,
brown dominant
over blue
Genotype vs Phenotype
genotype
homozygous
(dominant)
B
B
heterozygous
B
b
homozygous
(recessive)
b
b
phenotype
appearance
Punnett Square
If male & female are
heterozygous for eye
color
B
b
B
B
b
B
b
B
B
B
b
b
b
female
X
B
male
b
b
brown:
blue:
3/4 offspring
1/4 offspring
allele
E
e
unconnected earlobe
connected earlobe
P
gametes
F1
gene
EE x ee
E
unconnected
e
Ee
connected
F1
Ee x Ee
gametes
1/2 E 1/2 e
1/2 E 1/2 e
E
Punnett
Square
F2
e
E EE
Ee
e
ee
Ee
1 EE 2 Ee 1 ee
Tongue Roller
R = Tongue Roller
r = Unable to Roll Tongue
Vulcan Greeting
V = Vulcan Greeting
v = Earthling Greeting
Widow’s Peak
W = Widows Peak
w = Lack of Widow’s Peak
Free Ear Lobe
Attached Ear Lobe
E = Free Ear Lobe
e = Attached Ear Lobe
Hitchhiker’s Thumb
H = Straight Thumb
h = Hitchhiker’s Thumb
Bent Little Finger
Bf = Bent Little Finger
bf = Straight Little Finger
Mid-digital Hair
M = Mid-Digital Hair
m = Absence of Mid-Digital Hair
Dimples
D = Dimples
d = Absence of Dimples
Short Hallux
Ha = Short Hallux
ha = Long Hallux
Short Index Finger
S = Short Index Finger
s = Long Index Finger
*Sex-Influenced Trait
Blaze
B = blaze
b = no blaze
Cleft Chin
C = no cleft
c = cleft
Where Does Genetic Diversity
Come From?
• Mutation
–Any change in the DNA
sequence
• Chromosomal Aberrations
• Genetic Recombination
–From crossing over during
sexual reproduction
Crossing Over of Nonsister Chromatids between
Homologous Chromosomes
Human Genome Project
U.S. govt. project coordinated by the Department of
Energy and the National Institutes of Health, launched
in 1986 by Charles DeLisi.
Definition: GENOME – the whole hereditary information of
an organism that is encoded in the DNA.
Project Goal: to identify the approximate 100,000 genes
in the human DNA.
- determine the sequences of the 3 billion bases that
make up human DNA.
- store this information in databases.
- develop tools for data analysis.
- address the ethical, legal, and social issues that arise
from genome research.
Autosomes & Sex
Chromosomes
X
X-bearing
sperm
Y
Y-bearing
sperm
X
X
Egg
Egg
XX
Female
XY
Male
Sex Determination
• Maleness derived
from Y
chromosome
• Female
reproductive
structures
degenerate
Genes of the Sex
Chromosome
X chromosome
• has over 1500 genes
• Most genes on X don’t have
corresponding alleles on the Y
chromosome
Y chromosome
• Has only 231 protein encoding genes
• Some genes are unique only to the Y
Sex Chromosomal Disorders
Turner Syndrome – XO only one sex
chromosome
• Short, thick neck and stature
• Do not undergo puberty, or menstruate,
• No breast development
Kleinfelter Syndrome – XXY
•
•
•
•
•
Testis and prostate underdeveloped
No facial hair
Breast development
Long arms and legs: big hands and feet
Can be mentally retarded
XXY
XO
Genetic Testing
Gel electrophoresis
Polymerase Chain Reaction
•
PCR way of copying specific DNA
fragments from small sample DNA
material "molecular photocopying"
•
It’s fast, inexpensive and simple
Genetic Testing
$299, looks at specific diseases
23 and me
Paternity Test $99
Dominance Mechanism
• Two alleles are carried for each trait
• In true-breeding individuals, both
alleles are the same (homozygous).
• Hybrids, on the other hand, have one
of each kind of allele (heterozygous).
• One trait is dominant, the other trait is
recessive
PKU
Each parent carries one gene for PKU.
P
p
P
X
P
p
p
Possible genotypes: 1PP
P
p
P
P
P
p
P
p
p
p
2Pp 1pp
Possible phenotypes:no PKU
PKU
Compare this to what would have happened
if one parent was homozygous for sickle
cell.
HbS
HbA
HbA
X
HbS
HbS
HbS
HbA
HbA
HbA
HbA
HbS
HbS
HbA
HbA
HbS
HbS
all offspring are carriers of sickle cell trait
Sickle Cell Mutation
NORMAL Hb
CTG ACT CCT GAG GAG AAG TCT
Leu Thr Pro Glu Glu Lys Ser
SICKLE CELL
CTG ACT CCT GAG GTG AAG TCT
Leu Thr Pro Glu Val Lys Ser
mutation
Autosomes and Sex Chromosomes
Red-Green Color Blindness
Sex-linked trait
XC
Y
Normal male
XC
X
XC
Xc
Normal female
recessive gene
Possible outcomes:
Xc
XC
Y
XC
XC
XC
Y
XC
Xc
Xc
Y
XCXC XCXc XCY
Normal Normal Normal
female Female male
(carrier)
XcY
Color-blind
male
Genotypes
Phenotypes
Experiment to determine
dominant vs. recessive
Complexities
• Multiple genes for one trait
• Example: eye color
• Blended traits (“incomplete dominance”)
• Influence of the environment (UV, smoking,
alcoholism)
Complexities
• Co-dominance-neither allele is recessive
and the phenotypes of both alleles are
expressed.
• Blood types- AB (not O); sickle cell anemia
heterochromia
Disorders
Down’s Syndrome (chrom 21)
Alzheimer’s (chrom 1, 10, 14, 19, 21)
Huntington’s (chrom 4)