Homunculus
How is “heredity passed on:
Spermist vs Ovists
Spermist
conception of a
human sperm
Homunculus
Leeuwenhoek’s black male and
white female rabbit
experiments: spermist “proof”
Mendelian
Genetics
Gregor Mendel
Mendel’s Three Principles
• Dominance
• Segregation
(1822-1884)
• Independent Assortment
The foundation of “classical” science
Dominance
• Traits of both parents inherited,
but one shows over the other
• Traits are not blended
Dominance Mechanism
• Two alleles are carried for each trait
• In true-breeding individuals, both
alleles are the same.
• Hybrids, on the other hand, have one
of each kind of allele.
• One trait is dominant, the other trait is
recessive
Segregation
• Half the gametes (egg or sperm)
will carry the traits of one parent
and half the traits for the other
parent
23n
23n
Independent Assortment
Two different parental characteristics
will be inherited independently of one
another during gamete formation.
Example: eye, hair or skin color
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.
Modeled Organisms
• Bacteria (E. coli, influenza, several
others)
• Yeast (Saccharomyces cerevisiae)
• Plant (Arabidopsis thaliana)
• Fruit fly (Drosophila melanogaster)
• Mouse (Mus musculus)
Craig Venter
Celera Genomics
Importance of genetics
• Understanding hereditary diseases and to
develop new treatments
• Donor matches
• Paternity
• Forensics
• Evolution
• Migration
Polynesian Origins
mtDNA
Bismarck
Archipelago
3.5ka
http://www.sciencedaily.com/releases/2011/02/110203124726.htm
Polynesian Origins
Genetic Testing
Would you want to know?
• Ethical concerns
• Cost
• Insurance companies
Autosomes & Sex
Chromosomes
Difference between Meiosis and Mitosis
Meiosis I
Interphase
Prophase I
Metaphase I
Anaphase I
Telephase I
Crossing Over of Nonsister Chromatids
between Homologous Chromosomes
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telephase II
X
X-bearing
sperm
Y
Y-bearing
sperm
X
X
Egg
Egg
XX
Female
XY
Male
Sex Determination
• Maleness derived
from Y
chromosome
• SRY gene
produces MIS
• 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
An XY Individual with Androgen
Insensitivity Syndrome
• XY Chromosomes
• Mutation in the SRY Gene causes
testes to develop
• Testes insensitive to testosterone
Intersex or hyperandrogenic?
Caster Semenya
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
Genetic Definitions
• Genes- genetic material on a
chromosome that codes for a
specific trait
• Genotype- the genetic makeup
of the organism
• Phenotype- the expressed trait
• Allel- an alternative form of a
gene
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
Genetic Information
Genes are traits
“Eye color”
Ear lobe connectedness
Genes produce proteins
Enzymes are proteins
Homologous Chromosomes
gene: location
allele: specific trait
Allele Example
Gene = “eye color”
Alleles
brown
blue
green
lavender
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
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
Where Does Genetic Diversity
Come From?
Mutation
Chromosomal
Aberrations
Genetic Recombination
(e.g., from sexual reproduction)
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
Sickle Cell treatment using CRISPR
red arrows show the sickled cells
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
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
Genotypes
Phenotypes
Experiment to determine
dominant vs. recessive
Genetic Sleuthing
My eye color phenotype is brown.
What is my genotype?
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)
Tongue Roller
R = Tongue Roller
r = Unable to Roll Tongue
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
Hi = Straight Thumb
hi = 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
Ss = Short Index Finger
S1 = Long Index Finger
*Sex-Influenced Trait
Blaze
B = blaze
b = no blaze
http://www.youtube.com/watc
h?v=gCPuHzbb5hA