human genetic traits
DESCRIPTION
Human Genetic Traits. Beliefs about Heredity. Fig. 1. De la propagation du genre humain, ou manuel indispensable pour ceux qui veulent avoir de beaux enfants de l’un ou l’autre sexe (Paris, Year VII). Image courtesy of the Bibliothèque Interuniversitaire de Médecine, Paris. Homunculus. - PowerPoint PPT PresentationTRANSCRIPT
Mendel’s Three Principles
• Dominance
• Segregation
• Independent Assortment
The foundation of “classical” scienceThe foundation of “classical” science
(1822-1884)
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
Pairs of alleles are separated (=segregated) during meiosisPairs of alleles are separated (=segregated) during meiosis
Two different parental characteristics will be inherited independently of one another during gamete formation.
Example: flower color and leaf shape
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.
• Bacteria (E. coli, influenza, several others)
• Yeast (Saccharomyces cerevisiae)• Plant (Arabidopsis thaliana)• Fruit fly (Drosophila melanogaster)• Mouse (Mus musculus)
Modeled Organisms
Importance of geneticsImportance of genetics• Understanding hereditary diseases and to Understanding hereditary diseases and to
develop new treatmentsdevelop new treatments• Donor matchesDonor matches• PaternityPaternity• ForensicsForensics• EvolutionEvolution• MigrationMigration
Polynesian OriginsPolynesian Origins
Bismarck Archipelago 3.5ka
http://www.sciencedaily.com/releases/2011/02/110203124726.htm
mtDNA
Crossing Over of Nonsister Chromatids Crossing Over of Nonsister Chromatids between Homologous Chromosomesbetween Homologous Chromosomes
• PCR way of copying specific DNA fragments from small sample DNA material "molecular photocopying"
• It’s fast, inexpensive and simple
Polymerase Chain Reaction
• 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
Genetic Definitions
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
Genotype vs Phenotype
homozygous(dominant)
heterozygous
homozygous(recessive)
genotype phenotype
appearanceappearance
B B
B b
bb
Punnett Square
If male & female are heterozygous for eye color
X
brown: 3/4 offspringblue: 1/4 offspring
male
female
b
bB
B
B
B
B
B
B
B
b
b
bb
bb
PKUEach parent carries one gene for PKU.
P p
P pX
P
p
pP
P
P
P
p
p
P
p
p
Possible genotypes: 1PP 2Pp 1pp
Possible phenotypes:no PKU PKU
Compare this to what would have happened if one parent was homozygous for sickle cell.
HbA HbA
HbS HbS
X
HbS
HbS
HbAHbA
HbA
HbS
HbA
HbS
HbS
HbA
HbS
HbA
all offspring are carriers of sickle cell trait
Where Does Genetic Diversity Where Does Genetic Diversity Come From?Come From?Where Does Genetic Diversity Where Does Genetic Diversity Come From?Come From?
MutationChromosomal AberrationsGenetic Recombination
(e.g., from sexual reproduction)
MutationChromosomal AberrationsGenetic Recombination
(e.g., from sexual reproduction)
mutationmutation
Sickle Cell Mutation
CTG ACT CCT GAG GAG AAG TCTLeu Thr Pro Glu Glu Lys Ser
CTG ACT CCT GAG GTG AAG TCTLeu Thr Pro Glu Val Lys Ser
NORMAL Hb
SICKLE CELL
Red-Green Color BlindnessSex-linked trait
XC Y
XC Xc
X
XC
Xc
YXC
XC
XC
XC
Y
Xc
XC
Y
Xc
Normal male
Normal female recessive gene
Possible outcomes: XCXC XCXc XCY XcYNormal female
Normal Female(carrier)
Normal male
Color-blind male
E unconnected earlobee connected earlobeE unconnected earlobee connected earlobe
alleleallele genegene
P EE x ee
gametes E e
F1 Ee
unconnected
connected
Genotypes Phenotypes
Experiment to determinedominant vs. recessiveExperiment to determinedominant 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
Short Index FingerShort Index Finger
Ss = Short Index FingerS1 = Long Index Finger
*Sex-Influenced Trait*Sex-Influenced Trait