Human Genetics
Gregor Mendel- father of genetics
Mendel’s Methods
• Monohybrid crosses-
an experimental
cross between
individuals that differ
by a single trait.
• First generation (F1).
Mendel’s F1 Observations
• One of the traits
could be seen in
the F1 generation=
Dominant
• One of the traits
was hidden in the
100% Purple
F1 generation=
Recessive
Genetic Terminology #1
• Phenotype- an
organisms traits.
• Genotype- an
organisms genetic
makeup.
• Homozygous- identical
alleles for a gene.
• Heterozygous- two
different alleles for a
gene.
Genetic Terminology #2
• Gene- a sequence of
DNA that codes for a W w
protein.
• Locus- the position
on a chromosome
occupied by a gene.
• Allele- one of 2 or
more alternative
forms of the same
gene.
Mendel’s F2
Observations
• Flower color
– Purple:white
705:224
3:1
Mendel’s
Dihybrid
Cross
• 315:108:101:32
= 9:3:3:1
Mendel’s Work Yielded
These Genetic Rules
• Alternative versions of genes (different alleles)
account for variations in inherited characters.
• For each character, an organism inherits two alleles,
1 from the mother and 1 from the father.
• If two alleles differ, then one, the dominant allele is
fully apparent in the organism’s appearance.
• The two alleles for each trait segregate during
gamete production.
• Alleles of a gene segregate independently of the
alleles of other genes.
THO1 THO1
Punnett Square
• Punnett square- a diagram
used to predict the result of
a genetic cross.
Complete Dominance
• The dominant allele produces a functional
protein and the protein’s effects are
apparent.
• The recessive allele produces a less
functional protein or none at all and the
trait is not apparent.
Codominance- blood types
• Codominance- the
effects of both alleles
are apparent.
Incomplete
Dominance
Incomplete Dominance
• Incomplete dominance-
inheritance in which the
F1 is intermediate in
phenotype between the
parents.
• Neither allele is
dominant.
Continuous Variation
Continuous Variation
is the result of
Polygenic
Inheritance
• Continuous variation-
a gradation in
phenotype; indicates
that a trait is
controlled by two or
more genes.
Eye Color
BB bb Brown
BB Gb Brown
BB GG Brown
Bb bb Brown
Bb Gb Brown
Bb GG Brown
bb GG Green
bb Gb Green
bb bb Blue
Linkage
• Linkage- the tendency for
certain genes to be
inherited together
because they are in
close proximity on the
same chromosome.
• Linked genes- genes that
are inherited together.
Position of Forensic STR Markers
on Human Chromosomes
TPOX
13 CODIS Core STR Loci
D3S1358
TH01
D8S1179
D5S818 VWA
FGA D7S820
CSF1PO
AMEL
Sex-typing
D13S317
D16S539 D18S51 D21S11 AMEL
AmpFlSTR®
Identifiler™ D8S1179 D21S11 D7S820 CSF1PO
6FAM
(blue)
TH01
D3S1358 D13S317 D16S539 D2S1338
VIC
(green)
TPOX
D19S433 VWA D18S51
NED
(yellow)
AMEL D5S818 FGA
PET
(red)
GS500 LIZ size standard
LIZ
(orange)
Allelic Ladders
D8S1179 D7S820 CSF1PO
D21S11
D3S1358 TH01 D13S317 D16S539 D2S1338
D19S433
VWA TPOX D18S51
FGA
AMEL D5S818
Paternity