Human Genetics
The Human Life Cycle Involves
• 1) Growth
– Mitosis- a nuclear division of a parental cell
that produces two daughter cells with the
same chromosome number as the parental
cell. (2N= 46)
• 2) Reproduction
– Meiosis- two nuclear divisions of a parental
cell that produces four daughter cells with
half the chromosome number as the
parental cell. (N= 23)
Gregor Mendel- father of genetics
Mendel’s Methods
• Monohybrid crossesan 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
F1 generation=
Recessive
100% Purple
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
protein.
• Locus- the position
on a chromosome
occupied by a gene.
• Allele- one of 2 or
more alternative
forms of the same
gene.
W
w
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.
Punnett Square
• Punnett square- a diagram
used to predict the result of
a genetic cross.
Cystic Fibrosis
• Black= cystic fibrosis Pink= carrier
• Blue= five ancestral families
Chorionic Villi Sampling and
Amniocentesis
Cri-du-chat
Karyotyping
Klinefelter Syndrome
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 dominanceinheritance 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 variationa gradation in
phenotype; indicates
that a trait is
controlled by two or
more genes.