Download Patterns of Human Inheritance

Patterns of Human Inheritance
Learning Outcomes
Describe dominant and recessive patterns of inheritance
in human disease traits.
Describe how sex is inherited in humans and the pattern
of inheritance observed for sex-linked genes
Explain X chromosome inactivation
The inheritance patterns –
DOMINANT or RECESSIVE
of most human traits has been determined by
pedigree analysis
black numbers - hands
red numbers - feet
Autosomal Dominant
Huntington’s disease
Autosomal Recessive
Sickle cell
cystic fibrosis
Autosomal Dominant
dominant the presence of the
dominant allele WILL
produce the phenotype
normal
mother
affected
father
meiosis
and gamete
formation
affected child
normal child
disorder-causing
allele (dominant)
Autosomal Recessive
recessive both the alleles MUST BE
recessive to produce
the phenotype
Sickle Cell Anemia
million
Cystic Fibrosis
over 1500 known mutations
Pleiotropy
a single gene affects multiple traits
Sickle Cell
Cystic Fibrosis
severe anemia
sickle crisis
(extremely painful)
swelling of hands/feet
more infections
stroke
thick/sticky mucus in lungs
repeated lung infections
pneumonia
pancreatitis
intestinal blockage
Sex-linked traits
hemophilia, red-green color blindness
dystrophin
(muscular dystrophy)
(anhidrotic ectodermal
dysplasia)
IL2RG (SCID-X1)
Sex-linked traits
~10% of protein coding
genes are on the
X chromosome
XIST X chromosome inactivation
control
(hemophilia B)
(hemophilia A)
X
(red-deficient color blind)
(green-deficient color blind)
Sex-linked traits
When we talk about sex-linked traits,
we are really talking about genes
on the X chromosome.
There are only a few genes on the
Y chromosome where mutations
are known to cause genetic diseases.
Queen Victoria
1819-1901
The Romanov Family ca. 1931
Human Traits
that are simple Mendelian inheritance
Cleft chin (dominant)
Cheek dimples (dominant)
Free (dominant) or attached (recessive) earlobes
Freckles (dominant)
Hitchhiker's thumb (recessive)
Widow's peak (dominant)
X Chromosome Inactivation—
A Colorful Story
X Chromosome Inactivation
Nuclei of:
XX cells
XY cells
In XX cells, one X chromosome in each cell is
permanently inactivated during embryonic development.
Epistasis
One gene regulates/controls the expression of another.
Gene #1 -- codes for cat fur color -2 alleles -- black or orange
Gene #2 -- dilute - controls how much expression -get lighter or darker variations
Gene #3 -- white spotting -completely turns off Gene #1 in some spots