Transcript Autosomal Single Gene Disorders Notes

Autosomal Single Gene
Disorders
Human Basics
Humans have 46 chromosomes in every
diploid body cell
Human Basics
2 sex chromosomes = they have genes that
determine a persons sex
44 autosomes = genes for all other traits
A karyotype is a picture of all 46 human
chromosomes grouped together in
homologous pairs
Autosomal?
These types of gene disorders are only
found in chromosome pairs 1-22
Gene Mutations
The instructions in 1 out of the 24,000 genes
gets messed up
Gene Mutations
Insertion, deletion or substitution of 1 or more
bases changes amino acids and makes the
protein incorrectly
“Normal” DNA sequence
DNA: TCACGATTT
mRNA: AGUGCUAAA
Ala
Lys
DNA: TCATGATTT
mRNA: AGUACUAAA
Ser
Thr
Ser
Mutated DNA sequence
Lys
Example: Cystic fibrosis (1 in 2000 Europeans)
Gene on chromosome 7
Normal dominant allele (N) makes a protein
to transport chloride ions across cells
Mutated recessive allele (n) makes a protein
that does not transport chloride ions
across cell
Result= mucus that clogs lungs and
pancreas=shortened life expectance to
early adulthood
NN=normal Nn=normal nn=cystic fibrosis
Example: Tay-Sachs disease (1 in 600 Jews)
Gene on chromosome 15
Normal dominant allele (N) makes a protein
that is an enzyme which breaks stuff down
in lysosome’s
Mutated recessive allele (n) makes an
enzyme that does not work
Result= build up of waste causes nerve cells
to die= brain damage and death in early
childhood
NN=normal Nn=normal nn=Tay-Sachs
Example: Sickle cell anemia (1 in 500 African
Americans)
Gene on chromosome 11
Normal dominant allele (N) makes a protein
that carries oxygen in red blood cells
Mutated recessive allele (n) makes a protein
that causes the cell to change shape
Result= Cylinder shaped red blood cells clog
blood vessels= damaged organs due to
lack of oxygen
NN=normal Nn=Normal nn= sickle cell anemia
Example: Huntington’s Disease (1 in
10,000)
Gene on chromosome 4
Normal recessive allele (n) makes a protein
that helps move vesicles in nerve cells
Mutated dominant allele (N) makes a
damaged protein which causes defected
nerves in brain
Result=at middle age loss of body function
and death
NN=Huntington’s disease Nn=Huntington’s disease
nn= normal
Example: Hutchinson Giford Progeria Syndrome
(1 in 4-8 million new borns)
Gene on chromosome 1
Normal recessive allele (n) makes a protein that
builds the nucleus (nuclear envelope)
Mutated dominant allele (N) makes a damaged
protein that makes the nucleus unstable and
misshapen
Result=The unstable nucleus becomes
damaged over time, leading to early death of
cells and early death of the individual
NN=Hutchinson Gilford diseaase Nn=Hutchinson Gilford
disease
nn= normal