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Proteus Syndrome
Neurofibromatosis
Angelman
Holoprosencephaly
Genetic Disorders
Cystic Fibrosis
Down’s Syndrome
When things don’t go right
Marfan
Tay-Sachs
Huntington’s Disease
Progeria
Karyotype - a picture of chromosome pairs
It shows us chromosomes!
1. Homologous chromosomes
2. Autosomal Chromosomes
3. Sex chromosomes
Pairing up chromosomes!
1. Size
2. Gene bands
3. Location of centromere
Humans have:
22 pairs of autosomes
1 pair of sex chromosomes tells gender,
total = 23 pairs or 46 chromosomes.
• Chromosomes are made up of _____
genes which are made up of ____
DNA & ______
protein
• Organisms’ chromosomes come in Homologous
_______________
pairs (one from mom, one from dad)
• Homologous pairs are evident during meiosis
______, where they then separate.
• The location of a gene on the chromosome is called its ______
locus
• Traits can be expressed as different ________
alleles at the gene locus
Allele for blue eyes (b)
Gene loci for eye color
Homologous chromosomes
Allele for brown eyes (B)
Crossing Over
• During Prophase 1
– Homologous chromosomes pair up (synapsis)
– Tetrads of 4 sister chromatids intertwine
– At the chiasma - homologous pairs swap
pieces of chromosome
– crossing over results in more genetic diversity
chiasma
tetrad
synapsis
Chromosomal Disorders due to Nondisjunction
• Homologous pairs are supposed to separate during anaphase I of Meiosis
• Then their sister chromatids are supposed to separate during anaphase II of Meiosis
• The number of chromosomes in gametes should be N (the haploid number)
Cell A
• Which is the most devastating?
Cell B
How many viable sperm for Cell A? cell B?
Sex Chromosome Disorders due to Nondisjunction
Autosomal Disorders due to Nondisjunction
Distinguish between:
Autosomal Disorders:
a. Cystic fibrosis
b. Tay-Sachs Disease
c. Sickle Cell Anemia
Sex-Linked Disorders:
a. Color-blindness
b. Duchenne Muscular Dystrophy
c. Hemophilia
Cystic Fibrosis
• The most common inherited disease among Caucasians 1 out of 25 is a carrier.
• Autosomal recessive
(7q31.2)
In one form of CF, a mutation in the DNA
causes a binding site on the CFTR
The Normal CFTR Protein in the Lungs:
protein to change shape, and the ATP
will not bind.
Using active transport, a Cl- ion is pumped
ATP will not bind at the mutated site.
across the cell membrane of normal lung
Cl- can not leave the cell. A thick,
cells through a Cl- ion channel.
stringy mucus builds up on the outside
The Cl- attracts water, which moistens the lung cell
of the lung cell membrane.
membrane, helping to produce a thin layer of
The thick mucus provides a home to
mucus.
bacteria which cause deadly infections.
Cl-
P
Tay-Sachs Disease
Warren Tay - Opthalmologist, who described the cherry-red spot on the retina
Bernard Sachs - Neurologist, who first described the changes in the brain
A rare autosomal recessive disorder of the
HEX A gene on the long arm (q) of chromosome 15 between position 23 and 24
Over 100 mutations have been identified
in the HEX A gene - single base
insertions, deletions, missense mutations,
splice phase mutations where introns are
not properly excised, etc. which alters the
gene’s normal protein production of a
lysosomal enzyme.
A progressive deterioration of nerve cells
due to a build up of gangliosides in the
brain’s nerve cells. Mental and physical
deterioration begins around six months of
age, often leading to death by age four.
Other Chromosome 15 Syndromes
Marfan Syndrome
An autosomal dominant disorder caused
by a mutation in the FBN1 gene which
produces fibrilin-1. Fibrillin-1 forms
fibers in connective tissue and is
supposed to bind to TGF-ß (a growth
factor), keeping it sequestered. Without
adequate Fibrillin-1, heart, blood vessels,
bones, joints, and eyes are compromised.
Prader-willi Syndrome
Rare genetic disease where 7 genes on
the paternal chromosome 15 are
deleted or silenced. Extreme and
insatiable appetite- thus often become
obese, narrow at the temple, poor
muscle tone, cognitively IQ’s tend to
range 35 - 85
Angelmann Syndrome
Rare genetic disease where genes on the
maternal chromosome 15 are deleted or
silenced. Seizures, jerky movements
(hand-flapping), happy laughing,
smiling demeanor, severe intellectual
and developmental disabilities.
A. Sickle Cell Anemia
http://www.pbs.org/wgbh/evolution/library/01/2/l_012_02.html
An autosomal recessive disorder caused by a point mutation (substitution) on Chromosome 11 at the
Beta Globin Gene, which is responsible for making hemoglobin, a complex protein structure in red
blood cells - the iron-rich oxygen carrying molecule of the circulatory system in all vertebrates.
Normal Red
Blood Cells
Sickle Cells get
Sickle Cells trapped in capillaries
A mutation occurs in the Beta Globin Gene and:
The codon CTT is changed to CAT, so instead of
making Glu (glutamic acid) --> it makes Val (valine)
1 amino acid change of 146 amino acids =
Sickle Cell Anemia
Heterozygous for sickle cell makes a
person immune to Malaria because
the presence of the protozoan
(transported by the mosquito) causes
the defective red blood cell to rupture
before the protozoan can reproduce.
C. Colorblindness
The Gene for Red Green Vision is carried on the X Chromosome. It is
an X-linked recessive disorder. One mutation causes Red-Green
colorblindness--found almost exclusively in males.
Women have an extra X chromosome, called a Barr Body,
That can serve as a “back up” if the first is faulty
ROYGBIV
What a person with normal color vision
sees.
http://colorvisiontesting.com/
How does the world look to a
color blind person?
YGBIV
What a person with red green colorblindness
sees.
Duchenne Muscular Dystrophy
A recessive, X-linked disorder caused by a
mutation in the dystrophin gene where exons
45 to 54 the short arm (p) of the X
chromosome at Xp21.2 are deleted.
Dystrophin is an important structural
component within muscle tissue providing
structural stability, without sufficient
amounts, leads to muscle degeneration and
eventually death.
Hemophilia
A recessive, X-linked disorder
caused by a mutation in the F8
gene (Classic Hemophilia A Factor VIII deficiency) or F9 gene
(Christmas Disease or Factor IX
deficiency) where normal clotting
proteins are either missing, lacking
or ineffective in coagulation to seal
damaged blood vessels and
prevent excessive loss of blood.