Transcript 14-2 Human Chromosomes - Lincoln Park High School

1. Genes that are located close together
on the same chromosome are linked
2. Those genes may be inherited
together
3. The total human genome (all of the
different genes in humans) is …………
• How many genes make up the human
genome?
• There are 20,000-25,000 genes
in the human genome
1. Sex- Linked
Genes- Any gene
located on a sex
chromosome (X
or Y)
2. Most sex-linked
genes are
located on the X
chromosome
3. Sex-Linked
genetic disorders
mostly affect
males
a) b/c they only
have one X
c’some
b) Many genes
located on the X
c’some do not
exist on the Y
c’some
4. Common Sex-Linked Genetic Disorders
• Colorblindness; a defective gene for vision
color which is located on the X c’some
5. Hemophilia;
results from two
defective genes to
control blood
clotting which are
located on the X
c’some
1.
A scientist Mary Lyon discovered that in
human females one X c’some is randomly
switched off.
• Once the X c’some is turned off a dense area in the
nucleus is formed.
• Barr Body- the dense area of an inactivated X
chromosome
Barr Bodies
2.
3.
The same process
happens in other
mammals
Female cats have
multiple coat
patterns as a
result of X
chromosome
inactivation
1. Nondisjunction- happens when
homologous c’somes do not separate
during meiosis
2. Tisomy- An individual with three copies
of a chromosome
3. Down
Syndrome - a
disorder that
results from an
extra copy of
chromosome 21