Transcript How is DNA packed in the nucleus?

HUMAN GENOME PROJECT
HOW DOES DNA ORGANIZE ITSELF
INTO A CHROMOSOME?
a. DNA is a double
helix molecule.
b. DNA coils around
proteins called
histones (similar to
spools of thread).
c. DNA supercoils
itself (like a
telephone cord).
d. DNA is then
organized into 2
sister chromatids
connected together
at the centromere.
WHAT IS THE HUMAN GENOME
PROJECT?
From 1990 to 2003, scientists from the National
Institutes of Health and the U.S. Department of
Energy worked together to…
 determine the sequence of the 3 billion chemical
base pairs that make up human DNA
 identify all of the 20,000 to 25,000 genes in
human DNA
 store this information in databases
 address the ethical, legal and social issues that
arise from this project
WHY IS THE HUMAN GENOME PROJECT
IMPORTANT?
to compare human sequences with other
species to provide insight into human
embryonic development and genetic
relationships
 to identify genes associated with diseases
 to develop of treatments and preventions
for genetic disorders

FUN FACTS ABOUT THE HUMAN
GENOME


The human genome
contains about 3 billion
chemical nucleotide bases
(A, C, T, and G).
The average gene
consists of 3000 bases,
but sizes vary greatly,
with the largest known
human gene being
dystrophin at 2.4 million
bases.
Chromosome Poster



Chromosome 1 has the
most genes (2968), and
the Y chromosome has the
fewest (231).
The total number of genes
is estimated at 20,000 to
25, 000 Almost all (99.9%)
nucleotide bases are
exactly the same in all
people.
The functions are unknown
for over 50% of
discovered genes.
Can you make a relationship between the number of chromosomes
and the complexity of an organism? Why or why not?
TRISOMY 21: DOWNS SYNDROME
How do you
think this
individual
inherited an
extra
chromosome?
HINT: Think
about
meiosis!
HOW CAN CHROMOSOMES BE
DAMAGED?





Nondisjunction – a pair of homologous
chromosomes or sister chromatids fail to
separate during meiosis. i.e. Downs syndrome
Duplication- part of a chromosome is repeated.
Deletion- part of a chromosome is lost
Inversion- part of chromosome is reversed
Translocation- part of chromosome attaches to a
non homologous chromosome
WHAT KIND OF INFORMATION IS
PROVIDED IN A PEDIGREE?
A pedigree is a family tree that records
and traces the occurrence of a trait in a
family.
 It can determine whether a trait is
inherited.
 It shows how a trait is passed from one
generation to the next.
 It can determine if an allele is dominant or
not.

HEMOPHILIA: THE ROYAL DISEASE
What is the inheritance pattern for hemophilia?
How does a pedigree enable you to determine it?
HOW ARE GENETIC DISORDERS
INHERITED?
An individual with one copy of a recessive
allele is called a carrier.
 Since most genetic disorders are
recessive, they are self limiting.
 Males more commonly exhibit sex linked
traits because they only need one
recessive allele located on the X
chromosome.
