Download DNA These “genes” never go out of style!!

DNA
These “genes” never go out of
style!!
Ms. Kooiman
La Serna High School
Chapter 12-1
Vocabulary
Nucleus
Structure found at the center of eukaryotic cells.
Contains genetic information.
DNA
Deoxyribonucleic acid
Chromosomes
Threadlike structures found within the nucleus
containing genetic information passed on
from one generation to the next.
Chromatid
Tightly coiled or condensed DNA wrapped around
proteins.
Centromere
Area where chromatids of a chromosome are
attached.
Gene
Sequence of DNA located on the chromosomes. A
set of codes that determine which protein
will be made.
Scientific History
 1928
– Griffith and Transformation
–The early experiments told
scientists that cells contain some
substance that allows traits to be
passed from one generation to the
next
 1944
– Avery and DNA
–Later experiments showed that
substance was DNA
Scientific History
 1952
– Hershey-Chase Experiment
 1952 – Rosalind Franklin
 1953 – James Watson and Francis Crick
–Experiments beginning in the
1950’s focused on the structure of
DNA
 2000 – Human Genome Project
– Research still continues today to further
understand and map out the each gene
found on the human genome!
DNA Structure
DNA - Deoxyribonucleic acid
 A molecule that enables organisms to
reproduce their genetic information to the
next generation.
 Contains thousands of genes (unit of
inheritance)
 DNA contains information which is
translated into proteins that carry out
most biological functions.

DNA Structure

DNA is a macromolecule
– Nucleic Acid – made up of long chains of
nucleotides
– Nucleotides are made of 3 parts
 Sugar (5 carbon deoxyribose)
 Phosphate group
 Nitrogen base
DNA Structure cont…..
Nucleotides can
have four
different
nitrogen bases
C = Cytosine
T = Thymine
A = Adenine
G = Guanine
DNA Structure cont…..

Nucleotides are
held together
with a
phosphate-sugar
backbone
DNA Structure cont…..
DNA is
double-stranded
 Nitrogen bases
link up and
attach with
hydrogen bonds

Chargaff’s Rules
Adenine = Thymine
and
Cytosine =Guanine
So…..when 2 strands of
DNA bond
A pairs with T
and
C pairs with G
These are called
“complimentary
base pairs”
The Double Helix
 DNA
has a
“Double Helix”
structure
– Two strands
wrap together
like a twisted
ladder or
winding
staircase
The Double Helix
Rosalind Franklin
 Used X-ray diffraction to help find
the structure of DNA
 Purified large amounts of DNA and
stretched the out the parallel strands
 Aimed a powerful X-ray beam and
recorded the pattern on film
 See example of data below….
Major contribution…….X-ray showed
the helical structure of DNA!!
Rosalind Elise Franklin, Ph.D., 1920-1957
Dr. Franklin was educated as a physical chemist.
She made major research breakthroughs in the
understanding of the double-helix structure of
DNA (deoxyribonucleic acid), the building block
of life or the genetic material of living organisms.
Apparently without her knowledge or permission,
Maurice Wilkins shared some of Dr. Franklin’s
data with James Watson and Francis Crick.
Watson, Crick and Wilkins later shared the
Nobel Prize for Physiology or Medicine in 1962
for their discovery of the structure of DNA.
Although this discovery was due in part to Dr.
Franklin’s work, she never received any of the
credit.
Francis Crick and James Watson
Were also working on finding the structure of
DNA through cardboard models
 1953, given Franklin’s X-ray information
 Published findings in a historic one-page paper
explaining that DNA was a double-helix in which
two strands of DNA were wound around each
other.
 Once this was discovered they explained the
base-pairing which explained Chargaff’s rules!!

DNA Summary

Many scientists worked for many years to
determine the structure of DNA, this is
what they found
– DNA is a made up of nucleotides
– Nucleotides are connected by a phosphatesugar backbone
– DNA is double-stranded helix
– Complimentary nitrogen bases bond to link
two strands of DNA