Download DNA vs. RNA - Chavis Biology

DNA vs. RNA
Standard H.B.4: The student will demonstrate
an understanding of the specific mechanisms
by which characteristics or traits are
transferred from one generation to the next
via genes.
Key Concepts

Nucleic Acids:
deoxyribonucleic acid (DNA)
 ribonucleic acid (RNA)


Nucleotides:


nitrogen base, sugar, phosphate group
Complementary base pairs
What you already know…
Students have no previous knowledge of
this concept. It has not been addressed in
previous grades.
It is essential for you to know…

Nucleic acids are organic molecules that serve as the
blueprint for proteins and , through the action of proteins,
for all cellular activity.

The two types of nucleic acids: DNA and RNA

DNA and RNA are both comprised of nucleotides that
each have three parts.

The basic structure of DNA and RNA are different (due
to their sugars).

DNA is double stranded whereas RNA is single
stranded.
Objectives
Compare DNA and RNA.
Recognize the chemical names of the DNA and
RNA molecules.
Identify the three parts of a nucleotide.
Interpret an illustration of a nucleotide.
Interpret an illustration of a DNA and a RNA
molecule.
Vocabulary Words
1.
2.
3.
4.
5.
Bacteriophage
Nucleotide
Double helix
Base pairing rules
Transformation
History:
Griffith & Transformation

1928, Frederick
Griffith

Did experiment to find
out why some
bacteria caused
pneumonia.

Discovered
transformation.
A transforming material passed from dead S
bacteria to live R bacteria, them deadly.
What exactly was transforming? He didnt quite know.
History:
Avery & DNA

1944, Oswald Avery

Repeated Griffith’s work
in order to determine
which molecule in the
bacteria caused it to be
transformed.

Discovered that DNA was
the nucleic acid that
stored and transmitted
genetic material.
History:
The Hershey-Chase Experiment


1952, Alfred Hershey
and Martha Chase
Studied viruses and
discovered
bacteriophages.
The Structure of DNA
DNA: Deoxyribonucleic Acid

A long molecule made up of units called
nucleotides.
phosphate group
deoxyribose (sugar)
nitrogen-containing
base
The Structure of DNA
3 Parts of a Nucleotide

5-carbon sugar


deoxyribose
A phosphate group
Purine

Nitrogenous base




Adenine (purines)
Guanine (purines)
Thymine (pyrimidines)
Cytosine (pyrimidines)
Pyrimidine
The nitrogen containing bases are the only
difference in the four nucleotides. There
can be a total of 4 different nucleotides.
The Structure of DNA
Has to be responsible for three things:
1) Genes
have to carry info from one generation
to the next.
2) Genes have to put that info to work by
determining heritable traits.
3) Genes have to be easily copied during cell
replication.
The Structure of DNA

The backbone of a
DNA chain is formed
by sugars and
phosphates

The nitrogenous
bases stick out
sideways from the
chains like the rungs
on a ladder & can be
joined together in any
way.

The backbone is connected by covalent
bonds.

The bases are connected by hydrogen
bonds.
hydrogen bond
covalent bond
Chargaff’s Rules

Erwin Chargaff

Discovered in any
sample of DNA that:



% of guanine and
cytosine are almost
equal
% of adenine and
thymine are almost
equal
G=C & A=T

Called base pairing
Nucleotides always pair in the
same way.

The base-pairing rules show
how nucleotides always pair
up in DNA.
– A pairs with T
– C pairs with G

Because a pyrimidine
(single ring) pairs with a
purine (double ring), the
helix has a uniform
width.
G
C
A T
X-Ray Evidence


Early 1950s Rosalind Franklin used X-Ray
diffraction to get information about the structure
of DNA.
Suggested that DNA is twisted in some type of
way.
The Double Helix

Francis Crick and
James Watson built
3-D models of DNA to
help understand its
structure.

Discovered that DNA
was a double helix.
The Structure of RNA
RNA: Ribonucleic Acid

A long molecule made up of units called
nucleotides.
phosphate group
ribose (sugar)
nitrogen-containing
base
The Structure of RNA
Nucleotides

5-carbon sugar


ribose
A phosphate group
Purine

Nitrogenous base




Adenine (purines)
Guanine (purines)
Uracil (pyrimidines)
Cytosine (pyrimidines)
Pyrimidine
The Structure of RNA

RNA: ribonucleic acid

Sugar is called ribose.

A disposable copy of
DNA.

Single stranded

Has uracil instead of
thymine like in DNA.
Types of RNA
There are three main types of RNA:
1)
Messenger RNA (mRNA)
carries copies of instructions for the assembly of
amino acids into proteins from DNA to rest of cell
2)
Ribosomal RNA (rRNA)
makes up the major part of ribosomes
3)
Transfer RNA (tRNA)
transfers amino acids to ribosomes during protein
synthesis
Transcription

Transcription is the
process of copying
DNA into RNA.


So that translation can
happen next
Happens in the
nucleus of eukaryotes
and the cytoplasm of
prokaryotes.

Wherever the DNA is