DNA (Deoxyribonucleic Acid)
Genetic material of cells…
GENES – units of genetic material that CODES FOR A SPECIFIC TRAITCalled NUCLEIC ACIDS
DNA is made up of repeating molecules called NUCLEOTIDES
A HISTORY OF DNA
Discovery of the DNA double helix
A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (1928)
B. Rosalind Franklin - X-ray photo of DNA.
C. Watson and Crick - described the DNA molecule from Franklin’s X-ray.
Watson & Crick proposed…
DNA had specific pairing between the nitrogen bases:ADENINE – THYMINE
CYTOSINE - GUANINE
CYTOSINE - GUANINE
DNA was made of 2 long stands of nucleotides arranged in a specific way called the “Complementary Rule”
DNA Double Helix
DNA Double Helix
Nitrogenous Bases
PURINES1. Adenine (A)
2. Guanine (G)
PYRIMIDINES
3. Thymine (T)
4. Cytosine (C)
Chargaff’s Rule
Adenine must pair with ThymineGuanine must pair with Cytosine
Their amounts in a given DNA molecule will be about the same.
BASE-PAIRINGS
Genetic Diversity…
Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.The Code of Life…
The “code” of the chromosome is the SPECIFIC ORDER that bases occur.A T C G T A T G C G G…
DNA Replication
DNA must be copiedThe DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing:A-T, G-C
Each strand of the original DNA serves as a template for the new strand See p. 298
DNA Replication
Semiconservative Model:1. Watson and Crick showed: the two strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand.
Parental DNA
Replication Quiz
1. Why is replication necessary?2. When does replication occur?
3. Describe how replication works.
Use the complementary rule to
create the complementary strand:
Replication Quiz
1. Why is replication necessary?So both new cells will have the correct DNA
2. When does replication occur?
During interphase (S phase).
3. Describe how replication works.
Enzymes unzip DNA and complementary nucleotides join each original strand.
4. Use the complementary rule to
create the complementary strand:
(1961) Watson & Crick proposed…
…DNA controlled cell function by serving as a template for PROTEIN structure.3 Nucleotides = a triplet or CODON
(which code for a specific AMINO ACID)
See p.303
AMINO ACIDS are the building blocks of proteins.
DNA Transcription
Both DNA & RNA are formed from NUCLEOTIDES and are called NUCLEIC acids.
DNA Translation
Transcription/Translation Quiz
Why is transcription necessary?Describe transcription.
Why is translation necessary?
Describe translation.
What are the main differences between DNA and RNA.
Using the chart on page 303, identify the amino acids coded for by these codons:
1. Why is transcription necessary?
Transcription makes messenger RNA (MRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm.2. Describe transcription.
RNA polymerase binds to DNA, separates the strands, then uses one strand as a template to assemble MRNA.
3. Why is translation necessary?
Translation assures that the right amino acids are joined together by peptides to form the correct protein.
4. Describe translation.
The cell uses information from MRNA to produce proteins.
5. What are the main differences between DNA and RNA.
DNA has deoxyribose, RNA has ribose; DNA has 2 strands, RNA has one strand; DNA has thymine, RNA has uracil.
Using the chart on page 303, identify the amino acids coded for by these codons: UGGCAGUGC
AMAZING DNA FACTS…
It contains information equal to some 600,000 printed pages of 500 words each!!!
(a library of about 1,000 books)
LET’S REVIEW DNA… LM p.44
List the conclusions Griffith & Avery, Hershey & Chase drew from their experiments.Summarize the relationship between genes & DNA.
Describe the overall structure of the DNA molecule.
What are the 4 kinds of bases?
Post a Comment