dna the molecule of heredity chapter 11.1. dna - deoxyribonucleic acid contains genetic information...
TRANSCRIPT
DNAThe Molecule of Heredity
Chapter 11.1
DNA - Deoxyribonucleic Acid
•Contains genetic information (genes)
•Strands of repeating molecules that
make up our chromatin and chromosomes
DNA is called the “Blueprint of Life”
Why? • DNA tells cells which proteins to make • The proteins then cause our individual
characteristics
The Structure of DNA- DNA is in a Double-helix shape- It is double-stranded and
wound up like a twisted ladder- 2 strands attached to each other
Discovery credited to James Watson and Francis Crick.
Watson and Crick with DNA Model, 1953.
DNA Structure continued
It is a very long molecule made up of repeating subunits called nucleotides
3 Parts of a Nucleotide
1) Phosphate group
2) Simple sugar-DNA has a Deoxyribose sugar
-RNA has a Ribose sugar
3) Nitrogenous base-A, T, C, or G
4 Nitrogenous Bases in DNA
1. Adenine
2. Thymine
3. Guanine
4. Cytosine
Pyrimidines Purines
Special BasePairing Rules
*Adenine pairs with Thymine:
A-T
T-A
*Cytosine pairs with Guanine:
C-G
G-C
The DNA Strand * Bases held
together by hydrogen bonds.
* Sugar and phosphate are considered backbone
What are the proper pairings for the base strands shown:
1. A T C G T T T A C G C G T
2. T G C T A T A C C G T A A
3. C T A G C G A T G T C G T
Answers
1. A T C G T T T A C G C G T
T A G C A A A T G C G C A
2. T G C T A T A C C G T A A
A C G A T A T G G C A T T
3. C T A G C G A T G T C G T
G A T C G C T A C A G C A
New Strand = Complementary strand
Old Strand = Template Strand
RNA - ribonucleic acid
- Molecules that “read” the DNA and make proteins using the information in DNA
-RNA are the worker molecules.
3 ways RNA is different from DNA
• 1. RNA is single stranded
• 2. RNA has the sugar ribose (not deoxyribose)
• 3. RNA has the nitrogen base uracil instead of thymine.
RNA nitrogenous bases • RNA bases
– Adenine– Uracil (in DNA this is thymine)– Cytosine– Guanine
– Rules: • Same pairing as DNA except a U goes where a T
was in DNA
– A pairs with U (A-U) and C pairs with G (C-G)
RNA base pairing examples
IF the DNA strand is
A T C G G C A T
Then the RNA complement strand is
U A G C C G U A
IF the DNA is
A T A C G T A C G
Then the RNA complement strand is
U A U G C A U G C
Practice Time!
Three types of RNA • mRNA = Messenger RNA
– Carries information from nucleus to cytoplasm (ribosomes in cytoplasm)
• rRNA = Ribosomal RNA– Make ribosomes which are where amino
acids are assembled into proteins
• tRNA = Transfer RNA– Carries amino acids to the ribosome to be
assembled into proteins
DNA Replication - 2 from 1
2. During what phase of the cell cycle does
replication occur?
1. Why do cells need toreplicate their DNA before dividing?
4 Steps to DNA Replication
Step 1: Enzyme (helicase) initiates (starts) replication by unzipping the DNA
Step 2: Another enzyme (DNA polymerase) attaches new nucleotides following base pairing rules
Step 3: Error Checking
As it moves down the strand, the enzyme DNA polymerase:
1. Checks for errors2. Then fixes them
This process is called
proofreading
Mistake causes a bulge
DNA poly. repairs with correct base
DNA poly. finds & piece is cut out
DNA poly. continues down strand
Step 4:Original DNA
Original DNA
New DNA
2 Identical copies-1 old strand (template) -1 new strand (complementary)
Enzymes twist the new strands (creating the double helix)
Steps of DNA Replication
1. Enzyme (helicase) unzips the DNA2. Enzyme (DNA polymerase) attaches
new nucleotides according to base pairing rules
3. DNA polymerase checks for errors and fixes them.
4. End up with two identical daughter DNA strands that enzymes retwist.
STOPPING POINT
DNA Sequencing
Each organisms has a unique sequence of DNA
The closer two individuals are related, the more alike their sequences are.
What are some ways that we use this knowledge?
The Central Dogma
DNA Structure and
Base Pairs
(Adenine) A = T (Thymine)
( Cystosine) C = G (Guanine)