Modern Biology
Chapter 10

10-1

DNA full name is
DeoxyriboNucleicAcid

The monomer of nucleic acids…

Structure of DNA
• Basic Structure
 three basic components
 deoxyribose: 5 C sugar

Structure of DNA
•
Basic Structure
 three basic components
 phosphate group (PO
4
) 3-

Structure of DNA
Basic Structure three basic components nitrogenous base adenine (A) guanine (G) thymine (T) cytosine (C)

Structure of DNA
•
The double helix
 many scientists worked to solve the structure of
DNA

• Concluded that A must bond with T and C with G

Structure of DNA
•
The double helix
 many scientists worked to solve the structure of DNA

Rosalind Franklin
 took X-ray photographs of DNA
 died in 1958 without recognition for her enormous contribution

Structure of DNA
•
The double helix
 many scientists worked to solve the structure of
DNA

Wilkins
 received Nobel prize with Watson and Crick

Structure of DNA
•
The double helix
 many scientists worked to solve the structure of
DNA

Watson and Crick
 first to construct a model of DNA molecule
 received Nobel prize for their work in 1962

Primarily piggy-backed on others’ work, but were the first to put the pieces together correctly

Structure of DNA
The double helix
 two nucleotide chains that wrap around each other
 base-pairs form the rungs of the ladder

Structure of DNA
•
The double helix
 alternating chains of phosphate groups and deoxyribose molecules form the backbone of the structure
 all rungs are of equal length
 approx. 10 base pairs per turn of DNA molecule

Structure of DNA
•
Complementary base pairing
 to ensure that the rungs are of equal length nucleic acids pair up
 base-pairing rules
 cytosine bonds with guanine (C-G)
 adenine bonds with thymine (A-T)

Structure of DNA connected by hydrogen bonds

C and G share
3 H-bonds

A and T share
2 H-bonds

Replication of DNA
• replication: process of copying DNA
 the steps:
 double chains must separate between the nucleic acids
 replication fork: point at which the chains separate
 helicase: enzyme that breaks apart DNA molecule
 nucleotide bases match up with their compliments
 DNA polymerase: enzyme that assembles new bases to original strand

Replication of DNA
• replication: process of copying DNA
 complimentary bases allow for accurate replication
 new strands of DNA actually contain one old strand and one new strand

Types of replication possible with a double strand

Animation Illustrating DNA Replication by
Complementary Base Pairing
• More complex view

Replication of DNA
•
Accuracy and Repair
 highly accurate with only 1 error per 10,000 pairs
 mutation: change in a nucleotide sequence

Replication of DNA
•
Accuracy and Repair
 proofreading and repair reduce error rate to
1 error per 1,000,000,000 base pairings
 enzymes proofread and repair any errors that are identified

Equivalent to 1,488,095 copies of Huckleberry
Finn

Replication of DNA
•
Accuracy and Repair
 some factors increase the rate at which DNA mutates
 radiation
 certain chemicals
 sun light

Excited electrons run around uncontrollably and cause problems.
We use this trait for helping patients battle cancer- chemo therapy.

Modern Biology
Chapter 10

Structure of RNA
• full name is RiboNucleic Acid

Structure of RNA basic structure
 backbone of phosphate groups and ribose
 single stranded
 uracil (U) replaces thymine in pairing with adenine

Types of RNA
• mRNA: messenger RNA
 carries copy of DNA strand from nucleus to ribosome
 single, uncoiled chain

Types of RNA
• tRNA: transfer RNA
 carries specific amino acids to ribosomes to pair with mRNA
 single chain (about 80 base pairs long) folded into a hairpin like shape

Types of RNA rRNA: ribosomal RNA

Along with proteins rRNA forms ribosomes
 globular form

Transcription
• process where genetic information is copied from DNA to RNA
•
ANIMATION OF THE PROCESS OF
TRANSCRIPTION

Transcription
• steps of transcription

RNA polymerase binds to DNA in specific sites called promoter regions

DNA unzips and nucleic bases follow complementary base-pairing rules

Termination sequence marks end of transcription
• products of transcription are all forms of
RNA
•
Movie Time

• DNA unzips
• RNA polymerase does it’s thing
• RNA is formed

Section 12-3
RNA can be
Messenger
RNA
Ribosomal
RNA
Transfer
RNA also called mRNA which functions to
Carry instructions also called rRNA which functions to
Combine with proteins also called tRNA which functions to
Bring amino acids to ribosome from to to make up
DNA Ribosome Ribosomes

Protein structure and composition
• proteins are polymers
• made up of long chains of amino acids
•
20 different amino acids
• proteins fold into specific shapes based on the sequence of amino acids

• genetic code determines sequence of amino acids in proteins nucleolus mRNA
DNA

• genetic code determines sequence of amino acids in proteins

The genetic code
• codon: each triad (group of three bases) on mRNA
 each codon codes for a specific amino acid
 many codons may code for the same amino acid
 start codon (AUG) codes for methionine
 stop codons (UAA, UAG, UGA) cause the ribosomes to disengage

Translation
• process of assembling amino acids to form proteins
• tRNA and anticodons
 amino acids are transported to ribosomes on tRNAs
 tRNAs have anticodons which match up with codons on mRNA

Translation
• ribosomes
 site of protein synthesis
 three binding sites
 mRNA binds to one
 two tRNAs with anticodons complementing the codons on mRNA bind to other two

Translation
• protein assembly
 ribosome attaches to start codon (AUG)
 first amino acid in every polypeptide is methionine
 ribosome moves along mRNA matching complementary tRNAs with the amino acids along the way
 amino acids form peptide bonds to form polypeptide chains
 ribosomes move 3 base pairs at a time (1 codon)
 stop codon ends process

• Raven's
• Test your “mad DNA” skills

Explain this to your neighbor!

• ANIMATION OF THE PROCESS OF
TRANSLATION
• Animation of Protein Folding

•the letters of the genetic alphabet are the nucleotides A , T , G , & C
•unit of information is CODON = genetic 'word'
 a triplet sequence of nucleotides CAT in a polynucleotide
 3 nucleotides = 1 codon (word) = 1 amino acid the definition of (codon) word = amino acid

≈ 3,000,000,000 base pairs or 1.5b in single strand genes
≈ 500,000,000 possible codons (words or amino acids)

to put it in perspective… average page your textbook = approx 850 words thus, the human genome is equal to
590,000 pages or 470 copies of bio text book reading at 3 bases/sec it would take you about
47.6 years @ 8h/d - 7d/w

Mice & humans (indeed, most or all mammals including dogs, cats, rabbits, monkeys, & apes) have roughly the same number of nucleotides in their genomes -- about 3 billion bp.