Unit4 – Lecture3

DNADNA = De-oxy-ribo-nucleic Acid

“blueprint” for traitsdouble helix shapecomposition:

polymer of nucleotide monomersnucleotide [3 parts]:

sugar [deoxyribose]phosphatenitrogen base

Nitrogen BasesNitrogen Bases:

are complementary:adenine [A] bonds with thymine [T]cytosine [C] bonds with guanine [G]

Nitrogen Bases – cont’dNitrogen Bases:

amount of A = amount of Tamount of C = amount of G

purines: A & Gpyrimidines: C & T

Discuss

With what you just learned, find the answer to the following math problem:

If your cells contained 12% adenine, how much of each of the other

nitrogen bases do your cells contain?

Discuss If your cells contained 12% adenine, how much

of each of the other nitrogen bases do your cells contain?

if A = 12% then T = 12% total = 24% A&T

100% - 24% = amount of C&G76% = amount of C&G

76 / 2 = amount of C or amount of GC = 38%, G = 38%

DNA – cont’dWatson & Crick [1953]

proposed the structure of DNAstole the work of Rosalind Franklin

X-Ray Crystallography

DNA Replication happens in the cell nucleusoccurs during interphase

DNA Replication – cont’denzyme unzips DNA double strand by

breaking the hydrogen bonds between basesfree-floating bases bond to open DNA

DNA Replication – cont’dcontinues…end result = 2 strands, ½ new & ½ old DNArepeat.

RNARNA – Ribo-nucleic Acid

sugar = ribose [instead of deoxyribose]single strandedhas nitrogen base Uracil instead of

ThymineA bonds with UC bonds with G

Discuss

Restate to your partner what the three differences are between RNA and DNA.

RNA – cont’d

Codon Chart

RNA – cont’d[RNA]

[three types:]tRNA – transfer

ferries amino acids to ribosomecontains “anticodons”

complementary to mRNArRNA – ribosomal

makes up the ribosomes

RNA – cont’d[RNA]

[three types:]rRNA – ribosomal

makes up the ribosomes

Discuss

Name and explain the three types of rna to your partner.

Protein SynthesistransCription

DNA mRNAoccurs in the

nucleusprocess begins at

“promoter”promoter tells

where to start copying DNA sequence

Protein SynthesistransCription

enzyme unzips DNA but RNA bases pair instead of DNA basescomplementary

bases are added

Protein SynthesistransCription

continue adding bases until a “termination sequence” is located.

mRNA carries message outside of the nucleus through nuclear pores into the cytoplasm

Protein SynthesistransLation

mRNA proteinribosomes read

mRNA and use tRNA to make proteins

steps:

Protein SynthesistransLation

ribosomes clamp onto mRNA strand

finds “start” codon [AUG]

tRNA molecule containing matching anti-codon moves to ribosome

tRNA enters ribosome; attaches to strand

Protein SynthesistransLation

another tRNA enters ribosome

ribosome bonds amino acids [peptide bond]

first tRNA leaves, another enters

repeat until “stop” codon is reached

Write this down!

Any nitrogen bases that are BEFORE the “start”

or AFTER the “stop”

are NOT translated into amino acids.

Protein SynthesistransLation

result – chain of amino acids linked by peptide bonds= polypeptide= proteinpolypeptide

processed and shipped using ER & Golgi.

Let’s Try ItC C A T A C G G T G T C T C C G A T A T T

T T Ais this DNA or RNA? how do you know?transcribe the DNA into mRNA

C C A T A C G G T G T C T C C G A T A T T T T A

G G U A U G C C A C A G A G G C U A U A A A A Ufind the start codon [AUG]

G G U A U G C C A C A G A G G C U A U A A A A U

Let’s Try ItG G U A U G C C A C A G A G G C U A U A

A A A Ubeginning with AUG, separate your

mRNA into codons.A U G / / C C A / / C A G / / A G G / / C U A / / U A

A / / A A Ubeginning with your AUG, translate

your mRNA into amino acidskeep translating until “stop” codon is

reached

Codon Chart

Let’s Try ItA U G / / C C A / / C A G / / A G G / / C U A / / U A

A / / A A U MET / / PRO / / GLN / / ARG / / LEU / /

(stop)