DDeoxyriboeoxyriboNNucleic ucleic AAcidcid

• Chemical code containing the information needed for an organism’s growth and function

History

1952– Rosalind Franklin used an X-ray crystallography technique to discover that DNA is made of two spiral chains

History

1953– James Watson and Francis Crick built on Franklin’s and many other scientists’ research to make the first DNA model. . . The Double Helix

Crick Watson

The

first

DNA

model

Photo #51

DNADNA Structure• It’s like a

ladder. . .the sides are the deoxyribose (sugar) and phosphate backbones and the rungs are the nitrogen bases.

Deoxyribose and phosphate group

Nitrogen bases

Four Nitrogen Bases

Stuff to remember. . .

amount of Cytosine = amount of Guanine and

amount of Adenine = amount of Thymine

So. . .

The bases occur in pairs in DNA!!!

Four Nitrogen Bases

Adenine Thymine

Guanine Cytosine

What is DNA Synthesis???

• The copying of DNA

Why copy DNA???

•To make new cells

Steps to synthesis. . . 1. An enzyme attaches to the starting point on

DNA.

2. The enzyme unzips the DNA to start copying.

3. New nitrogen bases attach to original DNA strands.

4. Two new, complete DNA strands are formed.

Let’s see it!!

RNA• RiboNucleic Acid• Carries codes from the nucleus to

the ribosome to make proteins• Guanine = Cytosine• Adenine = ???• Adenine = Uracil• 3 types of RNA

RNA• Messenger RNA- mRNAmRNA

– Sends code from nucleus to the ribosome

• Ribosomal RNA- rRNArRNA– Makes up the ribosome

• Transfer RNA- tRNAtRNA– Brings amino acids to the ribosome to make

proteins

Protein SynthesisProtein SynthesisStep 1: DNA Transcription

Step 2: DNA Translation

Step 1: DNA Transcription

Step 2: DNA Translation

DNA Transcription• Enzyme unzips DNA

• DNA is synthesized into RNA (mRNA, rRNA, or tRNA)

• RNA strand releases from the DNA after being copied

• DNA is zipped back into position by the same enzyme

• New RNA is transported outside the nucleus of the cell

DNA TranslationDNA Translation• mRNA binds to the rRNA of the ribosome

and signals it is ready to be translated

• One end of tRNA which is 3 nitrogen bases (a codon) that code for a specific amino acid binds with mRNA

• The mRNA binds several different tRNA units connecting the amino acids to make a protein

UGA. . .UGA. . .

More than just a university,More than just a university,

It’s also a stop codon!!It’s also a stop codon!!

What’s a codoncodon???

• It’s the basic unit of genetic code.

• 3 nitrogen bases = 1 codon

• Can signal to start or stop a process or can stand for a certain amino acid

• Examples: UGA, UAA, and UAG are stop codons for the translation process