Nucleus• Structure: Surrounded by

nuclear envelope with pores; contains genetic information (DNA)

• Function: Contains the genetic information that gives the cell instructions to make proteins

The way the nucleus gives instructions to cells is called Central Dogma

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Central Dogma

RNA

Protein

DNA

• Describes the flow of information in a cell:

1. Genetic information is stored in DNA 2. It is transferred into individual

transportable copies, made of RNA (mRNA=messenger RNA)

3. Each mRNA copy transfers the information to make one particular protein.

• Central Dogma was proposed by Crick (1958)

Central Dogma

RNA

Protein

DNA deoxyribonucleic acid

Player #1: DNA

DNA structure: key to the central dogma

• DNA is double stranded• The two DNA strands

run in opposite directions

• Uses 4 bases – A, G, C, T

• Fixed base-pairing rules– A-T– G-C

• Each strand is complementary to the other:

ATGGATTACCTA

Central Dogma

RNA

Protein

DNA

ribonucleic acid

Player #2: RNA

RNA

• Single stranded molecule• Uses 4 bases

– A, G, C, U

• Can fold on itself• Base pairing rules:

G-CA-U

• RNA has 3 types of RNA:– mRNA (messenger RNA)– tRNA (transfer RNA)– rRNA (ribosomal RNA)

• Each type has a different job

Player #3: Proteins

• Chains of amino acids (aa)

• 20 different aa can be used

• Different order of aa= different functions for proteins

Central Dogma

RNA

Protein

DNA

Antibodies (www.biology.arizona.edu/.../ graphics/ribbons.gif)

Insulin

Examples of Proteins made through Central Dogma:

Transcription

• The process by which a new RNA molecule is formed from DNA.

RNA

Protein

DNA

Transcription

Central Dogma: Step #1

Transcription1. The two strands of DNA are opened up

2. One strand is used as a template

3. A new RNA molecule is formed on the template

RNADNA

RNApolymerase

Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)

Copyright Pearson Edication Inc.

Analogy: Original handwritten precious grandma’s chocolate recipe (1 DNA strand )

Your new handwritten copy to bring home (RNA)

12 2

3

Translation

• The process by which the information carried by the RNA is used to make proteins at the Ribosomes.

RNA

Protein

DNA

Transcription

Translation

Central Dogma: Step #2

mRNA

Ribosome

Methionine

Phenylalanine tRNALysine

Translation• The cell uses information from

the RNA to produce proteins.• The “code” is read in triplet form

called a codon: every three bases on mRNA has information for only one amino acid.

• The 3 types of RNA have different jobs at this point:– mRNA brings the message– tRNA brings the amino acid– rRNA + other proteins forms

the ribosome where translation happens

Codon Charts:

• I prefer this one: • But this is one seen in many textbooks:

Genetic Code

• The Central Dogma dictionary: – from “DNA/RNA language” to “protein

language”– Use the Codon Chart

• An analogy of this is:– Grandma’s special recipe is in German and

when it is being rewritten it is translated into Spanish.

– Use the dictionary

www.stanford.edu/.../ f_ae01centralDogma.gif

Summary of Central Dogma