DNA, RNA and

PROTEIN SYNTHESIS

sections 12.3 and 12.4

What is protein synthesis?

What is the relationship between

DNA and RNA

and protein synthesis?

What functions do proteins

perform in living things?

Ribonucleic Acid (RNA)…

• organic compound (contains C+H)• polymer - composed of monomers called nucleotides• composed of a SINGLE STRAND of nucleotides • carries out protein synthesis (the making of proteins)

3 types of RNA…. messenger RNA (mRNA) transfer RNA (tRNA) ribosomal RNA (rRNA)

Ribonucleic Acid (RNA)

RNA takes on 3 different shapes.

All are used in protein synthesis.

Transfer RNAMessenger RNA

Ribosomal RNA

RNA nucleotide has 3 parts…

1. a ribose sugar covalently2. a phosphate group bonded3. a nitrogen base

of which there are 4 kinds - A, U (uracil), C,G

In RNA – uracil takes the place of thymine

In RNA…. A pairs with U C pairs with G

RNA nucleotide structure:

Phosphate GroupNitrogen Base (A, U, C, G)

Ribose Sugar

RNA nucleotide structure:

PHOSPHATE GROUP

RIBOSE SUGAR

NITROGEN BASE

(A, U, C, G)

RNA differs from DNA:

RNA has… 1. ribose sugar

(instead of deoxyribose) 2. a single strand of nucleotides

(instead of a double helix) 3. the N base uracil

(instead of thymine)

Transcription…the process of making RNA from DNA

template2 steps:

1. an enzyme separates N-bases of DNA

2. a complementary RNA chain is made

the RNA breaks away and

the DNA reforms

3 products: mRNA, tRNA, rRNA

Messenger RNA (mRNA)

• linear form

• carries the message from nucleus to a ribosome (site of protein synthesis)

mRNA

3 N bases = codon

each codon codes for a specific amino acid

Transfer RNA (tRNA)

• “t” shaped

• transfers amino acids to the site of protein synthesis (ribosome)

tRNA

3 N bases = anticodon

anti-codons align with codons on mRNA

Ribosomal RNA (rRNA)

• globular form

• makes up ribosomes

• this is where protein synthesis occurs

rRNA

Importance of Protein…

Your body uses the proteins you eat (the amino acids you ingest)

to make specialized proteins

that have specific jobs!!!

LIKE…. Insulin, Actin, Hemoglobin, Collagen and Elastin, Pepsin and Trypsin and other enzymes, Antibodies and many, many more…..

You need protein !!!!

PROTEIN TYPES FUNCTIONS EXAMPLE

enzymes catalyze specific reactions TRYPSIN PEPSIN

S structural proteins

strengthen cells COLLAGEN

storage proteins store nutrients ALBUMIN in egg white

transport proteins transport substances HEMOGLOBIN transports oxygen RBC’s

regulatory proteins control cell actions INSULIN hormone important in regulation

of blood sugar

motile proteins involved in cell movement ACTINprotein in muscle cells important

in contraction

protective proteins defend cells ANTIBODIES produced by some types of WBC’s

Proteins are the MOST VERSATILE cellular components

Translation….the making of proteins from the information encoded in DNA

this process makes ALL types of proteins

amino acids polypeptide chain proteinoccurs at a ribosome (site of protein synthesis)

In this process all 3 types of RNA are used . . . . . mRNA carries the instructions for making a protein tRNA transfers amino acids (materials) to the ribosome rRNA assists in the binding of mRNA and tRNA

Steps in Translation

1. mRNA leaves nucleus and goes to ribosome

2. tRNA carries amino acids to ribosome

3. codons (on mRNA) + anticodons (on tRNA) align and bring amino acids into their correct sequence

4. When100 amino acids are assembled = polypeptide chain

5. polypeptide chains will detach and wrap with other chains to form a protein

* process only begins with a start (AUG) codon

* process will only stop with a stop codon (UGA, UAG,…)

A look at translation…

Let’s look at it again

RNA Editing –

RNA molecules require a bit of editing before they are ready to go into action

Introns – a non-coding sequence of RNA

(does not code for a protein)

“a deleted sequence of RNA”

Exons – an expressed sequence of RNA

Introns – Deleted sequence of RNA Exons – Expressed sequence of RNA

The Genetic Codeamino acids polypeptide chains proteins

the genetic code is read 3 letters at a time

example - AUG, CAA, UCG, ACC, GAC

each sequence of 3 letters “codes” for

a specific amino acid

as amino acids are put into a specific order

they produce a specific type of protein

MUTATION = a change in the DNA (nucleotide) sequence

mutations may be helpful, harmful or have no affect at all mutagens – substances which cause mutations body cell mutation versus sex cell mutation

Mutations are of 2 kinds:• GENE MUTATIONS• CHROMOSOME MUTATIONS

GENE MUTATIONS• a mutation in a single gene• it may involve 1 or several nucleotides

GENE = REGION/SEGMENT OF DNA THAT CODES FOR A PARTICULAR TRAIT

POINT MUTATIONS

mutations that affect 1 nucleotide

substitution, insertion (addition) or deletion

original sequence ACC,UUA,GAC…

substitution ACG, UUA, GAC…

insertion ACC, CUU, AGA, C…

deletion _CCU, UAG, AC…

FRAMESHIFT MUTATIONS

a point mutation caused by the INSERTION or DELETION of a single nucleotide

results in a shift of the “frame of reference” in the reading of the N base sequence

original sequence ACC,UUA,GAC…

insertion ACC, CUU, AGA, C…

deletion _CCU, UAG, AC…

CHROMOSOME MUTATIONS

– involve segments or whole chromosomes

types of chromosome mutations include: deletion, inversion, translocation, nondisjunction

we have already studied these

Gene Regulation the ability to control (regulate) which genes are

transcribed (“turned on”) different genes may be transcribed (“turned on”) at

different times during an organism’s life a gene is expressed or “turned on” only if

transcription occurs

OPERON – segment of DNA that contains the genes for the proteins to be transcribed

OPERATOR – segment of DNA that acts as an on/off switch for transcription

Special Genes

Hox Genes (or homeobox genes) genes that determine the basic body plan of an

organism control what body part will develop in a given

location control DIFFERENTIATION - process through which

the cells become specialized in structure and function

a mutation in one of these genes can completely change the organs that develop in specific parts of the body

Special GenesOncogenes – genes that promote uncontrolled cell division which may

lead to cancer – genetic mutations may result to the activation of oncogenes

Tumor Suppressor Genes – genes that act to prevent DNA damage and inhibit uncontrolled cell division which may prohibit cancer development

ONCOGENES AND TUMOR SUPPRESSOR GENES ARE THOUGHT

TO BE IN A PERPETUAL TUG-OF WAR

Remember, a gene is not “turned on” until it goes through transcription

To summarize:

1. TranscriptionDNA RNA

2. TranslationRNA Protein