DNA AND PROTEIN SYSNTHESIS

DNA PROTEIN

What structures are found in the nucleus?

What is a gene? • Gene: a portion of DNA that contains

the codes (instructions) for one protein.

GENE

• A gene is a sequence of nucleotides that has the code (instructions) for making a specific protein

• The average gene is 3000 bases

• Total number of genes is 30,000 to 35,000

Protein Synthesis

The building of proteins from amino acids

• Why are proteins important?

–Make up important structures like muscles and cell membranes.

– Substances like enzymes, antibodies and hormones are made of proteins

– Traits like hair and eye color are the results of proteins

RIBOSOME

Where is DNA?

Where are proteins made? ribosome

• Where are proteins synthesized ?

By the ribosomes

In the cytoplasm.

• What are proteins made of?

–Proteins are long chains of amino acids

– There are 20 different amino acids

• The instructions for making proteins

(the order of the amino acids in a particular protein)

are encoded in the DNA

(the code)

CODON • Codon – a set of

three nitrogenous bases that represents an amino acid

Codon

• The bases are arranged in threes called codons.

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

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

Protein Synthesis takes

place in 2 stages

transcription

translation

RNA • RNA

– Ribonucleic acid

– RNA is similar to DNA but is single stranded

– RNA contains the sugar ribose (not deoxyribose)

– The nitrogen base uracil replaces thymine

Three Types of RNA • Messenger RNA

(mRNA)

– Is formed in the nucleus

–Carries the instructions from the DNA in the nucleus to the ribosomes in the cytoplasm

–“The Messenger”

CODON • Order of nitrogen

bases in mRNA that determines the type and order of amino acids in a protein

• mRNA has the CODON!

• There are 64 possible codons, but only 20 amino acids to code for

TRANSFER RNA • Transfer RNA (tRNA)

– Carries amino acids from the cytoplasm to the ribosome.

–Has the anticodon

– “The Worker”

RIBOSOMAL RNA (rRNA)

– The ribosome is made of rRNA.

Transcription

• During the production of proteins the “blueprints” (instructions) are located in the nucleus, in a code in the DNA

• DNA acts as a template for making messenger RNA

Complementary base pairing

DNA Base Complementary RNA

Base

G

C

A

T

C

G

U

A

Transcription

• mRna picks up the triplet code from the DNA

• m RNA leaves the nucleus.

• A ribosome attaches to the mRNA.

• The instructions carried by the mRNA will be used to assemble the amino acids in the proper order

•The instructions (codon) are

then carried to the cytoplasm

Translation

• The amino acids are brought to the ribosomes by the tRNA molecules to be assembled into a protein (translation)

• The order of the amino acids is determined by the codon on the mRNA

Protein Synthesis • The tRNA

anticodon pairs with the mRNA codon

• The tRNA releases the amino acid which bonds to the other AA ‘s forming a chain = protein

MUTATIONS

Mutations • If DNA is not copied exactly, proteins

made from its instructions could be made INCORRECTLY

• Mutation: any permanent change in the DNA sequence in a gene or chromosome.

• Factors that cause mutations: X rays, sunlight, and some chemicals

Results of a Mutation

• Genes control the traits you inherit.

• Without correctly coded proteins, an organism can’t grow, repair, or maintain itself.

• A change in a gene or chromosome can change the traits of an organism.

Results of a Mutation

• If the mutation occurs in a body cell, it might not be life threatening to the organism.

• If a mutation occurs in a sex cell, then all the cells that are formed from that sex cell will have that mutation.

Results of a Mutation

• Many mutations are harmful to organisms, often causing their death.

• Some mutations do not have any effect on the organism.

•Some mutations can be helpful and

give the organism a better chance of

surviving.

DNA and Mutations –

Lets looks at different mutations

THE DOG BIT THE CAT

Mutations - Substitution

THE DOG BIT THE CAT

• Substitution - Replace just one letter:

THE DOG BIT THE CAR

Deletion

THE DOG BIT THE CAT

• Deletion: Delete just one letter (T):

THE DOG BIT HEC AT

Insertions

THE DOG BIT THE CAT

• Insertion - Add just one letter (E):

THE DOE GBI TTH ECA T

Cells have “proof reading” proteins that

constantly check the DNA and fix errors, so most

are corrected