1. Humans share most of the same protein families with worms, flies, and plants

2. Hair grows by forming new cells at the base of the root. As they move upward through the skin they are cut off from their nutrient supply and start to form a hard protein called keratin in a process called keratinization. As this occurs, the hair cells die. The dead cells and keratin form the shaft of the hair.

3. Fingernails grow about three or four times as quickly as toenails

4. Each hair grows about 1/4 inch/month and grows for up to 6 years.

5. The most expressive muscles are the facial muscles. We need 17 muscles to smile and 43 muscles to frown.

6. The most numerous are the skeletal muscles. When we walk for instance, we use 200 muscles.

It is expected that students will… •Demonstrate knowledge of the basic steps of protein

synthesis, identifying the roles of DNA, mRNA, and ribosomes in the processes of transcription and translation. (p. 481-486) •Determine the sequence of amino acids coded for by a specific DNA sequence, given a table of mRNA codons. (p. 481) •Give examples of two environmental mutagens that can cause mutations in humans. (p. 490)

•Use examples to explain how mutations in DNA affect protein synthesis and may lead to genetic disorders (p. 490)

Unit E Protein SynthesisUnit E Protein Synthesis

_____ Adenine_____ Anti-codons_____ Central Dogma_____ Code_____ Codon_____ Complementary Base_____ Cytosine_____ Elongation_____ Endoplasmic reticulum_____ Exocytosis_____ Gene_____ Gene mutation_____ Genetic code_____ Golgi body/Apparatus_____ Guanine_____ Helicase_____ Histones_____ Hydrolytic enzymes_____ Initiation_____ Initiation codon_____ Messenger RNA (mRNA)

_____ Mutagen_____ Mutation_____ Peptide bonds_____ Peptidyl Transferase_____ Point mutation_____ Polypeptide_____ Polysome_____ Protein_____ Protein synthesis_____ Ribosomes_____ RNA Polymerase_____ Template_____ Terminator codon_____ Thymine_____ Transcription_____ Transfer RNA (tRNA)_____ Translation_____ Triplets_____ Uracil_____ Vesicle

PROTEIN SYNTHESIS

CRASH COURSE VIDEO:http://www.youtube.com/watch?

v=itsb2SqR-R0

1. Structural: proteins help make up all structures in living things

b) Keratin: nails, hair, horns, feathers

a) Actin & Myosin: (muscle proteins)

c) Collagen: bones, teeth, cartilage, tendon, ligament, blood vessels, skin

matrix

b) antibodies

c) Membrane proteins

d)

2. Functional: other proteins help us to keep our bodies functioning properly and to digest our food.

Hemoglobin

a) Enzymes: lower the energy of activation to digest our food and to assist in cellular metabolism.

A gene is a section of DNA that determines the 10 sequence of amino acids in a protein.

Therefore, the gene determines the shape and therefore, the function of the protein it codes for.

Protein structure is determined by the genetic code in your DNA. The section of DNA that codes for one protein is called a gene

(rRNA)(rRNA)

If the process of protein synthesis were a play, these would be the roles of all of the people involved

The director who has the master plan Three assistant directors

The cast

The stage

The stage crew

DNA (genes)mRNA, tRNA, rRNA

Amino acids

Ribosome

Enzymes

Act One: Transcription (Trans = across, cription = to write)

The coded message of a gene on DNA has specific instructions on how to make each particular protein that our bodies need

DNA mRNA

A

T

C

G

U

A

G

C

The instructions from a gene are copied from DNA to messenger RNA (mRNA) in the nucleus

Then, the mRNA moves through the nuclear pores and into the cytoplasm where the proteins are made.

The process of making mRNA is called TRANSCRIPTION

Watch the General Process

Step 1: Helicase unwinds the DNA (starting at the promoter).Step 2: Complementary RNA base pairs attach to form the mRNA strand

Step 3: RNA polymerase forms the RNA sugar-phosphate backbone and checks for mistakes

Step 4: The RNA detaches & leaves the nucleus, & the DNA winds back up

Take a closer look (how the RNA strand

forms)

Act Two: Translation

 The mRNA code is made up of groups of three nucleotide bases known as codons. Each codon codes for a specific amino acid.

Eg. AGC = Serine Eg. UGC = Cysteine

CAU?

GGC?

CUU? UGA?

AUG?

AAA?

(see text table 10-3, (see text table 10-3, p.172)p.172)

TRY IT!!!TRY IT!!!

It takes 3 nucleotides on the mRNA to code for 1 a.a.

Why a Triplet Code?

Why?

With a single nucleotide, there are only 4 possible codes (41). For two nucleotides, there are only 16 possible codes (42). However, for three nucleotides there are 64 possible codes (43), and that is enough to code for the 20 amino acids.

We must code for 20 different amino acids and there are only 4 letters (nucleotides) in the alphabet.

mRNA codon chart(see text table 10-3, (see text table 10-3, p.172)p.172)

•The written code (codons) on mRNA is ‘translated’ into a specific amino acid sequence by ribosomes in the cytoplasm.

•This is carried out with the help of relatively small transfer RNA (tRNA) molecules.

Translation

A tRNA molecule is a small piece of RNA that has a specific amino acid attached to it.

The tRNA also has a special sequence of 3 nucleotide bases known as an anticodon.

There is at least one type of tRNA for each of the 20 amino acids.

As the correct amino acids are brought to the ribosome by the tRNAs, they are joined together via dehydration synthesis to form the protein that the original DNA coded for.

Please note that there is more than one codon for each amino acid:

mRNA codons: U C U G C C

tRNA anti-codons:

SERINE ALANINE

Why do you think that is?Why do you think that is?

A G A

C G G

1. The mRNA molecule moves through a pore in the nuclear envelope and in to the cytoplasm. It joins with a ribosome and is translated one amino acid at a time.

The Steps of Translation:

2. ‘INITIATION’: the first codon on any mRNA molecule is called the ‘INITIATOR’. This codon is always AUG, which codes for the amino acid methionine. This is a message to START translation.  

This makes it possible for a peptide bond to be formed between the amino acids attached to the tRNA molecules. These amino acids chains make up the protein.

The enzyme that catalyzes this reaction is called PEPTIDYL TRANSFERASE.

3. ‘ELONGATION’: the ribosome’s job is to position the tRNA molecule onto the matching mRNA molecule.

The 1st tRNA leaves, the ribosome moves over one codon, and another tRNA brings the next amino acid.

Another peptide bond is formed, and the process continues for the length of the mRNA strand.

This codon will be either UAA, UAG, or UGA. These codons do not have a matching tRNA anticodon, so when no more tRNA’s attach, the ribosome, protein, and mRNA detach from each other.

4. TERMINATION: The last codon on any mRNA molecule is called the ‘TERMINATOR’ codon, which is a message to STOP translation.

What does translation look like?

CRACKING THE GENETIC CODE

DNA STRAND (one gene)

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

mRNA STRAND

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

tRNA STRAND U A C / A C G / C C G / C G A / A C U

anticodon

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

codons

* Master Strand of DNA

AMINO ACID SEQUENCE

Methionine---Cysteine---Glycine---Alanine---Stop

•PROTEIN SYNTHESIS ANIMATIONhttp://www.pbs.org/wgbh/aso/tryit/dna/#

LET’S REVIEW…

http://www.wisc-online.com/objects/index_tj.asp?objID=AP1302

A BAD NIGHT AT THE THEATRE

Question: What if something goes wrong during translation? Answer: MUTATION

• A change in the nucleotide sequence of DNA

• When the bases (‘letters’) change, the wrong amino acids are used to make the protein.

• The protein will NOT be able to do its job.

There are 2 types of MUTATION:1. Chromosomal mutations: a mutation of all or

part of a chromosome.

This usually involves MANY GENES, and therefore, MANY PROTEINS.

Example: Down’s syndrome.

2. Gene mutations: a mutation that occurs within a gene at some point along a chromosome. This mutation is only a change of 1 or a few ‘letters’ (nitrogenous bases).

It usually only affects ONE GENE, and therefore, ONE PROTEIN.

Example: Sickle cell anemia.