Translation• Once the DNA code has been Transcribed

onto a mRNA molecule, mRNA leaves the nucleus and moves into the cytoplasm. In the cytoplasm the mRNA combines with

the Ribosomes to make Enzymes/Proteins. The Process of reading the mRNA code

and building a(n) Enzyme/Protein is called Translation, or Protein Synthesis.

In order for Translation/Protein Synthesis to occur a cell needs:

• 1. mRNA (carrying the DNA code)

• 2. Ribosomes

• 3. Amino Acids

• 4. tRNA (picks up amino acids in the cytosol and carries them to the ribosomes where they

will be joined together to form a Protein)

The mRNA is made in the Nucleus through the process

of Transcription. mRNA is made up of RNA nucleotides.

Each group of 3 nucleotides is called a Codon and codes for one amino acid of the newly

forming Protein.

This Segment of a mRNA molecule is 7 codons long, 21 nucleotides, and will code for 7 amino acids

Ribosomes(the ribosomes are the actual site of Translation /protein synthesis)

Made in the Nucleolus, made up of Ribosomal RNA, rRNA

Animals and Plants get their amino acids the same way they get their Nucleotides.

Transfer RNA (tRNA)

• tRNA is a small, folded RNA chain (74-93 nucleotides) that

picks up and transfers specific amino acids to a growing polypeptide chain at the ribosomal site of protein

synthesis during translation.

• It has sites for Amino Acid attachment and an Anticodon.

• • The Anticodon is composed of

• complementary bases.

• Each tRNA molecule binds to only one type of amino acid.

• More than one tRNA exists for each amino acid.

Summary of TranslationSummary of Translation(or… so you want to make a Protein)(or… so you want to make a Protein)

Let’s begin in the nucleus…… The DNA has the code to instruct the

Ribosomes as to which Proteins to make. Ok, 2 problems here: 1.) the DNA

is in the Nucleus and the ribosomes are in the Cytoplasm, and 2.) the

ribosomes can’t read the DNA. Well there’s an easy way to fix both

problems… it’s called Transcription…. Through Transcription, the DNA

code is placed onto a mRNA molecule which can 1.) leave the nucleus,

travel into the cytoplasm and join with the ribosomes, and 2.) the ribosomes can Translate (read) the mRNA.

So now we have the DNA code, by way of mRNA, in the cytoplasm that can instruct the Ribosomes as to which protein to make….. By the way, the difference between one protein and another protein is the order of the amino acids, the number of amino acids and its 3 dimensional shape.

Now …… let’s say you are a ribosome….. you are just sitting around, in the cytoplasm, waiting for some amino acids to assemble into

protein….you already have the instructions, remember the mRNA, …… but you can’t get the amino acids yourself…… you need help…. you need tRNA. The tRNA can pick up specified amino acids.… and bring them to you in the correct order…..but how does I know which

amino acid to pick up?

The tRNA knows where to place its amino acid because the tRNA can read the mRNA codon......the mRNA codon is a transcribed version of

the DNA code……it instructs the mRNA as to where it should place the amino acid. By the way….the first amino acid is always

methionine, or sometimes referred to as “f-met”.

So…. It’s this simple….. you’re a tRNA molecule…. You have an amino acid attached to you…… you simply move up or down the mRNA

looking for the right place to drop off your amino acid…. you’ll easily recognize where to place the amino acid …..it’s where your anticodon

matches the mRNA codon. This process will continue until a “termination or stop” codon, located on the mRNA, instructs the

ribosomes to break apart…..ending translation.

Translation1st letter – Row

2nd Letter – Column

3rd Letter - Sentence

Gene RegulationSome genes can be “switched on” or “switched off”.

When a gene is switched on….a protein is produced…. when a gene is switched off a protein is no longer

produced…. How the organism is affected depends on the protein.

An Operon is a gene switch…. it is located on the DNA …. What an operon really is is a series of genes that code for a

particular protein.

The first operon discovered is known as the “lac-operon”.

The lac-OperonThe lac-OperonFour regions of DNA control the production of a protein such as the

enzyme Beta-galactosidease (which is used to digest lactose)

1. a structural gene that codes for the enzyme Beta-galactosidease.

2. an operator region right in front of the structural gene, where the repessor

molecule attaches to prevent Transcription.

3. a promoter region where the RNA

Polymerase binds to the DNA.

4. a regulator gene which codes for the Repressor.

5. A repressor is a molecule which binds to the operator and prevents

transcription.

The combined region of the operator and structural gene is called an operon.

regulator gene

DNA Lac-operon

Editing DNA

• About 65% of an organism’s DNA is not used…. it’s left over baggage from evolution.

• As a consequence, about 65% of the mRNA transcribed is also useless….. So the mRNA must be “edited” to remove

the useless codes.

• This editing is accomplished by enzymes.• The pieces of mRNA which are spliced out are called

Introns…. of course they cannot code for anything.

• The pieces of mRNA which are left in, after editing, are called Exons…. of course they are the expressed codes.

Examples of Genes containing Exons and IntronsExamples of Genes containing Exons and Introns

The Structure of a

Chromosome

Chromosome Maps• A

diagram that

shows the

location (locus, plural -

loci) of a gene.

MUTATIONSThe replication of DNA is usually extremely accurate because DNA polymerase proof reads the DNA as it is

produced.

If necessary, DNA polymerase removes the incorrect nucleotide and replaces it.

If the DNA is NOT repaired a Mutation will occur. A mutation is a change in the DNA….. This change will

affect the protein which is produced and can eventually

affect the organism's traits.

The 2 most common causes of mutations are:

1. Radiation (such as ultraviolet and x-ray) and,

2. Various reactive chemicals called Carcinogens.

If the Mutation occurs in a Somatic cell or body cell, it is not inheritable.

If the Mutation occurs in a gamete, it is heritable.

Types of Mutations(Changes in the DNA affecting the resulting traits)

The 2 most common mutations are:

1. Point Mutations

2. Frame-shift Mutations

Point Mutation

• Changes in one nucleotide in the genetic code.

• Effects - none to fatal.

• Example: Sickle Cell Anemia

Sickle Cell Anemia

Frame ShiftImagine a sentence should read:

“the red cat ate the rat”If a deletion occurs, a letter is removed, in this

case the first letter “e”… the sentence would read:

“thr edc ata tat her at”The addition of a letter, in this case the letter “o”

would result with a frame shift which looks like this…

“tho ere dca tat ath era t”

Insertions & Deletions

• The addition or loss of a base in the DNA

Which causes a frame shift mutation.

Biotechnologies

• Cloning

• The Human Genome Project

• Gene Splicing ...What are “Restriction Enzymes” and what are they used for?

• Gene Therapy