DNA PROCESSES

Replication, Transcription and Translation

Replication

Replication is the process in which chromosomes are copied.

When cell division occurs, 2 new cells with exactly the same genetic information as the original cell is created.

DNA cannot divide into two, but it can be copied!

Replication

During replication, an enzyme “unzips” the DNA molecule, allowing free nucleotides to join with their correct nitrogen bases.

Remember!!! Adenine always pairs with thymine, and cytosine always pairs with guanine.

When replication is complete, we are left with 2 new molecules of DNA, each containing an original parent strand and a new complimentary strand.

Transcription

Transcription is the process of transferring information from a strand of DNA to a strand of mRNA.

As we know, DNA can be found in the nucleus of cells. In order for proteins (building blocks of all living organisms) to be made, genetic information must be moved out of the nucleus to a ribosome. For this to be done messenger RNA (mRNA) must be used.

Steps in Transcription

Like in replication, an enzyme will unzip the DNA molecule and RNA nucleotides will join with the correct DNA nucleotides (G-C, A-U) to receive the genetic information.

Once the exchange of genetic information is complete, RNA becomes mRNA. (Think about it as if RNA now has a message to take to the ribosome waiting in the cells cytoplasm)!

mRNA, then leaves the nucleus and carries the code to the ribosome.

Transcription

Translation

Translation is the process in which information carried in a segment or part of mRNA is translated into a chain of amino acids, forming a protein.

IMPORTANT!

Every 3 nitrogenous bases on the mRNA strand is known as a codon. For example, AUG is a codon.

Each codon, codes for a specific amino acid.

Steps in Translation

Once the mRNA molecule is in the ribosome, a transfer RNA (tRNA) molecule will bind to the correct codon in mRNA.

Just as mRNA has a codon, tRNA has an anti-codon which is also made up of 3 nitrogenous bases. The tRNA anti-codon will join with the correct mRNA codon, thus translating that segment of mRNA.

Translation

As the tRNA anti-codons join with the correct codons a chain of amino acids are formed, which then makes a protein.

Amino acids

During protein synthesis (the making of proteins), a chain of amino acids have to be formed to create the protein.

As mentioned earlier, codons code for amino acids. So how do you know what codon stands for which amino acid? Easy! You use an amino acid table!

Amino Acids

How to find the amino acid… If you have the codon

AUG, the amino acid will be found in the 3rd block down (A Block), 1st column (U Column) and last row (G row) of that block.

AUG codes for Methionine!!

Remember a chain of amino acids make a protein!

Diagram Overview

Practice Questions!!!!April 2006 TAKS test

31. Sickle-cell anemia is a disorder resulting from a mutation that leads to the production of an abnormal protein. Which component of the DNA molecule provides instructions for the production of a protein?

A. The phosphate groups

B. The sugar molecules

C. Te sequence of nitrogen bases

D. The bonds that hold the sugars to the bases

Answer

The answer is C!!! A codon is a sequence of 3 nitrogen bases,

and codes for a protein.

QuestionFall 2005

CGGUAU

31. This is a short section of mRNA. Which DNA code probably produced this section of mRNA?

A. GCCTUT

B. GCCAUT

C. ATTGCC

D. GCCATA

Answer

The answer is D!!! mRNA CGGUAU

DNA GCCATA

Guanine ALWAYS pairs with Cytosine

In RNA Adenine pairs with Uracil.

QuestionJuly 2004

34. DNA passes information to RNA during the process of-

F. transcription

G. active transport

H. regeneration

J. osmosis

Answer

The answer is F!!! Transcription is the process of transferring

information from a strand of DNA to a strand of mRNA.

QuestionJuly 2004

45. Which molecule is most responsible for determining an organism’s eye color, body structure, and cellular enzyme production?

A. Complex Starch

B. Fatty acid

C. Carbohydrate

D. Deoxyribonucleic acid

Answer

The answer is D!!!! Deoxyribonucleic acid (DNA) is the blueprint

for how all living organisms are made.