RNA Transcription

The Structure of RNA

RNA consists of a long chain of nucleotides

• It is made of a 5-carbon sugar (ribose), phosphate group and nitrogen base

• RNA contains the four bases A, C, G, and U (uracil)

Comparing DNA and RNA

There are four main differences between DNA and RNA The sugar in RNA is ribose instead of

deoxyribose RNA is generally single-stranded RNA contains uracil instead of thymineThere are three types of RNA and only 1 type of

DNA.

Types of RNA

There are three main types of RNA 1. Messenger RNA – (mRNA) carries

copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell

2. Ribosomal RNA – (rRNA) makes up the major part of the ribosome 3. Transfer RNA – (tRNA) transfers amino acids to ribosomes during protein synthesis

RNA’s Functions

RNA can have many functions, but most RNA is involved in protein synthesis

The assembly of amino acids into proteins is done by RNA

Transcription

Transcription is the process where RNA molecules are produced by copying a sequence of DNA into a strand of RNA

Transcription requires an enzyme called RNA polymerase to bind to the DNA and separate the strands

One strand of DNA is used as a template to assemble nucleotides into a strand of RNA

Transcription Steps

1. RNA polymerase binds to the DNA in the promoter regions and cause the DNA to unzip and unwind.Promoter regions have specific base sequences that tell

where transcription should begin. Start and Stop

2. The enzyme directs the formation of H bonds between the bases on DNA and the complementary bases of RNA nucleotides.

3. RNA polymerase moves along the section of DNA and forms the sugar-to phosphate bonds between the RNA nucleotides.

4. The polymerase reaches a sequence of bases on DNA that signals transcription to stop.

5. The RNA strand detaches from the DNA and goes out into the cytoplasm.

6. The DNA reforms its H bonds and coils into the double helix.

ALL THREE types of RNA are transcribed in this manner.

TranscriptionNeeds to go to Ribosome for Translation

RNADNA

RNApolymerase

Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)

Translation

Beginning of Translation

The code is read three letters at a time Each group of three letters is called a

codon

Beginning of Translation

A codon is 3 consecutive nucleotides that specify a single amino acid that is to be added to the polypeptide

tRNA is responsible for bringing the amino acid and turning into a polypeptide chain.

Steps of Translation

Step 1: mRNA is transcribed (copied) from DNA in the nucleus and released into the cytoplasm

Step 2: mRNA attaches to a ribosome in the cytoplasmas each codon of mRNA is read in the ribosome, tRNA brings in the proper amino acidthe amino acids are turned into a polypeptide chain(each tRNA carries only one amino acid)each tRNA has 3 unpaired bases called anticodonsthe bases are complementary to one mRNA codon YOU WILL NEED TO MAKE A tRNA and cut out to explain your last step.

Steps of Translation

Step 3: The ribosomes form peptide bonds between the first and second amino acids the ribosome simultaneously breaks the bond between the tRNA and its amino acid causing the tRNA to be releasedStep 4: The polypeptide chain grows (elongation) until a stop codon is reached the polypeptide chain is released to complete its protein conformation.

Codon and Anti-codon

Methionine

Phenylalanine

Ribosome

Transfer RNAThe mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon.

Lysine mRNA

Start codon

tRNA

NucleusMessenger RNA Messenger RNA is transcribed in the nucleus.

Reading The Genetic Code

Protein Synthesis

Proteins are made by joining amino acids into long chains called polypeptides

Each polypeptide contains a different combination of the 20 amino acids

Each polypeptide contains a different combination of the 20 amino acids

Amino acids are biologically important organic compounds. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen.

Final ACT PROTEIN!!!!

When the Ribosome reaches the stop codon, the last polypeptide bond is formed and the protein chain is released. The mRNA is then released from the ribosome.

PRACTICE FROM BEGINNINGEveryone write in comp book

CHECK YOUR WORK

Transcription

mRNA Strand should look like this!!!

Translation

Final Process to make a protein