Chapter 10:RNA & Protein Synthesis

Mrs. Cook

Biology

http://www.cbsnews.com/video/watch/?id=50138899n

RNA Structure and Function

• A GENE is a segment of DNA that is located on a chromosome and that codes for a hereditary characteristic.

• The gene directs the making of the PROTEIN that causes the character to happen through the formation of a nucleic acid called Ribonucleic Acid, or RNA.

• Proteins made from RNA can also code for making other proteins, enzymes and organelles.

• http://video.about.com/biology/What-Are-the-Functions-of-Proteins-.htm

RNA Structure and Function

RNA is also made up of Nucleotides, but its structure is different in four ways:

RNA DNA .

1.Contains the sugar Ribose Deoxyribose

2. Nitrogeneous base Uracil instead of Thymine

3. RNA is single stranded double helix

4. RNA is only the length of 1 gene 3 feet long

RNA Structure and Function

RNA Structure and Function

• Three Types of RNA:

1. Messenger RNA or mRNA-

- single stranded

- carries instructions from a gene to make a protein

- carries the genetic message from DNA in the nucleus to the ribosomes in the cytosol.

RNA Structure and Function

2. Ribosomal RNA or rRNA

- is part of the structure of ribosomes

- found in globular form

3. Transfer RNA or tRNA

- transfers amino acids to the ribosome to make a protein

- is made of nucleotides linked together in a

T-shaped loop.

• Making Proteins based on information in DNA and carried out by RNA is called Protein Synthesis.

• Protein synthesis (synthesis means “to make”) is directed by DNA and takes place in 2 steps:

1. Transcription: DNA acts as a template to make RNA2. Translation: RNA directs the assembly of Proteins

Protein Synthesis (Gene Expression)

DNA RNA PROTEIN

http://www.youtube.com/watch?v=41_Ne5mS2ls

Protein Synthesis (Gene Expression)

• 3 STEPS OF TRANSCRIPTION (DNA to RNA)

1. RNA Polymerase binds to a PROMOTER.

- Promoter is a specific nucleotide sequence of DNA where RNA Polymerase binds and starts transcription.

2. RNA Polymerase adds free RNA nucleotides that are complementary to one of the DNA strands. As the RNA polymerase moves by the DNA molecule, strands rewind.

Protein Synthesis (Gene Expression)

Note: Only a specific region, or gene, on one of the two strands serves as a template.

3. RNA Polymerase reaches a termination signal, a specific sequence of nucleotides that marks the end of a gene, and releases both the DNA and the newly formed RNA.

- the RNA made can be any of the 3 forms:

mRNA, tRNA, or rRNA

Protein Synthesis (Gene Expression)

• THE GENETIC CODE• The Genetic Code is the term for the RULES that

relate how a sequence of bases in the nucleotides corresponds to a particular amino acid.

• 3 Nucleotides (letters) in mRNA specify an amino acid (word) in a polypeptide

• Each 3-Nucleotide sequence in mRNA that codes for an amino acid or a Start or Stop signal is called a CODON.

Protein Synthesis (Gene Expression)

• START CODON: AUG

• STOP CODONS: UAA

UGA

UAG

Protein Synthesis (Gene Expression)• 5 STEPS TO TRANSLATION (RNA to PROTEIN)

1. INITIATION: the ribosomal subunits (the mRNA and the tRNA-carrying amino acid) bind together.

- one end of the tRNA has the amino acid & the other has an ANTICODON, which has a 3 nucleotide sequence that is complimentary to amino acid codon on the mRNA.

mRNA: AUG AAG GCA UCA

tRNA: UAC UUC CGU AGU

(anticodon)

Amino Acid MET - LYS - ALA - SER

Protein Synthesis (Gene Expression)

• ELONGATION: The tRNA carrying the amino acid specified by the next codon binds to the codon. A Peptide Bond forms between the adjacent amino acids. The ribosome moves the tRNA and the mRNA

mRNA

anticodon

Polypeptide chain of amino acids

Protein Synthesis (Gene Expression)

• ELONGATION continues:

- the 1st tRNA detaches and leaves it’s amino acid behind. Elongation continues. The polypeptide chain continues to grow, one amino acid at a time.

• TERMINATION: The process ends when a STOP CODON is reached. A STOP CODON is one for which NO tRNA has a complimentary anticodon.

• DISASSEMBLY: The ribosome falls apart. The newly made Polypeptide is released.

• http://teachertube.com/viewVideo.php?title=Protein_Synthesis_Animation&video_id=60707

http://www.youtube.com/watch?v=983lhh20rGY

http://www.youtube.com/watch?v=h3b9ArupXZg

Mutations

• Mutations that occur during Meiosis and form gametes can be passed onto offspring.

• Mutations that occur during Mitosis and make body cells only affect the individual in which they occur.

Types of Mutations:

1. Gene Rearrangement

2. Gene Alterations (Point Mutations)

a. Insertion

b. Deletion

Mutations

1. Gene Rearrangements

TRANSPOSITION or Jumping Gene

- Change in a gene’s position disrupt the gene’s function because it is now in a new location.

(Like if you move to a new country and can’t speak the language. )

Mutations

2. Gene Alterations or Point Mutations

- placement of the wrong amino acid during protein assembly.

a. Insertion: a sizeable length or piece of DNA is inserted into a gene.

Mutationsb. Deletion: segment of a gene are lost, often

during meiosis.

The Human Genome Project

• The Entire Gene sequence of the Human Genome, the complete genetic content, is now known.

• There are 3.2 billion base pairs in the 23 human chromosomes.

• We now are working on learning what those DNA sequences actually encode.

• Learning which gene sequences control particular biological functions may help diagnose, treat, and prevent genetic disorders, cancers, and infectious diseases in the future.

http://www.youtube.com/watch?v=PhoVcL7Ssmk