RNA AND PROTEIN SYNTHESIS

RNA vs DNA RNA DNA

1. 5 – Carbon sugar (ribose) 5 – Carbon sugar (deoxyribose)

2. Phosphate group Phosphate group

3. Nitrogenous base Nitrogenous base

4. Single stranded Double stranded

5. Uracil base Thymine base

RNA MOLECULE

TYPES OF RNAMessenger RNA (mRNA)• Carries copies of instructions for

the assembly of amino acids

into proteins from DNA to the rest

of the cell

Ribosomal RNA (rRNA)• Makes of the major part of a ribosome

Transfer RNA (tRNA)• Transfers amino acids to ribosomes

during protein synthesis

TRANSCRIPTION• Transcription The process of producing RNA molecules by copying part of the nucleotide sequence of DNA into a complementary sequence in RNA Requires the enzyme RNA polymerase

• Binds to and separates the DNA strands• Uses one strand of DNA as a template to form RNA• Binds to regions of DNA known as promoters which have specific base sequences• Promoters are signals in DNA that indicate to the enzyme where to start and stop making RNA

GENE: coded DNA instructions that control the production of proteins in the cell

RNA EditingRNA molecules have sections called…• Introns: sections not coded for

making proteins

“cut” out or edited while still in

the nucleus• Exons: sections coded for making

proteins

“spliced” back together to form

final mRNA

THE GENETIC CODEThe Genetic Code

• The language of mRNA instructions

• Consist of 20 different amino acids

• With 64 possible codons

Codon: consist of 3 consecutive nucleotides that specify a specific amino acid (3 bases long)

Proteins are made by joining

amino acids into long chains

called polypeptides• The property of a protein is

determined by the order in which different amino acids are joined together to form polypeptides

TRANSLATION• Translation

The decoding of an mRNA message into a polypeptide chain (protein) Takes place on ribosomes in the cytoplasm

• Begins when mRNA in the cytoplasm attaches to a ribosome• Each codon of the mRNA moves through the ribosome• Proper amino acid is brought into the ribosome by tRNA• Amino acid is transferred to growing polypeptide chain in the

ribosome• Each tRNA carries only one kind of amino acid• Each tRNA has 3 unpaired bases called anticodons which are

complementary to one mRNA codon• Works like an assembly line• Polypeptide chain continues to grow until the ribosome reaches a

stop codon• Polypeptide chain is released Protein

TRANSLATION

PROTEIN SYNTHESIS

PROTEINS• Protein

Enzymes that catalyze and regulate chemical reactions

Act as microscopic tools to build or operate a component of a living

cell

Genes code for proteins that in turn determine genetic traits

MUTATIONSMutation• Changes in the genetic material• Effect on organism

Most effects are neutral Some effects are deadly Some lead to greater genetic variability in a species

• Causes Random mistakes during DNA replication or RNA transcription Prolonged exposure to excessive radiation or harmful chemicals

• Types of Mutations Point mutation: gene mutations involving changes in one or a few

nucleotides• Occur at a single point in the DNA sequence• Include substitutions, insertions and deletions

Substitution: one base is changed to another Insertions: base is inserted into the DNA sequence Deletion: Base is deleted from the DNA sequence

MUTATIONS

Frameshift mutation: mutations that shift the “reading” frame of the genetic message by inserting or deleting a nucleotide

• May change every amino acid that follows the point of mutation• Protein may be altered so much that it is unable to perform its normal function• May lead to termination of organism (death)

Chromosomal mutation: involves changes in the number or structure of chromosomes

• May change the locations of genes on chromosomes• DELETIONS: involve the loss or all or part of a chromosome• DUPLICATION: produce extra copies of parts of a chromosome• INVERSION: reverse the direction of parts of a chromosome• TRANSLOCATION: part of one chromosome breaks off and attaches to another

• Significance of Mutations Most are neutral Some are harmful

• Causes of genetic disorders• Causes of many types of cancer

Some lead to greater genetic variability in a species• Polyploidy: organism has extra sets of chromosomes (3N or 4N)• Can cause plants to be stronger and larger