MOLECULAR BIOLOGY OF THE GENE & PROTEIN SYNTHESIS

2 hours.

NUCLEIC ACIDS

These are polymers of nucleotides.

DNA

• Genetic material that stores information for its own replication and for the sequence of amino acids in proteins.

• Has AGTC.

• Double helix.

RNA

• Performs a wide range of functions within cells, including protein synthesis and regulating gene expression.

• Has AGUC.

• Single-stranded with no helix.

• PHOSPHATE

• PENTOSE SUGAR

• NITROGENOUS-BASE

Each nucleotide is composed of three parts (3):

DEHYDRATION SYNTHESIS

Nucleotides are joined together by a series of _________ reactions.

STRAND

Sequence of nucleotides.

PURINE

What type of nitrogenous bases are adenine and guanine?

PYRIMIDINE

What type of nitrogenous bases are thymine and cytosine?

COMPLEMENTARY BASE PAIRING

The bonding between the nitrogen-containing bases in DNA is referred to as?

HYDROGEN BONDS

The bond that holds the nitrogenous bases together.

EQUALS

The number of A + G (purines) always ____ the number of T + C (pyrimidines).

PROTEINS

• Serves as candidates for hereditary material (will help inherit characteristics).

• Contains 20 amino acids.

GENETIC MATERIAL

Characteristics expressed from the parents to their off-springs.

• ABLE TO STORE GENETIC INFORMATION

• STABLE & ABLE TO BE REPLICATED

• ABLE TO UNDERGO MUTATIONS

Requirements for the genetic material:

CHARGAFF’S RULES

• The amounts of A, T, G, and C in DNA:

  • Are constant among members of the same species.

  • Vary from species to species.

• In each species, A=T, G=C.

ROSALIND FRANKLIN

They studied the structure of DNA using X-rays.

DNA REPLICATION

• The process of copying a DNA molecule.

• Has to be completely the same as the original.

SEMICONSERVATIVE REPLICATION

• Each original DNA strand serves as a template for a new complementary strand.

• Each daughter DNA molecule contains:

  • 1 original (parental) strand

  • 1 newly synthesized strand

UNZIPPING

• Separation of the DNA molecule into individual strands.

• Breaking the hydrogen bonds.

DNA HELICASE

An enzyme that cuts the hydrogen bonds between bases, separating the two strands of parental DNA molecule into two individual strands.

COMPLEMENTARY BASE PAIRING STAGE

Forms a new strand paired with each old strand by hydrogen bonds formed between a new (floating) nucleotide and a nucleotide on the template strand.

DNA PRIMASE

An enzyme that places short primers (short RNA) on the strands to be replicated.

DNA POLYMERASE

• An enzyme that forms the complementary base pairs with the old strand and connects the new nucleotides to the nucleotide on the template strand.

• Converts the short RNA sequences into DNA.

JOINING OF NUCLEOTIDES

• The sugar molecule of one nucleotide bonds with the phosphate molecule of the adjacent nucleotide.

• Complementary base pairing forms a new strand paired with each old strand, which is then bonded together.

DNA LIGASE

An enzyme that serves as the “glue” that joins the DNA strands together.

mRNA

Takes a message from DNA in the nucleus to ribosomes in the cytoplasm.

tRNA

Transfers the appropriate amino acid to the ribosomes.

rRNA

Makes up ribosomes, along with ribosomal proteins, where polypeptides are synthesized.

CODON

A unique arrangement of three RNA nucleotides.

TRANSCRIPTION

Copies the DNA message to mRNA and transports it out of the nucleus.

TRANSLATION

• Production of the protein at the ribosome, which happens in the cytoplasm.

• mRNA codon sequence is translated into a protein (amino acid) sequence at the ribosome.

INITIATION

Begins when RNA polymerase attaches to a region of DNA called a promoter.

PROMOTER

Defines the start of transcription, the direction of transcription, and the strand to be transcribed.

ELONGATION

• Occurs as the RNA polymerase reads down the DNA template strand in the 3′ to 5′ direction and attaches complementary RNA bases.

• Refers to the growth in length of the polypeptide.

TERMINATION

• Occurs when RNA polymerase comes to a DNA stop sequence.

• The stop sequence causes RNA polymerase to stop transcribing the DNA and to release the mRNA molecule, now called an mRNA transcript.

• Does not code for an amino acid.

• UAA, UAG, UGA

ANTICODON

• The opposite end of the tRNA contains an ____.

• A group of three bases that is complementary and antiparallel to a specific mRNA codon.

GENE MUTATION

• A permanent change in the sequence of bases in DNA.

• Can either be effective or not.

SPONTANEOUS MUTATIONS

Chemical changes in DNA that lead to mispairing during replication.

INDUCED MUTATION

• Caused by mutagens such as radiation and organic chemicals.

• Many mutagens are also carcinogens (cancer-causing).

POINT MUTATION

• Involves a change in a single DNA nucleotide.

• Change one codon to a different codon.

FRAMESHIFT MUTATIONS

• One or two nucleotides are either inserted or deleted from DNA.

• The protein is always rendered nonfunctional.

• This leads to the wrong protein sequence, then the wrong folding.