Unit 8: DNA, RNA and Protein Synthesis

replication fork

A Y-shaped point that results when the two strands of a DNA double helix separate so that the DNA molecule can be replicated.

mutation

A change in the nucleotide-base sequence of a gene or DNA molecule.

deoxyribose

A five-carbon sugar that is a component of DNA nucleotides.

ribonucleic acid (RNA)

A natural polymer that is present in all living cells and that plays a role in protein synthesis.

purine

A nitrogenous base that has a double-ring structure; one of the two general categories of nitrogenous bases found in DNA and RNA; either adenine or guanine.

pyrimidine

A nitrogenous base that has a single-ring structure; one of the two general categories of nitrogenous bases found in DNA and RNA; thymine, cytosine, or uracil.

anticodon

A region of tRNA that consists of three bases complementary to the codon of mRNA.

bacteriophage

A virus that infects bacteria.

DNA polymerase

An enzyme that catalyzes the formation of the DNA molecule.

helicase

An enzyme that separates DNA strands.

RNA polymerase

An enzyme that starts (catalyzes) the formation of RNA by using a strand of a DNA molecule as a template.

nitrogenous base

An organic base that contains nitrogen, such as a purine or pyrimidine; a subunit of a nucleotide in DNA and RNA.

transfer RNA (tRNA)

Carries amino acids to the site of translation on the ribosome. Contains an anticodon.

messenger RNA (mRNA)

Carries the copied genetic code from the chromosomes in the nucleus to the ribosomes in the cytoplasm.

virulent

Describes a microorganism that causes disease and that is highly infectious; strictly, refers only to viruses that reproduce by the lytic cycle.

codon

In DNA, a three-nucleotide sequence that encodes an amino acid or signifies a start signal or a stop signal.

nucleotide

In a nucleic-acid chain, a subunit that consists of a sugar, a phosphate, and a nitrogenous base.

semi-conservative replication

In each new DNA double helix, one strand is from the original molecule, and one strand is new.

ribosomal RNA (rRNA)

Makes up the structure of the ribosomes.

protein synthesis

The formation of proteins by using information contained in DNA and carried by mRNA.

complementary base pair

The nucleotide bases in one strand of DNA or RNA that are paired with those of another strand; adenine pairs with thymine or uracil, and guanine pairs with cytosine.

translation

The portion of protein synthesis that takes place at ribosomes and that uses the codons in mRNA molecules to specify the sequence of amino acids in polypeptide chains.

transcription

The process of forming a nucleic acid by using another molecule as a template; particularly the process of synthesizing RNA by using one strand of a DNA molecule as a template.

DNA replication

The process of making a copy of DNA.

base pairing rules

The rules stating that cytosine pairs with guanine and adenine pairs with thymine in DNA, and that adenine pairs with uracil in RNA.

transformation

The transfer of genetic material in the form of DNA fragments from one cell to another or from one organism to another.