Genes and Genetic Code

Nucleus

Spherical structure between 10 and 20 µm across that controls cell activity and stores DNA.

Nuclear Envelope

Double membrane that controls the movement of materials in and out of the nucleus.

Nuclear Pores

Allow passage of large molecules in and out of the nucleus, but do not allow chromosomal DNA to exit.

Nucleoplasm

Jelly-like material that makes up the bulk of the nucleus.

Chromosomes

Protein-bound DNA that contains genetic information.

Nucleolus

Small spherical region within the nucleus that manufactures rRNA and assembles ribosomes.

tRNA

Transfer RNA involved in the protein synthesis process.

mRNA

Messenger RNA that carries genetic information from DNA to the ribosome.

rRNA

Ribosomal RNA that is a component of ribosomes.

Gene

A segment of DNA that codes for a protein or a chain of amino acids.

Locus

The specific location of a gene on a chromosome.

Triplet Code

A code in which three bases in DNA or RNA correspond to a single amino acid.

Degenerative Code

The concept that most amino acids are coded for by more than one triplet code due to 64 possible codons.

Codon

A triplet code in mRNA that specifies an amino acid or a stop signal.

Start Codon

The triplet code AUG that signals the beginning of protein synthesis.

Introns

Non-coding sequences in DNA that do not code for amino acids.

Stop Codon

Triplet codes (UAA, UGA, UAG) that signal the end of a peptide chain.

Exons

Protein-coding sequences in DNA.

Non-coding DNA

99% of DNA that does not code for proteins.