Chapter 9: Gene Expression and Regulation

Nucleotide

Repeated subunits of DNA that consist of a five-carbon sugar, a phosphate, and a nitrogenous base.

Deoxyribose

The pentagon-shaped sugar in DNA that is linked to a phosphate and a nitrogenous base.

Nitrogenous base

The component of a nucleotide that can be one of four different types: adenine, guanine, cytosine, or thymine.

Sugar-phosphate backbone

The scaffold for the bases in DNA, formed by the linkage of nucleotides through phosphate bonds between the sugars and the phosphates.

Double helix

The twisted ladder structure formed by the two strands of DNA wrapping around each other.

Base pairing

The predictable matching of adenine with thymine and cytosine with guanine in DNA, held together by hydrogen bonds.

Antiparallel

The orientation of the two strands of DNA in opposite directions, with the 5′ end of one strand opposite to the 3′ end of the other.

Hydrogen bonds

The type of bond that links the two strands of DNA together in base pairs.

Central Dogma

The process of DNA being transcribed into RNA and then translated into proteins, which are responsible for regulating cellular processes.

RNA

A single-stranded nucleic acid that contains the sugar ribose and the nitrogenous bases adenine, cytosine, guanine, and uracil.

Transcription

The process in which an RNA molecule is synthesized from a DNA template.

Translation

The process in which the sequence of nucleotides in mRNA is used to determine the sequence of amino acids in a protein.

Messenger RNA (mRNA)

A temporary RNA copy of a gene that carries the genetic information from the DNA to the ribosome for protein synthesis.

Ribosomal RNA (rRNA)

A type of RNA that makes up a part of the ribosome, the site of protein synthesis.

Transfer RNA (tRNA)

A type of RNA that carries amino acids to the ribosome for protein synthesis and matches anticodons to codons on the mRNA to ensure the correct amino acid is added to the growing protein chain.

Exons

Regions of DNA that express the genetic code

Introns

Noncoding regions of mRNA

Polycistronic transcript

Recipe in prokaryotes that can make several proteins

Monocistronic transcript

One gene transcribed to one mRNA and translated into one protein in eukaryotes

Splicing

Process of removing introns from mRNA by RNA-protein complex called spliceosome

Poly(A) tail

Sequence of adenine nucleotides added to 3' end of mRNA

5' GTP cap

Modified guanine nucleotide added to 5' end of mRNA

Start Codon

A–U–G, which codes for the amino acid methionine.

Anticodon

A sequence of three nucleotides forming a unit of genetic code in a transfer RNA molecule, corresponding to a complementary codon in messenger RNA.

Polypeptide

A polymer consisting of a large number of amino acids bonded together in a chain, forming a protein molecule.

Stop Codon

Three codons (UAA, UAG, and UGA) that do not code for any amino acid but instead signal the end of the protein chain.

Mutation

An error in the genetic code that can occur due to DNA damage that cannot be repaired or is repaired incorrectly.

Base Substitution

A type of point mutation that occurs when a single nucleotide base is substituted for another, resulting in nonsense, missense, or silent mutations.

Gene Rearrangements

Mutations that involve DNA sequences with deletions, duplications, inversions, and translocations that can result in the gain or loss of DNA or a gene, or cause a new trait.

Frameshift Mutation

A type of mutation that occurs due to insertions or deletions of bases, resulting in a change in the sequence of codons used by the ribosome, and causing errors in gene expression.

Transposons

Gene segments that can cut/paste themselves throughout the genome, interrupting a gene and causing errors in gene expression.