Chapter 7: DNA Structure and Gene Function

Vocabulary flashcards covering DNA structure, transcription, translation, RNA processing, and mutations from Chapter 7 notes.

DNA

A molecule of nucleic acid composed of nucleotides that stores the information cells need to produce proteins.

Nucleotide

The monomer subunit of DNA, consisting of a phosphate group, a deoxyribose sugar, and a nitrogenous base.

Deoxyribose

The five-carbon sugar in DNA.

Phosphate group

A phosphate group is part of the nucleotide backbone linking nucleotides together.

Nitrogenous base

A DNA base such as adenine, thymine, cytosine, or guanine.

Adenine (A)

A DNA base that pairs with thymine (A–T); in RNA, pairs with uracil (A–U).

Thymine (T)

A DNA base that pairs with adenine (T–A).

Guanine (G)

A DNA base that pairs with cytosine (G–C).

Cytosine (C)

A DNA base that pairs with guanine (C–G).

Base pairing

The specific pairing rules A–T and G–C that hold two DNA strands together.

Double helix

The two DNA strands wound into a helix.

Gene

A small region of a chromosome; its DNA sequence encodes a specific protein.

Protein

A molecule built from amino acids that performs cellular functions and is produced from gene expression.

Transcription

RNA synthesis using DNA as a template; occurs in the nucleus; RNA sequence is complementary to the DNA.

Translation

Protein synthesis at the ribosome; involves mRNA, rRNA, and tRNA; produces a polypeptide.

mRNA (Messenger RNA)

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

rRNA (Ribosomal RNA)

RNA that makes up the ribosome.

tRNA (Transfer RNA)

RNA that carries amino acids to the ribosome during translation.

Codon

A three-nucleotide sequence in mRNA that encodes one amino acid.

Genetic code

The mapping of mRNA codons to their corresponding amino acids.

RNA processing

Modifications in the nucleus that prepare RNA for function; introns removed, exons kept.

Intron

Noncoding sequences in genes that are removed during RNA processing.

Exon

Coding sequences that specify amino acids and are kept in mature mRNA.

Initiation (transcription)

First step of transcription; RNA polymerase binds and starts RNA synthesis.

Elongation (transcription)

Phase during transcription when the RNA chain grows as RNA polymerase moves along DNA.

Termination (transcription)

End of transcription; RNA polymerase releases the transcript.

Initiation (translation)

Assembly of the ribosome on mRNA to begin protein synthesis.

Elongation (translation)

Process of adding amino acids to the growing polypeptide chain.

Termination (translation)

Stop of translation when a stop codon is reached and the protein is released.

Ribosome

Molecular machine where translation occurs; consists of large and small subunits and rRNA.

Mutation

A change in a cell’s DNA sequence.

Point mutation

A mutation that changes one or a few base pairs.

Substitution

One base is replaced by another; can produce missense or nonsense mutations.

Missense mutation

A substitution that changes one amino acid in the protein.

Nonsense mutation

A substitution that creates a premature stop codon.

Insertion

Addition of nucleotides; can cause a frameshift.

Deletion

Removal of nucleotides; can cause a frameshift.

Frameshift mutation

An insertion or deletion that shifts the reading frame, altering many amino acids.

Expanding repeat

Mutation where a sequence is repeated more times, potentially affecting the protein.

Wild type

Original, non-mutated nucleotide sequence.

Allele

Alternative versions of the same gene.

Genetic variation

Differences in DNA among individuals; important for evolution; breeders may induce mutations to create new varieties.