BIO 1330 Unit 2.1: DNA, genes, chromosomes & transcription

DNA

Double-stranded nucleic acid made of nucleotides; stores genetic information.

RNA

Single-stranded nucleic acid; involved in protein synthesis and regulation.

Nucleotide

Building block of nucleic acids; consists of a phosphate group, 5-carbon sugar, and nitrogenous base.

DNA sugar

Deoxyribose (lacks oxygen at 2′ carbon).

RNA sugar

Ribose (has OH at 2′ carbon).

Nitrogenous bases

Purines: Adenine (A) & Guanine (G)

Pyrimidines: Cytosine (C), Thymine (T in DNA) & Uracil (U in RNA).

Base paring rules

A pairs with T (or U in RNA), G pairs with C.

Antiparallel strands

DNA strands run in opposite directions: one 5′→3′, the other 3′→5′.

Phosphodiester bond

Covalent bond linking nucleotides in a strand (3′ OH to 5′ phosphate).

Hydrogen bonds

Hold complementary bases together (A=T has 2 bonds; G≡C has 3 bonds).

GC content

Higher GC content increases DNA stability.

Gene

Region of DNA that codes for a protein or functional RNA.

Genotype

Complete set of genes in an organism.

Phenotype

Observable traits resulting from gene expression.

Chromatin

DNA + proteins; exists as euchromatin (active) or heterochromatin (inactive).

Histones

Proteins around which DNA wraps to form nucleosomes.

Nucleosome

DNA wrapped around histone proteins; “beads on a string.”

chromosome

Highly condensed chromatin visible during cell division.

Central dogma

DNA → RNA → Protein.

Transcription

Process of making RNA from DNA using RNA polymerase.

Translation

Process of making protein from mRNA using ribosomes

Catalyst

Substance that speeds up a reaction without being consumed (e.g., RNA polymerase, ribosome).

Promoter

DNA region signaling RNA polymerase where to start transcription.

Terminator

DNA region signaling RNA polymerase where to stop transcription.

RNA polymerase

Enzyme that synthesizes RNA from DNA template

Direction of RNA synthesis

RNA built 5′→3′ using DNA template strand (3′→5′)

Eukaryotic promoter

Contains TATA box; requires transcription factors.

introns

Noncoding sequences removed during RNA splicing.

Exons

Coding sequences retained in mature mRNA

Alternative splicing

Different combinations of exons produce multiple proteins from one gene.

5’ Cap

Modified guanine added to mRNA for stability and translation initiation.

Poly A Tail

String of adenines added to 3′ end for stability and nuclear export.

Spliceosome

Protein complex that removes introns from pre-mRNA.

Mature mRNA

Contains 5′ cap, coding sequence, 3′ poly-A tail, and UTRs.

mRNA degradation

Regulates protein production; frees nucleotides for reuse.

DNA Methylation

Blocks promoter access, reducing transcription.