DNA, Chromosomes, and Genes

A set of 22 vocabulary flashcards reviewing essential terms from the lecture on DNA, chromosomes, and genes.

DNA structure

Includes bases, sugars, and phosphates. Bases are made up of C, G, A, and T. Phosphates are held with phosphodiester bonds. Deoxyribose sugars are numbered 1-5, starting with the carbon attached to the base.

Gene

All the DNA that encodes the primary sequence of the gene product (polypeptide or functional RNA) plus associated regulatory regions such as promoters and enhancers.

B-DNA

The most common conformation of DNA in cells; a right-handed helix with a wide major groove and narrow minor groove.

A-DNA

A right-handed, shorter, and wider DNA helix that has a deep major groove and shallow minor groove.

Z-DNA

A left-handed DNA helix with a zig-zag backbone.

Plasmid

A small, circular DNA molecule found in the cytosol of many bacteria; often carries accessory genes such as those for antibiotic resistance.

Expression vector

An engineered plasmid designed to introduce and express a foreign gene in a host cell, typically for protein production. Includes a promoter, a multiple cloning site (MCS, where the gene of interest is inserted), an affinity tag (to purify), a cleavage site, and a terminator. It also includes antibiotic resistance to kill other bacteria so your gene of interest lives, and an origin of replication.

Histone

A small, basic protein around which eukaryotic DNA wraps; five main types (H1, H2A, H2B, H3, H4) rich in lysine and arginine.

Nucleosome

The fundamental unit of chromatin, consisting of ~146 bp of DNA in a tightly bound “beads-on-a-string” conformation including the bead plus ~54 bp connecting DNA. Beads are complexes of histones and DNA, including 2 copies of H2A, H2B, H3, and H4.

Chromatin

The complex of eukaryotic DNA, histone and non-histone proteins, and RNA that packages the genome into the nucleus. Includes two telomeres and a centromere; during S phase of interphase, the DNA replicates to produce sister chromatids.

Mitochondrial DNA (mtDNA)

Small circular duplex molecules (<20,000 bp in animals); encode rRNAs, tRNAs, and a few proteins.

Chloroplast DNA (cpDNA)

Circular duplex DNA (120,000–160,000 bp)

Intron

A non-translated, intervening DNA segment within a gene that is transcribed but removed from the pre-mRNA during splicing.

Exon

A coding DNA segment of a gene that remains in the mature mRNA after splicing and specifies amino acid sequence.

Regulatory sequence

A DNA segment (e.g., promoter, enhancer) that controls timing, location, or level of gene transcription, replication, or recombination.

Alternative splicing

A process in which different combinations of exons are joined to produce multiple mRNA and protein products from a single gene.

DNA base pairing

Two hydrogen bonds between A and T bases, 3 hydrogen bonds between G and C bases

Bacterial chromosome

Circular, supercoiled chromosome that is scaffolded by structural proteins

Eukaryotic chromosome

Contains DNA of eukaryotic cells; single, very large, duplex DNA molecule. Diploid (2n) depends on species

DNA content in order

Bacteria, yeast, nematode, plant, fruit flu, rice, mouse, human

Histone H1

Linker protein that binds each histone octamer and DNA

Regulatory sequences of a gene

Segments of DNA with purely regulatory functions at the beginning or end of genes. May influence transcription, or designate initiation points