DNA and Chromosomes



condition of DNA in which one strand reads in one direction (3′ to 5′), while the other reads in the opposite direction (5′ to 3′)

base pair

each set of nucleotides bonded to its complement


point on the chromosome that attaches spindle fibers during cell division


one of two identical halves of a replicated chromosome


packaged DNA that results when the DNA double helical structure is wrapped around histone proteins

chromatin remodeling complex

group of proteins bound together that adjusts the binding of histones to make any region of the DNA more or less accessible


tightly condensed molecule of DNA and proteins

complementary strand

strand of DNA that has nitrogenous bases complementary to another strand

DNA polymerase

enzyme in DNA replication that assembles the new strands of DNA from the template strands

DNA replication

process by which the cell makes a new copy of its DNA

double helix

pair of DNA or polynucleotide strands that wind around a central axis


study of heritable changes in the expression of genes that are caused by the environment


less tightly packed form of chromatin


unit of heritable material that codes for a particular trait

gene expression

process by which genes become observable traits

genetic code

sets of three nucleotide bases that encode hereditary information


entire genetic sequence of an organism


tightly packed form of chromatin


proteins in a chromosome around which DNA winds


number and appearance of the chromosomes of an organism

lagging strand

strand of DNA that is synthesized in short segments during DNA replication

leading strand

strand of DNA that is formed continuously during DNA replication


permanent change in the nucleotide sequence of DNA


consists of a set of 8 histone proteins around which a short region of DNA double-stranded helix is wound, and the short region of DNA that links it to the next nucleosome

Okazaki fragment

short segment of DNA being made on the lagging strand


small, circular piece of bacterial DNA that replicates on its own and can be transferred between cells

replication fork

location on a replicating DNA molecule where the new strands will be produced

replication origin

sequence of nucleotide bases that signals for the initiation of replication


repeating nucleotide sequence at each end of a chromosome

template DNA strand

DNA strand that already exists in DNA replication