Chapter 5: The Structure and Function of DNA

Flashcards covering key vocabulary from Chapter 5 lecture notes on DNA structure, function, and replication.

Nucleotide

The repeating unit of nucleic acids; composed of a sugar group, a phosphate group, and a nitrogenous base.

Chargaff’s Rule

In DNA, the percent composition of adenine is the same as thymine, and the percent composition of cytosine is the same as guanine.

Complementary Base Pairing

In DNA, the interaction of bases of nucleotides on opposite strands through the formation of hydrogen bonds.

Antiparallel

The directionality of the two strands in a DNA molecule; the strands run in opposite directions, with each end of a DNA molecule containing the 3' end of one strand and the 5' end of the other strand.

Genome

The complete genetic makeup of an organism; an organism’s total DNA sequence.

Gene

The basic unit of heredity that determines, in whole or part, a genetic trait; a specific sequence of DNA that encodes for proteins and RNA molecules, and can contain sequences that influence production of these molecules.

Nucleoid

A structure in bacteria that contains the chromosomal DNA.

DNA Supercoiling

The formation of additional coils in the structure of DNA due to twisting forces on the molecule.

Regulatory Sequence

A sequence of DNA that regulates the activity of a gene.

Histone

A member of a family of proteins that associate with DNA in eukaryotic cells, which acts to help compact the DNA.

Nucleosome

The condensed structure formed when double-stranded DNA wraps around an octamer of histone proteins.

Chromatin

The non-condensed form of genetic material that predominates for most of the eukaryotic cell cycle; consists of a complex of DNA and proteins.

DNA replication

The process of producing two identical DNA molecules from an original, parent DNA molecule.

Semi-conservative Replication

The mechanism of DNA replication in which each newly synthesized DNA molecule is composed of one strand from the original DNA molecule and one new strand.

Origin of Replication

The DNA sequence where replication begins.

Helicase

A group of enzymes that aid in the unwinding of DNA.

DNA Polymerase III

An enzyme that adds nucleotides to the 3' end of a growing polynucleotide strand.

Primer

In DNA replication, a short segment of RNA that is complementary to a part of the 3' to 5' DNA template strand and serves as a starting point for addition of nucleotides.

Okazaki Fragments

Short DNA fragments that are generated during the synthesis of the lagging strand in DNA replication.

DNA Polymerase I

An enzyme that removes RNA primer and fills gaps between Okazaki fragments on the lagging strand with DNA nucleotides; proofreads newly synthesized DNA.

DNA Ligase

An enzyme that catalyses the joining of Okazaki fragments.

DNA Polymerase II

An enzyme that proofreads newly synthesized DNA.

Mismatch Repair

A mechanism for repairing errors made during DNA replication, whereby a group of proteins recognize a mispaired nucleotide on the newly synthesized strand and replace it with a correctly paired nucleotide.

Telomere

A repetitive section of DNA, near each end of a chromosome; the presence of this sequence helps to protect from loss of important genetic information during replication of the linear DNA in eukaryotic cells.