DNA and RNA Structure and Replication

Flashcards from lecture notes

Nucleotide

The basic building block of DNA and RNA, composed of a five-carbon sugar, a phosphate group, and a nitrogenous base.

Chromosome

A structure composed of DNA and protein that contains genetic information; prokaryotes typically have circular chromosomes, while eukaryotes have linear chromosomes.

Plasmid

A small, circular piece of DNA that can replicate independently of chromosomal DNA, commonly found in prokaryotes.

Histone Protein

Proteins that help package DNA into a compact, organized structure called chromatin.

Nucleosome

A structural unit of eukaryotic chromatin consisting of a segment of DNA wound around a core of histone proteins.

Antiparallel Strands

Describes the orientation of the two strands of DNA, where one strand runs in the 5' to 3' direction and the other runs in the 3' to 5' direction.

DNA Replication

The process by which a cell duplicates its DNA prior to cell division.

Helicase

An enzyme that unwinds the DNA double helix by breaking hydrogen bonds between the two strands.

Okazaki Fragments

Short, discontinuous segments of DNA synthesized on the lagging strand during DNA replication.

Ligase

An enzyme that connects the sugar-phosphate backbone of DNA fragments by forming phosphodiester bonds.

Semiconservative Replication

The mechanism of DNA replication where each new DNA molecule consists of one original strand and one newly synthesized strand.

Base Pairing Rules

The rules that dictate the pairing of nitrogenous bases in DNA: Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).

Exonucleases

Enzymes that remove RNA primers from the newly synthesized DNA strand during replication.

Topoisomerase

An enzyme that alleviates the tension created by the unwinding of DNA, preventing supercoiling.

Leading Strand

The DNA strand that is synthesized continuously towards the replication fork during DNA replication.

Lagging Strand

The DNA strand that is synthesized discontinuously away from the replication fork, characterized by Okazaki fragments.

RNA Primer

A short segment of RNA synthesized by primase that provides a starting point for DNA polymerase during DNA replication.