AP Biology: DNA Structure and Replication

topoisomerase

A protein that breaks, swivels, and rejoins DNA strands. During DNA replication, topoisomerase helps to relieve strain in the double helix ahead of the replication fork.

helicase

An enzyme that untwists the double helix of DNA at the replication forks.

ligase

An enzyme 'glue' that connects two fragments of DNA to make a single fragment during DNA replication

single strand binding proteins

proteins that coat DNA to prevent re-annealing (SSBP)

DNA polymerase

Enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule

RNA primer

A short strand of RNA used to start synthesis of the lagging strand of DNA, and to start the polymerase chain reaction

primase

creates RNA primer

Watson and Crick

awarded the 1962 Nobel prize for their model of the DNA double helix

Maurice Wilkins

also awarded the 1962 Nobel prize along with Watson and Crick for aiding in the development of Franklin's image of the double helix - the image Watson and Crick's model was based on

Rosalind Franklin

English chemist and X-ray crystallographer who produced the X-ray diffraction image of the double helix structure of DNA; controversially not given Nobel Prize recognition for the discovery

double helix

The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape

nucleotides

Guanine, Adenine, Thiamine, Cytosine; make up all genes

amino acids

combination of three nucleotides; e.g.: GAC, TCG, ACT

DNA

deoxyribonucleic acid, a self-replicating material present in nearly all living organisms as the main constituent of chromosomes; the carrier of genetic information

mRNA

A type of RNA, synthesized from DNA, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein; also called messenger RNA.

tRNA

An RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA

rRNA

site of polypeptide synthesis in ribosomes; ribosomal RNA

Base Pairing Rule

the rules stating that cytosine pairs with guanine and adenine pairs with thymine in DNA, and that adenine pairs with uracil in RNA

wobble

Flexibility in the base-pairing rules in which the nucleotide at the 5' end of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position (3' end) of a codon

codon

the three letter code for an amino acid

central dogma

DNA transcribes into mRNA which translates into Proteins

transcription

the organic process whereby the DNA sequence in a gene is copied into mRNA

translation

the process whereby genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm

promoter

A specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA

operator

A specific DNA nucleotide sequence where transcriptional regulatory proteins can bind

leading strand

the new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' --> 3' direction

lagging strand

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork

SnRNA

Small nuclear RNA; Found only in the nucleus of eukaryotes and functions to remove introns from mRNA

frame shift

A mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide

substitution

A mutation in which a nucleotide or a codon in DNA is replaced with a different nucleotide

inversion

A kind of mutation in which the order of the genes in a section of a chromosome is reversed

Okazaki fragments

Short fragments of DNA that are a result of the synthesis of the lagging strand during DNA replication.