Nucleic acids

Biochemistry

B-DNA

the most common or principal form of the DNA double helix that occurs in nature

A-DNA

a form of a DNA double helix characterized by having a fewer residues per turn and major and minor grooves

Z-DNA

a form of a DNA double helix that has a zigzag look of the phosphodiester backbone when viewed from the side

negative supercoiling

introduces a torsional stress that favors unwinding of the righthanded B-DNA double helix

topoisomerase

enzymes that are involved in changing the supercoiled state of the DNA

class I topoisomerase

a topoisomerase that cuts the phosphodiester backbone of one strand of the DNA

class II topoisomerase

a topoisomerase that cuts both strands of the DNA, pass some of the remaining DNA helix between the cut ends, and then reseals

DNA gyrase

a bacterial topoisomerase that introduces negative supercoils into the DNA

chromatin

a complex of DNA and protein found in eukaryotic nuclei

nucleosome

a globular structure in chromatin in which DNA is wrapped around an aggregate of histone molecules

chromosomes

an individual DNA molecule bound to a group of proteins

telomere

complexes of DNA plus proteins used to maintain structural integrity that protect the chromosomes

DNA replication

the biochemical process by which DNA molecules produce exact duplicates of themselves

replication fork

the point at which the DNA double helix is unwinding

leading strand

the strand that grows continuously

lagging strand

the strand that is synthesized in small segments

okazaki fragments

refers to short segments as the DNA unwinds

nicks

the breaks or gaps in the daughter strand

DNA helicase

influences the unwinding of DNA double helix and the hydrogen bonds between complementary bases are broken

DNA polymerase III

verifies that the base pairing is correct and then catalyzes the formation of a new phosphodiester linkage between the nucleotide and the growing strand

primase

synthesizes short stretches of RNA that are completely complementary and antiparallel to the DNA template

RNA primer

RNA that prime and initiates DNA synthesis

DNA polymerase I

excise or removes RNA primers from fragments and replace it with the required nucleotide

DNA ligase

connects two strands of DNA together by forming a bond between the phosphate group of one strand and the deoxyribose group on another

cancer

a disease characterized by rapid uncontrolled cell division

antimetabolites

a class of anticancer drugs that interfere with the DNA replication because their structures are similar to molecules required for normal DNA replication

methotrexate

a structural analog of folic acid that inhibits the conversion of folic acid to its needed derivative and shuts down DNA synthesis

adenine

which nitrogenous base does 6-Mercaptopurine mimic?

guanine

which nitrogenous base does thioguanine mimic?

thymine

which nitrogenous base does 5-Fluorouracil mimic?

snRNA

a type of RNA that facilitates conversion of hnRNA to mRNA

mRNA

a type of RNA that carries instructions or genetic information to the sites of protein synthesis

rRNA

a type of RNA that combines with specific proteins to form and the most abundant type of RNA in a cell

tRNA

a type of RNA that delivers amino acids to the sites for protein synthesis

transcription

the process by which DNA directs the synthesis of hnRNA/mRNA molecules that carry the coded information needed for protein synthesis

gene

a segment of DNA strand that contains the base sequence for the production of a specific hnRNA/mRNA molecule

genome

refers to all of the genetic material or the total DNA contained in the chromosome of an organism

informational strand

a DNA strand that gives the base sequence present in the hnRNA strand being synthesized

exon

a gene segment that conveys or codes for genetic information

intron

a gene segment that does not convey genetic information

splicing

the process of removing introns from an hnRNA molecule and joining the remaining exons together to form an mRNA molecule

spliceosomes

a large assembly of snRNA molecules and proteins involved in the conversion of hnRNA molecules to mRNA molecules

alternative splicing

a process by which several different proteins that are variations of a basic structural motif can be produced from a single gene

transcriptome

refers to all of the mRNA molecules that can be generated from the genetic material in a genome

codon

a three nucleotide sequence in an mRNA molecule that codes for a specific amino acid

anticodon

a three-nucleotide sequence on a tRNA molecule that is complementary to a codon on an mRNA molecule

wobble

refers to the ability of certain anticodons to pair with codons that differ at the third base

translation

the process by which mRNA codons are deciphered and a particular protein molecule is synthesized

erythromycin

an antibiotic that binds to the larger bacterial ribosome subunit, blocking the exit of a growing peptide chain

terramycin

an antibiotic that blocks the A-site location on the ribosome, preventing the attachment of amino acid carrying tRNAs

streptomycin

an antibiotic that binds to the smaller bacterial ribosome subunit causing a shape change, which in turn causes a misreading of mRNA information

neomycin

an antibiotic that binds to the smaller bacterial ribosome subunit in a manner similar to streptomycin

chloramphenicol

an antibiotic that binds to the ribosome and interferes with the formation of peptide bonds between amino acids

mutation

an error in a base sequence in a gene that is reproduced during DNA replication

mutagen

a substance or agent that causes a change in a structure of a gene

gene or DNA mutation

a permanent alteration in the sequence that makes up a gene

chromosome mutation

an alteration that affects the whole chromosome and whole genes rather than just individual nucleotides

point mutation

a mutation in which one base in a DNA base sequence is replaced with another base

silent mutation

a type of mutation in which single nucleotide is changed but the new codon still specifies the same amino acid

nonsense mutation

a type of mutation in which a base substitution results in a stop codon ultimately truncating translation and most likely leading to a non functional protein

missense mutation

a type of mutation in which a change in one DNA base pair results in the substitution of one amino acid for another in the protein made by a gene

conservative missense

a type of missense mutation in which it results to an amino acid change but the properties of the amino acid remain the same

nonconservative missense

a type of missense mutation in which it results in an amino acid change that has different properties than the wild type

frameshift mutation

a type of mutation that occurs when the addition or loss of a DNA base changes a gene's reading frame and results to a nonfunctional protein

deletion mutation

a type of mutation in which it changes the number of DNA bases by removing a piece of DNA