Unit 6 Ap bio

Anticodon

A nucleotide triplet at one end of a tRNA molecule that base-pairs with a particular complementary codon on an mRNA molecule

Antiparallel

Referring to the arrangement of the sugar-phosphate backbones in a DNA double helix

Chromatin

The complex of DNA and proteins that makes up eukaryotic chromosomes.

Codon

A three-nucleotide sequence of DNA or mRNA that specifies particular amino acid or

termination signal; the basic unit of the genetic code

Deletion

A mutational loss of one or more nucleotide pairs from a gene

DNA LIGASE

linking enzyme essential for DNA replication

DNA Polymerase

An enzyme that catalyzes the elongation of new DNA by the addition of nucleotides to the 3’ end of an existing chain

DNA Replication

The process by which a DNA molecule is copied; also called DNA synthesis

DNA Sequencing

Determining the order of nucleotide bases in a gene or DNA fragment

Gel Electrophoresis

A technique for separating nucleic acids or proteins on the basis of their size and electrical charge

Genetic engineering

The direct manipulation of genes for practical purposes.

Helicase

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

two strands and making them available as template strands

Insertion

A mutation involving the addition of one or more nucleotide pairs to a gene

Lagging strand

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

Leading strand

The new complementary DNA strand synthesized continuously along the template

strand toward the replication fork in the mandatory 5’→ 3’ direction

mRNA

A type of RNA, synthesized using a DNA template, that attaches to ribosomes in the

cytoplasm and specifies the primary structure of a protein

Missense Mutation

A nucleotide-pair substitution that results in a codon that codes for a different amino acid

Mutation

A change in the nucleotide sequence of an organism’s DNA or in the DNA or RNA of a virus

Nonsense Mutation

A mutation that changes and amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein

Okazaki Fragment

A short segment of DNA synthesized away from the replication fork on a template strand during DNA replication. Many such segments are joined together to make up the lagging strand of newly synthesized DNA

Operon

A unit of genetic function found in bacteria and phages, consisting of a promoter, an operator, and a coordinately regulated cluster of genes whose products function in a common pathway

Origin of replication

Site where replication of DNA molecule begins

PCR

A technique for amplifying DNA in vitro by incubating it with specific primers, a

heat-resistant DNA polymerase, and nucleotides

Point Mutation

A change in a single nucleotide pair of genes

Primase

An enzyme that joins RNA nucleotides to make a primer during DNA replication, using the parental DNA strand as a template

Primer

A short stretch of RNA with a free 3’ end, bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication

Promotor

A Y-shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are being synthesized

Restriction Enzymes

An type of enzyme that recognizes and cuts DNA molecules foreign to a bacterium. The enzyme cuts at a specific nucleotide sequences

Ribosome

A complex of rRNA and protein molecules that functions as a site of protein synthesis in the cytoplasm; consists of a large subunit and a small subunit

RNA Polymerase

An enzyme that links ribonucleotides into a growing RNA chain during transcription based on complementary binding to nucleotides on a DNA template

RNA Processing

Modification of RNA primary transcripts, including splicing out introns, joining together or exons, and alteration of the 5’ and 3’ ends

Silent Mutation

A nucleotide-pair substitution that has no observable effect on the phenotype; for example, within a gene, a mutation that results in a codon that codes for the same amino acid

Single stranded binding proteins

A protein that binds to the unpaired DNA strands during DNA replication, stabilizing them and holding them apart while they serve as templates for the synthesis of complementary strands of DNA

Terminator

In bacteria, a sequence of nucleotides in DNA that marks the end of a gen and signals

RNA polymerase to release the newly made RNA molecule and detach from the DNA

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

Transcription

The synthesis of RNA using a DNA template

tRNA

An RNA molecule that functions as a translator between nucleic acid and protein languages by carrying specific amino acids to the ribosome, where they recognize the appropriate codons in the mRNA

Translation

The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of “language” from nucleotides to amino acids