ap bio vocab - unit 6 🧬

transformation

a change in genotype and phenotype due to the assimilation of external DNA by a cell

bacteriophages

bacteria-eating viruses

virus

a particle little more than DNA or RNA enclosed by a protective coat

antiparallel

parallel but moving in opposite directions

DNA replication

the copying of DNA

semiconservative model

a model of DNA replication in which the replicated DNA consists of one old strand derived from the parent molecule and a new one

conservative model

a model of DNA replication in which the two parental strands somehow come back together

dispersive model

a model of DNA replication where all four strands of DNA have a mixture of old and new DNA

origins of replication

the particular sites where the replication of chromosomal DNA begins

replication fork

a Y-shaped region where the parental strands of DNA are being unwound

helicases

enzymes that untwist the double helix at replication forks, separating the two parental strands and making them available as template strands

single-strand binding proteins

proteins that bind to the unpaired DNA strands during DNA replication, keeping them from re-pairing

topoisomerase

an enzyme that helps relieve the strain caused by the untwisting of the double helix by breaking, swiveling, and rejoining DNA strands

primer

a short RNA chain produced during DNA synthesis

primase

the enzyme that synthesizes primer

DNA polymerases

enzymes that catalyze the synthesis of new DNA by adding nucleotides to the 3’ end of an existing chain

leading strand

the DNA strand made by elongating in the 5’ to 3’ direction

lagging strand

the DNA strand elongating in the direction away from the replication fork

Okazaki fragments

the segments of the lagging strand

mismatch repair

when enzymes remove and replace incorrectly paired nucleotides resulting from evaded proofreading from DNA polymerases

nuclease

a DNA-cutting enzyme that cuts the segment of DNA containing damaged replication

nucleotide excision repair

a DNA repair system using nuclease to repair incorrectly replicated segments

telomeres

special nucleotide sequences at the end of chromosomal DNA

nucleosomes

the basic, 10nm-fiber organizational units of chromatin

heterochromatin

a type of interphase chromatin in a highly condensed state

euchromatin

a type of interphase chromatin less compacted and more dispersed

histones

small proteins with large amounts of positively charged amino acids that bind to negatively charged DNA

nucleic acid hybridization

the base pairing of one strand of a nucleic acid to a complementary sequence on a different nucleic acid strand

genetic engineering

the direct manipulation of genes for practical purposes

DNA cloning

preparing well-defined segments of DNA in multiple identical copies

plasmids

small circular DNA molecules that are replicated separately

recombinant DNA molecule

a molecule containing DNA from two different sources

gene cloning

the production of multiple copies of a single gene

cloning vector

a DNA molecule that can carry foreign DNA into a cell and be replicated there

restriction enzymes

enzymes that cut DNA molecules at a limited number of locations

restriction site

a particular short DNA sequence recognized by a restriction enzyme

restriction fragments

DNA segments that result from the cutting of DNA by a restriction enzyme

sticky end

a single-stranded end of a double-stranded restriction fragment

gel electrophoresis

a technique where gel is used to separate a mixture of nucleic acids by length

polymerase chain reaction

a technique for amplifying DNA that can make billions of copies of a target DNA within a few hours

DNA sequencing

the exploiting of the principle complementary bases pairing in order to determine the gene’s nucleotide sequence

CRISPR-Cas9 system

a powerful new technique for gene editing found in bacterial cells

gene drive

the engineering of a new allele so that it is much more highly favored for inheritance than the wild-type allele in insects

gene expression

the process by which DNA directs the synthesis of proteins

transcription

the synthesis of RNA using information in DNA

messenger RNA

a type of RNA molecule that is a faithful transcript of a gene’s protein-building instructions

translation

the synthesis of a polypeptide using the information in mRNA

ribosomes

molecular complexes that facilitate the orderly linking of amino acids into polypeptide chains

primary transcript

the initial RNA transcript from any gene, including those specifying RNA that is not translated into protein

triplet code

the genetic instructions for a polypeptide chain are written in DNA as a series of nonoverlapping, three-nucleotide words

template strand

one of the two DNA strands that is transcribed

codons

the mRNA nucleotide triplets

reading frame

the symbols in the correct groupings used to translate mRNA

RNA polymerase

an enzyme that pries two strands of DNA apart and joins together RNA nucleotides complementary to the DNA template strand

promoter

the DNA sequence where RNA polymerase attached and initiates transcription

terminator

the sequence that signals the end of transcription in bacteria

transcription unit

the stretch of DNA downstream from the promoter that is transcribed into an RNA molecule

start point

the nucleotide where RNA polymerase begins synthesizing mRNA

transcription factors

a collection of proteins that mediate the binding of RNA polymerase and the initiation of transcription

transcription initiation complex

the whole complex of transcription factors and RNA polymerase II bound to the promoter

TATA box

a crucial promoter DNA sequence in forming the initiation complex at a eukaryotic promoter

RNA processing

the modification of pre-mRNA in specific ways in the eukaryotic nucleus before being dispatched to the cytoplasm

poly-A tail

50-250 added adenine nucleotides at the 3’ end of pre-mRNA

RNA splicing

a stage of RNA processing in which large portions of an RNA molecule are removed and the remaining portions are reconnected

introns

the noncoding segments of nucleic acid that lie between coding regions

exons

regions in RNA that are eventually expressed by being translated into amino acid sequences

alternative RNA splicing

giving rise to two or more different polypeptides depending on which segments are treated as exons during RNA processing

spliceosome

a large complex made of proteins and small RNAs that accomplishes the removal of introns

ribozymes

RNA molecules that function as enzymes

transfer RNA

the translator of the series of codons along an mRNA molecule

anticodon

the particular nucleotide triplet that base-pairs to a specific mRNA codon

aminoacyl-tRNA synthetases

a family of related enzymes that carry out the correct matching up of tRNA and amino acid

wobble

the flexible base pairing at the 5’ end of a tRNA anticodon

ribosomal RNAs

RNA molecules that make up ribosomes along with proteins

P site

the peptidyl-tRNA binding site that holds the tRNA carrying the growing polypeptide chain

A site

the aminoacyl-tRNA binding cite that holds the tRNA carrying the next amino acid to be added to a polypeptide chain

E site

the exit site where discharged tRNAs leave the ribosome

signal peptide

a sequence of about 20 amino acids at or near the leading end of a polypeptide that targets it to the endoplasmic reticulum or other organelles

signal-recognition particle

a protein-RNA complex that escorts a ribosome to a receptor protein built into the ER membrane

mutations

changes to the genetic information of a cell

point mutations

changes in a single nucleotide pair of a gene

nucleotide-pair substitutions

the replacement of one nucleotide and its partner with another pair of nucleotides

silent mutation

a mutation that has no observable effect on the phenotype

missense mutations

substitutions that change one amino acid to another one

nonsense mutation

a point mutation that also changes a codon for an amino acid into a stop codon

insertions

additions of nucleotide pairs in a gene

deletions

losses of nucleotide pairs in a gene

frameshift mutation

a mutation that occurs whenever the number of nucleotides inserted or deleted is not a multiple of three and alters the reading frame of the genetic message

mutagens

physical and chemical agents that interact with DNA in ways that cause mutations