Bio Unit 6

Transformation

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

bacteriophages

viruses that infect bacteria

virus

infectious particle consisting of DNA or RNA surrounded by protein, must infect a cel to reproduce

DNA replication

The process in which DNA makes a duplicate copy of itself.

semiconservative model

DNA replication in which the replicated double helix consists of one old strand and one newly made strand

Origins of replication

site where DNA replication begins consisting of a specific sequence of nucleotides

replication fork

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

helicases

enzymes that untwist the double helix at replication forks

single-stranded binding proteins

bind to unpaired DNA strands, keeping them from re-pairing

Topoisomerase

enzyme that helps relieve strain by breaking, swiveling, and rejoining DNA strands

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

Leading s trand

new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5' to 3' direction

lagging strand

a discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in 5' to 3' direction

Okazaki fragments

Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.

DNA ligase

enzyme catalyzing the covalent bonding of the 3' end of one DNA fragment to the 5' end of another DNA fragment

mismatch repair

enzymes remove and replace incorrectly paired nucleotides

nuclease

DNA/RNa cutting enzyme and fills it with proper nucleotides

nucleotide excision repair

A repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide.

telomere

repetitive DNA at the end of a eukaryotic chromosome, protects genes from being eroded

gene expression

the process by which DNA directs the synthesis of proteins

transcription

synthesis of RNA using information in DNA

mRNA

RNA that specificies the primary structure of a protein

translation

synthesis of a polypeptide using the information in the mRNA

primary transcript

initial RNA transcript from any gene, pre-mRNA

triplet code

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

template strand

one strand of DNA that serves as template for RNA synthesis

codon

3-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal

coding strand

nontemplate DNA strand

reading fram

triplet grouping of ribonucleotides used by translation machinery during polypeptide synthesis

RNA polymerase

enzyme that links ribonucleotides into a growing RNA chain during transcription

promoter

DNA sequence where RNA polymerase attaches and initiates transcription

transcription unit

a region of DNA that is transcribed into an RNA molecule

start point

nucleotide where RNA polymerase actually being synthesizing the mRNA

transcription factors

a collection of proteins in eukaryotes that help guide the binding of RNA polymerase and initiation of transcription

transcription initiation complex

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

RNA processing

modification of RNA primary transcripts, including splicing out of introns, joining together of exons, and alteration of the 5' and 3' ends

poly-a tail

a sequence of 50-250 adenine nucleotides added onto the 3' end of a pre-mRNA molecule

RNA splicing

large portions of the RNA primary transcript molecules are removed and the remaining portions are reconnected

intron

noncoding segments of nucleic acid that lie between coding regions

exons

a sequence within a primary transcript that remains in RNA after RNA processing

ribozymes

RNA molecules that function as enzymes

alternative RNA splicing

different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are traeated as exons and which are treated as introns

domains

discrete structural and functional region of a protein

transfer RNA tRNA

RNA molecule that functions as a translator etween nucleic acids and protein languages

anticodon

nucleotide triplet that base-pairs to a specific mRNA codon

aminoacyl-tRNA synthases

enzymes that carry out matching of tRNA and amino acid pairing

wobble

tRNA being able to code for multiple codons

ribosomal RNA rRNA

RNA molecules that, along w/ proteins, make up ribosomes

P site

holds the tRNA carrying the growing peptide chain

A site

holds tRNA carrying next amino acid to be added to the chain

E site

where discharged tRNAs leave the ribosome

initiation stage

brings together mRNA, tRNA bearing first amino acid, and two subunits of a ribosome

elongation

amino acids are added one by one to the previous amino acid at c-terminus of growing chain

termination

stop codon reaches A site and hydrolyzes end of chain

signal peptide

sequence of amino acids telling ribosome to go to endoplasmic reticulum

signal-recognition particle SRP

protein-RNA complex that directs ribosome to ER

polyribosomes

strings of ribosomes

point mutations

single change in a nucleotide pair of a gene

nucleotide-pair substitution

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

silent mutation

nucleotide-pair substitution with no observable effect on phenotype

missense mutations

nucleotide-pair substitution that codes for a different amino acid

nonsense mutation

mutation that causes protein translation to be terminated early

insertion

addition of nucleotide pair in a gene

deletion

loss of nucleotide pair in a gene

frameshift mutation

mutation when nucleotides are inserted or deleted from a gene and is no longer a multiple of three, all later pairs downsream will be improperly grouped into codons

mutagens

physical and chemical agents that react with DNA to cause mutations

gene editing

altering genes in a specific, predictable way

operator

nucleotides near the start of an operon to which an active repressor can attach

operon

promoter, operator, and a coordinated regulated cluster of genes whose products function in a common pathway

repressor

binds to an operator preventing RNa polymerase from transcribing the genes

regulatory gene

gene for protein that controls transcription of other genes

corepressor

small molecule binding to repressor or protein that changes protein's shape, turning it off

inducer

attaches to repressor protein, rendering it inactive

cyclic AMP cAMP

second messenger molecule, regulator of some operons

activator

a protein that binds to DNA and stimulates transcription of agene

differential gene expression

expression of different genes by cells with the same genome

histone acetylation

attachment of acetyl groups to certain amino acids of histone proteins

DNA methylation

presence of methyl groups on DNA bases

epigenics

study of inheritance of traits not involving the nucleotidesequence

control elements

segments of noncoding DNA that serve as binding sites for the transcription factors

enhancer

segment of DNA containing multiple control elements

ncRNA

RNA that does not code for proteins

microRNA miRNA

small, single0stranded RNA molecules capable of binding to complementary sequences in mRNA molecules

small interfering RNA siRNA

small, single-stranded RNA, associates with one or more proteins in a complex that can degrade or prevent translation of an mRNA with a complementary sequence

RNA interference RNAi

blocked of gene expression by siRNAs

long noncoding RNA lncRNA

RNA between 200 and hundreds of thousands of nucleotides in length that does not code for protein but is expressed at significant levels

differentiation

the process by which cells become specialized in structure and function

morphogenesis

development of the form of an organism and its structures

cytoplasmic determinants

maternal substances in the egg that influence the course of early development

induction

process in which a group of cells or tissues influences the development of another group through close-range interactions

determination

the point at which an embryonic cell is irreversibly committed to becoming a particular cell type

pattern formation

development of a multicellular organism's spatial organization, the arrangement of organs and tissues in their characteristic places in 3D space

positional information

molecular cues that control pattern formation

homeotic genes

master regulatory genes that control placement and spatial organization of body parts in animals, plants, and fungi by controlling the developmental fate of groups of cells

embryonic lethals

mutation with phenotypes causing death at the embryonic or larval stage

maternal effect gene

a gene when mutant in the mother results in mutant phenotype in offspring

morphogens

provides positional information in the form of a concentration gradient along an embryonic axi

oncogenes

gene that is involved in triggering molecular events that can lead to cancer

proto-oncogenes

genes that code for normal cell growth and division

epigenetic changes

mutation in a gene for a chromatin-modifying enzyme can lead to loosening of chromatin and inappropriate expression of a proto-oncogene