Unit 6 Test

Chapters 16, 17, 18

Transformation

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

bacteriophages (phages)

viruses that infect bacteria

Virus

DNA in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host.

semi-conservative

1 old strand and 1 new strand

conservative

2 parental strands come together

disperse

have a mixture of old and new strands.

origins of replication

short stretches of DNA having a specific sequence of nucleotides

replication fork

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

Helicases

enzymes that untwist the double helix at the replication forks

single strand binding proteins

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

Topoisomerase

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

primer

A short segment of RNA that acts as the starting point for a new strand

primase

synthesizes RNA primer

DNA polymerase

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

leading strand

DNA strand that is replicated CONTINUOUSLY

lagging strand

DNA strand that is replicated DISCONTINUOUSLY

Okazaki fragments

segments of the lagging strand

DNA ligase

an enzyme that eventually joins the sugar-phosphate backbones of the Okazaki fragments

Telomeres

Repeated DNA sequences at the ends of eukaryotic chromosomes.

Telomerase

An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells.

gene expression

the process by which DNA directs the synthesis of proteins

Transcription

the synthesis of RNA using info in the dna

mRNA

a transcript of gene's protein-building instructions

Translation

the synthesis of a polypeptide using the info in the mRNA

Ribosomes

site of protein synthesis

template strand

provides the pattern for the sequence of nucleotides in an RNA transcript

codons

A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code.

reading frame

Reading mRNA nucleotides in the correct groupings.

RNA polymerase

Enzyme that links together the growing chain of ribonucleotides during transcription.

Promoter

specific region of a gene where RNA polymerase can bind and begin transcription

terminator

A special sequence of nucleotides in DNA that marks the end of a gene.

Transcription unit

the stretch of DNA that is transcribed

start point

the nucleotide where RNA synthesis actually begins

transcription factors

Collection of proteins that mediate the binding of RNA polymerase and the initiation of transcription.

transcription initiation

RNA polymerase attaches to the promoter region of DNA strand, and synthesis begins

TATA box

A promoter DNA sequence crucial in forming the transcription initiation complex.

RNA processing

both ends of the primary transcript are altered

5'cap

The 5' end of a pre-mRNA molecule modified by the addition of a cap of guanine nucleotide.

poly-A tail

Modified end of the 3' end of an mRNA molecule consisting of the addition of some 50 to 250 adenine nucleotides.

- facilitate export of mature mRNA from nucleus

- protect mRNA from degregation

RNA splicing

Process by which the introns are removed from RNA transcripts and the remaining exons are joined together.

Introns

Noncoding segments of nucleic acid that lie between coding sequences.

exons

Coding segments of eukaryotic DNA.

spliceosome

A large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons.

Ribozymes

RNA molecules that function as enzymes

alternative RNA splicing

Genes giving rise to two or more different polypeptides depending upon which segments are treated as exons.

domains

Discrete structural and functional regions of proteins.

tRNA

transfer RNA; type of RNA that carries amino acids to the ribosome

Anticodon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

aminoacyl-tRNA synthetase

family of enzymes that facilitates the endergonic process of joining a specific amino acid to each tRNA

Ribosomal RNA

are in ribosomes proteins

Psite

holds the tRNA carrying the growing polypeptide chain

Asite

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

Esite

exit site

polyribosome

string of ribosomes simultaneously synthesizing same protein

signal peptide

targets the protein to the ER

signal recognition particle (SRP)

A protein-RNA complex that recognizes a signal peptide as it emerges from a ribosome and helps direct the ribosome to the endoplasmic reticulum (ER) by binding to a receptor protein on the ER.

Mutations

a random error in gene replication that leads to a change

point mutation

gene mutation in which a single base pair in DNA has been changed

feedback inhibition

A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.

operator

on/off switch

operon

the operator, the promoter, and the genes they control

repressor

protein that binds to the operator in an operon to switch off transcription

regulatory gene

codes for repressor protein

Corepressor molecule

Takes inactive repressor proteins and makes it an active repressor protein.

inducer

A specific small molecule that inactivates the repressor in an operon.

positive regulation

a transcription factor is required to bind at the promoter in order to enable RNA polymerase to initiate transcription

cAMP

small molecule that binds to allorestic regulatory protein (CAP)

activator

A protein that binds to DNA and stimulates transcription of a specific gene.

differential gene expression

The expression of different sets of genes by cells with the same genome.

histone acetylation

The attachment of acetyl groups to certain amino acids of histone proteins.

loosens dna - Eurochromatin

neutral charge\=no binding

histone methylation

the condensing of chromatin structure (heterochromatin), prevents transcription

epigenetic inheritance

Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence.

Control Segment

segments of noncoding DNA that serve as binding sited for the proteins called transcription factors

alternative RNA splicing

A type of regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns.

Proteasomes

A giant protein complex that recognizes and destroys proteins tagged for elimination by the small protein ubiquitin.

microRNA

small single stranded RNA molecules that bind to mRNA and can degrade mRNA or block its translation.

RNA interference (RNAi)

introduction of double-stranded RNA into a cell to inhibit gene expression

due to small interfering RNAs (siRNA)

cell differentiation

Cell specialization in structure and function.

Morphogenesis

the development of the form of an organism and its structures

cytoplasmic determinants

Maternal substances in egg that influence the course of early development.

Induction

signals that cause changes in target cell

determination

the events that lead to observable differentiation of a cell

- marked by gene expression for specific proteins

pattern formation

The development of a spatial organization of tissues and organs.

positional formation

the molecular cues that control pattern formation, tells a cell its location relative to the body axes and to neighboring cells

homeotic genes

Any of the 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

mutations with phenotypes causing death at the embryonic or larval stage

maternal effect genes

(also called egg-polarity genes)

A gene that, when mutant in the mother, results in a mutant phenotype in the offspring, regardless of the genotype.

bicoid

'Two Tailed', a defect in an embryo that results in two posterior structures (two tails, no head)

morphogens

A substance that provides positional information in the form of a concentration gradient along an embryonic axis.

Oncogenes

cancer causing genes

protooncogenes

genes whose normal protein products stimulate the cell cycle

tumor suppressor genes

A gene whose protein product inhibits cell division, thereby preventing the uncontrolled cell growth that contributes to cancer.

ras gene

A gene that codes for Ras, a G protein that relays a growth signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases, ultimately resulting in stimulation of the cell cycle.