BCS DENNIS Exam Unit 3 141

isotopes

different forms of the same element are

protons, neutrons

two different isotopes of a given element have the SAME number of ___ but each has a DIFFERENT number of __ in its nucleus

unstable

having different numbers of neutrons makes an atomic nucleus

radioactive decay

the process by which an unstable atomic nucleus loses energy by emitting ionizing particles or radiation

griffith

demonstrations of bacterial transformation was discovered by

Avery, McCarty, and macleod

transforming factor is separable was discovered by

Hershey and chase

transforming factor is DNA was discovered by

chargaff

ratios of DNA within and between species was discovered by

Watson and crick

description of the 3D DNA structure was discovered by

franklin

X-ray crystallography of DNA was discovered by

Chargaff's rules, T, C

___ ___ state that in any species there is an equal number of A and _ bases, and an equal number of G and _ bases

meselson and stahl

semi-conservative replication was done by

Franklin

____ produced a picture of the DNA molecule using x-ray crystallography

purine, pyrimidine

base pairing a __ with a ___ resulted in uniform diameter width consistent with the x-ray

Watson-crick, T, C

the ___ __ model explains chargaff's rules: in any organism the amount of A=__ and the amount of G=__

replicated

every time a cell divides dna must be

helicase

____enzymes that untwist the double helix at the replication forks

topoisomerase

relieves the strain of twisting caused by unwinding

primase

makes a primer -a short RNA starting point - for synthesis of a DNA strand

polymerase

polymerizes a new strand of dna by adding nucleotides

ligase

ligates or joins together nucleic acids

origins of replication

replication begins at special sites called ___ __ ___ where the two dna strands are separated, opening up a replication bubble

replication

proceeds in both directions from each origin, until the entire molecule is copied

single-strand binding

___ protein binds to and stabilizes single-stranded dna until it can be used as a template

dna polymerases

enzymes called __ __ catalyze the elongation of new dna at a replication fork

nucleoside triphosphate

each nucleotide that is added to a growing dna strand is a __ __

deoxyribose, ribose

dATP has __ sugars while ATP has __ sugars

antiparallel, replication

the __ structure of the double helix affects __

3', 5', 3'

dna polymerases add nucleotides only to the free __ end of a growing strand; therefore, a new dna strand can elongate only in the __ to __ direction

replication fork

along one template strand of dna, the DNA polymerase synthesizes a leading strand continuously, moving toward the __ __

dna polymerases

___ __ proofread newly made dna, replacing any incorrect nucleotides

nucleotide excision repair

in __ __ __, a nuclease cuts out and replaces damaged stretches of dna

telomeres

eukaryotic chromosomal dna molecules have at their ends nucleotide sequences called

nucleotides

the information content of dna is in the form of specific sequences of __

proteins

the links between genotype and phenotype

gene expression

the process by which dna directs protein synthesis

Archibald Garrod

in 1909, British physician __ __ first suggested that genes dictate phenotypes through enzymes that catalyze specific chemical reactions

metabolic pathway

linking genes to enzymes required understanding that cells synthesize and degrade molecules in a series of steps known as a __ __

rna

__ is the intermediate between genes and the proteins for which they code

transcription

__ is the synthesis of RNA under the direction of dna

transcription, (mRNA)

__ produces messenger RNA

translation

__ is the synthesis of a polypeptide which occurs under the direction of mRNA

ribosomes

the sites of translation

translated

in prokaryotes, mRNA produced by transcription is immediately __ without more processing

nuclear envelope

in a eukaryotic cell, the __ separates transcription from translation

mRNA

eukaryotic rna transcripts are modified through RNA processing to yield finished __

dna, rna, protein

the central dogma is the concept that cells are governed by a cellular chain of command: __ -> __ -> __

primary transcript

the initial rna transcript from any gene

triplet code

the flow of information from gene to protein is based on a __ __: a series of non overlapping, three-nucleotide words

template strand

during transcription one of the two dna strands called the __ __ provides a template for ordering the sequence of nucleotides in an RNA transcript

codons, 5', 3'

during translation the mRNA base triplets called __ are read in the __ to __ direction

3

(#) RNA bases (a codon) correspond to an amino acid

uracil, thymine

RNA synthesis follows the same base-pairing rules as DNA, except __ substitutes for __

rna synthesis

__ __ is catalyzed by rna polymerase, which pries the dna strands apart and hooks together the rna nucleotides

promoter, terminator

the DNA sequence where rna polymerase attaches is called the __, in bacteria, the sequence signaling the end of transcription is called the __

transcription unit

the stretch of dna that is transcribed is called a

promoters

__ signal the initiation of rna synthesis

transcription factors

mediate the binding of rna polymerase and the initiation of transcription

initiation, elongation, termination

the three stages of transcription/translation

transcription initiation complex

the completed assembly of transcription factors and rna polymerases 2 bound to a promoter is called a __ __ __

terminator

in bacteria, the polymerase stops transcription at the end of the __

5' cap, guanine

the ends of a eukaryotic pre-MRNA are processed such that: the 5' ends receive a ___, a modified __ nucleotide

poly-A tail, adenine

the ends of a eukaryotic pre-MRNA are processed such that: the 3' end gets ___, 50-250 ___ nucleotides

introns, exons

RNA splicing removes __ and joins __ creating an mature mRNA molecule with a continuous coding sequence

spliceosomes

____ consist of a variety of proteins and several small nuclear ribonucleoproteins (snRNPs) that recognize the splice sites

alternative RNA splicing

where some genes can encode more than one kind of polypeptide, such variations are called

can form 3D structure, contains functional groups, can hydrogen-bond with other nucleic acid molecules

three properties of RNA that enable it to function as an enzyme:

exon shuffling

_____ may result in the evolution of new proteins

transfer RNA (tRNA)

a cell translates an mRNA message into protein with the help of ___ ___

amino acid

molecules of tRNA are not identical: each carries a specific __ on one end (the 3' end)

anticodon, codon

molecules of tRNA are not identical: each has a(n) ___ on the other end which base-pairs with a complementary __ on mRNA

protein synthesis

ribosomes facilitate specific coupling of tRNA anticodons with mRN codons in __ __

P

the site that holds the tRNA that carries the growing polypeptide chain

A

the site that holds the tRNA that carries the next amino acid to be added to the chain

E

the exit site, where discharged tRNAs leave the ribosome

start codon (AUG)

the small subunit moves along the mRNA until it reaches the ____

termination

occurs when a stop codon in the mRNA reaches the A site of the ribosome

polyribosome

a number of ribosomes can translate a single mRNA simulataneously forming a

polyribosomes

__ enable a cell to make many copies of a polypeptide very quickly

free ribosomes, bound ribosomes

two populations of ribosomes are evident in cells: __ __ and __ __

cytosol

free ribosomes mostly synthesize proteins that function in the __

endomembrane

ER-bound ribosomes make proteins of the __ system and proteins that are secreted from the cell

signal peptide

polypeptides destined for the ER or for secretion are marked by a

point

__ mutations can affect protein structure and function

mutations

changes in the genetic material of a cell or virus

point mutations

chemical changes in just base pair of a gene

abnormal protein

the change of a single nucleotide in a dna template strand can lead to the production of a

base-pair substitution

a mutation that replaces one nucleotide and its partner with another pair of nucleotides

silent

__ mutations have no effect on the amino acid produced by a code because of redundancy in the genetic code

misense

__ mutations still code for an amino acid, but not necessarily the right amino

nonsense

__ mutations change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein

insertions, deletions

__ and __ are additions or losses of nucleotide pairs in a gene (a type of base-pair mutation)

frameshift

insertion or deletion of nucleotides may alter the reading frame, producing a ___ mutation

spontaneous

____ mutations can occur during dna replication, recombination, or repair

mutagens

physical or chemical agents that can cause mutations

feedback inhibition, gene regulation

a cell can regulate the production of enzymes by __ or by __

operon model

gene expression in bacteria is controlled by the ____

genes

the operon is a cluster of functionally related __ can be under corrdinated control by a single on-off switch

operon

a __ is the entire stretch of dna that includes the operator, promoter, and the genes that they control

promoter

the regulatory switch is a segment of DNA called an operator usually positioned within the ___