bio test 3

nirenberg and leder devised a system for synthesizing specific codons and were able to decipher the genetic code by determining which of the 64 codons coded for each of the 20 amino acids

...

the ribosome is a molecular machine that synthesizes proteins in a 3 step sequence 1. 2. 3.

1. an aninoacyl tRNA carrying the correct anticodon for the mRNA codon enters the A site 2. a peptide bond forms between the amino acid on the aminoacyl tRNA in the A site and the growing polypeptide on the tRNA in the P site 3. the ribosome moves ahead THREE bases and all 3 tRNAS move down one position; the rRNA in the E site leaves

elongations 3 steps?

1. arrival of the aminoacyl tRNA 2. peptide bond formation 3. translocatin

mutations fall into one of three categories?

1. beneficial mutations increase the fitness of an organism 2. neutral mutations fo not affect the organisms fitness --> silent mutations usually neutral 3. deleterious mutations decrease the fitness of the organism

three phases of translation?

1. initiation 2. elogation 3. termination

biologists can work forwards or backwards in the central dogma to:

1. predict the codons and maino acid sequence encoded by a particular DNA sequence 2. approximate the mRNA and DNA sequence that would code for a particular sequence of amino acids

important properties of the code: 1. it is ____ - all amino acids except two are encoded by more than one codon 2. it is ___ - one codon never codes for more than one amino acid 3. it is ____ - with a few mino exceptions, all codons specify the same amino acids in all organisms 4. it is ____ - the first two bases are usually identical within a codon when multple codons specifiy the same amino acid

1. redundant 2. unambiguous 3. nearly universal 4. conservative

dna is an information storage molecule, and that the sequence of bases in dna is a kind of code in which different combinations of bases could specify the _______ amino acids

20

george gamow predicted that each word in the genetic code contains _ bases

3

the ____ serves as a recognition signal for the translation machinery

5' cap

primary RNA transcripts also processed by the addition of a ____ and a _______

5' cap and poly(A) tail

as there are 20 amino acids and only four difference RNA bases, a three-base code is the least that coudl specify enough amino acids- it could code for 4x4x4 or __ amino acids

64

after peptide bond formation, the polypeptide on the tRNA in the P site is transferred to the tRNA in the ____ site

A

the ___ site is now available to accept a new aminoacyl tRNA for bending to the next codon

A

the ___ site of the ribosome is the ACCEPTOR site for an aminoacyl TRNA

A SITE

an aminoacyl tRNA binds to the codon in the ______ via complementary base pairing between anticodon and codon

A site

there is one start codon (_____) which signifies the start of the protein-encoding sequence in mRNA

AUG

___ pf the same gene differ in their DNA sequence. Tus, the proteins produced by different alleles of the same gene frequently differ in their amino acid sequence

Alleles

the _______ at the 3' end of each tRNA is the bidning site for amino acids

CCA --> covalently bonded nucleic acids

the TNA polymerase does not bind ___ to the promoter

DIRECTLY

what is the central dogma order?

DNA--> RNA--> Proteins

RNA polyerase performs a template-directed synthesis in the 5' to 3' prime direction. but unlike DNA polymerases , RNA polymerases _____ ___ require a PRIMER to begin transcription

DO NOT

the ___ is where tRNAs no longer bound to an amino acid EXIT the ribosome

E site

the tRNA that was in the P site moves to the ___ site, adn if the ___ site is occupied, that tRNA is EJECTED

E..E

___ are the coding regions of eukaryotic genes that will be part of te final mRNA product

Exons

the ___ phase of translation begins at the ____ start codon

Initiation........... AUG

was found to carry information from DNA to the site of protein synthesis

Messenger RNA (mRNA)

the ___ site is where PEPTIDE BOND forms that adds an amino acid to the growing peptide chain

P SITE

peptide bonds form between amino acids on the tRNAS in the ___ and __ sites

P and A

____ act as a ink between genes, found in the cell's nucleus, and the protein-manufacturing centers, located in the CYTOPLASM

RNA molecules

the enzyme, _____, synthesizes RNA according to the information provided by the sequence of bases in a particular stretch of DNA

RNA polymerase

many of the eukaryotic promotrs include a unique sequence called the _____ ___ centered about 30 base pairs upstream the transcription start site

TATA box

there are 3 stop codons ( ___, ___, ___) in the genetic code that signal the end of the protein-coding sequence

UGA UAA and UAG

a three-base code provides more than enough messafes to code for all 20 amino acids. this 3-base code is known as

a triplet code

the information encoded in the base sequence of DNA is NOT directly translated into the _____ _____ _____ of proteins

amino acid sequence

Additons or deletions of individual nucleotides will cause a shift in the reading frame o f a gene

and delete on nucleotide acid shown in red, and we get a ___ FRAMESHIFT

___ is the addition or deletion of a chromosome

aneuploidy

the triplet on the loop at the opposite end of the CCA is the ______ that base pairs with the mRNA codon

anticodon

all three rRNAS are bound at their ____ to the correpsonding ______ codon

anticodons mRNA

summarizes the flow of information in cells. it states that DNA codes for RNA which codes for protiens

central dogma

chromosome-level mutations may involve changes in ___ number

chromosome

are larger in scale, often resulting from the addition or deletion of chromosomes form the individuals KARYOTYPE

chromosome-level mutations

the group of three bases that specifies a particular amino acid is called a

codon

in eukaryotes, transcription and translation are separated. mRNAs are synthesized and processed in the nucleus and then transported to the ___ for translation by ribosomes

cytoplasm

in bacteria, however, the information in DNA is converted to mRNA _____.

directly

there were two hypotheses regardign the specification of amino acid sequence by a sequence of nucleotide bases: 1. mRNA codons and amino acids interact ____ 2. crick proposed that an adapter molecule holds amino acids in place while interacting directly and specifically with a codon in MRNA (RIGHT))))))

directly

once the pattern of information flow in a cell was determined, biologists next strove to determine exactly how the sequence of bases in a strand of mRNA codes for the sequence of amino acids in a protein

eidaiedjeidjia

during the ____ phase of transcription, RNA polyermase moves along the DNA template and synthesizes RNA in the 5'---->3' direction

elogation

at the start of the _____ phase, the initiator tRNA is in the P site, and the E and A sites are EMPTY

elongation

the secondary structure of tRNA?

folds over to form an L-Shaped Tertiary structure

a particular stretch of DNA (a _______) contains the information to specify the amino acid sequence of one protein

gene

____ ____ is the process of translating the information in DNA into functioning molecules within the cell

gene expression

the sequence of bases in a particular stretch of DNA specifies the sequence of bases in an RNA molecule, which specifies the sequence of amino acids in a protein. in this way _____ ultimately code for proteins

genes

the ______ contains the rules that specify the relationship between a sequence of nucleotide bases in DNA or RNA and the corresponding sequence of amino acids in a protein

genetic code

a cell builds the proteins it needs from instructions encoded in its ___ according to the _____ ___ of molecular biology

genome central dogma

according to the central dogma, an organisms ___ is determined by the sequence of bases in its DNA, while its ____ is a product of the proteins it produces

genotype phenotype

in eukaryotes, however, the product of transcription is an ____ ____ ____, or __> before these can be translated, they have to be processed in a complex series of steps

immature primary transcript, or pre-mRNA

many genes code for RNA molecuels that do not function as mRNAS and are not translated into proteins. -these and other RNAs perform ___ functions in the cell

important

the interaction between the small subunit and the mRNA is mediated by ______

initiation factors

the intervening noncoding sequences are called ___, and are not in the final mRNA

introns

chromosome composition can also change: . ___ occur when sections of a chromosome break and rotate before rejoining the chromosome ._____ occurs when a broken section of one chromosome becomes attatched to another chormosome

inversions translocation

chromosome lvel mutations can be visualized via the ____ of a cell

karyotype

with the addition of cap and tail and completion of splicing, processesing the primary RNA transcript is complete. the product is _______

mature mRNA

point mutations that result in changes in the amino acid sequence of the encoded protein

missense or replace mutations

eukaryotic genes are much larger than their corresponding mature __

mrna

a ___ is any permanent change in an orgamisms dna. it is a modification in a cell's information archive- a change in its gentotype. ____ create new ALLELES

mutation

most mutations are ___ or ____

neautral or slightly deleterious

the other DNA stradn is called the_____ or the _____ which matches the sequence of the mRNA except that RNA has U in place of T

non template or coding stradn

the protein-coding regions of eukaryotic genes are interrupted by _____ regions - to make a functional mRNA, these regions must be removed

noncoding

where is dna found? where does protein synthesis take place?

nucleus cytplasm

occur when the DNA polyermase inserts the wrong base into the newly synthesized strand of DNA -->results in a change in the DNA base sequence if the DNA polyermase proofreading and mismatch repair systems fail

point

result from a single base change

point mutations

the ___ extends the life of an mRNA by protecting it from degradation

poly(A)tail

the _____ opens the DNA double helix and the template strand is threaded through the RNA polymerase active site

polymerase

___ is an increasse in the number of each type of chromosome

polyploidy

the transcription of eukaryotic genes by RNA polyermase generates a _________ that contains exons and introns -----> introns are removed by _____

primary RNA splicingh

rather, RNA polyermase binds to a ___, a specific sequence of DNA upstream (more 5') of a gene that is to be transcribed. and this _____ transcription

promoter initiates

because the ____ ___ of a gene is dependent on the TRIPLICATE CODON STURCTURE, the amino acid encoded will depond on which NUCLEOTIDE of a codon is read first

reading frame

found that the ______ _____ (sequence of codons) of a gene could be destroyed by a mutationn but then restored inf the the total number of deletions or additions were multiples of three

reading frame

the triplet code is_____ with some amino acids being specified by more than one triplet code

redundant

sometimes information flows in the opposite direction-from RNA back to DNA - for example, some viral genes are composed of RNA and use ________, a viral polymerase, to synthesize a DNA version of the virus's RNA genes

reverse transcriptase

an incoming ______ pairs with a complementary base on the DNA template strand, and RNA polymerization occurs ___proccess requires ___ coupling

ribonucleoside triphosphate (NTP) endergonic energetic

ribosomes contain protein and _____

ribosomal rna (rRNA)

____ catalyze translation of the mRNA sequence into protein

ribosomes

do notchange the amino acid sequence of the gene product

silent mutations

____________ form a complex called a _________. this ________ catalyzes the splicing reaction

small nuclear ribonucleoproteins (smRNPs) spliceosome and spliceosome

ribosomes can be separated into 2 subunits: 1. ____ holds the mRNA in place during translation 2. ___ where peptide bonds form

small subunit large subunit

RNA polymerase perfroms this synthesis by transcribing only ONE strand of dna called

template strand

transcription ends with a _____ phase . in this phase, RNA polymerase encounters a transcription termination signal in the DNA template

termination

Dna is ____ to messanger RNA by RNA polymerase

transcribed

the first step in converting genetic information into proteins is ______

transcription

the process by which the hereditary information in DNA is copied to RNA

transcription

the synthesis of an mRNA version of the instructions stored in DNA

transcription

a group of proteins called ____ ___ bind to the DNA promoter, thus initiating transcriptoin

transcription factors

the adapter molecule was later found to be a small rna called__-

transfer RNA (tRNA)`

the mRNA is ___ to protein

translated

in ____ the sequences of bases in the mRNA is converted to an amino acid sequence in a protein

translation

the process wherein the language of nucleic acids, the order of the nucleotide bases, is converted to the language of proteins, the order of amino acids

translation

____ occurs when ____ factors move the mRNA down the ribosome THREE nucleotides at a time, and the tRNA attached to the growing protein moves into the P site

translocation... elongation factors

all of the tRNAS in a cell havethe same strucutre, shaped like an ____. they vary at the ____ and ______

upside-down L anticodon and attatched amino acid