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
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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