Biology I-unit 3: ch 10

In step __ in the elongation stage of translation binding occurs due to codon/anticodon recognition, factors hydrolysis GTP to provide energy to bind tRNA to A site. Peptidyl trna is in the P site. Aminoacyl tRNA is the in A site.

1

Aminoacyl - tRNA synthetase steps

1. A specific amino acid and ATP bind to aminoacyl-tRNA synthetase 2. The amino acid is activated by the covalent binding of AMP, and pyrophosphate is released 3. The correct tRNA binds to the snythetase. The amino acid is covalently attached to the tRNA. AMP is released 4. The charged tRNA is released

Elongation stage in translation

1. Aminoacyl tRNA brings a new amino acid to the A site 2. Peptide bond is formed between the amino acid at the A site & the growing polypeptide chain 3. Movement or translocation of the ribosome towards the 3' end of the mRNA by one codon

The stages of translation:

1. Initiation-mRNA, the first tRNA and ribosomal subunits assemble into a complex 2. Elongation- synthesis of a polypeptide at the ribosome moves from the start codon to stop codon in the mRNA 3. Termination- complex disassembles at stop codon releasing the completed polypeptide

Poly A Tail

100-200 adenine nucleotides added to 3' end, increases stability and lifespan in cytosol, not encoded in gene sequence

In step __ in the elongation stage of translation the polypeptide is removed from the tRNA in the P site and transferred to the amino acid at the A site and is called the peptidyl transfer reaction. rRNA catalyzes peptide bond formation (the ribosome is a ribozyme)

2

Ability of aminoacyl-tRNA synthetase to recognize appropriate tRNA has been called the ___ _______ ____

2nd genetic code

In step __ in the elongation stage of translation translocation shifts tRNAs at the P and A sites to the E and P sites, the next codon is now at the A spot, and the u charged tRNA exits from the E spot.

3

Translation is read in groups of _ nucleotides known as codons

3

A region is the template strand of DNA used for transcription is 3'-AGCTTGAG-5'. What sequence of RNA would be transcribed?

5'-UCGAACUC-3'

E. coli uses ___% of its cellular energy to translate mRNA into polypeptides

90

In termination the release factors binds to stop codon at the __ site.

A

tRNA

A molecule with two functional sites: one- the anti codon- binds to a codon in mRNA; a second site- the 3' single stranded region (where an appropriate amino acid is attached.

Transcription

Act of making a copy

Most codons specify a particular ______ ______, also _____ & ______ condons

Amino acid, start & stop

Structural differences between prokaryote and eukaryote ribosomes are exploited by ________ to inhibit bacterial ribosomes only.

Antibiotics

The reading frame of tRNA:

Anticodon: 3 RNA nucleotide part of tRNA molecule. Allows binding of tRNA to mRNA codon

Bacterial translation

Bacterial mRNA has a 5' ribosomal-binding site, start codon usually AUG->Methionine, typical polypeptide is a few hundred amino acids in length, stop codons (aka termination or nonsense)-> UAA, UAG, UGA

Eukaryotic transcription:

Basic features identical to prokaryotes, however each step has more proteins. Three forms of RNA polymerase.

Reactions result in tRNA with amino acid attached is now called a _______ tRNA or a _______ tRNA

Charged or aminoacyl

Common features of tRNA

Cloverleaf structure, anticodon on 2nd loop, acceptor stem for AA binding

Exons

Coding sequence segments found in mature mRNA (expressed regions)

The reading frame of mRNA

Codon: set of 3 RNA nucleotides. T of DNA substituted for U of RNA

Termination stage

Complex disassembles at stop codon and releases the completed polypeptide

Proteins are

Composed of one or more polypeptides, key components that affect the structure and function of cells, largely responsible for the outcome of an individuals traits.

Ribosome

Composed of rRNA molecules and many proteins, the ribosome provides a location where mRNA and tRNA molecules can properly interact with each other. The ribosome also catalyzes the formation of covalent bonds between adjacent amino acids so that a polypeptide can be made.

mRNA

Contains the information for the sequence of amino acids in a polypeptide sequence according to the genetic code

Central dogma

DNA -> RNA -> protein

During transcription, ________ is used as a template to make ________.

DNA and RNA

__________ _____: more than one codon can specify the same amino acid. 20 AA -> 64 codons

Degenerate code

Different tRNA molecules are encoded by _________ genes

Different

In termination ribosomal subunits and release factors __________

Disassociate

tRNA synthetases

Enzymes that catalyze attachment of AA to tRNA. One for each of 20 different amino acids, named for the specific amino acid it attaches to tRNA

In _________ transcription occurs in the nucleus, and translation occurs in the cytoplasm

Eukaryotes

_________ have distinct ribosomes in different cellular compartments (cytosol, mitochondria, & chloroplast)

Eukaryotes

___________ also have an intervening step called RNA processing where pre-mRNA is processed into active mRNA. DNA -> pre-mRNA -> mRNA -> protein

Eukaryotes

___________ mRNAs are made in longer pre-mRNA form that requires processing into mature mRNA

Eukaryotic

Comparisons of small subunit rRNAs among different species provide basis for establishing ___________ _________

Evolutionary relationships

Nirenberg and Leder

Found that RNA triplets can promote the binding of tRNA to ribosomes

_______ constitute the genetic material. The "blueprint" for organisms characteristics.

Genes

_______ ____: sequence of bases in an mRNA molecule. (Nearly universal)

Genetic code

In termination a bond between polypeptide and tRNA __________ to release polypeptide

Hydrolyzed

Three stages of transcription

Initiation -> elongation -> termination

3 eukaryotic differences in initiation translation

Instead of ribosomal-binding sequence, mRNAs have guanosine cap at 5' end (recognized by cap-binding proteins) Position of start codon is more variable (many cases, first AUG codon is used as the start codon) The initiator tRNA carries a methionine, not formal-methionine

Other genes code for RNA ________ as a product.

Itself

Both prokaryotes and eukaryotes are composed of _______ and _____ subunits.

Large and small

Capping

Modified guanosine attached to 5' end, needed for mRNA to exit nucleus and bind ribosome

The expression of genes at the ____________ level affects the structure and function of cells which, in turn, determine the traits that organism displays.

Molecular

We can look at gene function at two levels:

Molecular function of the protein product and organisms traits conferred by the gene (these levels are connected)

Translocation

Movement of the ribosome toward the 3' end of the mRNA by one codon

Reading frame

Order in which codons are read during translation (read in 3's = triplet)

Discrete sites for tRNA binding & polypeptide synthesis

P site: peptidly site A site: aminoacyl site E site: exit site

In ________ both transcription and translation occur in the cytoplasm.

Prokaryotes

_______ have one kind of ribosome

Prokaryotes

Structural genes code for polypeptides. One or several polypeptides act as a ________ to play some role in the cell.

Protein

Translation factors:

Proteins needed for the three stages of translation 1. Initiation factors are required for the assembly of mRNA, the first tRNA, and ribosomal subunits. 2. Elongation factors are needed to synthesize the polypeptide. 3. Realize factors are needed to recognize the stop codon and disassemble the translation machinery. Several translation factors use GTP as an energy source to carry out their functions.

Some genes do not encode polypeptides, a _______ is the final functional product.

RNA

Termination stage for transcription

RNA polymerase reaches termination sequence: causes both the polymerase and newly made RNA transcript to dissociate from DNA

Start codon defines the ______ _____ (order in which codons are read during translation)

Reading shift

Initiation stage of transcription

Recognition step. In bacteria, sigma factor causes RNA polymerase to recognize promoter region. Stage is complete when DNA strands separate near promoter to form an open complex.

Initiation stage

Recognition, ribosomal subunits assemble into a complex

Termination in translation is recognized by _______ ______

Release factors

Splicing

Removal of introns and connection of exons

The genetic material provides a blueprint for

Reproduction

___________ use RNA as a template to make DNA

Retroviruses

rRNA and tRNA are self-splicing, they are called ________: RNAs that can catalyze reactions

Ribozymes

rRNA and tRNA are _________

Self-splicing

Elongation stage of transcription

Sigma factor is released. RNA polymerase synthesizes RNA: template strand or coding strand used for RNA synthesis, noncoding strand is not used, synthesized 5' to 3', uracil substituted for thymine

Promoter

Signals the beginning of transcription

Terminator

Signals the end of transcription

Regulatory sequence

Site for the binding of regulatory proteins. The role of regulatory proteins is to influence the rate of transcription.

Most structural genes have one or more introns, ___________ removes introns precisely-composed of snRNPs(small nuclear RNA + proteins)

Spliceosome

Alternative splicing

Splicing can occur more than one way to produce different products

UAA, UAG, UGA are the three ______ codons

Stop

Activities of proteins determine the _________&________ of cells.

Structure & function

Elongation stage

Synthesis of a polypeptide as the ribosome moves from the start codon to stop codon

Other modifications is the addition of _____ & _______

Tails and caps

The steps of ___________ are 1. A release factor binds to the stop codon at the A site 2. The polypeptide is released from the tRNA in the P site. The tRNA is then released 3. Ribosomal subunits and release factors disassociate

Termination

_________ in translation is when a stop codon is found in the A site and translation ends.

Termination

Transcribed region

This region contains the information that specifies an amino acid sequence

Cellular activity, taken together in an organism determines their ________ or ________.

Traits or characteristics

An organized unit of nucleotide sequence that enables a segment of DNA to be _______ into RNA & ultimately results in the formation of a functional product.

Transcribed

RNA polymerase II

Transcribes mRNA and requires 5 general transcription factors to initiate transcription

RNA polymerase I & III

Transcribes nonstructural genes for rRNA and tRNA

__________ is the first step in accessing the information that is stored in DNA

Transcription

Central dogma steps of gene expression

Transcription-"act of making a copy" produces a transcript (RNA copy) of a gene, this messenger RNA (mRNA) specifies the amino acid sequence of a polypeptide Translation-"translating the message into AA sequence" process of synthesizing specific polypeptide on a ribosome using the mRNA template

Translation

Translating the message into AA sequence

Most cells use a substantial amount of energy on _______

Translation

Addition of a _ shifts the reading frame & changes the codons & amino acids specified

U

Peptidyl transfer reaction

______ _______ _______ is when the polypeptide is removed from the tRNA in the P site and transferred to the amino acid at the A site

Bacterial mRNAs can be translated ____________

immediately

During translation, the information within _______ is used to make ________.

mRNA and a polypeptide

Initiation stage of translation in bacteria

mRNA binds to small ribosomal subunits facilitated by ribosomal-binding sequence Start codon is a few nucleotides downstream Initiator tRNA recognizes start codon in mRNA Large ribosomal subunits associate And at the end the imitator tRNA is in the P site

A cell must make many components, so polypeptides can be made:

mRNA, tRNA, ribosomes, translation factors

Initiation stage in translation

mRNA, the first tRNA and ribosomal subunits assemble Requires help of ribosomal initiation factors Requires input of energy(GTP hydrolysis)

Ribosomal RNA (rRNA)

part of the ribosome (site of translation)

Central dogma

provides the basic framework for how genetic information flows from a DNA sequence to a protein product inside cells, this process of genetic information flowing from DNA to RNA to protein is called gene expression

Overall ribosome shape is determined by _____

rRNA

Introns

transcribed but not translated (intervening regions)

Transfer RNA (tRNA)

translates mRNA into amino acids