Biology Concept Guide Final

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RNA

Back 1

Ribonucleic acid...
-consists of one polypeptide strand
-sugar found in ribose
-forth base found is uracil

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RNA Polymerase

Back 2

An enzyme that catalyzes the formation from a dna template

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Retrovirus

Back 3

an rna virus that contains reverse transcriptase.

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Ribosome

Back 4

a small particle in the cell that is the site of protein synthesis

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RNA splicing

Back 5

the last stage of rna processing in eukaryotes, in which the transcripts of introns are excited through the action of nuclear ribonucleoprotein particles (snRNP)

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transcription

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the synthesis of rna using one strand of dna as a template

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Translation

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the synthesis of a protein (polypeptide). Takesplace on ribosomes, using the information encoded in messenger RNA.

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Reverse Transcription

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an enzyme that catalyzes the production of DNA.

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Ribosomal RNA

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Several species of rna that are incorperated into the ribosome. involved in peptide bond formation.

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Messenger RNA

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carries copy of a DNA sequence to site of protein synthesis at the ribosome

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Transfer RNA

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carries amino acids for polypeptide assembly

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Ribosomal subunits

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In eukaryotes, the large subunit has three molecules of ribosomal RNA (rRNA) and 49 different proteins in a precise pattern.
The small subunit has one rRNA and 33 proteins.

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A Site

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A(amino acid) site binds with anticodon of charged tRNA

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P Site

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(polypeptide) site is where tRNA adds its amino acid to the growing chain

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E Site

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(exit) site is where tRNA sits before being released from the ribosome.

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Mutation

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inherited genotypic changes

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Promotor

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special sequence of DNA
-tells RNA polymerase where to start and which strand of DNA to transcribe.

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genetic code

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Specifies which amino acids will be used to build a protein

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Codon

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A sequence of three bases—each codon specifies a particular amino acid.

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Anticodon

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At the midpoint of the tRNA sequence—site of base pairing with mRNA. Unique for each species of tRNA.

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RNA polymerases

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-catalyze synthesis of RNA
-are processive—a single enzyme-template binding results in polymerization of hundreds of RNA bases.

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Stop codons

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UAA, UAG, UGA—stop translation and polypeptide is released.

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Start codon

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AUG—initiation signal for translation.

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introns

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Eukaryotic genes may have noncoding sequences

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exons

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The coding sequences

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snRNPs

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(small nuclear ribonucleoprotein particles)
Newly transcribed pre-mRNA is bound at ends by _________

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Nucleic acid hybridization

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reveals introns
Target DNA is denatured, then incubated with a probe—a nucleic acid strand from another source.

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G Cap

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is added at the 5′ end (modified guanosine triphosphate)—facilitates mRNA binding to ribosome.

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Poly A tail

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added at 3′ end.
AAUAAA sequence after last codon is a signal for an enzyme to cut the pre-mRNA; then another enzyme adds 100 to 300 adenines—the “tail.”

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Central Dogma of Molecular Biology

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It states that information cannot be transferred back from protein to either protein or nucleic acid.

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(Translation) Initiation

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a charged tRNA and small ribosomal subunit, both bound to mRNA.
In prokaryotes rRNA binds to mRNA recognition site “upstream” from start codon.
In eukaryotes the small subunit binds to the 5′ cap on the mRNA and moves until it reaches the start codon.

Initiation factors are responsible for assembly of the initiation complex

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(Translation) Elongation

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The second charged tRNA enters the A site.
Large subunit catalyzes two reactions:
It breaks bond between tRNA in P site and its amino acid
Peptide bond forms between that amino acid and the amino acid on tRNA in the A site

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(Translation) Termination

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Translation ends when a stop codon enters the A site.
Stop codon binds a protein release factor—allows hydrolysis of bond between polypeptide chain and tRNA on the P site.
Polypeptide chain separates from the ribosome—C terminus is the last amino acid added.

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(Transcription) Initiation

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requires a promoter—a special sequence of DNA.
RNA polymerase binds to the promoter.
Promoter tells RNA polymerase where to start and which strand of DNA to transcribe.
Part of each promoter is the initiation site.

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(Transcription) Elongation

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RNA polymerase unwinds DNA about ten base pairs at a time; reads template in 3′ to 5′ direction.
The RNA transcript is antiparallel to the DNA template strand, and adds nucleotides to its 3′ end.
RNA polymerases do not proofread and correct mistakes.

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(Transcription) Termination

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Is specified by a specific DNA base sequence.
Mechanisms of termination are complex and varied.
For some genes the transcript falls away from the DNA template and RNA polymerase—for others a helper protein pulls it away.