Chapter 15 Flashcards
Genes and Proteins
produces an RNA copy of the DNA through mRNA
Transcription
converts nucleotide-based information into a protein product
translation
states that genes specify the sequence of mRNAs, which in turn specify the sequence of proteins
Central Dogma
three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation
codon
(of the genetic code) describes that a given amino acid can be encoded by more than one nucleotide triplet; the code is degenerate, but not ambiguous
degenerate
strand of DNA that specifies the complementary mRNA molecule
template strand
the strand not used as a template in transcription
coding strand
sequence present in protein-coding mRNA after completion of pre-mRNA splicing
exon
non–protein-coding intervening sequences that are spliced from mRNA during processing
intron
three-nucleotide sequence in a tRNA molecule that corresponds to an mRNA codon
anti-codon
What are the two main sequences in the assembly of proteins from DNA?
Translation and Transcription
What is mRNA? What is its function?
messenger RNA that copies genes and decodes to amino acids
Understand what is meant by the central dogma of molecular biology.
flow of genetic information DNA-mRNA-proteins
How many possible nucleotide triplets are there? How many amino acids? How is this discrepancy used to an advantage?
64
20
Gives more variation in genes that are produced
What does the term degenerate mean in this sense?
a given amino acid can be encoded by more than one codon that can protect against mutation
Four of the codons do not strictly code for amino acids. Which four are unique and what are their special functions?
AUG=start
UAA, UGA, and UAG=stop
What does it mean to say the genetic code is universal?
virtually all species use the same genetic code for protein synthesis
the same codons code for same amino acids in all
Transcription occurs from which strand of the double-stranded DNA?
template strand
What is the term used to describe the strand of DNA that does not function as the template during transcription? What is its relationship with mRNA?
coding strand the mRNA is the same but with U not T
Name the enzyme that performs transcription in prokaryotes and eukaryotes.
RNA polymerase 5’-3’ direction
What are the 4 cellular components responsible for actual protein synthesis?
mRNA template
ribosomes (rRNA)
tRNA
Enzymes
What is tRNA? Where does it perform its job?
transfer RNA
ribosomes
What is the anti-codon region of tRNA and why is this region so important in translation?
complement to the mRNA code being read
How is the genetic code physically turned into a chain of amino acids?
tRNA brings amino acids corresponding to codon and adds it to growing polypeptide chain
Which amino acid does the first tRNA bring to position #1?
Methionine (Met)
How does elongation of the polypeptide chain occur? What are the three binding sites or compartments on the large ribosomal unit that advance the growing amino acid chain?
assembly line
Aminoacyl site
Peptidyl site
Exit site
The stop codons signal for termination of translation. How does this occur?
nonsense codons
UAA, UGA, UAG
ribosome subunits dissociate from mRNA and each other
What happens to the cellular components when translation is finished? What happens to the mRNA?
mRNA is degraded, amino acids are modified, and the nucleotides are reused
How does the rate of transcription in prokaryotes compare to eukaryotes?
prokaryotes=translation + transcription occur at the same time
eukaryotes= asynchronous because you must move the mRNA to the ribosomes
Why are transcription and translation able to be coupled in prokaryotes, but must be performed independently in eukaryotes?
no membrane bound organelles so you don’t have to move the mRNA
What are the two main ways listed in your notes that transcription/translation differ between prokaryotes and eukaryotes?
Eukaryote need to process the RNA before translation
it is also asynchronous
What are exons and introns?
exons-coding sequences that remain
introns-sequences that don’t code for functional proteins and are removed
