BIO U3 CARDS

what are the groups of 3 nucleotide bases that make up the genetic code called?

codons

what does it mean for the genetic code to be degenerate?

degenerate bc more than one codon can specify the same amino acid. in most cases, the third base in the codon is the degenerate. (ex: codons GGU, GGC, GGA, and GGG all code for glycine.)

ribosomal-binding site

site that is located near the 5’ end of the mRNA and provides a location for the ribosome to bind to the mRNA

start codon

• the first codon that is used in translation, determines where translation begins.

• start codon is AUG, which codes for methionine.

• Start codon is usually only a few nucleotides from the ribosomal-binding site.

coding sequence

region that begins w start codon and specifies the entire amino acid sequence of a polypeptide, consisting of many codons

stop codon

last codon, signals for end of translation. aka termination codons. do NOT code for an amino acid and include: UAA, UAG, and UGA

which strand is used to make mRNA?

template strand. the resulting mRNA strand corresponds to the coding strand of DNA, except that the U in mRNA substitutes for T in the DNA

recognition between what two things initiates the translation of nucleotide sequence of mRNA into amino acid?

recognition between mRNA and transfer RNA (tRNA molecules)

anticodon

three base sequence in a tRNA molecule this is complementary to a codon in mRNA. due to the complementarity, the anticodon in tRNA and a codon in mRNA bind to each other.

what is the amino end of a polypeptide called?

The N-terminus. place of first amino acid in translation!

which type of bond connects amino acids together?

peptide bonds. covalent bonds that form between carboxyl (COOH) groups of previous amino acid and the amino group of the next

where is the last amino acid said to be located in a completed polypeptide ?

on the carboxyl end, or C-terminus. always found at the end (ex N to C)

aminoacyl-tRNA synthetases

the enzymes that catalyze the attachment of amino acids to tRNA molecules

in which organelle does translation take place?

in the ribosome

what are the three stages of translation?

initiation, elongation, and termination

what happens in initiation

an mRNA, the first tRNA, and the ribosomal subunits assemble into a complex.

what happens in elongation?

the ribosome moves in the 5 to 3 direction from the start codon in the mRNA in toward the stop condo, synthesizing a polypeptide according to the sequence of codons in the mRNA

what happens in termination?

the ribosome reaches a stop codon and the complex disassembles, releasing the completed polypeptide.

what is translation?

the transfer of information between nucleic acid and amino acid “languages” (producing proteins from mRNA)

what determines the reading frame of an RNA?

the start codon (AUG) and it’s placement. areas upstream of reading frames are called UTR, “untranslated region”

what is the region of RNA/DNA used to make the protein called?

protein-coding region or ORF (open reading frame)

T/F: UTRS are exonic sequences.

true, bc they are present in mature mRNA

transfer RNAs (tRNAs)

non-coding RNAs that bridge the two languages (transfer the info), using anticodon, which forms base pairs with the codon via hydrogen bonding

role/function of aminoacyl-tRNA synthetases

enzymes that attach amino acids onto tRNAs. they are important for “charging” tRNAs with the correct amino acid.

role of ribosome in translation

a complex of RNA and protein that catalyzes peptide bond formation

difference between initiation in prokaryotes vs eukaryotes

in eukaryotes, they bind the cap (5’ end) and scan towards the start codon. for prokaryotes, they bind the RNA internally, right next to the start codon which no scanning or 5’ caps to bind).

role of release factor protein in translation

works in termination. when a STOP codon enters the A site, instead of tRNA, release factor binds and hydrolyzes the peptide off the tRNA (breaks the bond by adding water), and the ribosome disassembles.

substitution mutation

changes the identity of one base pair for another. if the mutation does not change the encoded amino acid, it is called a silent mutation and has minimal if any effect on function. if the mutation DOES change the encoded amino acid, it is called missense mutation, and codes for the wrong thing which can have varying effects. if mutation introduces a STOP codon before the intended stop, it is called a nonsense mutation and codes for nothing and the level of badness depends on how early into the protein the stop was coded

insertion/deletion mutations

add or remove bases, respectively. when in multiples of 3 bases “in frame,” just adds or removes amino acids. however, can be super bad when in not a multiple of 3 bc will lead to frameshift mutation which shifts the entire reading frame and scrambles everything. often also brings a STOP codon into frame which causes premature termination

gene expression

the conversion of the information in a gene into a functional product (RNA/Protein)

gene regulation

a cell’s ability to control (increase or decrease) the expression of a gene