chapter 17: from gene to protein Flashcards
what is transcription?
the synthesis of RNA using a DNA template
what does transcription produce? what is used as a template?
- it produces RNA
- uses DNA strands as a template
what is translation?
- the synthesis of a polypeptide using information in the mRNA
- it occurs on ribosomes in the cytoplasm or ER
what does translation produce? what is used as a template?
- it produces proteins
- uses mRNA molecule as a template
what is mRNA?
“messenger RNA”, is a type of RNA, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein
what are some of the differences between DNA and RNA?
DNA: double-stranded, uses thymine, contains 2 oxygen atoms, and contains a deoxyribose sugar
RNA: single-stranded, uses uracil, contains 3 oxygen atoms, and contains a ribose sugar
how many amino acids are there?
20 amino acids
what is a codon? how large is it?
- a 3-nucleotide sequence of DNA or mRNA, that codes for a particular amino acid or termination sequence
- each codon consists of 3 nucleotides
what are 3 important general notions about the “genetic code”?
- the code is universal
- the code is redundant
- the code is not ambiguous (each codon signifies one amino acid)
what is a coding strand?
a strand of DNA that is not used for transcription and is identical in sequence to mRNA (except it contains thymine instead of uracil)
what is a transcription factor?
a regulatory protein that binds to DNA and affects transcription of specific genes
what is a promoter?
a specific nucleotide sequence in the DNA of a gene that binds RNA polymerase
what are the 3 subphases in transcription?
initiation, elongation, and termination
what is a TATA box? what attaches to a TATA box?
- a DNA sequence found in eukaryotic promoters (helps build transcription initiation complex)
- proteins, called transcription factors, can bind to the TATA box
what is RNA processing?
- 5’ cap
- poly A tail on 3’ end
- cut out of introns and joining of exons
what is a “UTR”?
a DNA sequence that is not translated into a RNA sequence
what are exons?
expressed sequence of DNA, coding for a protein
do introns or exons code for a protein?
exons
what is tRNA?
“transfer RNA”, a RNA molecules that carries amino acids to the ribosome
what is rRNA?
“ribosomal RNA”, is a type of non-coding RNA that is the primary component of ribosomes (carrying out protein synthesis in ribosomes)
where does translation occur?
in ribosomes in the cytoplasm
where does transcription and RNA processing happen in a eukaryotic cell?
- transcription, in eukaryotes, takes place in the nucleus
- RNA process takes place in nucleolus
what is the 5’ cap?
a modified form of guanine nucleotide added onto the 5’ end of a pre-mRNA molecule
what is a poly-a-tail?
a sequence of 50-250 adenine nucleotides added onto the 3’ end of a pre-mRNA molecule
RNA processing only happens where?
in eukaryotic cells
what is a start codon? what is a stop codon?
start codon: marks the site at which translation into protein sequence begins
stop codon: marks the site at which translation ends
what is a reading frame?
on mRNA, the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis
what are the 3 active sites of a ribosome?
P site: protein binding site
A site: amino acid binding site
E site: exit site
what is an anticodon?
a nucleotide triplet at one end of a tRNA molecule that base-pairs with a particular complementary codon on a mRNA molecule (3’ to 5’ direction)
what is a polyribosome?
a group of several ribosomes attached to the same mRNA molecule
what direction is mRNA building in?
5’ to 3’
what is the link between genotypes and phenotypes?
proteins
what are introns?
noncoding segments of nucleic acid that lie between coding segments (are removed by RNA splicing)
list the start and stop codons
start: AUG
end: UAA, UAG, UGA
