Chapter 12B: DNA and RNA - QUIZ
how is genetic code read?
3 letters at a time
what does each tRNA carry?
ONE kind of amino acid, it contains an anticodon that is complementary to the codon being read at the ribosome
what does the enhancer act as a magnent for?
RNA polymerase
what is each 3-base sequence called?
a codon
what is an operon?
a group of genes that operate together
what kind of bonds does the ribosome form?
a peptide bond between the 1st and 2nd amino acid and breaks the 1st amino acid from its tRNA and making room for another codon to be read
what are the 2 regulatory regions on the side of the operon?
a promotor (P) which begins transcription and the operator (O)
what does each codon code for?
a specific amino acid
what does a typical gene have?
a start signal for transcription, a stop signal for transcription, a promoter (RNA polymerase binding sight), regulatory sites, and the nucleotide sequence that is transcribed
what is a nonsense mutation?
a stop codon is introduced producing a truncated protein
Which types of RNA are involved in protein synthesis?
all 3, mRNA, tRNA, and rRNA
how do many proteins function?
as enzymes or structures, able to produce the characteristics of organisms (such as color, size, shape, etc.)
what is an insertion?
base inserted into the DNA sequence, can have a dramatic effect because it causes the codon groupings to shift, therefore coding for entirely different amino acids
what is an enhancer sequence?
can regulate genes because proteins can bind here; some proteins open up tightly packed chromatin, others attract RNA polymerase, others block access to genes, etc
what is messenger RNA?
carries copies of the instructions (from DNA) for the assembly of amino acids into proteins
what does gene regulation in eukaryotes allow for?
cell specialization
what is a gene?
coded DNA instructions that control the production of proteins within the cell
what is translation?
decoding of an mRNA molecule into a polypeptide chain
which is more complex - gene regulation in eukaryotes or prokaryotes?
eukaryotes
what is an example of a gene encoded protein?
eye color
what is ribosomal RNA?
forma part of ribosomes, where proteins are assembled
what is an expressed gene?
gene that is transcribed into RNA; only a fraction of the genes in a cell are expressed at any given time. if a specific kind of protein is not continually used by a cell, the gene for that protein is turned on and off at different times
what is a chromosomal mutation?
involve changes in the number of structure of chromosomes, locations of genes on chromosomes, or number of copies of genes
what is a point mutation?
involves changes in one or a few nucleotides
what happens to the mRNA prior to translation?
it is transcribed from DNA in the nucleus and released into the cytoplasm
how does ribosome reading work?
it reads the entire mRNA molceule, like an assembly line or ticker tape
what is the protein that can bind to the O region and prevent transcription?
lac repressor
what can the lac repressor also bind to?
lactose
what is a deletion?
loss of all or part of a chromosome
what does the cell use information from during translation?
mRNA to produce proteins
what are the 2 types of substitutions?
missense mutation and nonsense mutation
are operons generally found in eukaryotes?
no
what is the lac operon turned off and on by?
off by repressors, on by the presence of lactose
What is a missense mutation?
one amino acids changes in the protein
what is substitutions?
one base changed to another
in ecoli what must be expressed?
operon for the bacterium to be able to use the sugar lactose (therefore called the lac operon)
what is a translocation?
part of one chromosome breaks off and attaches to another
what have molecular biologist identified?
patterns in the DNA sequences of genes
what is a regulatory site?
place where other proteins bind directly to the DNA sequence and regulate transcription, help to determine whether a gene is turned off or on
what is transcription?
process in which a sequence of DNA is copied into a complementary sequence of RNA
what do gene mutations do?
produce changes in a single gene
what is a duplication?
produces extra copies of parts of a chromosome
what does the lac operon code for?
proteins that allow lactose to be brought across the cell membrane and broken down into its two components, glucose and galactose
what do genes code for?
proteins, which are able to build/operate components of cells
what is a inversion?
reverses the direction of parts of a chromosome
where does translation take place?
ribosomes
what is a frameshift mutation?
shift the reading frame of the DNA strand; caused by insertions and deletions; can change every amino acid and drastically alter the protein (sometimes to the point that it isn't functional)
what is the TATA box?
short region of DNA about 30 base pairs long; seems to help position RNA polymerase on the promoter and stabilize its binding
what does RNA control?
the assembly of amino acids into proteins, each type of RNA accomplishes a different job in this process
what will a point mutation cause?
the cell to make an incomplete polypeptide if the mutation results in a stop codon
what happens if lactose is present?
the lactose molecules bind to protein, which causes it to change shape and fall of the operator, enabling transcription to take place
what happens as each codon is read?
the matching amino acid is brought by a tRNA and added to the growing polypeptide
where does RNA polymerase bind?
the regions of DNA called promoters, like a start signal, similar signals in DNA to cause it to stop
what happens after the polypeptide chain stops growing?
the ribosome releases it and the mRNA molecule
what is transfer RNA?
transfers the amino acids as coded by the (mRNA) to the ribosome
how many bonding sites does the ribosome have?
two, so the next codon is also read
how long does the polypeptide grow?
until the ribosome reaches the stop codon on the mRNA strand
when does translation stop?
when a stop codon is reached
how does translation begin?
when the mRNA attatches to a ribosome, it begins at AUG the start codon