rna review
ribonucleic acid, single stranded, different sugar than dna (ribose), uracil base instead of thymine
three types of dna
as follows
mRNA (messenger)
- temporary copy of a gene that encodes a protein (carries the genetic message from DNA)
- made through transcription
- provides the pattern that determines the order of amino acids of a protein strand
rRNA (ribosomal)
- along with proteins makes up the ribosomes
- 80% of the rna in a cell
tRNA (transfer)
- amino acids are attached to it and are linked together during the process of translation
2 major processes
as follows
transcription
- making mRNA from the genetic code of DNA
- pieces of DNA called introns that do not code for proteins are removed leaving the coding segments called exons 809
3 steps of transcription
1. rna polymerase unzips the DNA double helix (initation)
2. rna nucleotides are formed from the nucleotides in the dna template strand (elongation)
3. the mRNA that is formed leaves the nucleus (termination)
translation
- the synthesis of proteins using the codons of mRNA matched with the anticodons of tRNA
- determines the amino acid sequence in a protein
- 64 different three base codons "code" for 20 amino acids (carried by tRNA)
- there are also start (1) and stop (3)
3 steps in translation
1. initiation - the ribosome attaches at a specific site of the mRNA (the start codon aug)
2. elongation - peptide bonds join the amino acids together in sequence, this is done by matching the tRNA anticodons with the mRNA codons, the tRNA molecules enter
distinguish between the roles of transcription and translation
transcription produces mRNA while translation provides the synthesis of protein based on the information contained in mRNA
what is the genetic code?
the sequence of bases in DNA or RNA that determines the sequence of amino acids in a protein
what is transcription? where does it take place in prokaryotes?... in eukaryotes?
transcription is the synthesis of mRNA from DNA, it takes place in the cytoplasm of prokaryotes and in the nucleus of eukaryotes
what does rna polymerase do?
rna polymerase joins rna nucleotides to make rna molecules
compare the roles of introns and exons in mRNA production.
introns are noncoding pieces of dna that are spliced out when mRNA is processed. exons are the coding segments of DNA that are spliced together to form funtional mRNA when introns are removed.
distinguish the functions of mRNA, tRNA, and rRNA
mRNA carries the message coded in DNA into the cytosol. tRNA brings the appropriate amino acids to mRNA during protein synthesis in the cytosol. rRNA makes up 80% of ribosomes.
describe the steps involved in adding amino acids to the polypeptide chain on a ribosome.
- a tRNA anticodon binds to the mRNA codon in the A site a ribosome
- the polypeptide chain attached to the tRNA in the P site is attached to the incoming amino acid with a peptide bond
- the ribosome moves one codon along the mRNA, releasing the tRNA tha
why is accurate initiation of protein synthesis important?
- accurate initiation of protein synthesis is important to avoid mistakes in the amino acid sequence
what part do anticodons and codons play in translation?
codons of mRNA match to the anticodons of tRNA
the DNA code for an amino acid consists of consists of __ nitrogen bases taken from __ possible bases
3/4
true or false - neither dna or rna molecules are chains of nucleotides
false, both
dna in the nucleus controls the activities in the rest of the cell by serving as a template for ___
RNA
the ___ of the cell are sites for synthesis of proteins
ribosomes
proteins are synthesized from less complex organic molecules known as
amino acids
true or false - dna controls protein synthesis by encoding amino acid sequence
true
true or false - genes act by directing the synthesis of lipids
false, proteins
dna and rna are both ___ acids
nucleic
true or false - the correct sequence for a gene transcribed into a RNA molecule is a. attachment of rna polymerase to dna; b. initiation of synthesis; c. elongation of dna; d. termination of synthesis and release of the transcript
true
the enzyme that initiates the first stage of transcription of is rna __
polymerase
the function of tRNA molecules is to transport ___ cytoplasm to mRNA
amino acids
true or false - the production of proteins is directed by the DNA because it is the template for mRNA, tRNA, and rRNA
true
translation takes place on the ___ of the cell
ribsomes
true or false - the following series of words is arranged according to increasing size of structures: nucleus, chromosomes, DNA, nucleotide
false, the opposite
true or false - the specific protein produced in a cell is directly related to the nucleotide sequence in the DNA molecule
true
true or false - transcription provides for the synthesis of proteins while translation produces mRNA
false, translation then transcription
true or false - introns are noncoding pieces of DNA that are spliced out when mRNA is processed while exons are the coding segments of DNA that are spliced together to form functional mRNA
true
what is the anticodon sequence of UUA?
AAU
what is the mRNA sequence that is the complement of the following coded sequence of DNA? TTT AAA TTT CGC
AAA UUU AAA GCG
the presence of which nitrogen base indicates the molecule in RNA?
uracil
the association between the ribosome and mRNA occurs in the __
cytoplasm
the function of transfer RNA molecules is to
transport amino acids to mRNA
this molecule carries a specific code from the nucleus to the ribosomes
mRNA
the genetic code of one amino acid molecule consists of
three nucleotides
RNA polymerase is considered an
enzyme
if the DNA template strand has a sequence of T-A-G-C-C-T-A, then the corresponding RNA is
A-U-C-G-G-A-U
the three base sequenc in the pink molecule represent a
codon
anticodons that match up to codons are located on which molecule?
tRNA
the molecule that carries the genetic code from DNA is called
mRNA
the pieces of DNA that do not code for proteins that are removed are called
introns
both transcription and the translation include
all of the above - initiation, termination, elongation