ch 17- transcription

Question 1

gene expression

Answer 1

the process by which DNA directs protein synthesis
includes two stages : transcription and translation

Question 2

basic principles of transcription

Answer 2

is the synthesis of RNA using DNA as a template
produces RNA of all kinds (mRNA)
mrna is the type that eventually leads to building polypeptides

Question 3

RNA structures

Answer 3

differs from DNA
RNA uses ribose sugar
bases are A,G,C, and U
single stranded

Question 4

types of RNA

Answer 4

mRNA (messenger)
tRNA (transfer
rRNA (ribosomal)
primary/pre RNA

Question 5

mRNA

Answer 5

carries information specifying amino acid sequences of proteins from DNA to ribosomes

Question 6

transfer RNA

Answer 6

serves as adapter molevcule in protein synthesis
translates mRNA codons into amino acids

Question 7

primary/pre RNA

Answer 7

serves as precursor to mRNA, rRNA, or tRNA before being processed by splicing or cleavage

Question 8

properties that enable RNA to perform many different functions

Answer 8

single stranded
can hydrogen bond to other nucleic acids
can assume a three-dimensional shape
has functional groups that allow it to act as a catalyst

Question 9

messenger rna how it is built

Answer 9

strand of 1000 to 10000 nucleotides
blueprint for a protein
built from DNA template
goes to ribosomes in cytoplasm

Question 10

ribosomal RNA

Answer 10

made from DNA in nucleolus
combined with proteins
2 ribosomal subunits passed out through nuclear pores

Question 11

anticodon

Answer 11

3 base code on lower loop of transfer RNA
bonds to complementary CODON on mRNA and brings correct amino acids to ribosome/mRNA complex

Question 12

how is translation and transciption different in prokaryotes and eukaryotes

Answer 12

in prokaryotes transcription and translation occur together
in eukaryotes rna transcripts are modified before becoing true mrna

Question 13

what is the flow of information from gene to protein based on

Answer 13

a triplet code
codon
a series of nonoverlapping, three-nucleotide words
these triplets are the smallest units of uniform length that can code for all the amino acds

Question 14

what provides a template for ordering the sequence of nucleotides in an RNA transcript

Answer 14

a DNA strand called the template strand

Question 15

what does the GENE determine in transcription

Answer 15

the sequence of bases along the length of an mRNA molecule

Question 16

how is a language shared by all living things

Answer 16

same codon codes for same AA in all organisms

Question 17

RNA synthesis

Answer 17

catalyzed by RNA polymerase enzyme
follows the same base-pairing rules as DNA, except that in RNA, uracil substitutes for thymine

Question 18

RNA polymerase

Answer 18

separates the DNA strands at the appropriate point and bonds the RNA nucleotides as they base-pair along the DNA template

Question 19

difference and similarities between RNA and DNA polymerase

Answer 19

like DNA, RNA polymerase can only assemble a polynucleotide in its 5’ to 3’ direction
unlike DNA RNA are able to start a chain from scratch

Question 20

stages of transcript

Answer 20

initiation
elongation
termination

Question 21

before RNA synthesis

Answer 21

specific sequence of nucleotides on DNA strand mark beginning and ending of gene

Question 22

initiation - rna transcript

Answer 22

rna pol binds to promoter
segment of DNA unwinds
RNA polym initiates RNA synthesis by binding to promoter at start point on DNA template strand

Question 23

promoter

Answer 23

includes TATA box and proteins called transcription factirs
it is crucial in forming the initiation complex in eukaryotes

Question 24

what does the promoter tell DNA

Answer 24

where to start transcription
which of the two DNA strands to transcribe

Question 25

elongation

Answer 25

polymerasae complex moves and unwinds DNA adds RNA nucleotides to 3' end New RNA peels away from DNA template DNA helix reforms

Question 26

termination

Answer 26

rna transcript is released and polymerase detaches from DNA

Question 27

how is termination diferent from prokaryotes and eukaryotes

Answer 27

in prokaryotes the polymerase stops transcription at the end of the terminator, both RNA and DNA are then released by RNA pol in eukaryotes the pre-mRNA is cleaved from the growing RNA chain while RNA pol II continues to transcribe the DNA

Question 28

termination in eukaryotes

Answer 28

the polymerase transcribes a DNA sequence called the polyadenylation signal sequence that codes for a polyadenylation sequence in the pre-mRNA at a point past the sequence the pre-mrna is cut from the enzy=me the polymerase keeps transcribing for nucleotides transcriptionis terminated when polymerase eventually falls off

Question 29

key concept of termination

Answer 29

in most cases termination stops when RNA polymerase reachs a DNA sequence that functions as a transcription termination signal

Question 30

how does transcription differ from DNA replicatin

Answer 30

only ne region on DNA strand is used as a template rna polym is used not dna pol results in single stranded dna no need for primer

Question 31

how is rna modified after transcription

Answer 31

enzymes modify pre-mrna before the genetic messages are dispatched to cytoplasm during rna processing, both ends of the primary transcript are usually altered usually some interior parts of the molecule are cut out and other parts are spliced together

Question 32

how is the 5' end of premrna modified

Answer 32

receives a modified nucleotide cap helps tell ribosome where to attacah when translation begins

Question 33

how is the 3' end of pre-mrna modified

Answer 33

the 3' end gets a poly-tail facilitates transport of mRNA out og nucleus and inhibits degradation by enzymes

Question 34

RNA splicing

Answer 34

removes introns and joins exons

Question 35

introns

Answer 35

in between sequences = junk dna

Question 36

exons

Answer 36

expressed seuqneces

Question 37

ribozymes

Answer 37

catalytic rna molecules that function as enzymes and can splice rna

Question 38

spliceosomes

Answer 38

sometimes carries out RNA splicing consist of a variety of proteins and small nuclear ribonucleoproteins that recognize the splice sites

Question 39

alternative RNA splicing

Answer 39

some genes being able to encode more than one kind of polypeptide depending on which segments are treated as exons during RNA splicing makes the number of different proteins an organism can produce, much greater than its number of genes

Question 40

translation

Answer 40

the actual synthesis of a polypeptide, which occurs under the direction of mRNA occurs on ribosomes in the sytoplasn