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unit 6 > ch 17- transcription > Flashcards

ch 17- transcription Flashcards

1
Q

gene expression

A

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

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2
Q

basic principles of transcription

A

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

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3
Q

RNA structures

A

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

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4
Q

types of RNA

A

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

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5
Q

mRNA

A

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

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6
Q

transfer RNA

A

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

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7
Q

primary/pre RNA

A

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

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8
Q

properties that enable RNA to perform many different functions

A

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

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9
Q

messenger rna how it is built

A

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

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10
Q

ribosomal RNA

A

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

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11
Q

anticodon

A

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

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12
Q

how is translation and transciption different in prokaryotes and eukaryotes

A

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

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13
Q

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

A

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

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14
Q

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

A

a DNA strand called the template strand

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15
Q

what does the GENE determine in transcription

A

the sequence of bases along the length of an mRNA molecule

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16
Q

how is a language shared by all living things

A

same codon codes for same AA in all organisms

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17
Q

RNA synthesis

A

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

18
Q

RNA polymerase

A

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

19
Q

difference and similarities between RNA and DNA polymerase

A

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

20
Q

stages of transcript

A

initiation
elongation
termination

21
Q

before RNA synthesis

A

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

22
Q

initiation - rna transcript

A

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

23
Q

promoter

A

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

24
Q

what does the promoter tell DNA

A

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

25
Q

elongation

A

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

26
Q

termination

A

rna transcript is released and polymerase detaches from DNA

27
Q

how is termination diferent from prokaryotes and eukaryotes

A

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

28
Q

termination in eukaryotes

A

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

29
Q

key concept of termination

A

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

30
Q

how does transcription differ from DNA replicatin

A

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

31
Q

how is rna modified after transcription

A

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

32
Q

how is the 5’ end of premrna modified

A

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

33
Q

how is the 3’ end of pre-mrna modified

A

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

34
Q

RNA splicing

A

removes introns and joins exons

35
Q

introns

A

in between sequences = junk dna

36
Q

exons

A

expressed seuqneces

37
Q

ribozymes

A

catalytic rna molecules that function as enzymes and can splice rna

38
Q

spliceosomes

A

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

39
Q

alternative RNA splicing

A

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

40
Q

translation

A

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

unit 6 (5 decks)

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