chapter 14 lecture 16

Question 1

the royal disease

Answer 1

single change at a splicing junctions
A-G mutationo upstream of exon 4 in the F9 gene and predicted to create a new splice acceptor site => truncated factor IX protein

Question 2

what evidence indicated that eukaryotic genes are not colinear with their proteins?

Answer 2

when DNA way hybridized to the mRNA transcribed from it, regions of DNA that did not correspond to RNA looped out

Question 3

colinearity

Answer 3

suggest that a continuous sequence of nucleotides in DNa encodes a continuous sequence of amino acids in a protein
- the case in prokaryotes

Question 4

noncolinearity

Answer 4

means that there are introns

• discovered by hybridizing DNA and mRNA
• coding sequences of many eukaryotic genes are disrupted by noncoding introns

Question 5

intron

Answer 5

a nucleotide sequence within a gene that is removed by RNA splicing during maturation of final RNA product

Question 6

Exon

Answer 6

part of a gene that will become a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing

Question 7

What are 4 major types of introns?

Answer 7

Group I

• self-splicing
• genes of eubacteria, bacteriophages and eukaryotes

group II

• self spicing
• genes of eubacteria ,archaea, and eukaryotic organeles

Nuclear pre-mRNA

• spliceosomal
• protein encoding genes in the nucleus of eukarotes

tRNA

• enzymatic
• tRNA genes of eubacteria, archaea, and eukarotes

Question 8

the gene includes

Answer 8

• DNA sequences that code for all exons and introns
• sequences at the beginning and end of the RNA that are not translated into a protein , the transcription unit consists of
• the promoter
• the transcribed RNA sequence (coding and noncoding )
• the terminator

Question 9

shine-Dalgarno sequence

Answer 9

a ribosomal binding site in prokaryotic messenger RNA, generally located around 8 bases upstream of the start codon AUG. the 6 base consensus sequence is AGGAGG

Question 10

three primary regions of mature mRNA

Answer 10

• 5’ intranslated region
• protein-coding region
• 3’ untranslated region

5’ and 3’ do not encode any amino acids of a protein but contain information that is important in translation, RNA stability, and regulation of gene expression

Question 11

addition of 5’ cap

Answer 11

• nucleotide with 7-methylguanine
• facilitates binding of ribosome to 5” end of mRNA,
• increase mRNA stability,
• enhances RNA splicing

Question 12

3’ cleavage and addition of poly(A) tail

Answer 12

• 50-200 adenine nucleotides added to 3’ end of the mRNA
• increases stability of mRNA
• facilitates binding of ribosome to mRNA

Question 13

RNA splicing

Answer 13

removed noncoding introns from pre-mRNA
0 facilitate export of mRNA to cytoplasm
- allows for multiple proteins to be produced through alternative splicing
- has to do with nearly perfection
- consensus sequences at 5’ splice site and 3’ splice site

Question 14

RNA editing

Answer 14

alter nucleotide sequence of mRNA

Question 15

where does RNA splicing take place?

Answer 15

withing the spliceosome

-

Question 16

spliceosome

Answer 16

large and complex molecular machine found withing the nucleus of eukaryotic cells
- assembles from snRNAs and proteins complexes

Question 17

Why are pre-mRNAs capped, but tRNAs an rRNAs not?

Answer 17

a protein that adds the 5’ cap is associated with rNA polymerase II which transcribes pre-mRNAs but is absent from RNA polymerase I and III, which transcribe rRNA and tRNAs

Question 18

if a splice site were mutated so that splicing did not take place, what would be the effect on the mRNA?

a. it would be shorter than normal
b. it would be longer than normal
c. it would be the same length but encode a different protein

Answer 18

b. it would be longer than normal

Question 19

Alternative splicing

Answer 19

dynamically regulate in both space and time
- results in different (ratios) splice isoforms in different tissues, in different cells within the same tissue, in the same tissue at different stages of development or in response to pathological processes

Question 20

Alternative 3’ cleavage sites result in

a. multiple genes of different lengths
b. multiple pre-mRNAs of different lengths
c. multiple mRNAs of different lengths
d. all of the above

Answer 20

c. multiple mRNAs of different lengths

Question 21

What specifies the modified sequence of nucleotides found in an edited RNA molecule?

Answer 21

guide RNAs

Question 22

tRNAs:

Answer 22

• all are similar in size and have a common secondary structure known as the cloverleaf
• contain modified bases and are extensively processed after transcription in both bacterial and eukaryotic cells

Question 23

How are rare bases incorporated into tRNAs?

a. encoded by guide RNAs
b. by chemical changes to one of the standard bases
c. encoded by rare bases in DNA
d. encoded by sequences in introns

Answer 23

b. by chemical changes to one of the standard bases

Question 24

What types of changes take place in rRNA processing?

a. methylation of bases
b. cleavage of a larger precursor
c. nucleotides are trimmed from the ends of rRNAs
d. all the above
e. ubiquination

Answer 24

d. all the above

mature rRNA can also be pseudouridylated(most abundant post-transcriptionally modified nucleotide in various stable RNAs of all organisms

Question 25

RNA interference

Answer 25

limits the invasion of foreign genes and censors the expression of their own genes

Question 26

what RNAs are produced from double-stranded RNAs

Answer 26

siRNAs and miRNAs

Question 27

How do siRNAs and miRNAs target specific mRNAs for degradation or for the repression of translation?

Answer 27

an siRNA or miRNA combines with proteins to form RISC, which then pairs with mRNA through complementary pairing between bases on the siRNA or miRNA and bases on the mRNA

Question 28

CRISPR RNAs

Answer 28

function in defense against invasion of foreign DNAs, such as DNA from bacteriophage and plasmids