chapter 14

Question 1

rna coding regions

Answer 1

exons

Question 2

noncoding regions

Answer 2

introns

Question 3

where does the splicing of pre-mrna take place

Answer 3

nucleus

Question 4

gene

Answer 4

dna sequence that encodes an rna molecule

Question 5

what did brenner, jacob and meselson demonstrate

Answer 5

that ribosomes were not the agents by which genetic information was moved to the cytoplasm for the production of protein

Question 6

codon

Answer 6

each amino acid of a protein is specified by a set of three nucleotides

Question 7

mrna three primary regions

Answer 7

5’ untranslated region, protein coding region, and 3’ untranslated region

Question 8

how is mrna transribed in bacteria v. in eukaryotes

Answer 8

mrna is transcribed directly from dna but in eukaryotes a pre-mrna is first transcribed from dna and then processed to yield mrna

Question 9

shine dalgarno sequence

Answer 9

in bacterial mrna this region contains a consensus sequence (AG-GAGG) and serves as the ribosome binding site during translation

Question 10

protein coding region

Answer 10

has codons that specify the amino acid sequence of the protein and begins with a start and stop codon

Question 11

where does transcription/ translation take place

Answer 11

in the nucleus and in the cytoplasm

Question 12

addition of 5 cap

Answer 12

binding of ribosome to 5 end of mrna and increases stability
- infleunces removal of introns

Question 13

3 cleavage and addition of poly A tail

Answer 13

increases stability, aids in export of mRNA of the nucleus and facilitates binding of ribosome to mRNA

Question 14

RNA splicing

Answer 14

removes noncoding introns from pre mrna and export of mRNA to cytoplasm, allows for multiple proteins to be produced

Question 15

rna editing

Answer 15

alters nucleotide sequence of mRNA

Question 16

internal rna modification

Answer 16

influence splicing, mrna degradation and translation

Question 17

5’ cap

Answer 17

• formed by the addition of ectra guanine nucleotide to the 5’ end of the mrna and the addition of methyl groups to the base in the guanine
• consists of 7-methylguanosine attached to pre-mrna and a 5-5 bond

Question 19

poly A tail

Answer 19

addition of 50 - 250 more adenine nucleotides at the 3’ end and added in polyadenylation

Question 20

what determines where cleavage will take place

Answer 20

consensus sequence AAUAAA
- after cleavage has been completed, adenine nucleotides are added without a template to the new 3’ end creating the poly A tail

Question 21

what do internal modifications consist of

Answer 21

addition of a methyl group to nitrogen to the 6 position of adenine

• found near stop codons and in 3 untranslated regions of mrna

Question 22

where does rna splicing takes place

Answer 22

takes place in the nucelus, before the rna moves to the cytoplasm

Question 23

splicing code

Answer 23

three sequences in the intron
5’ splice site, 3’ splice site and the branch point
- most introns begin with GU and end with AG

Question 24

where does splicing take place

Answer 24

spliceosome which is largest molecule and consists of 5 rna molecules and 300 proteins

Question 25

process of splicing

Answer 25

1. mrna is cut at 5’ splice site
2. the 5’ end of the intron attaches to the branch point
3. a cut is made at the 3’ splice site
4. the intron is released as the lariat
5. two exons are spliced together and exported to the cytoplasm and translated

Question 26

lariat

Answer 26

5’ end of the intron attaches to the branch point and guanine nucleotide with the adenine nucleotide at branch point

Question 27

trans-splicing

Answer 27

mrna produced by splicing togetehr sequences from two or more different rna molecules

Question 28

recursive splicing

Answer 28

long introns are removed in multiple steps

Question 29

alternative processing pathway

Answer 29

-single pre-MRNA used to make different protein sequences using the same dna sequence

Question 30

alternative splicing

Answer 30

same pre-mrna is spliced in more than one way to yield different mrna that are translated into different amino acid sequences andthus proteins

Question 31

multiple 3’ cleavage sites

Answer 31

two or more potential sites for cleavage and polyadenylation are present in the pre-mrna and results in different lengths

Question 32

rna editing

Answer 32

coding sequence of mrna molecule is altered after transcription, so the translated protein has an amino acid sequence that differs from that encoded by the gene

Question 33

how many amino acids are found in proteins

Answer 33

20

Question 34

what is trna

Answer 34

serves a link between genetic code in mrna and the amino acids that make up a protein

Question 35

anticodon

Answer 35

arm at the end of tRNA where there are 3 nucleotides and correpspond with a codon to ensure that mRNA is in the correct order

Question 36

functional ribosome

Answer 36

consists of a large ribosomal unit and a small ribosomal unit

Question 37

RNA interference

Answer 37

powerful and precise mechanism used by eukaryotic cells to limit the invasion of foreign genes

• triggered by double stranded rna molecules and chopped up by an enzyme called cier resulting in siRNA and miRNA

Question 38

RISC (rna induced silencing complex)

Answer 38

siRNA and miRNA combine with proteins

• cleaves mrna leading to degradaation or represses translaition of mrna

Question 39

crispr rna

Answer 39

only in prokaryotes and encoded by dna sequences found in bacterial and archael genomes

Question 40

three stages of CRISPR

Answer 40

acquisition- bacteria enters and is identified and inserted into CRISPR , expression and interference