Cell Biology Chapter 18

Question 1

The principle of directional information flow from where?

Answer 1

DNA to RNA to protein; is the central dogma of molecular biology

Question 2

What is a genetic code?

Answer 2

the relationship between the DNA base sequence and the linear order of amino acids in the protein products

Question 3

The coded information of DNA is used to what? There are how many DNA bases and how many amino acids?

Answer 3

to guide production of RNA and protein molecules; 4 DNA bases, 20 amino acids

Question 4

What is a triplet code and how many possible combinations are there? What is transcription?

Answer 4

combinations of 3 bases that specify amino acids; have 64 possible combinations more than enough for all 20 amino acids; synthesis of RNA molecule

Question 5

DNA serves as a template for what? What does transcription refer to?

Answer 5

synthesis of an RNA molecule which then directs the synthesis of a protein product; refers to RNA synthesis using DNA as a template

Question 6

What is translation? What is mRNA?

Answer 6

synthesis of protein using the information in the RNA; RNA that is translated into protein (only translated RNA)

Question 7

What is rRNA? What is tRNA?

Answer 7

integral component of the ribosome; molecules serve as intermediaries, bringing amino acids to the ribosome (functional RNA)

Question 8

Bacteria doesn’t have a what? TranslationofmRNAcanbeginbeforewhen?The compartmentalization of eukaryotic cells leads to what?

Answer 8

nuclear envelope, before its transcription is completed; spatial separation of transcription and translation

Question 9

The gene is written how? Inserting or deleting a nucleotide causes what?

Answer 9

in a language of 3 letter word; the rest of the sequence to be read out of phase - this is a shift in the reading frame

Question 10

What are frameshift mutations? There are 64 combinations of what and 20 combinations of what?

Answer 10

mutations that cause insertion or deletion of a nucleotide causing a shift on the reading frame; nucleotide triplets, amino acids

Question 11

The genetic code is what and what is it’s definition? The genetic code is what and what is it’s definition? It is also what and what is it’s definition?

Answer 11

degenerate- a particular amino acid can be specified by more than 1 triplet; unambiguous- every codon has one meaning only; nonoverlapping- reading frame advances 3 nucleotides at a time

Question 12

All 64 codon are used in what? 61 of them specify the addition of what? AUG role and UAA, UAG, UGA role? What else do codons do and not do

Answer 12

in the translation of mRNA; specific amino acids to a growing polypeptide chain; start a codon; stop a codon; terminate polypeptide synthesis and doesn’t code for any amino acid

Question 13

In mRNA synthesis only what is copied? What is a template strand?

Answer 13

DNA strand; used as a template to make the mRNA

Question 14

What is the coding strand?

Answer 14

The genetic information is the same as the mRNA; except that T in the DNA are U in the mRNA

Question 15

RNA is chemically similar to what? It has a base of what? It is usually what?

Answer 15

DNA but contain ribose instead of deoxyribose; base of uracil instead of thymine; single stranded

Question 16

Transcription begins when ?

Answer 16

when RNA polymerase binds to a promoter sequence triggering local unwinding of the double helix

Question 17

RNA polymerase then initiates what? The mechanisms for initiation are different between what?

Answer 17

synthesis of RNA using one DNA strand as a template; prokaryotes and eukaryotes

Question 18

The RNA polymerase moves along the what? What is a transcription bubble?

Answer 18

the DNA template unwinding the helix and elongating the RNA; unwound DNA

Question 19

RNA polymerase dissociates from what?

Answer 19

DNA template leading to termination of synthesis and release of the RNA molecule

Question 20

RNA polymerase binds to what and its definition?

Answer 20

DNA promoter site- a sequence of several dozen base pairs that determines where RNA synthesis will start

Question 21

The terms what and what do they refer to? The promoter is what?

Answer 21

upstream and downstream refer to sequences located toward the 5’ or 3’ end of the transcription unit; upstream of the transcribed sequence

Question 22

In bacteria a sigma subunit is key to what? What is a sigma factor?

Answer 22

initiate transcription; provides specificity for promoter recognition and it is needed to initiate transcription but dissociates shortly after initiation

Question 23

Initiation of RNA synthesis takes place when? One of the DNA strands serve as a what?

Answer 23

once the DNA is unwound; a template for RNA synthesis

Question 24

RNA polymerase uses what? RNA polymerase catalyzes what?

Answer 24

ribonucleoside triphosphate molecules that are complementary to the template strand; the formation of a phosphodiester bond between the NTPs

Question 25

Chain elongation continues as what? RNA is elongated in which direction? As the polymerase moves along the DNA strand, the double helix ahead of the polymerase is what?

Answer 25

RNA polymerase moves along the DNA molecule; 5’ to 3’ direction with each new nucleotide added to the 3’ end; unwound and the DNA behind it is rewound into a double helix

Question 26

Termination uses what? Intrinsic termination is what? These RNA molecules contain what?

Answer 26

specific sequences; most common termination in bacteria; contain a short GC-rich sequence followed by several U’s at the end of the transcript

Question 27

The GC region in the RNA forms a what? Then the weaker bonds between the what of the template strand breakreleasingwhat?

Answer 27

hairpin loop pulling the RNA molecule away from the DNA; between the U’s and A’s break releasing RNA

Question 28

Transcription in Eukaryotic Cells has what? RNA polymerase in eukaryotes requires what?

Answer 28

additional complexity compared with prokaryotes; additional proteins called transcription factors

Question 29

The transcription factors do what? The RNA polymerase is able to do what?

Answer 29

recognize and bind the promoter; to bind the promoter

Question 30

More transcription factors join what? RNA polymerase dissociates from what?

Answer 30

join after to trigger initiation; the transcription factors and carries out transcription

Question 31

After initiation, RNA polymerases move along the what? For RNA polymerase 2, transcripts are cleaved at what?

Answer 31

the DNA and synthesize a complementary RNA; specific site before transcription ceases

Question 32

The cleavage site is what? The cleavage site of polymerase 2 transcripts is also the site forwhat?

Answer 32

10-35 nucleotides downstream of AAUAAA sequence in the RNA; for addition of poly(A) tail

Question 33

This is a string of adenine nucleotides added to what? RNA cleavage is more important than what?

Answer 33

the 3’ end of most eukaryotic mRNAs; termination of transcription

Question 34

A newly produced RNA molecule is called what? It must undergo what before it can what? Eukaryotic transcripts must be exported form where?

Answer 34

primary transcript or pre-mRNA; RNA processing function in the cell; the nucleus to be translated

Question 35

Substantial processing occurs where? Pre-mRNAs are processed by what? The C-terminal domain of one of the subunits of RNA polymerase 2 acts as what?

Answer 35

the nucleus before export; removal of sequences and addition of 5’ caps and 3’ tails; as a platform for protein complexes involved in processing

Question 36

Eukaryotic mRNAs have a what? The 5’ cap is a guanosine that is methylated at it is bound to what?

Answer 36

modified nucleotide called the 5’ cap and the 3’ ends have a long stretch of adenines called the poly(A) tail; to the RNA molecule by 5’ -> 5’ triphosphate linkage rather than the usual 3’ -> 5’ bond

Question 37

The 5’ cap is added when? The cap contributes to what?

Answer 37

soon after transcription is initiated; to mRNA stability by protecting the RNA from nucleases

Question 38

The cap plays a role in what? The poly(A) tail is a string of what?

Answer 38

in positioning the RNA on the ribosome for initiation of translation; string of A nucleotides and is added by the enzyme poly (A) polymerase

Question 39

A signal for addition of the poly(A) tail, AAUAAA, is located where? The poly(A) tail protects what from what?

Answer 39

just upstream of the polyadenylation site, and a GU- or U-rich element is located downstream from it; the mRNA from nuclease attack the length of the tail influences stability

Question 40

Poly(A) tail is also required for export of the what? It may also help ribosomes how?

Answer 40

of the transcript to the cytoplasm; it may also help ribosomes recognize and bind mRNAs

Question 41

What are exons? What are introns?

Answer 41

coding sequences that appear in the final mRNA; noncoding present in most protein-coding genes that separate the exons

Question 42

What of introns varies considerably? What is RNA splicing?

Answer 42

the size and number; the process of removing introns and joining the exons

Question 43

Sequences commonly found where determines what? The 5’ end of an intron typically starts with what and terminates with what?

Answer 43

at the intron-exon boundaries determine the 5’ and 3’ splice sites; starts with GU and terminates with AG at the 3’ end

Question 44

What is branch point A? What is spliceosomes?

Answer 44

one additional sequence near the 3’ end of the intron; intron removal is catalyzed by large molecular complexes

Question 45

The presence of intron allows what? What is alternative splicingispossibleviamechanismsallowingwhat?

Answer 45

allows each gene’s pre-mRNA molecule to be spliced in multiple ways, leading to production of multiple protein products; allowing certain splice sites to be activated or skipped

Question 46

Many RNA processing events occur how? The long C-terminal domain (CTD) of RNA polymerase is responsible for what?

Answer 46

contranscriptionally; responsible for this processing

Question 47

Many repeats of a seven-amino-acid sequence of the CTD bind enzymes needed for what?

Answer 47

capping, splicing, and cleavage/polydenlylation