Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Molecular Cell Bio > chapter 7 > Flashcards

chapter 7 Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

RNA differs from DNA chemically in two respects: (1) the nucleotides in RNA are _—that is, they contain the sugar _ (hence the name ribonucleic acid) rather than the _ found in DNA; and (2) although, like DNA, RNA contains the bases adenine (A), guanine (G), and cytosine (C), it contains _ (U) instead of the _ (T)
found in DNA

A

ribonucleotides
ribose
deoxyribose
uracil
thymine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

The first step a cell takes in expressing one of its many thousands of genes is to copy the nucleotide sequence of that gene into RNA. The pro- cess is called _

A

transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Whereas DNA always occurs in cells as a double-stranded helix, RNA is largely _.

A

single-stranded

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

RNA polymer- ases make about one mistake for every _ nucleotides copied into RNA

A

10^4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The majority of genes carried in a cell’s DNA specify the amino acid sequences of proteins. The RNA molecules encoded by these genes— which ultimately direct the synthesis of proteins—are called _ (_).

A

messenger RNAs
mRNAs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

When an RNA polymerase collides randomly with a DNA molecule, the enzyme sticks weakly to the double helix and then slides rapidly along its length. RNA polymerase latches on tightly only after it has encountered a gene region called a _.
As it binds tightly to this sequence, the RNA polymerase opens up the double helix immediately in front of the _ to expose the nucleotides on each strand of a short stretch of DNA.

A

promoter
promoter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Elongation then continues until the enzyme encounters a second signal in the DNA, the _, where the polymerase halts and releases both the DNA template and the newly made RNA transcript

A

terminator (or stop site)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

The terminator sequence itself is _, and it is the interaction of this _ with the polymerase that causes the enzyme to let go of the template DNA.

A

also transcribed
3’ segment of RNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

a segment of DNA will be transcribed only if _.

A

it is preceded by a promoter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

RNA polymerases I and III transcribe the genes encoding _, _ RNA, and various other RNAs that _ in the cell.

A

transfer RNA
ribosomal
play structural and catalytic roles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

RNA polymerases _ transcribe the genes encoding transfer RNA, ribosomal RNA, and various other RNAs that play structural and catalytic roles in the cell

A

I and III

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

RNA polymerase _ transcribes the rest, including all those that encode _—which constitutes the majority of genes in eukaryotes

A

II
proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

WhereasthebacterialRNApolymerase(alongwithitssigmasubunit) is able to initiate transcription on its own, eukaryotic RNA polymerases require the assistance of a _ Principal among these are the _, which must assemble at each promoter, along with the polymerase, before transcription can begin.

A

large set of accessory proteins.
general transcription factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

And before it can be exported to the cytosol, a eukaryotic RNA must go through several RNA processing steps, which include _, _, and _

A

capping
splicing
polyadenylation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

In short, capping modifies the _ of RNA, and polyadenylation adds _ to _ in eukaryotic cells. These changes help the RNA to be _, _, and _.

A

front (5’ end)
a long tail (poly-A tail)
the back (3’ end)
stable
exported
translated properly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

RNA splicing is carried out largely by RNA molecules rather than proteins. These RNA molecules, called _, are packaged with additional _ to form _

A

small nuclear RNAs (snRNAs)
_
proteins
_
small nuclear ribonucleoproteins (snRNPs, pro- nounced “snurps”).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Together, these snRNPs form the core of the _, the large assembly of RNA and protein molecules that carries out RNA splicing in the nucleus.

A

spliceosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

the transcripts of many eukaryotic genes can be spliced in different ways, each of which can produce a distinct protein called:_

A

alternative splicing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

the translation of mRNA into protein depends on adaptor molecules that bind to a codon with one part of the adaptor and to an amino acid with another. These adaptors consist of a set of small RNA molecules known as _, each about 80 nucleotides in length.

A

transfer RNAs (tRNAs)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

ecognition and attachment of the correct amino acid depend on enzymes called _

A

aminoacyl-tRNA synthetases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

This _ tRNA always carries
the amino acid methionine

A

initiator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

In eukaryotes, an initiator tRNA, charged with methionine, is first loaded into the _ site of the small ribosomal subunit, along with additional proteins called _

A

P
translation initiation factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

These enzymes, which degrade proteins, first to short peptides and finally to individual amino acids, are known collectively as _.
proteins are broken down by large protein machines called _

A

proteases
proteasomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Proteins must then fold into the correct, three-dimensional shape (as we discuss in Chapter 4). Some proteins do so spontaneously, as they emerge from the ribosome. Most, however, require the assistance of _, which steer them along productive folding path- ways and prevent them from aggregating inside the cell

A

chaperone proteins

25
Q

The conversion of the genetic instructions in DNA into RNAs and proteins is termed _.

A

gene expression

26
Q

Cells make several functional types of RNAs, including messenger RNAs (mRNAs), which carry the instructions for making proteins; _, which are the crucial components of _; and transfer RNAs (tRNAs), which act as adaptor molecules in protein synthesis.

A

ribosomal RNAs (rRNAs)
ribosomes

27
Q

To begin transcription, RNA polymerase binds to specific DNA sites called promoters that lie immediately upstream of genes. To initiate transcription, eukaryotic RNA polymerases require the assembly of a complex of general transcription factors at the promoter, whereas bacterial RNA polymerase requires only an additional subunit, called _.

A

sigma factor

28
Q

Introns are removed from the RNA transcripts in the nucleus by RNA splicing, a reaction catalyzed by _ known as snRNPs. Splicing removes the introns from the RNA and joins together the exons—often in a variety of combinations, allowing multiple proteins to be produced from the same gene.

A

small ribonucleoprotein complexes
snRNPs

29
Q

Eukaryotic pre-mRNAs go through several additional RNA process- ing steps before they leave the nucleus as mRNAs, including 5ʹ RNA capping and 3ʹ polyadenylation. These reactions, along with splicing, take place _

A

as the pre-mRNA is being transcribed.

30
Q

tRNAs act as adaptor molecules in protein synthesis. Enzymes called _ covalently link amino acids to their appropriate tRNAs. Each tRNA contains a sequence of three nucleo- tides, the anticodon, which recognizes a codon in an mRNA through complementary base-pairing.

A

aminoacyl-tRNA synthetases

31
Q

The stepwise linking of amino acids into a polypeptide chain is catalyzed by an _ in the _, which thus acts as a _.

A

rRNA molecule
large ribosomal subunit
ribozyme

32
Q

The concentration of a protein in a cell depends on _. Protein degradation in the cytosol and nucleus occurs inside large protein complexes called _.

A

the rates at which the mRNA and protein are synthesized and degraded
_
proteasomes

33
Q

From our knowledge of present-day organisms and the molecules they contain, it seems likely that life on Earth began with the evolution of _.

A

RNA molecules that could catalyze their own replication

34
Q

The chemical linkage between nucleotides in RNA—a _ bond—is the same as that in DNA.

A

phosphodiester

35
Q

The nontemplate strand of the gene (here, shown at the
top) is sometimes called the _
because its _.

A

coding strand
sequence is equivalent to the RNA product

36
Q

RNA molecule is usually depicted with its _ end, which is the first part to be synthesized.

A

5’

37
Q

Bacterial RNA polymerase (light blue) contains a subunit called _ (yellow) that recognizes the promoter of a gene (green).
Once transcription has begun, _ is released, and the polymerase moves forward and continues synthesizing the RNA. Elongation continues until the polymerase encounters a sequence in the gene called the _ (red ). After transcribing this sequence into RNA (dark blue), the enzyme halts and releases both the DNA template and the newly made RNA transcript. The polymerase then reassociates with a _ and searches for another promoter to begin the process again.

A

sigma factor
sigma factor
terminator
free sigma factor

38
Q

To begin transcription, eukaryotic RNA polymerase
II requires _

A

a set of general transcription factors.

39
Q

Most eukaryotic promoters contain a DNA sequence called the _.

A

TATA box

40
Q

The TATA box is recognized by a _, called the _.

A

subunit of the general transcription factor TFIID
TATA-binding protein (TBP)

41
Q

The binding of TFIID enables the adjacent _.
The rest of the _, as well as the _ itself, then assemble at the promoter.

A

binding of TFIIB.
general transcription factors
RNA polymerase

42
Q

TFIIH _ at the transcription start point, using the energy of _, which exposes the template strand of the gene.
TFIIH also _, releasing the polymerase from most of the general transcription factors, so it can begin transcription.
The site of phosphorylation is a _ that extends from the polymerase.

A

pries apart the double helix
ATP hydrolysis
phosphorylates RNA polymerase II
long polypeptide “tail”

43
Q

Once the polymerase moves away from the promoter, most of the general transcription factors are released
from the DNA; the exception is _, which remains bound through multiple rounds of transcription initiation.

A

TFIID

44
Q

Splicing is carried out by a collection of _ called _.

A

RNA–protein complexes
snRNPs

45
Q

In the first steps of splicing, U1 recognizes the _ and U2 recognizes the _ through complementary base-pairing.

A

5’ splice site
lariat branch-point site

46
Q

U6 then “_” the _ by displacing _ and base-pairing with this intron sequence itself.

A

re-checks
5’ splice site
U1

47
Q

In the next steps, conformational changes in _—triggered by the _ by spliceosomal proteins (not shown)— drive the formation of the _.

A

U2 and U6
hydrolysis of ATP
spliceosome active site

48
Q

Once the splicing reactions have occurred (see Figure 7–21), the spliceosome deposits a group of _, known as the _(red ), on the mRNA
to mark the splice site as successfully completed.

A

RNA-binding proteins
exon junction complex

49
Q

Translation takes place in a _, which
is repeated over and over during the synthesis of a protein.

A

four-step cycle

50
Q

In
step 1 (translation), a charged tRNA carrying the next amino acid to be added
to the polypeptide chain binds to the _ on the ribosome by forming base pairs with the mRNA codon that is exposed there.

A

vacant A site

51
Q

The A and P sites are sufficiently close together that their two tRNA molecules are _, with no stray bases in-between. This positioning of the tRNAs ensures that the correct _ will be preserved throughout the synthesis of the protein.

A

forced to form base pairs with codons that are contiguous
_
reading frame

52
Q

In step 2, the carboxyl end of the polypeptide chain (amino acid 3 in step 1) is _ from the tRNA at the _ site and joined by a _ to the free amino group of the amino acid linked to the tRNA at the _ site. This reaction is carried out by a catalytic site in the _.

A

uncoupled
P
peptide bond
A
large subunit

53
Q

In step 3, a shift of the_ relative to the _ moves the two bound tRNAs into the _ sites of the _ subunit.

A

large subunit
small subunit
E and P
large

54
Q

In step 4, the _ subunit moves exactly three nucleotides along the mRNA molecule, bringing it back to its original position relative to the _ subunit. This movement ejects the _
and resets the ribosome with an empty _ site so that the next charged tRNA molecule can bind

A

small
large
spent tRNA
A

55
Q

Initiation of protein synthesis in eukaryotes requires _ and a _.

A

translation initiation factors
special initiator tRNA

56
Q

efficient translation initiation also requires additional
proteins that are bound at the _ of the mRNA.
In this way, the translation apparatus can ascertain that both ends of the mRNA are _ before initiating translation.

A

5’ cap and poly-A tail
intact

57
Q

Proteins marked by a _ chain are degraded by
the proteasome.

A

polyubiquitin

58
Q

Proteins in the _ (blue) recognize proteins marked by a specific type of polyubiquitin chain (red ).
The _ unfolds the target protein and threads it into the _ (yellow), which is lined with _ that chop the protein to pieces.

A

stopper of a proteasome
stopper
proteasome’s central cylinder
proteases

Molecular Cell Bio (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions