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Cytogenetics > BVI. Transcription and Translation > Flashcards

BVI. Transcription and Translation Flashcards

1
Q

The genetic code is written in linear form, using as “letters” the [?] that compose mRNA molecules. The ribonucleotide sequence is derived from the complementary nucleotide bases in DNA.

A

ribonucleotide bases

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2
Q

Each “word” within the mRNA consists of (?), thus referred to as a triplet code. With several exceptions, each group of three ribonucleotides, called a codon, specifies one amino acid.

A

three ribonucleotide letters

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3
Q

Each triplet specifies only a single amino acid.

A

unambiguous

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4
Q

A given amino acid can be specified by more than one triplet codon. This is the case for 18 of the 20 amino acids.

A

degenerate

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5
Q

The code contains [?] “start” and [?] “stop” signals, triplet s that initiate and terminate translation, respectively.

A

one
three

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6
Q

Thus, the code is said to be commaless. Once translation of mRNA begins, the codons are read one after the other with no breaks between them (until a stop signal is reached).

A

No internal punctuation

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7
Q

After translation commences, any single ribonucleotide within the mRNA is part of only one triplet.

A

nonoverlapping

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8
Q

The sequence of codons in a gene is [?], with the sequence of amino acids making up the encoded protein.

A

colinear

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9
Q

‘With only minor exceptions, a single coding dictionary is used by almost all viruses, prokaryotes, archaea, and eukaryotes

A

Nearly universal

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10
Q

The complex, multistep process begins with the [?] stored in DNA to RNA.

A

transfer of genetic information

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11
Q

process by which RNA molecules are synthesized on a DNA template.

A

Transcription

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12
Q

It results in an mRNA molecule complementary to the gene seq uence of one of the two strands of the double helix.

A

Transcription

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13
Q

Each triplet codon in the mRNA is, in turn, complementary to the anticodon region of its corresponding tRNA, which inserts the correct amino acid into the polypeptide chain during translation.

A

Transcription

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14
Q

Transcription: RNA is involved as an intermediate molecule in the process of information flow between

A

DNA and protein

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15
Q

DNA is, for the most part, associated with chromosomes in the (?) of the eukaryotic cell.

However , protein synthesis occurs in association with ribosomes located outside the nucleus, in the (?).

Therefore, DNA does not appear to (?) in protein synthesis.

A

nucleus
cytoplasm
participate directly

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16
Q

RNA is synthesized in the (?) of eukaryotic cells, in which DNA is found, and is chemically similar to DNA.

A

nucleus

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17
Q

Following its synthesis, most RNA migrates to the (?), in which protein synthesis (translation) occurs.

A

cytoplasm

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18
Q

The amount of RNA is generally proportional to the amount of (?) in a cell.

A

protein

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19
Q

Collectively, these observations suggested that genetic information, stored in DNA, is transferred to an (?), which directs the synthesis of the proteins.

A

RNA intermediate

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20
Q

As with most new ideas in molecular genetics, the initial supporting experimental evidence for an RNA intermediate was based on studies of

A

bacteria and bacteriophages

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21
Q

Translation of mRNA is the biological polymerization of (?) into (?). This process occurs only in association with (?), which serve as nonspecific workbenches.

A

amino acids
polypeptide chains
ribosomes

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22
Q

In association with a ribosome, mRNA presents a (?) that calls for a specific amino acid.

A

triplet codon

23
Q

A specific tRNA molecule contains within its nucleotide sequence three consecutive ribonucleotides complementary to the codon, called the (?), which can basepair with the codon.

A

anticodon

24
Q

Another region of this tRNA is covalently bonded to the codon’s corresponding (?)

A

amino acid

25
Q

(?) of tRNAs to mRNA holds amino acids in proximity to each other so that a peptide bond can be formed between them.

A

Hydrogen bonding

26
Q

The process occurs over and over as (?) runs through the ribosome, and amino acids are polymerized into a polypeptide.

Before looking more closely at this process, we will first consider the structures of the ribosome and transfer RNA.

A

mRNA

27
Q

Ribosomes, when they are not involved in translation, are dissociated into their large and small subunits.

A

INITIATION

28
Q

Initiation of translation in E. coli involves the (?), an mRNA molecule, a specific charged initiator tRNA, GTP, Mg2+, and three proteinaceous initiation factors (IFs) that enhance the binding affinity of the various translational components and — AUG facilitate the process.

A

small ribosomal subunit

29
Q

In prokaryotes, the initiation codon of mRNA — calls for the modified amino acid called

A

N-formylmethionine (fmet).

30
Q

Lengthening of the growing polypeptide chain by one amino acid.

A

ELONGATION

31
Q

third phase of translation

A

Termination

32
Q

The process is signaled by the presence of any one of the three possible triplet codons appearing in the A site: UAG, UAA, or UGA. These codons do not specify an amino acid, nor do they call for a tRNA in the A site. They are called (?).

A

stop codons, termination codons, or nonsense codons

33
Q

Often, several consecutive stop codons are part of an mRNA. When one such termination stop codon is encountered, the polypeptide, now completed, is still part of the peptidyl tRNA in the (?), and the (?) is empty.

A

P site
A site

34
Q

The (?) signals the action of a GTP-dependent release factor, which stimulates hydrolysis of the polypeptide from the peptidyl tRNA, leading to its release from the translation complex (Step 1). Then, the (?) is released from the ribosome, which then dissociates into its subunits (Step 2)

A

termination codon
tRNA

35
Q
  1. Early studies of the genetic code revealed it to be triplet in nature and to be [?].
A

nonoverlapping, commaless, and degenerate

36
Q
  1. The use of [?] and [?] in a cell-free protein synthesizing system allowed the determination of the composition, but not the sequence, of triplet codons designating specific amino acids.
A

RNA homopolymers
mixed copolymers

37
Q
  1. Use of the [?] and of repeating [?] allowed the determination of the specific sequences of triplet codons designating specific amino acids.
A

triplet-binding assay
copolymers

38
Q
  1. The complete coding dictionary reveals that of the [?] possible triplet codons, [?] encode the [?] amino acids found in proteins, while three triplets terminate translation. One of these [?] is the initiation codon and specifies methionine.
A

64
61
20
61

39
Q
  1. Confirmation for the coding dictionary, including codons for initiation and termination, was obtained by comparing the complete nucleotide sequences of [?] with the [?]of the corresponding proteins. Other findings support the belief that, with only minor exceptions, the code is universal for all organisms.
A

phage MS2
amino acid sequence

40
Q
  1. —the initial step in gene expression—is the synthesis, under the direction of RNA polymerase, of a strand of RNA complementary to a DNA template.
A

Transcription

41
Q
  1. Like DNA replication, the processes of transcription can be subdivided into the stages of [?]. Also like DNA replication, transcription relies on base-pairing affinities between complementary nucleotides
A

initiation, elongation, and termination

42
Q
  1. Initiation of transcription is dependent on an upstream (5′) DNA region, called the [?], that represents the initial binding site for RNA polymerase. [?] contain specific DNA sequences, such as the TATA box, that are essential to polymerase binding.
A

promoter

43
Q
  1. The process of creating the initial transcript during transcription is more complex in eukaryotes than in prokaryotes including the addition of a [?] and a [?].
A

5′ 7-mG cap
3′ poly-A tail, to the pre-mRNA

44
Q
  1. The [?] in eukaryotes reflects the presence of intervening sequences, or introns, present in DNA, which must be spliced out to create the mature mRNA.
A

primary transcript

45
Q
  1. Translation is the synthesis of [?] under the direction of mRNA in association with ribosomes.
A

polypeptide chains

46
Q
  1. Translation depends on [?] that serve as adaptors between triplet codons in mRNA and the corresponding amino acids.
A

tRNA molecules

47
Q
  1. Translation occurs in association with [?] and, like transcription, is subdivided into the stages of initiation, elongation, and termination and relies on base-pairing affinities between complementary nucleotides.
A

ribosomes

48
Q
  1. Inherited metabolic disorders are most often due to the [?] resulting from mutations in genes encoding those proteins.
A

loss of enzyme activity

49
Q

Their work with nutritional mutations in Neurospora led them to propose that one gene encodes one enzyme.

A

Beadle and Tatum’s

50
Q

[?], the end products of genes, demonstrate four levels of structural organization that together describe their three dimensional conformation, which is the basis of each molecule’s function.

A

Proteins

51
Q
  1. Of the myriad functions performed by proteins, the most influential role belongs to [?], which serve as highly specific biological catalysts that play a central role in the production of all classes of molecules in livi ng systems.
A

enzymes

52
Q
  1. In eukaryotes, proteins contain one or more functional domains, each prescribed by [?] regions interspersed within genes. Specific domains impart specific functional capacities to proteins and appear to have been “shuffled” between genes during evolution
A

exon

53
Q

Investigations oh Hb from px with sickle-cell anemia led to the modification of the one-gene: one-enzyme hypothesis to indicate that one gene encodes one polypeptide chain

A

Pauling and Ingram

Cytogenetics (11 decks)

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