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BIO 130.01 Genetics, Lecture > Chapter 13: Translation and Proteins > Flashcards

Chapter 13: Translation and Proteins Flashcards

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1
Q

Biological polymerization of

amino acids into polypeptide chains.

A

Translation

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2
Q

This class of molecules adapts specific triplet codons in mRNA to their correct amino acids. (Adaptor hypothesis)

A

transfer RNA

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3
Q

Three consecutive ribonucleotides complementary to the

codon of the mRNA.

A

Anticodon

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4
Q

True or False. Electron microcopy reveals that the bacterial ribosome is about 40 nm at its largest dimension and consists of two subunits, one large and one small.

A

True

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5
Q

Composition of ribosome subunit.

A
  1. one or more molecules of RNA

2. ribosomal proteins

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6
Q

When the two subunits are associated with each other in a single ribosome, the structure is sometimes called?

A

Monosome

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7
Q

Reflection of the density, mass, and shape of ribosome subunits (RNA components and ribosomal proteins).

A

Svedberg coefficient (S)

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8
Q

Size of prokaryotic monosome.

A

70S particle (50S large subunit and 30S small subunit)

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9
Q

Size of eukaryotic monosome.

A

80S (60S large subunit and 40S small subunit)

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10
Q

True or False. Sedimentation coefficients, which reflect the variable rate of migration of different-sized particles and molecules, are additive.

A

False

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11
Q

Are part of the moderately repetitive DNA fraction and are present in clusters at various chromosomal sites. Part of the DNA that transcribes RNA.

A

rRNA gene (rDNA)

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12
Q

True or False. In humans, these gene (rDNA)
clusters have been localized near the ends of chromosomes
13, 14, 15, 21, and 22.

A

True

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13
Q

True or False. In humans, a gene cluster encoding 5S rRNA has been located on chromosome 1.

A

True

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14
Q

True or False. In pro and eukaryotic organisms, tRNAs are transcribed as larger precursors, which are cleaved into mature 4S tRNA molecules.

A

True

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15
Q

A number of nucleotides are unique to tRNA. These bases are called?

A

Modified base

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16
Q

True or False. Modified structures of tRNA are created after transcription of tRNA. (posttranscriptional modification)

A

True

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17
Q

True or False. The presence of modified bases enhances hydrogen bonding efficiency during translation.

A

True

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18
Q

This arrangement created a series of paired stems and unpaired loops resembling the shape of a clover-
leaf.

A

cloverleaf model of tRNA

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19
Q

The end of the tRNA molecule where the

amino acid is covalently joined to the terminal adenosine residue. All tRNA molecules possess this sequence.

A

CCA-3’

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20
Q

True or False. Shapes of the intervening loops may be recognized by the specific enzymes responsible for adding amino acids to tRNAs.

A

True

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21
Q

The tRNA molecules must be chemically linked to their respective amino acids. This process of called?

A

Charging

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22
Q

Charging of amino acid to the tRNA is mediated by what enzyme?

A

Aminoacyl tRNA synthetases.

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23
Q

True or False. Because of the ability of the third member of a triplet code to “wobble,” it is now thought that there are only 31 different tRNAs.

A

True

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24
Q

True or False. It is also believed that there are only

20 synthetases, one for each amino acid, regardless of the greater number of corresponding tRNAs.

A

True

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25
Q

The subset of tRNA molecules that recognize a common amino acid is called?

A

Isoaccepting tRNAs

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26
Q

True or False. Synthetases are highly specific thus, there are only 20 types of synthetases corresponding to the 20 different amino acids.

A

True

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27
Q

True or False. Most ribosomes, when they are not involved in translation, are dissociated into their large and small subunits.

A

True

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28
Q

Upon initiation of translation, these molecules enhance the binding affinity of the various translational components.

A

Initiation factors (IFs)

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29
Q

In prokaryotes, the initiation codon, AUG calls for the modified amino acid called?

A

formylmethionine (fmet)

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30
Q

This sequence is composed of six ribonucleotides precedes the initial AUG start codon. This is also where the IF1-small ribosomal small subunit complex bind before translation proceeds.

A

Shine–Dalgarno sequence

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31
Q

True or False. Shine–Dalgarno sequence contains only pyrimidines.

A

False.

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32
Q

In the initiation phase, this molecule serves to inhibit the small subunit from associating with the large subunit.

A

Initiation factor 3 (IF3)

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33
Q

In the initiation phase, this molecule primarily blocks the A site from being bound to a tRNA

A

Initiation factor 1 (IF1)

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34
Q

In step 2 of the initiation phase of translation, this molecule serves as a GTPase and interacts with the mRNA and the charged tRNA, stabilizing them in the P site.

A

Initiation factor 2 (IF2)

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35
Q

The aggregate, upon release of IF3, then combines with the large ribosomal subunit forming what molecule in bacteria?

A

70S initiation complex

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36
Q

The first phase of translation is?

A

Initiation

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37
Q

The second phase of translation is?

A

Elongation

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38
Q

In step 1 of elongation, Charged tRNAs are transported into the ribosome complex by one of the elongation factors called?

A

EF-Tu

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39
Q

True of False. EF-Tu is a GTPase and is bound by a GTP, the hydrolysis of which provides energy for the process.

A

True

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40
Q

Lengthening of the growing polypeptide chain by one amino acid is called?

A

Elongation

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41
Q

This molecule is embeded in the large ribosome subunit and is responsible for creating the peptide bonds linking one amino acid to the next as well as the hydrolysis of covalent bond between the preceeding tRNA and its cognate amino acid.

A

23S rRNA of the ribosome large subunit (an example of ribozyme, an RNA capable o of catalyzing a reaction). This function is formerly thought to be performed by peptidyl transferase.

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42
Q

Third site on the ribosome where uncharged tRNA exits the ribosome large subunit.

A

E (exit) site

43
Q

The entire mRNA–tRNA–aa2–aa1 complex then shifts in the direction of the P site by a distance of three nucleotides. This process is called?

A

Translocation

44
Q

True or False. The energy produced by the hydrolysis of GTP is utilized to lock the proper structures in place during each step of elongation.

A

True

45
Q

True or False. the role of the small subunit during elongation is one of “decoding” the triplets present in mRNA, whereas the role of the large subunit is peptide bond synthesis.

A

True

46
Q

Third phase of translation.

A

Termination

47
Q

These codons do not specify an amino acid, nor do they call for a tRNA in the A site. They signal the termination of the translation process.

A

Stop codons, termination codons, nonsense codons

48
Q

What are the stop codons.

A

UAG, UAA, UGA

49
Q

The action of this enzymes is signaled by the termination codon. These enzymes cleave the polypeptide chain from the terminal tRNA, releasing it from the translation complex.

A

GTP-dependent release factors

50
Q

As elongation proceeds and the initial portion of mRNA has passed through the ribosome, the mRNA is free to associate with another small subunit to form a second initiation complex. This process results to?

A

Polyribosomes or polysomes

51
Q

About one-third of the 16S RNA is responsible for producing a flat projection called?

A

Platform

52
Q

Modulates movement of the mRNA–tRNA complex during translocation.

A

Platform

53
Q

True or False. The interface between the two subunits, considered to be the location in the ribosome where polymerization of amino acids occurs, is composed almost exclusively of RNA. In contrast, the numerous ribosomal proteins are found mostly on the periphery of the ribosome.

A

True

54
Q

Prokaryotic and Eukaryotic rRNA share the same structure called?

A

Core sequence

55
Q

The addition of this sequence impart addition function to the core sequence in eukaryotic rRNA.

A

Expansion sequence

56
Q

True or False. Transcription and translation are coupled in prokaryotes, in eukaryotes these two processes are separated both spatially and temporally.

A

True

57
Q

True or False. In eukaryotic cells, transcription occurs in the nucleus and translation in the cytoplasm.

A

True

58
Q

Significance of the temporal and spatial separation of transcription and translation in eukaryotes.

A

This separation provides multiple opportunities for regulation of genetic expression in eukaryotic cells.

59
Q

Its presence in eukaryotes is considered to increase the efficiency of translation by interacting with the initiator tRNA.

A

Kozak sequence

60
Q

Three key differences between eukaryotic and prokaryotic mRNA.

A
  1. 5′-end of mRNA is capped with a 7-methylguanosine (7-mG)
  2. Many mRNAs contain a purine (A or G) three bases upstream from the AUG initiator codon, which is followed by a G (A/GNN -AUG-G). This sequence is called the Kozak sequence.
  3. Eukaryotic mRNAs require the posttranscrip-
    tional addition of a poly-A tail on their 3′-end (polyadenylated)
61
Q

Kozak sequence is considered analogous to what sequence found in the upstream region of prokaryotic mRNAs.

A

Shine–Dalgarno sequence

62
Q

In the absence of this sequence, mRNA potential messages are rapidly degraded in the cytoplasm.

A

Poly-A

63
Q

True or False. In eukaryotes the amino acid formylmethionine is not required as it is in prokaryotes. However, the AUG triplet, which encodes methionine, is essential to the formation of the translational complex, and a unique transfer RNA (tRNA-Met) is used during initiation.

A

True

64
Q

Individuals afflicted with this disorder have an important metabolic pathway blocked. As a result, they cannot metabolize the alkapton 2,5- dihydroxyphenylacetic acid, also known as homogentisic acid.

A

Alkaptonuria

65
Q

True or False. Parents who are so related have a higher probability than unrelated parents of producing offspring that express recessive traits because such parents are both more likely to be heterozygous for some of the same recessive traits.

A

True

66
Q

The confirmation about mutant genes that alter the eye color of fruit flies could be linked to biochemical errors that, in all likelihood, involved the loss of enzyme function led to what hypothesis?

A

one-gene:one-enzyme hypothesis (later modified into one-gene:one-polypeptide chain hypothesis)

67
Q

True or False. Nearly all enzymes are proteins, not

all proteins are enzymes.

A

True

68
Q

Individuals affected by this disease have erythrocytes that, under low oxygen tension, become elongated and curved because of the polymerization of hemoglobin.

A

Sickle cell anemia

69
Q

True or False. Polypeptides and proteins. Both are molecules composed of amino acids. They differ, however, in their state of assembly and functional capacity.

A

True

70
Q

This aspect of a protein is essential to the function of the molecule.

A

3-D conformation

71
Q

Building blocks of proteins.

A

Amino acid (there are 20 of these)

72
Q

True or False. When released from the ribosome following translation, a polypeptide folds up and assumes a higher order of structure. When this occurs, a three-dimensional conformation emerges. In many cases, several polypeptides interact to produce this conformation. When the final conformation is achieved, the molecule is now fully functional and is appropriately called a protein.

A

True

73
Q

Gross structure of an amino acid.

A

Each amino acid has:

  1. a carboxyl group
  2. an amino group
  3. an R (radical) group (a side
    chain) bound covalently to a central carbon (C) atom
74
Q

What amino acid component gives its chemical identity?

A

R (radical) group aka the side chain

75
Q

Chemical identity of an amino acid as identified by its r (radical) group may be:

A
  1. nonpolar (hydrophobic)
  2. polar (hydrophilic)
  3. positively charged
  4. negatively charged
76
Q

Amino group of one amino acid reacts with the carboxyl group of another amino acid during a dehydration reaction, releasing a molecule of H2O. The resulting covalent bond is called?

A

peptide bond

77
Q

The free amino group at one end of a polypeptide chain is called?

A

N-terminus

78
Q

The free hydroxyl group at one end of a polypeptide chain is called?

A

C-terminus

79
Q

Four levels of protein structure are recognized. These are?

A
  1. Primary
  2. Secondary
  3. Tertiary
  4. Quaternary
80
Q

The sequence of amino acids in the linear backbone of the polypeptide is called?

A

Primary structure

81
Q

Certain regular or repeating configurations in space assumed by amino acids lying close to one another in the polypeptide chain.

A

Secondary structure

82
Q

One type of a secondary structure composed of a spiral chain of amino acids stabilized by hydrogen bonds.

A

Alpha helix

83
Q

One type of a secondary structure characterized by a single-polypeptide chain folding back on itself, or several chains running in either parallel or antiparallel fashion next to one another.

A

Beta-pleated sheet

84
Q

Defines the three-dimensional conformation of the entire chain in space. Each protein twists and turns and loops around itself in a very particular fashion, characteristic of the specific protein.

A

Tertiary structure

85
Q

Applies to those proteins composed of more than one polypeptide chain and indicates the position of the various chains in relation to one another.

A

Quaternary structure

86
Q

A spontaneous process whereby a linear molecule exiting the ribosome achieved a three-dimensional, thermodynamically stable conformation based solely on the combined chemical properties inherent in the amino acid sequence.

A

Protein folding

87
Q

Proteins that function by mediating the folding process by excluding the formation of alternative, incorrect patterns.

A

Chaperons (molecular chaperons or chaperonins)

88
Q

As misfolded proteins are transported out of the endoplasmic reticulum to the cytoplasm, they are “tagged” by another class of small proteins called?

A

Ubiquitins

89
Q

The protein–ubiquitin complex moves to a cellular structure called _____, within which the ubiquitin is released and the misfolded proteins are degraded by proteases.

A

Proteasome

90
Q

These are aggregates of misfolded protein that causes scrapie in sheep, bovine form encephalopahty (mad cow disease) in cattle, and Creutzfeldt–Jakob disease.

A

Prions

91
Q

The misfolded protein (called PrPSc ) is

an altered version of a normal cellular protein called?

A

PrP^c

92
Q

True or False. The difference between PrP^c and PrP^Sc lies in their secondary protein structures. Normal, noninfectious PrP^c folds into a beta-pleated sheet , whereas infectious PrP^Sc folds into an alpha-helix.

A

False. Normal, noninfectious PrP^c folds into an alpha-helix. Infectious PrP^Sc folds into a beta-pleated sheet.

93
Q

Respiratory pigments that transport oxygen, which is essential for cellular metabolism.

A

Hemoglobin and myoglobin

94
Q

Are structural proteins associated with the skin,

connective tissue, and hair of organisms.

A

Collagen and keratin

95
Q

Are contractile proteins, found in abundance in muscle tissue.

A

Actin and myosin

96
Q

The basis of the function of microtubules in mitotic and meiotic spindles.

A

Tubulin

97
Q

Proteins that function in the immune system of vertebrates.

A

immunoglobulins

98
Q

Proteins involved in the movement of molecules across membranes; some of the hormones and their receptors, which regulate various types of chemical activity.

A

Transport protein

99
Q

Proteins that binds DNA in eukaryotic organisms

A

Histone

100
Q

Protein that regulate gene expression.

A

Transcription factors

101
Q

Sequences, usually between 50 and 300 amino acids, and represent modular portions of the protein that fold into stable, unique conformations independently of the rest of the molecule.

A

Protein domain

102
Q

True or False. Different domains impart different functional capabilities. Some proteins contain only a single domain, while others contain two or more.

A

True

103
Q

The significance of domains resides in the tertiary structures of proteins. Each domain can contain a mixture of secondary structures, including alpha-helices and beta-pleated sheets. The unique conformation of a given domain imparts a specific function to the protein.

A

True

BIO 130.01 Genetics, Lecture (16 decks)

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