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(Biology 211) Cellular Biology > Chapter 15 - Genes And Proteins > Flashcards

Chapter 15 - Genes And Proteins Flashcards

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1
Q

What are genes composed of and how are they arranged?

A

They are composed of DNA and linearly arranged on chromosomes

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2
Q

Genes specify the sequence of what?

A

Amino acids

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3
Q

Transcription generates what type of RNA? What is it?

A

Messenger RNA, a mobile molecular copy of one or more genes

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4
Q

What is mRNA code made up of, what is mRNA’s chemical composition (how does it closely relate to DNA)

A

mRNA code is made up of A,U,C,G and is single stranded and has 1 more oxygen atom than DNA

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5
Q

Basically mRNA is a copy of what?

A

A gene

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6
Q

What does the ribosome translate?

A

The mRNA code which is in base pair language (A,U,G,C) into an amino acid sequence (protein language)

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7
Q

How many amino acids are there?

A

20 commonly occurring (used) ones

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8
Q

In the process of transcription it allows DNA itself to remain…

A

Intact, and protected

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9
Q

In transcription what molecule makes the complementary pairs? And what ratio?

A

RNA polymerase pairs one RNA nucleotide for one DNA nucleotide being copied

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10
Q

What is the ratio in translation of mRNA to an amino acid?

A

Every 3 mRNA’s correspond to one amino acid (the genetic code)

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11
Q

The genetic code is a triplet code, a three nucleotide sequence codes for what?

A

One amino acid

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12
Q

Can an amino acid be encoded by more than one nucleotide triplet?

A

Yes

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13
Q

Coded triplets are called?

A

Codons

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14
Q

What happens when there is an addition or deletion of one or two nucleotides in translation?

A

It can shift the reading and frame and result in an incorrect amino acid producing a nonfunctional protein

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15
Q

What does a degenerate code allow?

A

It allows a given amino acid to be encoded by more than just one nucleotide triplet

“This amino acid can be specified by multiple similar codons”

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16
Q

In what order is reading the code done in translation? How is knowing the base sequence then determining the amino acid done?

A

It starts with the first base letter in the left column and follows its row until it meets the column of the second base letter to find one of the 16 blocks, then using the third base letter on the right side and reading back to the specific amino acid

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17
Q

What does it mean that the genetic code is virtually universal?

A

All species use the same code

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18
Q

What do prokaryotes have in addition to their large chromosome?

A

Plasmid DNA

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19
Q

In prokaryotes the double helix partially unwinds exposing 2 single DNA strands in a region called what?

A

The transcription bubble

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20
Q

The strand that is read by RNA polymerase in prokaryotes is called what?

A

The template strand

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21
Q

The mRNA strand that is built in prokaryote transcription is complementary to what? The other strand that is made resembles what strand but has what difference?

A

The mRNA strand that is built is complementary to the template strands

The other strand is almost identical to the mRNA strand except that in mRNA all of the T nucleotides are replaced with U nucleotides

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22
Q

The mRNA strand being synthesized is always added where?

A

On the 3’ end by RNA polymerase

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23
Q

In prokaryotes the first nucleotide base pair ready by RNA polymerase and mRNA synthesized is called what?

A

The +1 site (initiation site)

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24
Q

In prokaryotes What are the preceding and proceeding nucleotides from the initiation site called? What does this mean?

A

Preceding are upstream nucleotides that do not produce mRNA but are important in finding the initiation site and are called (promoters)

-proceeding are downstream nucleotides and are the ones read and mRNA synthesized from

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25
Q

Multiple initiation sites cna start in the bacterial chromosome resulting in…

A

Many mRNAs being quickly synthesized

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26
Q

How many RNA polymerase molecules are used to transcribe prokaryotic genes?

A

Only one

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27
Q

Prokaryotic RNA polymerase has how many subunits? What are they called? What other subunit plays a role and collectively what are they called with that other subunit?

A

It has 4 subunits called the core enzyme which have specific roles in transcription. There is a fifth subunit which initiates transcription at the appropriate initiation site, all 5 are collectively called the holoenzyme

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28
Q

What is a prokaryotic promoter?

A

An upstream DNA sequence into which the transcription machinery binds and then initiates transcriptions (includes RNA polymerase itself)

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29
Q

What promoter sequences are consensus to various bacterial specious?

A

-10 that is TATAAT
AND AT
-35 TTGACA

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30
Q

What subunit recognizes the promoter consensus sequences?

A

The fifth subunit of RNA polymerase and binds to those sequences

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31
Q

What does the A-T rich -10 regions do?

A

Facilitate unwinding of the DNA templates

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32
Q

The transcription elongation phase begins with what?

A

The 5th subunit being released from from RNA polymerase, and the core enzyme proceeding along the DNA template

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33
Q

mRNA is synthesized in the 5’ to 3’ direction at what rate?

A

40 nucleotides per second

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34
Q

When is the DNA unwound and wound in prokaryotic elongation?

A

DNA is unwound before the core enzyme and rewound behind it

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35
Q

RNA polymerase acts as a stable linker between what?

A

The DNA Template and the new RNA strand

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36
Q

Once a gene is transcribed in prokaryotic cells what needs to happen?

A

The RNA polymerase must be instructed to dissociate from the DNA template and liberate the newly formed mRNA

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37
Q

What are the 2 kinds of termination signals that exist in prokaryotic cells?

A

1 - Rho-dependent termination

2 - Rho-independent termination

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38
Q

When does the Rho-dependent termination occur? What happens?

A

It occurs when the rho protein which tracts along behind the growing mRNA chain, near the end of a gene string of G nucleotides on the DNA strand stalls transcription and releases the mRNA from the transcription bubble

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39
Q

When does Rho-independent termination occur?

A

When a C-G rich area which bind back on each other forming a stable hairpin causing the RNA polymerase to stall and when it hits the complementary A-U region the core enzyme breaks away liberating the new mRNA molecule

40
Q

In prokaryotic cells there is no compartmentalization allowing for what to happen in the protein making process?

A

Transcription and translation of proteins concurrently

41
Q

In eukaryotic cells can transcription and translation take place concurrently?

A

No, these two places are seperate

42
Q

There are a few key differences between eukaryotic and prokaryotic transcription, name the main 3 (while there are others)

A
  • three different RNA polymerases are used in eukaryotes
  • eukaryotic mRNAs are monogenic (one per gene)
  • mRNA must be transported out of the nucleus to the ribosomes in the cytoplasm and must be protected from degradation
43
Q

In addition to RNA polymerase what is needed in initiation of transcription in eukaryotes

A

Transcription factors

44
Q

How do transcription factors work?

A

They bind to the promotor region and then help recruit the appropriate RNA polymerases

45
Q

Each eukaryotic RNA polymerase is composed of how many subunits?

A

Atleast 10

46
Q

What does RNA polymerase 1 do

A

It synthesizes all of the ribosomal RNAs, and are considered structural RNAs because they are not translated into proteins but make up ribosomes (rRNA)

47
Q

What does RNA polymerase 2 do?

A

It is responsible for transcribing the overwhelming majority of eukaryotic genes

48
Q

What does RNA polymerase 3 do?

A

Transcribes a variety of precursors for structural RNAs called transfer RNA

49
Q

What does transfer RNA (tRNA) do?

A

Plays a critical role by acting as the “adaptor molecule” between the mRNA molecule and the growing polypeptide chain at the ribosome

50
Q

What are the promotor regions and what are they called in eukaryotes?

A

-10 TATA box and a TATAAA sequence near -30 (relative to +1)

51
Q

Transcription factors that bind to promoters are called what? What do they do?

A

They are called basal transcription factors and they stabilize the pre-initiation complex and contribute to the recruitment of the RNA polymerase 2

52
Q

Genes that are constantly being expressed by the cell have conserved elements such as…

A

CAAT box at -80, and some not as relative others

53
Q

What else do these transcription factors do that are not involved in main processes?

A

They bind to upstream enhancers and silencers affecting the transcription depending on the cell type

54
Q

what is the relative complexity of RNA polymerase 1 and 3 compared to 2 in respect to transcription factors

A

1 and 3 are far less complex than 2

55
Q

How does elongation occur in eukaryotes? And when?

A

It occurs when the pre-RNA polymerase 2 is released from the transcription factors and elongation occurs as it does in prokaryotes in the 5’ to 3’ direction

56
Q

How is eukaryotic DNA packed?

A

DNA is packed around histone proteins in complexes called nucleosomes of 146 nucleotides of DNA would around 8 histones

57
Q

What does FACT stand for?

A

Facilitates chromatin transcription

58
Q

What must happen for FACT to work? And what does it do?

A

The histone proteins must be moved out of the way whenever a nucleosome is encountered by the FACT protein, it also replaces histones once the mRNA strand is synthesized

59
Q

When does termination in eukaryotes occur? What happens to the leftover part?

A

1-2 thousand nucleotides beyond the end of the gene being transcribed, this pre-mRNA tail is removed during mRNA processing

60
Q

All eukaryote RNA must undergo what before it can be translated?

A

Processing

61
Q

Are eukaryotic coding sequences continuous?

A

No they are not, in prokaryotes they are

62
Q

What are the coding and non coding sequences called in eukaryotes. What happens to extend the life of a typical mRNA strand in eukaryotes?

A

The coding sequences are called exons and are interrupted by non coding sequences called introns, and must be removed to make a translatable mRNA allowing eukaryotic mRNA to last for several hours while a typical prokaryotic mRNA lasts no more than 5 seconds

63
Q

What do stabilizing proteins do?

A

They cover the pre-mRNA preventing it from degradation as it’s processed and transported out of the nucleus

64
Q

What 3 things must happen in the pre-mRNA processing steps (3 most important)

A

5’ and 3’ ends must be stabilizes

Introns must be removed

Exons must be spliced

65
Q

What is the 5’ end capped by? What does it do?

A

It’s capped by 7-methylguanosine by a phosphate linkage preventing degradation, and helps the ribosome recognize the mRNA and start translation

66
Q

What is added to the 3’ and what puts it there? What is the function of the molecule added?

A

An enzyme called poly-A polymerase adds a strong of about 200 A residues called a poly-A tail which prevents degradation, it’s also important for exporting the processed mRNA to the ribosome through the cytoplasm

67
Q

If introns are not removed, or exons are not spliced with out one nucleotide being missed then what might occur?

A

Frameshift mutations may oxcur

68
Q

What is the spliceosome and what does it do?

A

It’s a complex of proteins and RNA molecules that find the beginning and end of each intron: GU at 5’ and AG at 3’

69
Q

What 2 RNA molecules do not get translated?

A

tRNA and rRNA

70
Q

Where do rRNAs get transcribed, processed, and assembled? How much do they make up of a typical ribosome?

A

The nucleolus, they make up roughly 50 percent of a ribosome

71
Q

Where are tRNA transcribed and processed? Where do they go after? And why?

A

They are transcribed and processed in the nucleus and then released into the cytoplasm where they link to their specific amino acids in preparation for protein synthesis at the ribosome

72
Q

What is the structure of a mature tRNA molecule?

A

A complex 3d structure with an amino acid binding site on one end and the nucleotide binding site at the other end called the anticodon

73
Q

What is the anticodon?

A

A three nucleotide sequence that interacts with a mRNA codon through complementary base pairing (the genetic code)

74
Q

What single process consumes more of a cells energy and any other metabolic process?

A

Protein synthesis

75
Q

In simple terms what is protein synthesis? What is its scientific name?

A

It’s called translation, and involved the decoding of a mRNA message into a polypeptide (protein) product

76
Q

Amino acids are covalent bonded by what? What is the byproduct of this connection?

A

Interlinking peptide bonds hold them together with a water molecule as the byproduct of

77
Q

What are the 2 types of rRNAs?

A

Structural and catalytic

78
Q

Where are ribosomes found?

A

Freely floating in the cytoplasm and attached to the RER

79
Q

What can ribosomes dissociate into?

A

Small and large subunits

80
Q

Mammalian ribosomes have what subunits? What does it total?

A

40s subunits and 60s subunits (totaling 80s, not additive)

81
Q

What subunit of the ribosome binds to where?

A

The small subunit binds to the mRNA template, the large subunit binds to the tRNAs

82
Q

In what direction to ribosomes read mRNA?

A

From 5’ to 3’

83
Q

How many types of tRNAs exist? And where?

A

40-60, in cytoplasm

84
Q

What does each tRNA carry?

A

A specific amino acid and recognizes one or more mRNA codons which defines the order of the amino acid (primary sequence)

85
Q

What do tRNA molecules translate?

A

The language of RNA molecules into the language of proteins

86
Q

How many possible mRNA codons are there?

A

64

87
Q

The codon AUG-Met encodes for what?

A

The initiation of translation

88
Q

What 3 codons encode for the termination of protein synthesis?

A

UAA, UAG, UGA

89
Q

tRNA anticodons form base pairs with what for its amino acid?

A

mRNA

90
Q

The mRNA sequence CUA will bind to what tRNA then expressing what complementary sequence?

A

the mRNA sequence CUA will bind to a Leu tRNA expressing the complementary sequence GAU

91
Q

What 3 things MUST happen for the tRNAs

A

MUST be recognized by the correct aminoacyl synthetase

MUST be recognized by the ribosome

MUST bind to the correct mRNA sequence (codon)

92
Q

Once the tRNA is processed and sent to the cytoplasm the process of charging occurs which is what?

A

Each tRNA is bonded to its correct amino acid by enzymes called aminoacyl tRNA synthetases

93
Q

Each of the 20 amino acids has how many tRNA synthetases?

A

Each amino acid has one type of aminoacyl tRNA synthetase

94
Q

How does the charging reactions work? What powers it?

A

ATP drives the charging reaction and forms a high energy bond that attaches the amino acid to its tRNA that uses its energy ti drive the formation of the peptide bond at the ribosome

95
Q

How is each tRNA named?

A

After its specific amino acid eg. Glu-tRNA

(Biology 211) Cellular Biology (12 decks)

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