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Biology > Chapter 14 > Flashcards

Chapter 14 Flashcards

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1
Q

what is mutation

A

a change in genetic information not caused by recombination

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2
Q

what is a mutagen

A

any agent (chemical, radiation, etc.) that increases the mutation rate

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3
Q

what is the one-gene, one-polypeptide relationship

A

the idea that each gene int he genome encodes a single polypeptide, there is a one-to-one correspondence between genes and polypeptides

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4
Q

what happens if a gene is mutated

A

this results in a non-functional enzyme and the reaction doesn’t occur

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5
Q

do all genes code for polypeptides

A

no, they have other functions

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6
Q

what is transcription

A

the information in a DNA sequence (a gene) is copied into a complimentary RNA sequence (transcribe: convert, like changing trumpet music into clarinet music)

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7
Q

what is translation

A

the RNA sequence is used as a template to create the amino acid sequence for a polypeptide sequence (translate: turn from one language to another)

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8
Q

what is the central dogma of molecular biology

A

it describes how information flows in a cell, transcription to translation into a polypeptide,

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9
Q

what are the 3 RNA’s used in transcription and translation

A

mRNA (messenger RNA), rRNA (ribosomal RNA), and tRNA (transfer RNA)

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10
Q

what is mRNA

A

it is one of the strands of DNA that is transcribed to the complimentary RNA strand that goes through processing to become mRNA, travels from nucleus to cytoplasm where it is translated into a polypeptide, nucleotide sequence on mRNA determine sequence of amino acids on polypeptide

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11
Q

what is rRNA

A

part of the ribosome, catalyzes peptide bond between amino acids to for polypeptide

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12
Q

what is tRNA

A

can bind a specific amino acid and recognize specific sequences of nucleotides in mRNA, tRNA recognizes which amino acid should be added next to the growing polypeptide chain

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13
Q

RNA is made complimentary to the DNA strand except for what 2 differences

A

Uracil (U) replaces Thymine (T)
Ribose replaces the deoxyribose

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14
Q

how does RNA keep the message if it looks nothing like the template strand

A

it looks very similar to the non-template strand except for the U and T switch

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15
Q

what is transcription

A

the formation of a specific RNA strand from a specific DNA strand

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16
Q

what does transcription require

A

a DNA template for complimentary base pairing
the four ribonucleosides triphosphates (ATP, GTP, UTP, and CTP) because they act as substrates
an RNA polymerase enzyme that catalyzes the synthesis of RNA from DNA template, share a common structure, catalyze the addition of nucleotides form 5’ end to 3’ end, and doesn’t need a primer

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17
Q

what is initiation in transcription

A

a promoter tells the RNA polymerase where to start, initiation site, and which strand to transcribe

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18
Q

what is a promoter

A

a special sequence of DNA to which the RNA polymerase binds to initiate transcription

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19
Q

what is elongation in transcription

A

RNA polymerase unwinds DNA, reads template from 3’ to 5’ end, RNA strand forms 5’ end then other nucleotides added to 3’ end, it also uses the (ribo)nucleoside triphosphates as substrates which removes 2 of the phosphates which the energy released because of this is used to drive polymerization rxn’s, and there is no proofreading

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20
Q

what is termination in transcription

A

specified by a specific DNA sequence, the RNA polymerase reaches the termination site to which the RNA transcript and polymerase are released from the template

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21
Q

what is precursor mRNA

A

pre-mRNA, initial gene transcript before it is modified to produce functional mRNA, the primary mRNA

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22
Q

what is modified

A

the mRNA strand because there are parts of it that doesn’t code for polypeptide chains, which are called introns which are spliced out, exons are what reach the ribosome

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23
Q

what is pre-mRNA processing

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A

modification of the primary transcript before it leaves the nucleus, both ends are modified, and the introns are removed

24
Q

what is added to the 5’ end

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A

5’ cap that facilitates the binding of mRNA to the ribosome for translation and protects mRNA from being digested by ribonucleases that break down RNAs

25
what is added to the 3' end
poly A tail that assists in the export of the mature mRNA from the nucleus and is important for mRNA recognition and stability of in the cytoplasm
26
and is an intron
portion of the gene within the coding region that is transcribed into pre-mRNA but is spliced out during mRNA processing. it interrupts , but doesn't scramble the DNA sequence
27
what is an extron
portion of a gene that is present in mature mRNA, encode polypeptide sequences
28
what is RNA splicing
last stage of RNA processing, removes introns and splices the extrons together
29
what happens after RNA processing
the protein bound to the 5' nucleotide cap during processing is recognized by a nuclear pore receptor, mRNA is lead through the pore, and the mature mRNA moves into the cytoplasm while the unprocessed or the incompletely processed mRNA stays
30
what is genetic code
the information key by which a sequence of mRNA nucleotides corresponding to a gene is translated into the sequence of amino acids composing of the protein expressed by the gene
31
how does the genetic code specify which amino acids will be used to build a protein
it uses a series of sequential, non-overlapping, three letter "words" which represent the three adjacent nucleotide bases in the mRNA polynucleotide
32
what is a codon
the three nucleotides in mRNA that direct the placement of a particular amino acid into a polypeptide chain, complementary to the corresponding triplet of bases in the DNA molecule from which it was transcribed
33
what is a start codon
initiation signal for translation (AUG)
34
what is a stop (nonsense) codon
termination signals for translation (UAA,UAG,UGA)
35
what is a sense codon
the 61 codons that encode the 20 amino acids
36
what is the correlation between the codon and the amino acid
a given amino acid may be by more than one codon, but a codon can only code for one amino acid
37
what is Common Genetic Code
nearly universal: the codons are the same in all organisms a common language for evolution allows genetic engineering
38
what is translation
the process by which the information in mRNA is used to specify and link a specific sequence of amino acids, producing a polypeptide
39
what is the translator used in translation
transfer RNA (tRNA) which reads the mRNA codons and brings the corresponding amino acid to the ribosome
40
what happens after the amino acid is brought
components of the ribosome catalyze the formation of peptide bonds between amino acids
41
what are the 3 functions of tRNA
bind to a particular amino acid: tRNA binds to a specific enzyme which attaches to one of the 20 amino acids which is covalently attached to the 3' end of the tRNA binds to mRNA: at the midpoint of the tRNA chain, there is a triplet base called the anticodon (complimentary to the mRNA codon for the specific amino acid that the tRNA carries) and interacts with the ribosome: ribosome sites fit the tRNA molecule, interaction is noncovalent
42
what is said about the tRNA when the amino acid is attached
it is charges, which requires ATP, the high energy bond forms between the aa and tRNA, the energy is later used to form a peptide bond
43
what is the ribosome and what does it do
a workbench where translation occurs, holds mRNA and charged tRNAs in the correct position, allows peptide chain assembly
44
does the ribosome have subunits
yes, large and small which are held non-covalently
45
what do the ribosomal subunits do
they bring the ribosome back together if it is pulled apart
46
how many sites which tRNA and the large and small subunits are there
3, A site, P site, and E site
47
what does the A site do
the charged tRNA anticodon binds to the mRNA codon, this lines up the correct amino acid wto be added to the growing polypeptide chain
48
what does the P site do
the tRNA adds its amino acid to the polypeptide chain
49
what does the E site do
the uncharged tRNA has given up its amino acid, it waits to be released back to the cytoplasm to pick up another amino acid to start the process again
50
how does the ribosome know if it has the right amino acid
the anticodon and the codon will bond together via hydrogen bonds, the small subunit will validate the bond, if it is the wrong match, it will be rejected
51
what is initiation in translation
the initiation complex forms, which is when the small ribosomal subunit binds to the mRNA to which the anti-codon and start codon bind, the large ribosomal subunit joins the initiation complex with the charged tRNA now at the P site with the A site aligned with the second mRNA codon
52
what is elongation in translation
the anticodon of an incoming tRNA binds to the codon at the A site to which the bond between tRNA in the P site and its amino acid is broken and a peptide bond forms between the aa and the aa on tRNA in the A site. After the first tRNA released its aa it moves to the E site where it detaches from the mRNA and moves into the cytoplasm where it can be charged again. the amino acid chain grows called protein synthesis
53
what is termination in translation
translation ends when a stop codon enters the A site which a protein release factor binds to the complex, the protein release factor disconnects the polypeptide from the tRNA in the P site by hydrolyzing the bond between them, the polypeptide seperates from the ribosome while the mRNA and the ribosomal subunits also seperate
54
what is added after translation
a signal sequence that indicates where in the cell the polypeptide chain has to go, if it doesn't have one it stays where it was synthesized and sometimes they need to be processed more in the RER
55
what are the modifications that can happen after translation
proteolysis: polypeptide is cut by proteases, the signal sequence is removed glycosylation: sugars are added to the chain to form glycoproteins, the sugars act as signals while others form membrane receptors phosphorylation: a phosphate group is added, the charged phosphate group changes the conformation and may expose active and binding sites

Biology (12 decks)

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