From Gene to Protein: Chp 17 Flashcards

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1
Q

gene expression

A

the process by which DNA directs the synthesis of proteins

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2
Q

one gene-one polypeptide hypothesis

A

states that each gene codes for a polypeptide, which can be-or can constitute a part of-a protein

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3
Q

transcription

A

the synthesis of RNA using DNA as a template. takes place in the nucleus

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4
Q

messenger RNA (mRNA)

A

produced during transcription. it carries the genetic message of DNA to the protein-making machinery of the cell in the cytoplasm, the ribosome

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5
Q

translation

A

the production of a polypeptide chain using mRNA transcript and occurs at the ribosomes

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6
Q

triplet code

A

series of three-nucleotide groups that instruct the building of a polypeptide chain

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7
Q

codons

A

mRNA base triplets

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8
Q

rna polymerase

A

an enzyme that separates the two DNA strands and connects the RNA nucleotides as they base-pair along the DNA template strand

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9
Q

transcription unit

A

the entire stratch of DNA that is transcribed into an RNA molecule

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10
Q

three main stages of transcription

A

initiation, elongation, and termination

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11
Q

initiation transcription

A

in eukaryotes, RNA polymerase 2 cannot bind to the promotoer without transcription factors that assist the binding of RNA polymerase to the promoter and, thus, the intitiation of transcription. the whole complex of RNA polymerase 2 and transcription factos is called a transcription initiation complex.
in bacteria, RNA polymerase recognizes and binds to the promoter

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12
Q

elongation transcription

A

rna polymerase moves along the DNA, continuing to untwist the double helix. rna nucleotides are continually added to the 3’ end of the growing chain. as the complex moves down the DNA strand, the double helix reforms, with the new RNA molecules straggling away from the DNA template

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13
Q

termination transcription

A

after RNA polymerase transcribes a terminator sequence in the DNA, the RNA transcript is released, and the polymerase detaches. In eukaryotes there is an addition of a 5’ cap and poly-A tail. the 5’ cap and poly-A tail facilitate the export of mRNA from the nucleus, help protect the mRNA from degradation by enzymes, and facilitate the attachment of mRNA to the ribosome

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14
Q

RNA splicing

A

occurs in eukaryotic cells. large portions of the newly synthesized RNA strand are removed (introns). The sections that remain(called exons) are spliced together by a spliceosome.

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15
Q

small nuclear RNA

A

snRNA plays a makor role in catalyzing the excision of the introns and joining of the exons. when RNA serves a catalytic role, the molecules is termed a ribozyme.

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16
Q

tRNA

A

(transfer RNA) functions in transferring amino acids from a pool of amino acids in the cell’s cytoplasm to a ribosome. the ribosome accepts the amino acid from tRNA and incorporates the amino acid into a growing polypeptide chain

17
Q

anticodon

A

nucleotide triplet

18
Q

codon

A

an mRNA triplet (1 amino acid per codon)

19
Q

wobble

A

relaxation of base-pairing between the third base of a codon

20
Q

rRNA

A

(ribosomal RNA) complexes with proteins to formt he two subunits that form ribosomes

21
Q

ribosomes three binding sites

A
P site (holds the tRNA that carries the growing polypeptide chain)
A site (holds the tRNA that carries the amino acid that will be added to the next chain)
E site (exit site for tRNA)
22
Q

three stages of translation

A

initiaion, elongation, and termination

23
Q

initiation (translation)

A

1: a small ribosomal subunit binds to mRNA in such a way that the first codon of the mRNA strand, which is alwasy AUG, is placed in the proper position
2: tRNA with antocodon UAC, which carries the amino acid methionine, hydrogen bonds to the first codon
3: large subunit of ribosome attaches, allowing the tRNA with methionine to attach tothe P site. (A site is now available to the tRNA that will bring the second amino acid)

24
Q

elongation (translation)

A

1: codon recognition: tRNA basepairs with the complementary mRNA codon in the A site
2: peptide bond formation: polypeptide in the P site attaches to the amino acid in the A site
3: translocation: translocates the tRNA in the A site to the P site while the empty tRNA in the P site moves to the E site

25
Q

termination (translation)

A

a stop codon in the mRNA is reached and translation stops

26
Q

point mutations

A

alterations of just one base pair of a gene

27
Q

nucleotide-pair substitution

A

the replacement of one nucleotide and its partner with another pair of nucleotides

28
Q

missense mutations

A

those substitutions that enable the codon to still code for an amino acid although it might not be the correct one

29
Q

nonsense mutations

A

those substitutions that change a regular amino acid codon into a stop codon, ceasing translation

30
Q

insertions

A

additions of nucleotide pairs in a gene

31
Q

deletions

A

losses of nucleotide pairs in a gene

32
Q

frameshift mutation

A

interference of the codon groupings which causes the mRNA to be read incorrectly

33
Q

mutagens

A

substances or forces that interact with DNA in ways that cause mutations