From Gene to Protein: Chp 17

Question 1

gene expression

Answer 1

the process by which DNA directs the synthesis of proteins

Question 2

one gene-one polypeptide hypothesis

Answer 2

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

Question 3

transcription

Answer 3

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

Question 4

messenger RNA (mRNA)

Answer 4

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

Question 5

translation

Answer 5

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

Question 6

triplet code

Answer 6

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

Question 7

codons

Answer 7

mRNA base triplets

Question 8

rna polymerase

Answer 8

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

Question 9

transcription unit

Answer 9

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

Question 10

three main stages of transcription

Answer 10

initiation, elongation, and termination

Question 11

initiation transcription

Answer 11

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

Question 12

elongation transcription

Answer 12

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

Question 13

termination transcription

Answer 13

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

Question 14

RNA splicing

Answer 14

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.

Question 15

small nuclear RNA

Answer 15

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.

Question 16

tRNA

Answer 16

(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

Question 17

anticodon

Answer 17

nucleotide triplet

Question 18

codon

Answer 18

an mRNA triplet (1 amino acid per codon)

Question 19

wobble

Answer 19

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

Question 20

rRNA

Answer 20

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

Question 21

ribosomes three binding sites

Answer 21

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)

Question 22

three stages of translation

Answer 22

initiaion, elongation, and termination

Question 23

initiation (translation)

Answer 23

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)

Question 24

elongation (translation)

Answer 24

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

Question 25

termination (translation)

Answer 25

a stop codon in the mRNA is reached and translation stops

Question 26

point mutations

Answer 26

alterations of just one base pair of a gene

Question 27

nucleotide-pair substitution

Answer 27

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

Question 28

missense mutations

Answer 28

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

Question 29

nonsense mutations

Answer 29

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

Question 30

insertions

Answer 30

additions of nucleotide pairs in a gene

Question 31

deletions

Answer 31

losses of nucleotide pairs in a gene

Question 32

frameshift mutation

Answer 32

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

Question 33

mutagens

Answer 33

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