Nucleic Acids and Transcription

Question 1

nucleotides

Answer 1

DNA subunits; made of 5-carbon sugar, a nitrogen-containing base, and one or more phosphate groups

Question 2

purines

Answer 2

double ring structue; adenine (A) or guanine (G)

Question 3

pyrimidines

Answer 3

single-ring structure; thymine (T) or cytosine (C)

Question 4

nucleoside

Answer 4

molecule consisting of a 5-carbon sugar and a base

Question 5

phosphodiester bond

Answer 5

covalent bond that forms when a phosphate group in one nucleotide is joined to the sugar unit in another nucleotide; joins 3’ carbon to 5’ carbon via C-O-P-O-C

Question 6

polarity

Answer 6

top of a strand has free 5’ posphate and the bottom has free 3’ hydroxyl

Question 7

antiparallel

Answer 7

individual DNA strands in the double helix run opposite to each other; 5’ to 3’ paired with 3’ to 5’

Question 8

complimentary pairings

Answer 8

A-T (2 H-bonds) and G-C (3 H-bonds)

Question 9

base stacking

figure E

Answer 9

stabilizing force that occurs because nonpolar, flat surfaces of the bases group away from water molecules and thus stack on top of one another as tightly as possible

figure E

Question 10

replication

Answer 10

the process of copying DNA so genetic information can be passed from cell to cell or from parent to offspring

Question 11

replication steps

Answer 11

two strands of parental doible helix unwind → separate into single strands → each parental strand serves as a tamplate for the synthesis of a complementary daughter strand → when the process is complete there are two molecules, each containing one parental strand and one daughter strand

Question 12

mutation

Answer 12

an unrepaired error in DNA replication which changes the genetic information/sequence of DNA

Question 13

gene regulation

Answer 13

transcription and translation are regulated at all times in all cells even though all cells in an individual contain the same DNA

Question 14

ribonucleic acid

Answer 14

a molecule chemically related to DNA that is synthesized by proteins from a DNA template

Question 15

transcription

figure F

Answer 15

genetic information of DNA is used as a template to generate a molecule of DNA

figure F

Question 16

translation

figure F

Answer 16

a molecule of RNA is used as a code for the sequence of amino acids in a protein

figure F

Question 17

prokaryotes

Answer 17

transcription and translation occur in the cytoplasm

Question 18

eukaryotes

Answer 18

transcription occurs in the nucleus while translation occurs in the cytoplasm

Question 19

RNA complimentary groups

Answer 19

A-U (uracil instead of thymine)

Question 20

RNA qualities

Answer 20

in DNA is a monopsphate while in RNA it is a triphosphate; RNA is shoter and single-stranded

Question 21

RNA world hypothesis

Answer 21

the hypothesis that the earliest organisms relied on RNA for both catalysis and information storage

Question 22

RNA transcript

figure G

Answer 22

the RNA sequence synthesized from a DNA template

figure G

Question 23

RNA polymerase

Answer 23

the enzyme that carries out polymerization of ribonucleoside triphosphates from a DNA template to produce a RNA transcript

Question 24

initiation (1st stage)

Answer 24

RNA polymerase and other proteins are attracted to DNA → DNA strands are separated → transcription of the template begins

Question 25

elongation (2nd stage)

Answer 25

RNA polumerase adds successive nucleotides to the 3’ end of the RNA transcript (RNA transcript is synthesized 5’ to 3’ while DNA template is read 3’ to 5’)

Question 26

termination (3rd step)

Answer 26

RNA polymerase encounters a sequence in the template strand which causes the transcription to stop → RNA transcript is released

Question 27

promoter

figure H

Answer 27

initiates transcription; regions of a few hundred base pairs where RNA polymerase and associated proteins bind to DNA duplex

figure H

Question 28

TATA box

Answer 28

DNA sequence present in many promotes in eukaryotes and archaeons that serves as a protein-binding site for a key general transcription factor; includes sequence 5’-TATAAA-3’

Question 29

terminator

Answer 29

transcription stops at terminator → transcription is released

Question 30

sigma factor

Answer 30

a protein associated with RNA polumerase in bactera that facilitates its binding to specific promoters

Question 31

general transcription factors

Answer 31

proteins that assemble at the promoter of a gene; assembly is necessary for transcription to occur, but not sufficient

Question 32

transcriptional activator protein

figure I

Answer 32

binds to a specific DNA sequence known as an enhancer; helps to control when and in which cells transcription of a gene will occur

figure I

Question 33

mediator complex

Answer 33

once transcriptional activator proteins have bound to enhancer DNA sequences, they can attract a mediator complex of proteins which recruits RNA polymerase complex to the promoter

Question 34

primary transcript

Answer 34

RNA transcript that comes off template DNA strand; contains complement of eery base transcribed from DNA template

Question 35

messenger RNA (mRNA)

Answer 35

RNA molecules that combine with the ribosome to direct protein synthesis; carries the genetic “message” from DNA to the ribosome

Question 36

RNA processing

Answer 36

converts primary transcript into finished mRNA, which can then be translated by the ribosome

Question 37

5’ cap

figure J

Answer 37

5’ end of primary transcript is modified by the addition of 7-methylguanosine; ribosome recognizes an mRNA by its 5’ cap

figure J

Question 38

5’ cap

figure J

Answer 38

5’ end of primary transcript is modified by the addition of 7-methylguanosine; ribosome recognizes an mRNA by its 5’ cap

figure J

Question 39

polyadenylation

Answer 39

the addition of 250 consecutive A-bearing ribonucleotides to the 3’ end; forming a poly(A) tail

Question 40

exons

Answer 40

regions of protein-coding sequence

Question 41

introns

Answer 41

noncoding regions

Question 42

RNA splicing

figure K

Answer 42

process of removing an intron; catalyzed by a complex of RNA and protein known as “spliceosome”

figure K

Question 43

alternative splicing

Answer 43

primary transcripts from the same gene can be spliced in different ways to yeild differnt mRNAs; results in different protein products

Question 44

ribosomal RNA (rRNA)

Answer 44

makes up the bulk of ribosomes; essential for translation; in eukaryotic cells genes and transcipts for rRNA are concentrated in the nucleolus

Question 45

transfer RNA (tRNA)

Answer 45

carries individual amino acids for the use in translation

Question 46

small nuclear RNA (snRNA)

Answer 46

essential component of spliceosome required for RNA processing; miRNA and siRNA)