EXAM 4

Question 1

The composition of DNA was well established by the 1950s. Models showed different arrangements of the components and sometimes introduced additional ones (such as magnesium), but all contained ______, ______, and ______.

Answer 1

sugars, phosphates, & bases

Question 2

Chargaff’s observation suggested that _ would always pair with _ and _ would always pair with _ in a DNA molecule.

Answer 2

A-T and G-C

Question 3

Adjacent nucleotides in the sugar-phosphate backbone are held together by the strongest type of chemical bond, __(2)__.

Answer 3

covalent bonds

Question 4

The bonds or interactions that hold together complementary bases from opposite strands of DNA are __(2)__. These allow complementary DNA strands to _____ during S phase replication.

Answer 4

H-bonds - “unzip”

Question 5

The bonds or interactions between stacked nucleotide units that help hold the DNA molecule together are ________.

Answer 5

van der Waals

Question 6

The ___ end of a DNA strand has an exposed -OH group, and the ___ end has a phosphate group.

Answer 6

3’ - 5’

Question 7

The T2 phage consists of a protein coat and DNA. It is the ____ that contains P.

Answer 7

DNA

Question 8

After allowing phages grown with bacteria in a medium that contained 32P and 35S, Hershey and Chase used a centrifuge to separate the phage ghosts from the infected cell. They then examined the infected cells and found that they contained _____, which demonstrated that _____ is the phage’s genetic material.

Answer 8

labeled DNA - DNA

Question 9

To elongate the lagging strand in the mandatory direction, DNA pol III must work along the other template strand in the direction __(2)__ the replication fork.

Answer 9

away from

Question 10

The enzyme that can replicate DNA is called __(2)__.

Answer 10

DNA polymerase

Question 11

_______ are enzymes that untwist the double helix at the replication forks, separating the 2 parental strands and making them available as template strands.

Answer 11

Helicases

Question 12

The leading strand is built ______, but the lagging strand is built in _______.

Answer 12

continuously - pieces

Question 13

The untwisting of the double helix causes tighter twisting and strain ahead of the replication fork, but _______ helps relieve this by breaking and rejoining DNA strands.

Answer 13

topoisomerase

Question 14

The initial nucleotide chain that is produced during DNA synthesis is actually a short stretch of ____, not DNA. This ____ chain is called a primer and is synthesized by the enzyme _____.

Answer 14

RNA x 2 - primase

Question 15

DNA polymerase can only add nucleotides to the ____ end of a new DNA strand.

A new DNA strand can only ELONGATE in the ____ to ____ direction.

Answer 15

3’ / (5’ to 3’)

Question 16

Multiple primers are needed for the _____ strand, but only 1 (polymerase III) is needed for the _____ strand.

Answer 16

lagging - leading

Question 17

______ lays down RNA primer. ______ starts at end of RNA primer and adds DNA nucleotides.

Answer 17

Primase - DNA Polymerase III

Question 18

DNA polymerase 1 is involved in the _____ of _____ from the fragments and replacing the gap by relevant nucleotides, whereas DNA polymerase 3 is mainly involved in the ______ of the leading and lagging strands.

Answer 18

removal of primers

synthesis

Question 19

DNA _____ closes the gap between fragments A & B on the _____ strand.

Answer 19

ligase - lagging

Question 20

The correct DNA replication model is _____ and produces 2 double helices: ____ dark blue and ____ light blue strand per double helix in the 1st replication.

The 2nd replication produces 4 double helices: 2 of them each have 1 dark & 1 light blue strand, while the other 2 both have ____ blue strands.

Answer 20

semiconservative - 1 & 1 - light blue (or daughter DNA)

Question 21

The evolutionary significance of altered DNA nucleotides is that _____ are the source of genetic _____ upon which natural selection operates. Sequence changes may become ____ and be _____ down to next generation.

Answer 21

mutations - variation

permanent - passed

Question 22

If chromosomes of germ cells became shorter each round of cell division, this could cause essential genes to be _____ from the ____ they produce. The enzyme _____ catalyzes the lengthening of telomeres in germ cells.

Answer 22

missing - gametes - telomerase

Question 23

Not all cells have active telomerase (catalyze lengthening of telomeres in germ cells), but high ____ cells do.

In cancer cells, telomerase can be turned __(2)__ and allow division when they shouldn’t!

Answer 23

turnover

back on

Question 24

Proteins called ____ are responsible for the first level of DNA packing in chromatin and there are ____ types.

Answer 24

histones - 4

Question 25

_____ are like beads on a string and consists of DNA wound 2x around a protein core of 8 _____.

Answer 25

Nucleosomes - histones

Question 26

Because of its compaction, ______ DNA is largely ______ to the machinery in the cell responsible for transcribing the genetic information coded in the DNA.

Answer 26

heterochromatic - inaccessible

Question 27

Understanding DNA structure and replication makes genetic _____ possible. The 2 strands of DNA are _____ to each other, which is the basis for nucleic acid ______.

Answer 27

engineering - complementary - hybridization

Question 28

Common tools for genetic engineering include recombinant ____, DNA c____, r_____ enzymes, gel e____, and PCR.

Answer 28

DNA - cloning - restriction - electrophoresis

Question 29

Gene cloning/engineering rely on use of ______ enzymes that cut DNA molecules at specific locations.

Answer 29

restriction

Question 30

DNA is ______ to messenger RNA (mRNA), and the mRNA is _____ to proteins on the ribosomes.

Answer 30

transcribed - translated

Question 31

Transcription begins when a molecule of RNA polymerase binds to a _____. Then RNA poly ____ gene. Once it reaches the ______, it exits the gene and releases RNA.

Answer 31

promoter - transcribes - terminator

Question 32

RNA molecules do not have (_) or ____ like DNA does. Instead it has (_) or ____. Base pairing between DNA & DNA is always A-_ and G-_, but when DNA pairs w/ RNA it is A-_ and G-_.

Answer 32

T or thymine - U or uracil A-T and G-C / A-U and G-C

Question 33

Synthesis of _____ is not directly coded in DNA, but it is for mRNA, p_____, & DNA.

Answer 33

organelles - proteins

Question 34

A gene has 2 main parts, a regulatory region containing a _____ and a transcription region which contains the _____ information for a protein product.

Answer 34

promoter - coding

Question 35

A sequence of 3 nucleotides on an mRNA molecule is called a ______. What codon codes for _____ and functions as a start signal?

Answer 35

codon - Methionine (met) - AUG

Question 36

When RNA is modified before translation, it is called RNA ______. During this time, a __(2)__ nucleotide is added to the ____ end as a "cap".

Answer 36

processing - modified guanine - 5'

Question 37

During RNA processing, a _____ tail is added to the ____ end of the RNA.

Answer 37

poly-A - 3'

Question 38

______ delete portions of the RNA called _____ and connect remaining segments called ______ or expressed regions.

Answer 38

Spliceosomes - introns exons

Question 39

Translation or protein _______ takes place in the ______ at the _____.

Answer 39

synthesis - cytosol - ribosome

Question 40

________ is the process by which the ribosome slides down the mRNA so a new cycle of elongation can begin.

Answer 40

Translocation

Question 41

Triplets of RNA bases are called _____. A ribosome facilitates the pairing of each mRNA ______ w/ a particular tRNA a_______.

Answer 41

codons - codon - anticodon

Question 42

What can RNA polymerases (i.e., primase) do that DNA polymerases cannot?

Answer 42

RNA polymerases (primase) can add new nucleotides w/o the 3' -OH group, but DNA polymerases cannot.

Question 43

Gene cloning is useful for two basic purposes: to make many ______ of (or amplify) a particular gene and to produce a _____ product from it.

Answer 43

copies - protein

Question 44

Gene Cloning using copies of GENE: 1. Gene for _____ resistance is inserted into plant. 2. Gene is used to alter ______ for cleaning up _____ waste.

Answer 44

pest bacteria - toxic

Question 45

Gene Cloning using harvested PROTEIN product: 1. HGH used to treat ______ growth. 2. Protein dissolves blood _____ in heart attack therapy.

Answer 45

stunted clots

Question 46

Gene cloning and genetic engineering generally rely on the use of enzymes that cut DNA molecules at a _______ number of specific locations. These enzymes are called __(2)__.

Answer 46

limited - restriction enzymes

Question 47

Proteins are the link between genotype and phenotype. Gene expression is the process by which DNA directs the synthesis of _______ (or, in some cases, just _____). The ______ of genes that code for proteins includes two stages: transcription and translation.

Answer 47

proteins - RNAs expression

Question 48

Proofreading corrects many errors, but sometimes a few get through. Mismatch ______ helps catch and remove these errors right after DNA synthesis. __(2)__ then replaces the missing errors.

Answer 48

repair - DNA polymerase

Question 49

Some genes don't encode ______. Some genes actually encode functional ______ molecules instead.

Answer 49

polypeptides - RNA

Question 50

The genetic code is r______, not _______, and nearly ______.

Answer 50

redundant - ambiguous - universal

Question 51

The start codon for RNA is always __ U __ that codes for the AA ______.

Answer 51

AUG - Met

Question 52

The 3 stop codons are UAA, UAG, and _____.

Answer 52

UGA

Question 53

The codons are read by the translation machinery in the ___ to ___ direction along the mRNA.

Answer 53

5' --> 3'

Question 54

The 3 stages of transcription include: initiation, ______, and t______.

Answer 54

elongation - termination

Question 55

Several transcription _____ bind to the DNA. RNA poly II attaches to and initiates transcription at the ______. Transcription initiation _____ forms. The stretch of DNA downstream from the promoter that is transcribed into an RNA molecule is called a __(2)__.

Answer 55

factors - promoter - complex - transcription unit

Question 56

There are 3 RNA polymerases: RNA poly I makes _____ transcripts. RNA poly II makes _____ which code for proteins. RNA poly III makes _____ and plays a role the translation process.

Answer 56

rRNA mRNA tRNA

Question 57

During termination of transcription: Bacteria trxn proceeds through a ______ sequence in the DNA and the transcript goes straight to translation. In eukaryotes, RNA polymerase II transcribes a sequence on the DNA called the _______ signal sequence, which specifies a "signal" (AAUAAA) in the pre-mRNA. The pre-mRNA requires further _____ before translation.

Answer 57

terminator polyadenylation - processing

Question 58

The modified ends may promote the export of _____ from the nucleus, and they help protect it from ______.

Answer 58

mRNA - degradation

Question 59

A modified __(2)__ is added to the ___ end of the pre-mRNA, which is synthesized first, after the first 20–40 nucleotides have been transcribed.

Answer 59

guanine nucleotide - 5'

Question 60

At the ___ end, an enzyme then adds 50–250 more adenine (A) nucleotides, forming a __(2)__.

Answer 60

3' - poly-A tail

Question 61

The stretch of DNA downstream from the promoter that is transcribed into an RNA molecule is called a __(2)__.

Answer 61

transcription unit

Question 62

What mediates the binding of RNA polymerase and the initiation of transcription? (a collection of proteins)

Answer 62

transcription factors

Question 63

The 5′ UTR and 3′ UTR do not code for _______, but they are parts of ________ because they remain in the mRNA.

Answer 63

protein - exons

Question 64

_______ RNA ______ is a type of eukaryotic gene______ at the RNA-processing level in which different mRNA molecules are produced from the same primary ______, depending on which RNA segments are treated as exons and which as introns.

Answer 64

alternative RNA splicing - regulation - transcript

Question 65

BC of alternative RNA splicing, the number of different protein products an organism produces can be much greater than its number of _______.

Answer 65

genes

Question 66

_____ translates the "message" from mRNA and transfers __(2)__ from the cytoplasm to the growing polypeptide in a _____ via ___ bonds.

Answer 66

tRNA - amino acids - ribosome - H-bonds