Unit 2: Ch. 9b

Question 1

In DNA and RNA where are the phosphodiester bonds located?

Answer 1

the phosphodiester bond connects the 5’ C of the sugar molecular of one nucleotide to the 3’ C of sugar molecule of the next nucleotide

Question 2

what are the purines?

Answer 2

Adenine and Guanine

Question 3

what are the pyrimidines?

Answer 3

Thymine and Cytosine

Question 4

the amount of purines is equal to…

Answer 4

the amount of pyrimidines

Question 5

the amount of A is equal to ____ and the amount of C is equal to ____ but __ + __ does not equal the amount of __ + __

Answer 5

T, G, C, G, A, T. The ratio of C+G to A+T varies among species

Question 6

Who made the double helix model?

Answer 6

Watson and Crick

Question 7

Base pairs stacked on top of each other are ___ apart

Answer 7

3.4Å (0.34nm)

Question 8

10 base pairs per one complete turn of a helix is __ long

Answer 8

34Å (3.4nm)

Question 9

The diameter of the double helix is __ long

Answer 9

20Å (2nm)

Question 10

The strands on the double helix are _______

Answer 10

antiparallel

Question 11

how many hydrogen bonds do A & T base pairs form?

Answer 11

2

Question 12

how many hydrogen bonds do G & C base pairs form?

Answer 12

3

Question 13

why are G-C bonds somewhat stronger than A-T bonds?

Answer 13

Because G-C bonds have more hydrogen bonds

Question 14

the two DNA strands are held together by

Answer 14

hydrogen bonds between nitrogenous bases

Question 15

In RNA, the sugar ______ replaces deoxyribose of DNA and ______ replaces thymine of DNA

Answer 15

ribose (OH), uracil

Question 16

most RNA is _____ stranded

Answer 16

single

Question 17

some viruses have a _____-_____ RNA genome

Answer 17

double-stranded

Question 18

What are the three kinds of cellular RNAs that function during gene expression?

Answer 18

• Messenger RNA (mRNA)
• Ribosomal RNA (rRNA)
• Transfer RNA (tRNA)

Question 19

what does mRNA do?

Answer 19

Carries genetic information from DNA of the gene to the ribosome; vary in size reflecting size of protein/gene

Question 20

what does rRNA do?

Answer 20

constitutes for 80 percent of all RNA in a cell; act as workbenches during translation

Question 21

what does tRNA do?

Answer 21

Carries amino acids to ribosomes for protein synthesis

Question 22

_________ replaces thymine and is therefore complementary to adenine during transcription

Answer 22

uracil

Question 23

above critical temperature (__) DNA ________ and ______ when cooled

Answer 23

(75-85C), denatures, renatures

Question 24

what is molecular hybridization?

Answer 24

combines two molecules in a new, single chemical entity

Question 25

how do nucleic acids go through molecular hybridization?

Answer 25

denaturing (unwinding and separation of strands), and renaturing

Question 26

a probe is a

Answer 26

a single-stranded sequence of DNA or RNA used to search for its complementary sequence in a sample genome

Question 27

small DNA/RNA fragments migrate through a gel at a ________ rate than larger fragments

Answer 27

faster

Question 27

what is Nucleic acid electrophoresis

Answer 27

it is a way to separate DNA and RNA fragments by size

Question 28

DNA usually has a _________ charge

Answer 28

negative

Question 29

why do smaller DNA fragments travel farther down to the positive side of the gel container?

Answer 29

all DNA is attracted to the negative side of the gel container but the smaller DNA fragments can move through the gel particles easier than the larger ones