Nucleic Acids

Question 1

What are nucleic acids?

Answer 1

Large molecules in the cell nuclei

Question 2

What are the two types of nucleic acids?

Answer 2

DNA and RNA

Question 3

What are the roles of both DNA and RNA

Answer 3

Storage,transfer of genetic information and the synthesis of polypeptides

Question 4

What elements do nucleic acids contain?

Answer 4

Carbon, hydrogen, oxygen, nitrogen and phosphorus

Question 5

What is an individual nucleotide composed of?

Answer 5

• a pentose monosaccharide (sugar), containing five carbon atoms
• a phosphate group, PO42_^, an inorganic molecule that is acidic and negatively charged
• a nitrogenous base - a complex organic molecule containing one or two carbon rings in its structure as well as nitrogen

Question 6

How are nucleotides linked together?

Answer 6

Condensation reactions

Question 7

What is the polymer of nucleotides called?

Answer 7

Polynucleotides

Question 8

Where are phosphodiester bonds formed in a polynucleotide?

Answer 8

The phosphate group at the fifth carbon of the pentose sugar (‘5) of one nucleotide forms a covalent bond with the hydroxyl (OH) group at the third carbon (3’) of the pentose sugar of an adjacent nucleotide

Question 9

How are phosphodiester bonds broken?

Answer 9

hydrolysis which releases the individual nucleotides

Question 10

Why is DNA replication necessary?

Answer 10

To ensure we have the correct amount of DNA before cell division

Question 11

What does DNA helicase do?

Answer 11

unwinds double helix

Question 12

What does DNA polymerase do?

Answer 12

joins one nucleotide to the next

Question 13

What does the term lagging mean in DNA replication?

Answer 13

the original strand running 5’ to 3’

Question 14

What does the term leading mean in DNA replication?

Answer 14

the original strand running 3’ to 5’

Question 15

What does DNA ligase do?

Answer 15

joins together small sections of DNA

Question 16

What are Okazaki fragments?

Answer 16

separated sections of DNA

Question 17

What are the purine bases?

Answer 17

Guanine and adenine

Question 18

What are the complimentary base pairs?

Answer 18

Adenine and thymine, cytosine and guanine

Question 19

What types of bonds exist between base pairs?

Answer 19

hydrogen bonds

Question 20

What type of bonds exist between phosphate and sugar in a nucleotide?

Answer 20

phosphodiester, which is a type of covalent bond

Question 21

How many hydrogen bonds are between a thymine and an adenine?

Answer 21

2

Question 22

What is in the backbone of a DNA double helix?

Answer 22

sugar and phosphate

Question 23

What are the types of RNA?

Answer 23

mRNA- messenger RNA
tRNA- transport RNA
rRNA- ribosome RNA

Question 24

what does the semi-conservative replication of DNA do?

Answer 24

involves separation of the DNA strands followed by replication of each strand separately to produce DNA, which is half parental and half new

Question 25

what is mRNA?

Answer 25

a copy of DNA and a code for the amino acids

Question 26

what is a triplet code?

Answer 26

every 3 bases will code for one amino acid

Question 27

what is the genetic code?

Answer 27

the way in which DNA codes for amino acids within organisms

Question 28

what is the universal code?

Answer 28

all organisms use the same triplet for the same amino acids

Question 29

what is the degenerate code?

Answer 29

some amino acids are coded for by more than one triplet

Question 30

what is the non overlapping code?

Answer 30

the code is always read from the same starting point, each base is only read once in the sequence

Question 31

what is the triplet code?

Answer 31

when bases are read three times

Question 32

what is transcription in proteinsynthesis?

Answer 32

making a copy of the DNA using mRNA

Question 33

what is translation in proteinsynthesis?

Answer 33

translating mRNA code into a sequence of amino acids

Question 34

what is the process of transcription in proteinsynthesis?

Answer 34

1) hydrogen bonds break between complementary bases and DNA unzips (catalysed by DNA helicase) 2) expose sense strand (coding which runs 5' to 3') and anti sense strand (templates which run 3' to 5') 3) free nucleotides bind to exposed bases on antisense strand of DNA by complimentary base pairing 4) RNA polymerases catalyses formation of phosphodiester bonds between RNA nucleotides 5) at the end of the gene, mRNA is released from DNA and passes out of the nucleus through nuclear pore into cytoplasm 6) resulting mRNA is a copy of the sense strand, aside from substitution of U for T.

Question 35

what is the process of translation?

Answer 35

1) mRNA binds to ribosomes first 6 bases attached to small subunits and exposed to large one 2) second tRNA binds to next codon 3) peptide bonds form between Met and Tyr (enzyme peptidyl transferase in small subunits catalyses this) 4) ribosomes move along mRNA to next codon and tRNA bearing next amino acid joins, peptide bond forms 5) process continues until stop codon reached, no tRNAs carry anticodons for stop codons so polypeptide chain terminates at previous codon. polypeptide is released

Question 36

during transcription, is the mRNA a copy of the sense or antisense strand?

Answer 36

sense

Question 37

how many tRNAs fit into a ribosome at one time?

Answer 37

2

Question 38

why does a stop codon result in termination of the polypeptide chain?

Answer 38

no anticodon exist

Question 39

where might a polypeptide chain be altered following translation?

Answer 39

golgi apparatus and rough endoplasmic reticulum

Question 40

what are some similarities between DNA replication and transcription?

Answer 40

- require making a new copy of DNA - they both occur in the cell nucleus

Question 41

what are some differences between DNA replication and transcription?

Answer 41

- DNA transcription is involved in conversion of DNA to RNA whereas replication is the process of making another copy of DNA - transcription makes RNA strands short whereas replication makes DNA strands long

Question 42

which bonds hold together the nucleotides in the sugar phosphate backbone?

Answer 42

phosphodiester bonds

Question 43

what are the names of the four bases?

Answer 43

adenine thymine guanine cytosine

Question 44

what bonds hold together the bases in a double helix?

Answer 44

hydrogen

Question 45

how many bonds form between cytosine and guanine?

Answer 45

3

Question 46

how many bonds form between thymine and adenine?

Answer 46

2

Question 47

describe the role of DNA helicase in DNA replication?

Answer 47

unravels the DNA by breaking down hydrogen bonds between complimentary bases

Question 48

describe the role of DNA polymerase in DNA replication?

Answer 48

makes DNA by joining one nucleotide to the next

Question 49

what is a codon?

Answer 49

3 bases on the mRNA- amino acid