DNA structure and function

Question 1

what elements does DNA contain?

Answer 1

carbon, hydrogen, oxygen, nitrogen and phosphorus

Question 2

what is DNA?

Answer 2

a polymer made from many monomers called nucleotides that are chemically joined together with a phosphodiester bond

Question 3

what do many nucleotides join together to make? how do these form?

Answer 3

a polynucleotide (DNA is made from two polynucleotide strands)

a condensation reaction joins nucleotides together

Question 4

what are the three components of a nucleotide?

Answer 4

a pentose sugar called deoxyribose (a sugar with 5 carbons), phosphate group and a base

Question 5

what element is in a DNA base? what are the 4 bases?

Answer 5

nitrogen

adenine, thymine, guanine and cytosine

Question 6

what is the phosphate of one nucleotide attached to on another nucleotide?

Answer 6

the deoxyribose of the next nucleotide so there are alternate phosphate then sugar all down the backbone of the strand

this structure is called the sugar-phosphate backbone

Question 7

what kind of bonds are the phosphodiester bonds in the polynucleotide strand?

Answer 7

strong covalent

Question 8

how do the two polynucleotide strands in DNA run?

Answer 8

anti-parallel to each other

one runs in the 5’ to 3’ direction whilst the other runs 3’ to 5’

Question 9

where is the 3’ end of a polynucleotide strand?

Answer 9

the hydroxyl group that is attached to the deoxyribose sugar of the strand

Question 10

where is the 5’ end of the polynucleotide strand?

Answer 10

the phosphate group

Question 11

what are the two polynucleotide strands in DNA held together by?

Answer 11

hydrogen bonds between complementary bases

Question 12

explain what is meant by ‘complementary base pairing’?

Answer 12

each base can only pair with a certain other base- adenine with thymine and cytosine with guanine

Question 13

how many hydrogen bonds are between A and T and C and G? how can we remember this?

Answer 13

adenine and thymine = 2
cytosine and guanine =3

tea for two!

Question 14

what do the two anti-parallel strands do?

Answer 14

twist to make the DNA double helix

Question 15

what are the functions of DNA?

Answer 15

-holds genetic info
-holds the genetic code for
production of proteins
-can replicate to produce DNA for new cells and cell division

Question 16

what is the benefit of DNA being large/long and being coiled around histones?

Answer 16

makes it compact and enables a large amount of genetic info to be stored in a cell

Question 17

what does the base sequence of DNA form?

Answer 17

the genetic code for making proteins with triplets of bases coding for one amino acid

Question 18

the base sequence of DNA determines where…

Answer 18

tRNA molecules carrying specific amino acids complementary base pair

and therefore determines the sequence of amino acids that forms the primary structure of proteins

Question 19

why is it important that the phosphodiester bonds strong?

Answer 19

so that the sugar-phosphate backbone gives strength and stability to the molecule

Question 20

what is meant by ‘strong phosphodiester bonds maintain the integrity of the code’?

Answer 20

nucleotides cannot easily break away and re-join in a different sequence

Question 21

what is the strength of the hydrogen bonds holding the polynucleotide strands together?

Answer 21

weak so easily broken

Question 22

why is it a benefit that hydrogen bonds are weak?

Answer 22

so strands can be separated and act as template strands for DNA replication and for transcription/ production of mRNA for protein synthesis.

Question 23

why is complementary base pairing important for DNA function?

Answer 23

enables DNA to be identically replicated

Question 24

what is the benefit of the MANY hydrogen bonds between polynucleotide strands?

Answer 24

gives strength and stability to the DNA molecule.

Question 25

who worked out the structure of DNA?

Answer 25

Watson and Crick, following the work of Rosalind Franklin

Question 26

what is RNA?

Answer 26

a relatively short polynucleotide chain in which the pentose sugar is always ribose (not deoxyribose like DNA)

Question 27

what are the bases of RNA?

Answer 27

adenine, guanine, cytosine and uracil

Question 28

what do the 3 types of RNA do?

Answer 28

1. transfers genetic information from DNA to the ribosomes

2.what makes up ribosomes, along with proteins

3. involved in protein synthesis