structure of DNA and RNA

Question 1

describe the basic functions of DNA and RNA in all living cells

Answer 1

DNA - holds genetic info which codes for polypeptides
RNA - transfers genetic info from DNA to ribosomes

Question 2

name the two types of molecule from which a ribosome is made

Answer 2

RNA and proteins

Question 3

draw and label a DNA nucleotide and RNA nucleotide

Answer 3

DNA
- phosphate group
- pentose: deoxyribose
- nitrogen containing organic base: adenine, thymine, guanine or cytosine

RNA
- phosphate group
- pentose: ribose
- nitrogen containing organic base: adenine, uracil.guanine or cytosine

Question 4

describe the differences between a DNA nucleotide and an RNA nucleotide

Answer 4

DNA pentose is deoxyribose, RNA pentose in ribose

DNA base can be thymine, RNA base can be uracil

Question 5

describe how nucleotides join together yo form polynucleotides

Answer 5

condensation reaction removing water
between phosphate group of one and deoxyribose/ribose of another
forming phosphodiester bonds

Question 6

why did scientists initially doubt that DNA carried the genetic code

Answer 6

the relative simplicity
chemically simple molecule with few components

Question 7

describe the structure of DNA

Answer 7

polymer of nucleotides
each nucleotide formed of deoxyribose, phosphate group and nitrogen containing organic base
phosphodiester bonds join adjacent nucleotides
2 polynucleotide chains held together by hydrogen bonds
between complementary base pairs - adenine and thymine and cytosine and guanime
double helix

Question 8

decribe the structure of RNA

Answer 8

polymer of nucleotides
each formed of ribose, phosphate group and nitrogen containing base
bases - uracil, adenine, cytosine, guanine
phosphodiester bonds join adjacent nucleotides
single helix

Question 9

compare and contrast the structure of DNA and RNA

Answer 9

DNA is deoxyribose, RNA is ribose
DNA has base thymine, RNA has base uracil
DNA is double helix, RNA is single helix
DNA is long, RNA is shorter
DNA has hydrogen bonds, RNA does not

Question 10

suggest how the structure of DNA relates to its functions

Answer 10

●Two strands → both can act as templates for semi-conservative replication
● Hydrogen bonds between bases are weak → strands can be separated for replication
● Complementary base pairing → accurate replication
● Many hydrogen bonds between bases → stable / strong molecule
● Double helix with sugar phosphate backbone → protects bases / hydrogen bonds
● Long molecule → store lots of genetic information (that codes for polypeptides)
● Double helix (coiled) → compact

Question 11

Suggest how you can use incomplete information about the frequency of
bases on DNA strands to find the frequency of other bases

Answer 11

1. % of adenine in strand 1 = % of thymine in strand 2 (and vice versa)
2. % of guanine in strand 1 = % of cytosine in strand 2 (and vice versa)
   Because of specific complementary base pairing between 2 strands