DNA and RNA

Question 1

what is the roles of DNA and RNA

Answer 1

DNA: hold genetic information
RNA: transfers genetic information from the DNA to the ribosome

Question 2

what are ribosomes formed from

Answer 2

RNA and proteins

Question 3

what are nucleotides composed of

Answer 3

-pentose sugar
-a nitrogen containing organic base
-a phosphate group

Question 4

how are polynucleotides formed

Answer 4

-many nucleotides joined together to form polynucleotide strand via a condensation reaction between the phosphate group of one nucleotide and the sugar of another

-forms a phosphodiester bond

Question 5

what is the chain of phosphate and sugar known as

Answer 5

sugar- phosphate backbone

Question 6

describe the structure of DNA

Answer 6

-polymer of nucleotides
-each nucleotides formed from a deoxyribose sugar, a phosphate group and a nitrogen containing organic base
- double helix formed by joing two polynucleotide strands via condensation reaction
-forms a phosphodiester bond between the nucleotides
- hydrogen bonds form between complementary base paring - Adenine with Thymine and Cytosine with Guanine

Question 7

what are the four possible bases in DNA nucleotide

Answer 7

-Adenine (A)
-Thymine (T)
-Cytosine (C)
-Guanine (G)

Question 8

how many hydrogen bonds form between
a) A and T
b) C and G

Answer 8

a) 2 hhydrogen bonds
b) 3 hydrogen bonds

Question 9

describe the structure of RNA nucleotides

Answer 9

-ribose sugar, phosphate group and a nitrogen containing organic base

Question 10

what are the possible bases for RNA nucleotide

Answer 10

-adenine
-cytosine
-guanine
-uracil

Question 11

compare the DNA and RNA

Answer 11

-SIMILARITIES
-both are polymers of nucleotide
-both made up of a sugar, phosphate group and an organic base
-both have the same organic bases of adenine, cytosine and guanine

DIFFERENCES
-DNA is double stranded whilst RNA is single stranded
-DNA is long polynucleotide strand whilst RNA is short polynucleotide strand
-sugar in RNA is ribose whilst for DNA its deoxyribose
DNA contains Thymine whilst RNA contains Uracil

Question 12

who discovered the structure of DNA and its model

Answer 12

-James Watson and Francis Crick

Question 13

what does semi conservative replication mean

Answer 13

-each of the DNA molecule contains one strand from the original DNA molecule and one strand that is brand new

Question 14

why does DNA replicate itself

Answer 14

• parental DNA copies itself before cell division so that each new cell has the full amount of DNA

Question 15

what does semi- conservative replication ensure

Answer 15

• ensures that there is genetic continuity between generation of cells ( I.e : cells produced by cell division inherit the genes from their parent cells

Question 16

what is the first step of DNA replication

Answer 16

1) the enzyme DNA helicase breaks the hydrogen bonds between the complementary base pairs between the two polynucleotide strands

• causes the the DNA double helix to unwind and form two single strands

Question 17

2nd step of DNA replication

Answer 17

-each of the separated parental DNA strands acts as a template
- the free floating DNA nucleotides are attracted to their complementary base pairs on the template strands of the parental DNA

Question 18

3rd step of DNA replication

Answer 18

• the adjacent nucleotides of the new strand join together by condensation reaction - catalysed the by the enzyme DNA polymerase

-hydrogen form between the original and new strands

Question 19

4th step of DNA replication

Answer 19

-two sets of the DNA daughter (new DNA molecule) now contains one strand of the parental DNA and the newly synthesised strand

Question 20

decribe how a phosphodiester bond is formed between two nucleotides within a DNA molecule

Answer 20

-via condensation reaction
-between deoxyribose sugar and phosphate group
-catalysed by the enzyme DNA polymerase