Nucleic acids - DNA

Question 1

Why is DNA well suited for its function?

Answer 1

stable as it has many weak hydrogen bonds in the double helix strands

strong as it has many covalent bonds within the sugar, phosphate backbone

complementary base pairing allows DNA to replicate itself exactly durng cell division. weak hydrogen bonds allow the strands to seperate

compact as DNA is a long, double helix shape and it can fit inside the nucleus

precise genetic code, determined by the specific sequence of bases, which contols protien synthesis

Question 2

semi - conservative replication ?

Answer 2

mechanism which DNA copies itself

Question 3

why does semi - conservative replication of dna occure ?

Answer 3

dna helicase - sperates the 2 strands of dna by breaking the weak hydrogen bonds

each exposed strand now acts as a template for the formation of a new strand

dna nucleotides line up alongside and attach to the exposed bases by complementary base pairing, new hydrogen bonds form between the bases

the new nucleotides are joined together by dna polymerase which catalyses the formation of phosphodiester bonds between nucleotides

mutation - spontaneous changes in the dna base sequence, nucleotides can be added or deleted

Question 4

How many bonds do each complementary base pair form ?

Answer 4

guanine and cytosene = 3 hydrogen bonds

adenine and thymine = 2 hydrogen bonds

Question 5

What are nucleic acids ?

Answer 5

dna and rna

polymers of nucleotides

have roles in storage, transfer genetic information

Question 6

What are nucleotides ?

Answer 6

monomers that join together to form polynucleotide chain strands

Question 7

Structure of dna ?

Answer 7

polymer made of long repeating nucleotides

deoxyribose pentose sugar

phosphate group

nitrogen containing base (GCAT)

Question 8

purines ?

Answer 8

2 rings

Question 9

pyramidines ?

Answer 9

1 ring

Question 10

Why are nucleotide chains held together ?

Answer 10

the phosphate group of each nucleotide is linked to the sugar of the next by strong phosphodiester bonds

condensation reaction involved

has a sugar phosphate backbone because sugars and phosphates are identicle

Question 11

what is dna and what does it consist of ?

Answer 11

dna is a molecule that stoes the coded information used by cells to make protiens

it consists of 2 strands of nucleotides (anti - parallel), twisting to form a double helix

bases in each strand are held together by hydrogen bonds

Question 12

DNA in eukaryotes ?

Answer 12

dna is coiled around histone protiens and makes up linear chromosomes

Question 13

DNA in prokaryotes ?

Answer 13

dna is smaller, circular and not associated with histone protiens

Question 14

synthesising dna ?

Answer 14

water is removed in condensation reaction between OH group of the phosphate and OH group of carbon 4 of sugar

phosphodiester bond is formed

Question 15

hydrolysing dna ?

Answer 15

water is added in hydrolosysis reaction

phosphodiester bond is broken

Question 16

what is a gene ?

Answer 16

a short section of dna which codes for one protien

occupies a fixed position on a chromosome called a locus

Question 17

what is an allele ?

Answer 17

different form of the same gene

Question 18

genome ?

Answer 18

all the genes within a cell

Question 19

what is a proteome ?

Answer 19

the full range of protiens that a cell is able to produce

Question 20

how does dna code for a protien ?

Answer 20

each triplet codes for a specific amino acid

the order of triplets determines the primary structure of the protien

Question 21

What happens if a dna is single stranded ?

Answer 21

the bases dont pair up and dont follow complementary base pairing rules so it is not possible to calculate