1B-more biological molecules

Question 1

what are DNA and RNA both a type of

Answer 1

nucleic acid

Question 2

what is teh DNA

Answer 2

deoxyribonucleic acid used to store your genetic info

Question 3

what is RNA

Answer 3

ribonucleic acid to transfer genetic info from DNA to ribosome

Question 4

what is a nucleotide structure

Answer 4

a pentose sugar, a base and a phosphate group

Question 5

how do nucleotides join to make a polynucleotide

Answer 5

condensation reaction between phosphate group and the pentose sugar of another nucleotide

Question 6

what bond forms between the pentose sugar and phosphate group in a polynucleotide

Answer 6

phosphodiester bond

Question 7

what is the sugar-phosphate backbone

Answer 7

the chains of phosphates and sugars

Question 8

what is teh structure of dna

Answer 8

double helix structure
they are really long and coiled up tightly so a lot of genetic info can fit in a small space

Question 9

what is teh sugar in a dna

Answer 9

deoxyribose sugar

Question 10

what are the four different bases and which ones they pair to

Answer 10

adenine and thymine
cytosine and guanine

Question 11

how many hydrogen bonds between adenine and thymine and cytosine and guanine

Answer 11

three hydrogen bonds between cytosine and guanine
two hydrogen between adenine and thymine

Question 12

how does the polynucleotides being antiparallel make a double helix

Answer 12

they go in opposite directions tow antiparallel strands twist to form dna double helix

Question 13

what is the sugar in RNA

Answer 13

ribose sugar

Question 14

difference between RNA and DNA bases

Answer 14

uracil replaces thymine as base

Question 15

differences between RNA and DNA

Answer 15

forms a single polynucleotide strand
RNA much shorter than most DNA polynucleotide

Question 16

why does DNA replicate

Answer 16

so each new DNA molecule has half the strands from the original DNA molecule meaning there is genetic continuity between generations of cells

Question 17

How does DNA replicate

Answer 17

the DNA helicase breaks the hydrogen bonds between the two polynucleotide strands making the helix unwind forming two single strands
each original single strands acts as a template for a new stand. free floating DNA nucleotides are attracted to their exposed complementary bases this is called compelmentary base pairing
condensation reactions join the nucleotides of the new strand together catalysed by the enzyme DNA polymerase
hydrogen bonds form between bases on the original and new strand
each new molecule contains one strand for the original DNA molecule and one new strand

Question 18

what is the action of DNA polymerase

Answer 18

the active site of DNA polymerase is only complementary to the 3’ end of the new DNA strand so can only add nucleotides to the 3’ end. so polymerase moves down template strand in 3’ to 5’ direction but new strand made in 5’ to 3’ direction

Question 19

why does the DNA polymerase on one template strand move the opposite direction to another on another templte strand

Answer 19

because they are antiparallel so they move in opposite directions refer to pg56

Question 20

the evidence for semi conservative replication

Answer 20

Two samples of bacteria were grown
one containing light nitrogen and one containing heavy nitrogen
as the bacteria reproduced they took the nitrogen to help make nucleotides for new DNA so nitrogen slowly became part of the DNA
A sample of DNA was taken from each sample of bacteria and spun in a centrifuge
the DNA with the heavy nitrogen settle toward the bottom of the tube
DNA with light nitrogen settled towards the top of the tube
then the bacteria with the heavy nitrogen was put with the bacteria with the light nitrogen and left for one round of DNA replication then spun in a centrifuge
if replication was conservative the original heavy DNA would settle at the bottom and the new light DNA would settle at the top of the tube
if the DNA replication was semi conservative the new bacterial DNA molecules would contain one stand of old DNA containing heavy nitrogen and one strand form new DNA containing light nitrogen so the DNA would settle in the middle of the tube
the DNA settled in the middle so it contained heavy and light nitrogen so semi conservative replication