nucleic acids

Question 1

what does DNA stand for

Answer 1

deoxyribonucleic acid

Question 2

what does RNA stand for

Answer 2

ribonucleic acid

Question 3

what does DNA do

Answer 3

hold genetic information

Question 4

what does RNa do

Answer 4

transfers genetic info from the DNA to the ribosomes

Question 5

strcutre of DNA

Answer 5

phosphate nitrogenous base deoxyribose sugar

Question 6

strcutre of RNA

Answer 6

phosphate nitrogenous base ribose sugar

Question 7

bases of DNA

Answer 7

adenine, guanine, cytosine, thymine

Question 8

bases of RNA

Answer 8

adenine, cytosine, guanine, uracil

Question 9

bonds in polynucleotide

Answer 9

phosphodiester

Question 10

what is formed when many nucleotides link to form a chain?

Answer 10

sugar phosphate backbone which is very strong and stable

Question 11

structure of dna

Answer 11

sugar phosphate backbone provides strength
large molecule stores a lot of info
helical so compact
double stranded so replication can occur semi conservatively because each strand can act as a template
complimentary base pairing allows accurate replication
many weak H bonds so it is strong

Question 12

dna replciation

Answer 12

DNA helicase unwinds DNA, breaking H bonds between complimentary bases
2 strands separate and both act as a template
new DNA nucleotides are attracted to exposed complementary bases on template strands by base pairing
DNA polymerase joins adjacent nucleotides via a condensation reaction to form phosphodiester bonds

Question 13

DNA polymerase

Answer 13

has a specific active site
only complimentary to the 5’ end of incoming free nucleotide and 3’ end of developing strand
this forms a phosphodiester bond via condensation reaction

Question 14

Meselson and Stahl

Answer 14

gen 0 - Heavy 15N leading to HEAVY 15N/15N DNA settling in a band low down in the testing tube after centrifugation

gen 1 - template strands are both heavy 15N
new DNA nucleotides have lighter 14N
leads to both new DNA molecules which have 15N template and 14N strand each
15N/14N lighter than 15N/15N so higher up in tube after centrifugation

gen 2 - template strands are 15N, 14N, 14N, 15N
leads to new DNA molecules being 15N/14N, 14/14N, 14N/14N and 15/14N
2 DNA molecules with 2 light strands, one DNA molecule with 1 light strand, one with a heavy

Question 15

Define the term exon

Answer 15

DNA base which codes for a polypeptide chain

Question 16

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

Answer 16

Condensation reaction between phosphate and deoxyribose sugar
Catalysed by DNA polymerase