A1.2 nucleic acids

Question 1

structure of a nucleosome

Answer 1

DNA molecule wrapped twice around 8 histone proteins held together by an additional histone proteins attach with linker DNA

Question 2

simple structure of DNA

Answer 2

double helix made of two antiparallel strands of nucleotides, linked by hydrogen bonds between complementary base pairs.

Question 3

specific examples of RNA

Answer 3

mRNA- molecule synthesized from gene
tRNA-transfers correct amino acids into amino acid chain
rRNA- used to create ribosomes
ATP-used in cells as chemical energy

Question 4

aspects to include when comparing RNA/DNA

Answer 4

-strand number
-present nucleotides
-type of sugar
-shape
-genetic code/not

Question 5

importance of directionality of DNA strands

Answer 5

both strands of DNA are synthesized working from 5’ to 3’ linkage and has a significance for replication, transcription and translation

-during transcription, the coding strand is read from 3’-5’ by enzymes which synthesize mRNA in 5’-3’ direction, creating template strand, exact copy.

Question 6

triplet codon

Answer 6

Each sequence of three bases (i.e. each triplet of bases) in a gene codes for one amino acid
These triplets code for different amino acids – there are 20 different amino acids that cells use to make up different proteins

Question 7

purines/ pyrimidines

Answer 7

purines= double ring nitrogenous base (A, G)
pyrimidines= single ring nitrogenous base ( T,C)

-purines always bond to pyrimidine.
-purines are larger then pyrimidines and forms the double helix shape, which is further stabilized by hydrogen bonds between base pairs

Question 8

function of histones

Answer 8

-histones are used for efficiently packaging DNA. It wraps around 8 proteins +1 additional
-packages and coil DNA in adjoining areas

Question 9

Hershey and chase experiment

Answer 9

aim=to prove that it was DNA that makes up our genetic material
process= 2 batches of bacteriophage (E-COLI) were prepared; one with DNA labelled with radioactive isotope P32 and another with its protein coat labelled with S35.
-bacteria was infected and mixture was centrifuged to isolate bacterial cells
RESULTS= P32 found inside bacterial cell (radioactivity in pellet)
S35 remained outside bacteria (radioactivity in supernatant)

Question 10

chargaff’s data

Answer 10

he analyzed the DNA composition of different organisms and found:
-number of purine bases were equal to the number of pyrimidine bases
-A bases equal to T bases
-G bases equal to C bases
-foundation of complementary base pairing

Question 11

importance of Chargaff’s rule

Answer 11

-showed proportion of A and T, G and C are equal
-falsified tetranucleotide theory