3.1.5 | NUCLEIC ACIDS ARE IMPORTANT INFORMATION CARRYING MOCLEULES

Question 1

what is the function of DNA

Answer 1

holds genetic information

Question 2

what is function of RNA

Answer 2

transfers genetic information from DNA to ribosomes

Question 3

name the two type of molecule from which a ribosome is made

Answer 3

RNA and proteins

Question 4

what is the general structure of a nucleotide

Answer 4

ribose sugar, nitrogenous base and phosphate group

Question 5

describe the structure of a DNA nucleotide

Answer 5

phosphate group, deoxyribose sugar and nitrogenous base (cytosine, adenine, thymine or guanine)

Question 6

describe the structure of a RNA nucleotide

Answer 6

ribose sugar, phosphate group, nitrogenous base (adenine, uracil, guanine or cytosine)

Question 7

describe how nucleotides join together to form polynucleotides

Answer 7

condensation reactions, eliminating water molecules, between the phosphate group of one nucleotide and the pentose sugar of another forming phosphodiester bonds

Question 8

describe the structure of a DNA molecule

Answer 8

polymer of nucleotides
each nuleotide formed from a deoxyribose sugar, a phosphate group and nitrogenous base
phosphodiester bonds join adjacent nucleotides
each DNA strand is held together by hydrogen bonds between complementary base pairs (adenine + thymine and cytosine + gunsine)
double helix

Question 9

describe the structure of mRNA

Answer 9

polymer of nucleotides
each nucleotides formed from ribose, a phosphate group and nitrogenous base
bases are uracil, adenine, cytosine and guanine
phosphodiester bonds join adjacent nucleotides
single helix

Question 10

suggest how the structure of DNA relates to its function

Answer 10

two strands → both can act as template for semi-conservative replication
hydrogen bonds between bases are weak → strands can be separated easily for replication
many hydrogen bonds between bases → stable/strong molecule
complementary base pairing → accurate replication
double helix with sugar phosphate backbone → protects bases/hydrogen bonds
large molecule → stores lots of genetic information
double helix (coiled) → compact

Question 11

why did many scientists initially double that DNA carried the genetic code

Answer 11

the relative simplicity of DNA - chemically simple molecule with few components

Question 12

why is semi-conservative replication important

Answer 12

ensure genetic continuity between generations of cells

Question 13

describe the process of semi-conservative replication

Answer 13

DNA helipads breaks hydrogen bonds between complementary bases, uniwinding ghe double helix
both strands act as templates
free DNA nucleotides attracted to exposed bases and join by specific complementary base pairing
hydrogen bonds form between complementary base pairs
DNA polymerase joins adjacent nucleotides on new strand by condensation reactions forming phosphodiester bonds

Question 14

what is formed as a result of semi-conservative replication

Answer 14

new DNA molecule(s) which consists of one original/template strand and one new strand

Question 15

use your knowledge of enzyme action to suggest why DNA polymerase moves in opposite directions along DNA strands

Answer 15

DNA has antiparrallel strands so shapes/arrangements of nucleotides on two ends are differentDNA polymerase is an enzyme with a specific shaped active site so can only bind to substrate with complementary shape

Question 16

name the two scientists who proposed models of the chemical structure of DNA and of DNA replication

Answer 16

Watson and Crick

Question 17

describe the work of Meselson and Stahl in validating the Watson-Crick model of semi-conservative replication