nucleic acids

• how is a nucleotide formed

  by condensation reactions
• what does a nucleotide consist of

  a phosphate head, pentose sugar and nitrogeous base
• what is a nucleic acid

  a chain of nucleotides
• how can nucleic acids be broken down

  hydrolysis reactions
• what free ends does a polynucleotide have

  free 5' end - free phosphate

  free 3' end - free sugar
• draw a nucleotide

  labels

  A) phosphate head

  B) nitrogenous base

  C) pentose sugar

  D) phosphodiester bond

  
• what bond is present in a nucleotide

  phosphodiester bond
• what bond joins subsequent nucleotides

  phosphodiester bond
• draw a polynucleotide

  label

  A) phosphate

  B) nitrogenous base

  C) pentose sugarr

  D) phosphodiester bond

  
• what does DNA stand for

  deoxyribonucleic acid
• describe DNA

  a molecule of DNA consists of 2 anti-parallel strands with the 2 strands being held together by hydrogen bonds between adjacent bases
• describe the base pairing in DNA

  adenine - thymine

  guanine - cytosine
• how many hydrogen bonds are between the base pairs

  adenine - thymine = 2

  guanine - cytosine = 3
• how is DNA arranged

  in a double helix
• describe the double helix and how it is formed

  each strand of DNA is wound round eachother like a twisted ladder by the bases, following base pairing rules

  every 10 bases = twist of helix
• draw a strand of DNA

  labels

  A) nucleotide

  B) 3 hydrogen bonds

  C) 2 hydrogen bonds

  D) guanine

  E) cytosine

  F) thymine

  G) adenine

  H) double helix

  I) phosphate

  J) nitrogenous base

  K) backbones

  
• how does RNA differ from DNA

  sugar ribose

  single stranded

  much shorter than DNA

  uracil replaces thymine to pair with adenine
• what are the 3 types of RNA and their short form

  messenger - mRNA

  transfer - tRNA

  ribosomal - rRNA
• what are the functions of DNA

  genetic code of all living organisms

  regulates the development of living organisms through the control of protein synthesis

  sequence of DNA determines the amino acid sequence of polypeptides

  one strand = coding (template) as the genetic code

  base triplet = sequence of 3 bases
• what is a gene

  a sequence of DNA that codes for a polypeptide
• describe DNA replication

  enzyme DNA helicase breaks hydrogen bonds holding base pairs and 'unzips' part of the DNA double helix, revealing the 2 strands

  each original strand = template for formation of new DNA molecules

  enzyme DNA polymerase moves along each strand - synthesis for new strand as it catalyses the joining of the free nucleotides to each of the exposed strands by base pairing rules - condensation reactions

  each new DNA molecule has one new strand and one original 'template' strand

  each DNA molecule is identical to the other and to the parent DNA
• what model is DNA replication called and why

  semi - conservative model

  each new DNA molecule has one new strand and one original parent strand (template)
• what model was believed before the modern one and what did it involve

  conservative model - like a photocopy
• what experiment proved the semi conservative model

  the meselson and stahl experiment 1958
• explain the m+s experiment

  e-coli bacteria was placed in a density gradient configuration

  14N went to the top (light)

  15N went to the bottom (heavy)
• describe the results of m+s experiment

  both strands 14N

  both strands 15N

  1 generation - all contained 1 strand 14N and one strand 15N

  2 generations - half both strands 14N, half one strand 14N and one strand 15N

  3 generations - 75% both 14N, 25% both 15N

  one strand 14N, one strand 15N = intermediate

  14N = light

  15N = heavy
• draw a diagram showing results of m+s experiment

  labels

  A) all 15N - heavy

  B) all intermediate - one strand 14N, one strand 15N

  C) 50% all 14N - light, 50% intermediate

  D) 75% all 14N, 25% all 15N

  E) light 14N

  F) intermediate

  G) heavy 15N

  H) 1 generation

  I) 2 generations

  J) 3 generations

  
• draw DNA replication

  labels

  
• what is the sugar called in DNA

  deoxyribose sugar