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Biology > Chapter 3- Nucleic Acids > Flashcards

Chapter 3- Nucleic Acids Flashcards

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1
Q

Where does a phosphodiester bond form?

A

Between the phosphate of one nucleotide and the pentode sugar of the next nucleotide

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2
Q

No. of bases that code for one amino acid?

A

3

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3
Q

How many diff bases combinations are there?

A

64

4 X 4 X 4

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4
Q

Why are there so many base combinations when there are only 20 amino acids?

A
  • several codons code for one amino acid

- some used as start and stop codons

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5
Q

Why is DNA replication considered semi- conservative?

A
  • one strand from original DNA and one strand newly formed

- original strand acts as a template for new strand

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6
Q

Why is complementary base pairing important in DNA replication?

A
  • same sequence of nucleotides produced
  • reduces occurrence of mutations
  • allows formation of hydrogen bonds
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7
Q

Describe structural relationship between deoxyribose and other components of DNA molecule

A
  • part of the nucleotide
  • bonded to phosphate at C5 and joined to base at C1
  • part of the backbone of DNA
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8
Q

Describe how a nucleotide base sequence in a gene is used to synthesise a polypeptide?

A

Transcription

  • DNA is transcribed to mRNA
  • done when free RNA nucleotides line up by complementary base pairing to form sense strand
  • catalysed by RNA polymerase

Translation

  • mRNA moves to ribosomes
  • tRNA anticodons bind to mRNA codons
  • correct amino acid attached to tRNA
  • peptide bond formed between the amino acids
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9
Q

Describe how the DNA molecule replicates

A
  • semi conservative replication
  • helix unwinds
  • 2 polypeptide chains unzip
  • h bonds between bases break
  • each strand acts as a template
  • free DNA nucleotides align with exposed bases by complementary base pairing in which pyramidine binds with purine
  • h bonds reform
  • DNA polymerase joins adjacent nucleotides together to form sugar phosphate backbone by phospodiester bonds
  • each new molecule has 1 old and 1 new strand
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10
Q

Difference in structure between DNA and RNA?

A
  • mRNA shorter
  • mRNA single stranded
  • mRNA non helical
  • RNA contains ribose. DNA contains deoxyribose
  • RNA contains uracil. DNA contains thymine
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11
Q

Why DNA is not able to leave nucleus?

A

Too big to fit through nuclear pore

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12
Q

Why mRNA is shorter than DNA?

A

-mRNA only codes for 1 protein but DNA codes for many proteins

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13
Q

Components of DNA nucleotide?

A
  • phosphate
  • deoxyribose sugar
  • nitrogenous base
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14
Q

What does a gene code for?

A

A protein

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15
Q

Suggest how changing the sequence of DNA nucleotides affects the final product the DNA codes for

A

-diff sequence of amino acids and thus a diff protein

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16
Q

Explain how the structure of DNA allows replication

A
  • double stranded. Each stand acts as a template
  • hydrogen bonds between bases breaks easily. Allows for complementary base pairing of free nucleotides in which purine is only able to bind with pyramidine
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17
Q

Suggest how info on the proportion of bases helps scientists figure out the structure of DNA

A
  • A always bonds to T
  • C always bonds to G
  • thus pyramidine bonds to purine
  • evidence for complementary base pairing
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18
Q

State the role of mRNA

A

Carries a copy of the gene out of the nucleus to the ribosome for protein synthesis

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19
Q

Which technique was used to determine the double helical structure of DNA?

A

X- ray crystallography

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20
Q

How many base pairs are there in one full turn of DNA?

A

10

21
Q

Which bases are pyramidine?

A

T
C
U

22
Q

How many polynucleotide strands are found in a tRNA molecule?

A

1

23
Q

How does tRNA add amino acids to the growing polypeptide chain?

A
  • anticodons base pairing with codons on mRNA
  • acceptor arm has specific amino acid attached
  • amino acid attached to polypeptide chain
24
Q

Why is complementary base pairing advantageous?

A

-to ensure genetic code copied correctly

25
Q

Function of histone?

A

-arrange DNA in nucleus

26
Q

Why helical shape of DNA advantageous?

A
  • makes molecule more compact
  • stores more info
  • genetic code is protected
  • easily replicated
27
Q

What is a codon?

A

-a sequence of 3 nucleotides that code for a particular amino acid during protein synthesis

28
Q

What is meant by non overlapping?

A

Each base is read only once

29
Q

What is meant by universal?

A
  • used by all organisms

- same codons code for same amino acid in diff organisms

30
Q

Describe transcription

A
  • DNA helicase unwinds the double helix
  • RNA nucleotides complimentary base pair with DNA template strand
  • thymine bass replaces with uracil in mRNA
  • RNA polymerase forms sugar phosphate backbone and forms phosphodiester bonds
  • mRNA produced
31
Q

How is the genetic code read?

A
  • read in a series of triplets containing 3 nucleotides

- each triplet codes for an amino acid

32
Q

What is a stop codon and how does it work?

A
  • is a nucleotide triplet at the end of mRNA

- tells the ribosome to stop translation

33
Q

Glycine is coded for by the codons GGU, GGA, GGG. Why is this advantageous?

A
  • substitution mutation could result in same amino acid

- thus same protein coded for

34
Q

Structure of tRNA molecule?

A
  • single strand of mRNA
  • contains 3 bases which are anti codons to mRNA strand
  • specific amino acid attached
35
Q

Function of tRNA in translation?

A

-reads the mRNA strand and determines which order amino acids should be attached

36
Q

What reaction is required for the formation of a polypeptide chain during translation?

A

Condensation

37
Q

Explain the path that a polypeptide chain, newly synthesised in translation, must take in order to appear in the cell surface membrane

A
  • polypeptide chain undergoes folding to form functional protein
  • occurs in rough er
  • vesicle transports protein to Golgi
  • this modifies and repackages protein
  • vesicle containing protein fuse with CSM
38
Q

Other than nucleus, where is DNA found in animal and plant cells?

A
  • mitochondria

- chloroplast

39
Q

Purpose of gene?

A

Section of DNA that codes for specific protein

40
Q

Not all DNA found in nucleus is coded into proteins. Explain?

A
  • introns = don’t code for amino acids

- exons= code for amino acids

41
Q

What is a mutation?

A

-a change in the base sequence of DNA

42
Q

Why could some mutations be harmful to the cell?

A
  • a change in base sequence
  • alters the specific order of amino acids
  • protein could be non functional
43
Q

Why is an insertion mutation potentially more detrimental than a substitution mutation?

A
  • insertion mutation means that an additional base is added to base sequence
  • the whole DNA base sequence is shifted to the right
  • thus, all amino acids after mutation are affected
  • substitution mutation could be silent as the genetic code is degenerate
  • may not affect the function of protein
44
Q

How Y allele codes for production of enzyme?

A
  • DNA base sequence codes for amino acid sequence
  • 1 amino acid = 3 bases
  • transcription: H bonds break at allele. RNA nucleotides bind to antisense strand by complementary base pairing. RNA polymerase forms phosphodiester bonds between RNA nucleotides. forms mRNA. mRNA same as sense strand (y allele)
  • Translation: mRNA binds to ribosomes on RER. tRNA binds to mRNA. tRNA brings specific amino acid. mRNA translated into polypeptide
45
Q

Why allele with a mutation codes for enzyme with different primary structure?

A
  • mutation could be substitution or frame shift
  • leads to diff base sequence of DNA
  • diff. sequence of amino acids
  • diff mRNA codon. diff tRNA anticodon will bind. tRNA brings diff amino acid.
  • amino acid sequence is primary structure
46
Q

Competitive inhibitor?

A
  • competes for active site of enzyme
  • prevents substrate binding to active site
  • prevents formation of ESC
47
Q

How competitive inhibitor will help to reduce spread of virus?

A
  • virus cannot leave cell
  • cannot spread to other cells
  • fewer viruses in droplets when sneezing / coughing
48
Q

Why scientists concentrated on plants that have already been used as traditional medicine?

A
  • already identified as likely to have medicinal properties
  • reduces time in finding plants
  • reduces cost
49
Q

Diseases associated with smoking?

A
  • lung cancer
  • stroke
  • heart attack

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