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biology > Module 2.1.3 Nucleotides Sambrook > Flashcards

Module 2.1.3 Nucleotides Sambrook Flashcards

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AP® Biology flashcards
1
Q

What are the purines in DNA?

A

Adenine
Guanine

DOUBLE ring structure

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2
Q

What are the Pyrimidines ?

A

Thymine
Cytosine
Uracil

SINGLE ring structure

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3
Q

Describe the structure of DNA

A

-DNA is made up of 2 complementary polynucleotide chains and the 2 strands are antiparallel.
-1 strand goes from 5’ to 3’ and the opposite strand goes from 3’ to 5’.
- hydrogen bonds hold the polynucleotide chains together.
- Ester bonds between the phosphate groups
- Hydrogen bonds between the nitrogenous bases
- this forms a double helix with major and minor grooves in an alternating pattern

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4
Q

What are nucleotides in DNA ?

A

-building blocks of DNA
-Made of a deoxyribose Pentosesugar molecule with hydrogen at 2’ position, phosphate group and a nitrogenous base.
-hold the genetic material of DNA
- deoxyribose
THYMINE

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5
Q

What is the significance of the nitrogenous base pairings in DNA ?

A

-Allows DNA to store and transmit genetic information.
-the specific pairing of the nitrogenous bases ensure that the genetic information is accurately copied during cell division.

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6
Q

How does DNA replication occur ?

A

-2 complementary strands of the DNA molecule separate
-each strand acts as a template for the formation of a new complementary strand.

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7
Q

How does the structure of DNA enable it to carry out its function?

A

1)Two strands = the DNA is stable
2)bases are inside the sugar phosphate back bone (spiral)= protected and the integrity of the genetic code is maintained
3)molecules are long = store a lot of genetic information
4) complementary base pairing = identical copies created

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8
Q

What are the components of RNA nucleotides?

A

-ribose pentose sugar with a hydroxyl group at the 2’ position (making is more susceptible to hydrolysis)
-URACIL

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9
Q

How many bonds are between adenine and thymine?

A

Two hydrogen bonds

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10
Q

How many bonds are between guanine and cytosine?

A

3 hydrogen bonds

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11
Q

What does helicase do?
(Step 1 of DNA replication)

A

-breaks down the hydrogen bonds between the 2 polynucleotide DNA strands.
-unzips helix.

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12
Q

What do we mean by semi-conservative?

A

One strand of the DNA is new and one is original

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13
Q

What direction does the leading strand go ?

A

3’ to 5’

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14
Q

What direction does the lagging strand go ?

A

5’ to 3’

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15
Q

What way does DNA polymerase move?

A
  • in one direction
  • 3’ to 5’
  • on the original (template) strand
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16
Q

What are okazaki fragments?

A
  • Short sequences of DNA nucleotides on the lagging strand.
    -going in the wrong direction (away from the replication fork) so DNA polymerase synthasises the fragments in a discontinuous manner.
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17
Q

What does Ligase do ?

A

Put the okazaki fragments together

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18
Q

Stage one of DNA replication

A

1) DNA helicase breaks the hydrogen bonds between the 2 polynucleotide strands
The helix unzips to form 2 separate strands.

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19
Q

What is stage 2 of dna replication ?

A

2) each original strand acts as a template for the new free floating DNA nucleotides to attach h at the complementary nitrogenous bases

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20
Q

What is stage 3 of DNA replication?

A

3) DNA polymerase joins the nucleotides on the strands together
This forms a sugar phosphate backbone
Hydrogen bonds form between the nitrogenous bases on the new strands and original

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21
Q

What is stage 4 of DNA replication ?

A

4) strands twist to form a double helix

22
Q

How do mutations occur ?

A

A change in the DNA base sequence

23
Q

What can happen if a mutation occurs?

A

They can alter the sequence of amino acids in a protein
Causing an abnormal protein to be produced

24
Q

What is genetic code non- overlapping?

A

Each codon ONLY codes for one amino acid
Base triplets don’t share their bases

25
Q

Why is the generic code degenerate?

A

different codons can encode for the same amino acid

26
Q

Why is genetic code universal?

A

All species use the same 4 nitrogenous bases
ATCG
each base codes for the same amino acid in all species

27
Q

What is the Role of tRNA ?

A

-Carries the amino acids that are used to make proteins to the ribosomes

28
Q

What is the role of mRNA?

A

-to deliver the genetic information from DNA to the ribosome to be translated into a protein

29
Q

What is the role of rRNA?

A

-helps catalyse the information of peptide between amino acids

30
Q

What is step one of transcription ?

A

1) rRNA polymerase attaches to the DNA at the beginning of a gene
The hydrogen bonds break separating the strands
The molecule uncoils with one of the strands being used as a template to make an mRNA copy

31
Q

What is step two of transcription?

A

2) RNA polymerase lines up free RNA nucleotides along the template strand u
Complementary base paring means the mRNA strand ends up being a complementary copy of the DNA template (except T is U)
RNA nucleotides pair up with specific bases forming mRNA

32
Q

What is the third stage of transcription?

A

3) RNA polymerase moves down the DNA, assembling the mRNA strand
The hydrogen bonds reform with RNA polymerase and the strands twist again

33
Q

What is the fourth stage of transcription ?

A

4)RNA reaches a stop codon and stops producing mRNA and detaches itself from DNA moving out the nucleus through nuclear pores
Attached to the ribosome I’m the cytoplasm

34
Q

What is the first stage of translation ?

A

1) tRNA carry amino acids to the ribosome
The codon on the mRNA attaches itself to an anticodon on the tRNA

35
Q

What is the second stage of translation ?

A

2) the rNA in the ribosome catalyses the formation of a peptide bond between two amino acids
The first tRNA moves away lwaving the amino acid behind
This continues until a stop codon is reached on the mRNA molecule forming a polypeptide chain

36
Q

What are nucleotides made of

A

-pentose sugar.
-nitrogenous base
-phosphate group
Elements: H,O,N and P

37
Q

What is DNA nucleotide made up of?

A

-Penrose sugar -> deoxyribose
-phosphate group
-nitrogenous base -> GCAT

38
Q

What is ADP made of?

A

-nitrogenous base -> adenine
-pentose sugar-> ribose
-TWO phosphate groups

39
Q

What is ATP made of ?

A

-nitrogenous base ->adenine
-pentose sugar-> ribose
-THREE phosphate groups

40
Q

Why does ATP and ADP have extra phosphate?

A

They have been phosphorylated

41
Q

How is ATP made?

A

Phosphorylated from ADP + P and a phosphate bond is formed during a condensation reaction creating ATP and water

42
Q

How is ATP released for use?

A

-energy is stored in phosphate bond
-ATP is broken back down into ADP and P
-energy is released from the phosphate bond

43
Q

Describe Polynucleotide structure

A

-join from phosphate group of one nucleotide and sugar of another
-condensation reaction
-phosphodiester bond is formed -> phosphate group and 2 ester bonds
-chain -> sugar phosphate back bone

44
Q

What reaction is used to purify DNA ?

A

Precipitate reaction

45
Q

What does DNA do ?

A

-codes for sequence of amino acids in primary structure of protein determining its 3D structure

46
Q

How to purify DNA using precipitation.

A

1) homogenise the cell with a detergent
2)filter to remove large debris
3) add salt to break hydrogen bonds between DNA and water molecules
4) add protease to digest the proteins
5) add ice-cold ethanol to precipitate the DNA out the solution (white strands)

47
Q

What is a codon ?

A

-every 3 bases in the sequence that’s coded for an amino acid

48
Q

Where is mRNA found?

A

-made in nucleus
-leaves into cytoplasm to go to ribosome

49
Q

Where is tRNA found?

A

Cytoplasm

50
Q

What is tRNA folded into ?

A

A clover leaf shape and bottom has 3 anticodons

51
Q

When does DNA replication occur?

A

S - phase in interphase

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