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PMP101 > Nucleic Acids & DNA Replication > Flashcards

Nucleic Acids & DNA Replication Flashcards

1
Q

What are the important factors/functions of nucleic acids ?

A

-They are carriers of genetic information
-They are made of nucleotides
-They are represented by DNA and RNA
-They are present in every type of cells

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2
Q

What is a nucleic acid?

A
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3
Q

What is a nucleotide?

A

-Monomers/ building blocks of nucleic acids (DNA and RNA) both exist in all types of cells both carriers of genetic information

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4
Q

What does DNA stand for ?

A

Deoxyribonucleic Acid

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5
Q

What does RNA stand for ?

A

Ribonucleic Acid

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6
Q

What is the common structure of Nucleotides?

A

One to three phosphate groups which are linked by a phosphoester bond to a pentose (5-carbon atom) sugar, which in turn is linked to a nitrogenous base by a glycosidic bond

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7
Q

What is a phosphate group?

A
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8
Q

What is a phosphoester bond ?

A
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9
Q

What is a pentose sugar?

A
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10
Q

What is a nitrogenous base ?

A
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11
Q

What is a glycosidic bond?

A
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12
Q

What pentose sugar is found in a RNA nucleotide ?

A

Ribose

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13
Q

What pentose sugar is found in a DNA nucleotide?

A

Deoxyribose

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14
Q

Add nucleotide diagrams

A
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15
Q

What bases are present in DNA ?

A

Purines- Adenine and Guanine
Pyrimidines - Thimaine and Cytsine

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16
Q

What bases are present in RNA ?

A

Purines-Adeneine and Guanine
Pyrimines- Uracil and Cytosine

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17
Q

What are Pyrimidines ?

A
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18
Q

What are Purines?

A
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19
Q

Learn to read images of the nucleotides and be able to name them

A
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20
Q

What does RNA have that DNA does not when trying to figure out what the nucleotide is from an image?

A

RNA- Ribose at 2’ an OH group is connected
DNA does not have this hydroxy group

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21
Q

What is the function of nucleotides?

A

Forming nucleic acid polymers (DNA and RNA)

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22
Q

What is the function of nucleotides as a monomer?

A

-Biological energy carriers carrying high energy phosphate bonds (triphosphate nucleotides-ATP, GTP)
-To form coenzymes, essential for enzymatic activity
-Intracellular signalling molecules (Cyclic AMP or GTP)

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23
Q

What is a triphosphate nucleotide?

A
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24
Q

What does an Adenosine Triphosphate (ATP) nucleotide look like?

A
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25
Q

What does a Cyclic adenosine monophosphate (AMP) nucleotide look like?

A
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26
Q

How do nucleotides join together?

A

-Link covalently with each other by phosphodiester bonds and form a linear polynucleotide strand (polymers backbone)

-The phosphodiester bond links the 5’ end of one sugar with the OH group of 3’ end of the next

  • Thus, nucleic acid strands have two ends. The directionality is 5’-3’ (e.g. 5’-ATGACGATC-3’)
  • In prokaryotes (e.g bacteria) the 5’ and 3’ ends of DNA strands are linked to give circular DNA. This also applies for plasmids and mitochondrial DNA (eukaryotes)
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27
Q

What bond links the 5’ end of one sugar with the OH group of the 3’ end of the next nucleotide?

A

Phosphodiester bond

28
Q

Two antiparallel polynucleotide strands of DNA can be held together by what bond?

A

H-bonds between complementary base pairs of double stranded nucleic acids

29
Q

How are the complementary base pairs matched together?

A
  • Two antiparallel polynucleotide strands of DNA can be held together by H-bonds between complementary base pairs of double stranded nucleic acids

1) A pairs with T (or U in RNA) through (2 H-bonds)

2) C pairs with G through (3 H-bonds, more stability as it requires more energy to break these 3 H bonds)

30
Q

Why is there always a purine joined to a pyrimidine?

A
31
Q

What is the DNA double helix?

A

The 2 DNA strands orientation is antiparallel, chains run in the opposite direction
-Its a 3D structure of DNA
-

32
Q

What are nitrogenous bases?

A
33
Q

What is the sugar-phosphate backbone?

A
34
Q

What is B form of DNA double helix?

A

-DNA in B form has helical grooves of different widths and accessibility
Major-wider
Minor-narrower

  • B-type duplex is not possible for RNA, RNA is usually single-stranded
35
Q

DNA can undergo reversible denaturation and renaturation.

What is DNA denaturation?

A

-DNA double strands can be separated into single strands through DNA DENATURATION, as H-bonds between complementary nucleotides can be broken, by increasing the temperature
-Higher temps are required to denature G-C pairs than A-T pairs due to its 3 hydrogen bonds

36
Q

DNA can undergo reversible denaturation and renaturation.

What is DNA Renaturation ?

A

-When the conditions are reversed (DNA renaturation) -lowering the temperature - the hydrogen bonds between the complementary base pairs could be reformed to generate the double helix again.

37
Q

What is the Mechanism for Heredity?

A
  • Genome contains the genetic program that instructs a cell how to behave
  • DNA provides biological messages thanks to precise sequence of their nucleotides
  • The ‘alphabet’ of DNA is composed of 4-letter nucleotides (A, C, T, G)
38
Q

What is a gene?

A
  • Unit of heredity. Human genome has approx 25,000 genes(<1.5% of DNA)
  • Genes contain instructions for producing specific proteins (DNA-RNA-PROTEINS)
  • The nucleotides sequence of a gene encoding the amino acids sequence of a protein (genetic code)
39
Q

What is a unit of heredity?

A

-A gene

40
Q

Where is DNA found in eukaryotic cells?

A

-In the nucleus (nuclear DNA)
-In the mitochondria (mitochondrial DNA)

41
Q

What is Nuclear DNA. ?

A
  • DNA molecules are packaged with histones into chromatin
  • Nucleosomes = chromatin units
42
Q

What are Nucleosomes?

A
43
Q

In dividing cells, chromatin is further condensed into what?

A

Chromosomes
- (series of coils and loops) Formed in Prophase of mitosis (X shape chromosomes because of the duplicated DNA)
- Number, size, shape of chromosomes is species-specific (Karyotype)

44
Q

What is Chromatin?

A
45
Q

What is a chromosome?

A
46
Q

How many PAIRS of chromosomes do human cells have?

A

22 pairs of homologous autosomal chromosomes + 2 sex chromosomes

47
Q

What are Gametes ? and how many chromosomes do they have?

A

-Sex cells (sperm and eggs) - Haploid cells
-These have one set of 23 chromosomes

-A set of 23 chromosomes is received from the mothers gamete and a set of 23 via fathers gamete

48
Q

What are haploid cells ?

A
49
Q

What are homologous cells?

A
50
Q

What is a Karyotype?

A
51
Q

What is DNA replication?

A
  • DNA replication is the process by which DNA makes a copy of itself
  • Before a cell can divide (Mitosis), its DNA (chromosomes) needs to be copied/ to obtain two two genetically identical daughter cells
  • Occurs in the nucleus during Interphase (Phase S synthesis)
  • During cell division, each of the 46 chromosomes contains two identical duplicated DNA molecules (two sister chromatids joined at the centrometre)
  • DNA must rapidly and accurately copy(replicate) its nucleotide sequence in order to avoid mistakes, mutations
52
Q

How does a cell divide?

A

-Through Mitosis

53
Q

How does DNA make a copy of itself?

A

-Through the process of DNA replication

54
Q

Where does DNA replication occur?

A

-In the nucleus during Interphase

55
Q

What are sister chromatids?

A
56
Q

What is the Centrometre?

A
57
Q

DNA must rapidly and accurately copy(replicate) its nucleotide sequence in order to avoid mistakes, mutations such as what?

A

-Risk of diseases in human cells e.g cancer

-Development of drug resistance in viruses or bacteria

58
Q

What is the DNA replication -Semi conservative process?

A

It produces two copies of DNA, each that contains one original strand and the one new strand
- DNA replication consists of 4 steps

59
Q

How many steps does DNA replication consist of and what are they?

A

4 steps

1) Replication Fork Formation
2) Initiation
3) Polymerase elongation
4) Termination

60
Q

What is Fork Formation?

A
  • DNA replication starts at a sequence (rich in A-T pairs) called origins (thousands/genome)
  • Double helix is opened by initiator proteins
  • At each origin, helicases proceed bidirectionally to unwind/unzip the DNA double strands, creating two Y-shaped junctions called replication forks.
  • Bidirectional DNA replication

(initial breakage of H bond, these attract helicases, in 2 point of the replication origin, move away in opposite directions)

61
Q

What is Initiation in terms of DNA replication ?

A
  • DNA polymerase needs a short RNA primer (produced by (enzyme, DNA primase) to start(free 3’ -OH end)
  • DNA polymerase allows the incorporation of nucleotides to the 3’ end of a growing DNA strand, using one parental DNA strand as a template
  • It requires nucleotide triphosphates (high-energy phosphate bonds fuel the reaction)
  • New DNA strands are synthesised from 5’ to 3’ (5 prime to 3 prime)
  • It forms a phosphodiester bond between the 3’ end of the growing DNA chain and the 5’ phosphate group of the incoming nucleotide (esterification)
62
Q

What is the replication fork?

A

Asymmetrical

63
Q

What are the 3 key players of DNA replication?

A

-DNA Polymerase
-DNA Helicase
-DNA Ligase

64
Q

What is DNA polymerase?

A

-Group/complex of polymerases

-Incorporates nucleotides to the growing DNA strands by forming phosphodiester bonds

-One nucleotide at a time (triphosphate form)

main function of DNA polymerase - adding nucleotides to the new DNA strands during replication

65
Q

What is DNA Helicase?

A

-Unwinds parental double helix

66
Q

What is DNA Ligase?

A

-Joins Okazaki fragments and seals other breaks in sugar-phosphate backbone

67
Q

What is the main function of DNA polymerase?

A

Adding nucleotides to the new DNA strand during replication

PMP101 (23 decks)

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