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PMP101 > week 7 nucleic acids and protein synthesis > Flashcards

week 7 nucleic acids and protein synthesis Flashcards

1
Q

DNA

A

deoxyribonucleic acid

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2
Q

RNA

A

ribonucleic acid

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3
Q

Common nucleotide structure?

A

1-3 phosphate groups
pentose (5 carbon) sugar
nitrogenous base (pyrimidine or purine)

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4
Q

1 phosphate group

A

Monophosphate (AMP)

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5
Q

2 phosphate groups

A

Diphosphate (ADP)

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6
Q

3 phosphate groups

A

Triphosphate (ATP)

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7
Q

Ribose (pentose sugar)

A

RNA only
2’ carbon hydroxyl group (OH)

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8
Q

Deoxyribose (pentose sugar)

A

DNA only
2’ carbon (H)

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9
Q

Purines

A

Adenine (A)
Guanine (G)

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10
Q

Pyrimidines

A

Uracil (U) - in RNA only
Thymine (T) - in DNA only
Cytosine (C)

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11
Q

Nucleoside

A

Nucleotide structure excluding the phosphate groups

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12
Q

Nucleotide functions (as monomers)

A

-building blocks of nucleic acids (RNA and DNA)
-Energy carriers (cell energy currency), carrying high-energy bonds between phosphate groups
-Form coenzymes (essential for enzymatic activity)
-Intracellular signalling molecules

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13
Q

Nucleic acid strand / backbone

A

In RNA/DNA, nucleotides are covalently linked to form a polynucleotide strand (backbone)

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14
Q

Phosphodiester bonds

A

Linking 5’ phosphate of one nucleotide to the 3’ OH of the next, creating a 3’-to-5’ directionality

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15
Q

Human cells

A

Nucleic acids of human cells have 5’ end and a 3’ end e.g., 5’-TCG-3’

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16
Q

Prokaryotic cells

A

5’ and 3’ ends of DNA strands are linked to form circular DNA, which is also found in plasmids and mitochondrial DNA

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17
Q

Hydrogen bonding between nucleotides

A

Two DNA strands are held together by hydrogen bonds between complementary base pairs in double - stranded nucleic acids

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18
Q

Purine-pyrimidine pairing

A

A with T (DNA) -> 2 hydrogen bonds
A with U (RNA)
C with G -> 3 hydrogen bonds, more stable than AT pairs

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19
Q

DNA double helix

A

The complementary base pairing cause the two DNA strands to twist around each other in helical manner -> stable DNA double helix
-Antiparallel (hains run in opposite directions)

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20
Q

DNA in B-form

A

Has two helical grooves of different widths, providing binding sites for proteins/drugs

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21
Q

Major

A

Wider

22
Q

Minor

A

Narrower

23
Q

RNA

A

Usually single stranded ssRNA in human cells
dsRNA (double stranded) is possible in nature - many viruses contain dsRNA chromosomes.
Immune cells recognise dsRNA as a viral signature, triggering antiviral responses

24
Q

DNA denaturation

A

Separation of the DNA double strands into single strands

25
Q

DNA renaturation

A

Restores DNA double helices (nucleotide pairs re-formed) When conditions are reversed, H bonds can be reformed

26
Q

Conditions for DNA denaturation

A

High temperatures (90-100 degrees C) break H bonds between complementary nucleotide pairs. Higher G-C content increases DNA stability and so more energy needed

27
Q

Gemome

A

Contains the genetic instructions guiding a cell’s survival and function
- Human genome has approx. 25,000 genes

28
Q
A

DNA provides biological messages through the precise sequence of nucleotides

29
Q

Gene

A

-A DNA segment that encode specific, inheritable traits
-Nucleotide sequence in genes determine the specific amino acid sequence of certain
proteins through the genetic code (DNA > RNA > PROTEINS)

30
Q

Pharmacogenomics

A

Variations in individuals’ genes can influence the response to drugs

31
Q

Eukaryotic DNA

A

-Nuclear DNA (nucleus)
-Mitochondrial DNA (mitochondria)

32
Q

Nuclear DNA

A

DNA molecules are packaged
with histones into chromatin

33
Q

Nucleosomes

A

Chromatin units

34
Q

Eukaryotic Chromosomes

A

Linear DNA stored in the nucleus, usually in the form of chromatin. In dividing cells (after DNA duplication) chromatin is further condensed to the X shaped chromosomes

35
Q

Karyotype

A

Representation of an individuals set of chromosomes

36
Q

Human Chromosomes

A

Number, size of chromosomes is species-specific

37
Q

Somatic cells

A

Human (somatic) cells have 46 chromosomes, 23 pairs -> in 22 pairs of homologous autosomal and a pair of sex chromosomes (XX/XY )

38
Q

Gametes

A

(sperm and egg cells) have one set of 23 chromosomes (haploid cells)

39
Q

Red blood cells

A

No DNA

40
Q

DNA replication

A

DNA replication is the process by which DNA makes a copy of itself, before cell divisions
-Each chromosome will result in 2 identical DNA
-Copied DNA is segregated into daughter cells
-Occurs in the nucleus during the S phase of interphase

41
Q

Mutations in DNA replication

A

DNA replicates rapidly and precisely to avoid errors (mutations)
-minimises mutations that can lead to disease
-Mutations in microorganisms can lead drug resistance

42
Q

SEMI-conservative process

A

DNA replication is a SEMI-conservative process, It produces two copies of DNA, each containing one original strand and one new one

43
Q

4 steps of DNA replication

A
  1. Replication Fork Formation
  2. Initiation
  3. Polymerase elongation
  4. Termination
44
Q
  1. Replication fork formation
A

-DNA replication starts at a sequences called
origin of replication (rich in A - T)
-At each, DNA is denatured by initiator proteins
-Helicase enzymes unwind/unzip the DNA double strands bidirectionally by breaking H-
bonds, creating two Y-shaped replication forks

45
Q
  1. Initiation
A

-DNA polymerase requires an RNA primer, created
by primase enzyme, to initiate synthesis
-DNA polymerase attaches to the 3’ end of the primer
and synthesises a new DNA strand in the 5’->3’
direction, using the parental strand as a template
-DNA polymerase forms phosphodiester bonds
between nucleotides, extending the new DNA strands
-The process requires deoxynucleotide triphosphates
(dNTPs) to drive the reaction

46
Q
  1. Polymerase elongation
A

-The replication fork is asymmetrical (antiparallel strands)
-Replication of leading strand is continuous, same direction as the growing replication fork
-Replication of the lagging strand is discontinuous
▪ It requires many RNA primers
▪ Synthesis in short DNA fragments (Okazaki
fragments), each initiated by a new RNA primer

47
Q
  1. Termination
A

-A nuclease degrades RNA primers
-The gaps are filled by DNA polymerase
-The enzyme DNA ligase joins adjacent Okazaki
fragments -> DNA Replication is complete

48
Q

Proofreading activity of DNA polymerase

A

DNA polymerase introduces approx. 1 error/1010 nucleotide copied
-DNA polymerase has proofreading activity to check &
correct base-pairing errors
▪ When a mismatch occurs, DNA polymerase removes the
incorrect nucleotide and replaces it with the correct one.
-Any uncorrected mistakes, can be fixed by many DNA
repair mechanisms available in human cells
▪ Inactivation of DNA repair pathways is common in tumours

49
Q

DNA polymerase summary

A

-A complex of polymerases
-Incorporates nucleotides to the growing DNA strands by forming phosphodiester bonds
-One nucleotide at a time (triphosphate form)

50
Q

Helicase summary

A

-Unwinds parental double helix

51
Q

Ligase summary

A

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

52
Q

Other important enzymes

A

Primase
-> Synthesise RNA primers for DNA polymerase to start the polymerisation process
DNA Topoisomerase
-> Unravel twists in DNA that occur as a result of DNA replication

PMP101 (21 decks)

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