4 - CENTRAL DOGMA Flashcards
1
Q
- Proposed by Watson and Crick in 1950
- Described the relationship between nucleic acid and proteins as a directional flow of information
- Deals with the detailed residue-by-residue transfer of sequential information
A
Central Dogma
2
Q
3 important steps of the central dogma
A
- Transcription
- Translation
- DNA Replication
3
Q
Monomer units or building blocks of nucleic acids
A
Nucleotides
4
Q
Components of nucleotides
A
Sugar + nitrogenous base + phosphate group
5
Q
Functions of nucleotides
A
- Part of the coenzymes
- Serves as donors of the phosphoric group (ATP, GTP), of sugars (UDP or GDP sugars), or of lipids
- Regulatory second messengers
- Chemotherapy and immune suppression
6
Q
- Nitrogen-containing heterocycles
- Cyclic compounds whose rings contain both carbon and other elements
- These are information-containing parts of the DNA because they form sequences
A
Nitrogenous Base
7
Q
thousand base pairs
A
Kilobase
8
Q
million base pairs
A
Megabase
9
Q
- 6-membered ring containing 2 nitrogens
- Cytosine, Uracil, Thymine
A
Pyrimidines (CUT)
10
Q
- 9-membered ring consisting of 4 nitrogens
- Adenine, Guanine
A
Purines (AG)
11
Q
- Pairing of the single ring pyrimidine with the double-ring purine
- Ensures the symmetrical double helix formation of the DNA
A
Complementary Base Pairs
12
Q
Complementary base pairs are held together by?
A
hydrogen bonds
13
Q
5-membered rings of sugar
A
Pentoses
14
Q
2 types of pentoses
RNA (hydroxyl group, OH)
A
Ribose
15
Q
2 types of pentoses
DNA, no oxygen (H)
A
Deoxyribose
16
Q
Derivatives of purine and pyrimidines that have a sugar linked to the ring of nitrogen
A
Nucleoside
17
Q
Nucleosides are linked by?
A
B-N-glycosidic bond
18
Q
- Forms the backbone of the DNA
- One chain runs in 5’ to 3’ direction while the other is 3’ to 5’
A
Phosphate
19
Q
opposing orientation of the 2 nucleotide chains
A
Antiparallelism
20
Q
links sugar base of one nucleotide and the phosphate group of the adjacent nucleotide
A
ester bonds
21
Q
- Production of new DNA for cell division
- Proceeds in a 5’ to 3’ direction
A
DNA Synthesis or Replication
22
Q
Absolute requirements for DNA synthesis
A
- Free 3’-OH group
- DNA template (ssDNA)
23
Q
- Helicase binds to ORI protein of the parent and separates strands
- Unwinding begins at the A-T rich region and binding proteins keep strands apart
- Primase makes a short stretch of RNA on the DNA template
A
Step 1: Unwinding of DNA
24
Q
Replication fork — appearance of the unwound DNA when it starts to form the leading and lagging strand
A
Step 2: Replication Fork Formation
25
* DNA polymerase adds DNA nucleotides to the RNA primer
* DNA polymerase proofreading activity checks and replaces incorrect bases
Step 3: DNA Polymerase Replication
26
* The primary replicase enzyme that performs the elongation of the DNA strand
* It adds nucleotides first to the RNA primer and then grows the chain by creating the phosphodiester bonds
* It also has a 3’-5’ proofreading (exonuclease) function that removes incorrectly incorporated nucleotides
DNA Polymerase
27
* Continuous strand synthesis continues in a 5’-3’ direction in the leading strand
* Discontinuous synthesis produces Okazaki fragments on the 5’-3’ template of the lagging strand
Step 4: Formation of Okazaki Fragments
28
* Enzymes — remove RNA primers
* Ligase — seals sugar-phosphate backbone and joins Okazaki fragments together
* Replication is completed by filling in the gaps by DNA polymerase and DNA ligase
Step 5: Removal of RNA Primers
29
* DNA molecules are extremely long, thus, it is packed into a chromosome that, during cell division, is only 2 micrometers (millionths of a meter long)
* To fit inside the nucleus, the DNA molecule must fold so tightly that its compacted length shrinks by a factor of 7,000
* DNA coils around proteins called histones that resemble beads on a string
DNA Synthesis
30
# Enzymes in DNA Replication
unwinds parental double helix
Helicase
31
# Enzymes in DNA Replication
stabilize separate strands
Binding proteins
32
# Enzymes in DNA Replication
adds short primer to template strand
Primase
33
# Enzymes in DNA Replication
binds nucleotides to form new strands
DNA polymerase
34
# Enzymes in DNA Replication
joins Okazaki fragments and seals other nicks in sugar-phosphate backbone
Ligase
35
A polymer of purine and pyrimidine ribonucleotides linked together by 3’-5’ phosphodiester bridges analogous to those in DNA
RNA
36
* Usually double-stranded
* Thymine as a base
* Deoxyribose as the sugar
* Maintains protein-encoding information
* Cannot function as an enzyme
* Persists
DNA
37
* Usually single-stranded
* Uracil as a base
* Ribose as the sugar
* Carries protein-encoding information and controls how information is used
* Can function as an enzyme
* Short-lived
RNA
38
* Long straight chain of nucleotides
* Made in the nucleus during transcription
* Copies DNA and leaves through nuclear pores
* Contains the nitrogen bases (A, G, C, U (no T))
* Carries the information for several amino acids forming a specific protein
* Made up of 500 to 1000 nucleotides long
* Contains the sequence of 3 bases called codon
mRNA — Messenger RNA
39
start codon
AUG (methionine)
40
stop codon
UAA, UAG, UGA
41
* Single strand, 100-3000 nucleotides long
* Globular in shape
* Made inside the nucleus of a cell by the nucleolus
* Associates with proteins to form ribosomes
* Helps protein synthesis
rRNA — Ribosomal RNA
42
* Clover-leaf shape
* Single-stranded molecule with attachment site at one end for an amino acid
* Opposite end has three nucleotide bases called the anticodon
tRNA — Transfer RNA
43
* First step in gene replication
* Because the DNA is too big to exit the nucleus, a small copy of it must be created and exits to the cytoplasm
Transcription
44
splits the DNA strand molecule
RNA polymerase enzyme
45
# 3 stages of transcription
control point that determines which genes are transcribed
Initiation
46
# 3 stages of transcription
RNA nucleotides are added
Elongation
47
# 3 stages of transcription
a terminator sequence/region signals the end of transcription
Termination
48
* The mRNA is translated to synthesize proteins
* Each amino acid is formed by 3 nitrogenous bases
* In the cytoplasm, the ribosomes read the sequence of the RNA in groups of three bases
* An anticodon or complementary codon is matched to the RNA coding for a specific amino acid
Translation/Protein Synthesis
