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BIOC 2300 > The Central Dogma 4 > Flashcards

The Central Dogma 4 Flashcards

1
Q

DNA

A
  • complementary nature of DNA is the basis of life
  • is anti parallel
  • Purines: A and G (have 2 rings)
  • Pyrimidines: C and T (have 1 ring)
  • A pairs with T (or U in RNA) forms 2 H bonds
  • G pairs with C forms 3 H bonds
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2
Q

Nucleotides

A
  • monomeric repeating unit of nucleic acids is the nucleotide
  • made up of:
    1. A nitrogenous aromatic base (A,C,T,G)
    2. A pentose sugar: ribose in RNA and 2’deoxyribose in DNA
    3. Phosphates attached to the 5’ and/or 3’ hydroxyl groups of the sugar
  • to maintain helix width, a purine always base pairs with a pyrimidine
  • base pair specificity arises from the number of H bonds
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3
Q

DNA Double Hleix

A
  • most common form of the double helix consists of 2 strands of nucleotide polymers with base pairs in the middle, stacked perpendicular to the helix axis
  • polar exterior (negative charge of phosphate (PO4))
  • non polar interior
  • minor and major grooves
  • one turn is 34A
  • 20A in width
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4
Q

DNA Denaturation and renaturation

A
  • double helix is stabilized by H-bonds, magnesium binding to phosphate backbone, and hydrophobic effect
  • melting point increases with GC content (due to base stacking, has 3 Hbonds)
  • denaturation is reversible
  • improper base pairing occurs when the denatured molecule is cooled too quickly far below the melting point
  • renaturation is important for polymerase chain reaction, DNA hybridization
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5
Q

Genome structure

A
  • the nucleosome is the basic structural unit of chromatin
  • condensation is due to basic histone proteins interacting with acidic DNA backbone
  • histone modifications help regulate packing and gene expression
  • each DNA molecule has been packaged into a mitotic chromosome that is 10,000fold shorter than its extended length
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6
Q

Genome structure (genetic view)

A
  • the gene is the basic unit of heredity
  • a DNA sequence that usually encodes a protein or informational RNA molecule
  • eukaryotic genes are often split into coding (exon) and intervening (intron) sequences
  • our genes are arrayed on 22 pairs of chromosomes (one set from each parent) plus sex chromosomes (X and Y)
  • total 20billion km of DNA per person
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7
Q

RNA

A
  • Contains 2’ hydroxyl on sugar (can be cleaved at basic pH)
  • uracil replaces thymine
  • mRNA: codes for proteins (5% of cellular RNA)
  • rRNA: assists protein synthesis on ribosomes
  • tRNA: translation and adaptors between mRNA and amino acids
  • miRNA: microRNAs regulate gene expression by blocking mRNA translation or stability
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8
Q

RNA polymerase

A
  • initiates transcription at the 5’ end of a gene: the promoter Region
  • the nucleotide sequence for mRNA corresponds to the coding (sense) strand of the original DNA and to the codons for translating
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9
Q

mRNA synthesis in eukaryotes

A
  • in prokaryotes a single transcript often includes several co-regulated genes (an operon), which does not contain introns
  • in eukaryotes each RNA transcript corresponds to a single gene, but mRNA synthesis also involves:
    1. addition of a 5’ cap
    2. removal of introns and exon joining by differential splicing (often tissue specific)
    3. addition of a 3’ poly-A tail
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10
Q

Translation

A
  • results in protein synthesis
  • occurs in the ribosome
  • tRNA carries amino acids to the ribosome and binds to its complement codon
  • amino acids are dictated by the genetic code
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11
Q

The genetic code

A
  • each of the 20 amino acids is specified by one or more 3-base codons
  • AUG(met) is the initiation codon for translation
  • there are 3 stop codons
  • genetic code is: degenerate, universal, unambiguous, non-overlapping, comma-less
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12
Q

Regulation of eukaryotic gene expression

A
  • some proteins are present in only a few copies per cell, others in thousands
  • controlling gene expression allows cell/tissue differentiation and environmental adaptability
  • genes may be regulated or constitutive
  • initiation of transcription is the dominant control point
  • regulation of gene expressions is often coordinated with other cellular events by signalling pathways
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13
Q

Oligonucleotide

A
  • a polynucleotide whose molecules contain a relatively small number of nucleotides
  • short DNA or RNA molecules
  • often used in research and genetic testing
  • usually 13-25 nucleotides
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14
Q

Chromatin

A
  • a complex of macromolecules found in cells, consisting of DNA, protein, and RNA
  • package DNA into more compact, denser shape
  • Chromatin=DNA+histone
  • basic structural unit of chromatin is the nucleosome
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15
Q

Nucleosome

A
  • basic structural unit of chromatin

- DNA wraps around histone proteins to form nucleosome, which couple to become chromatin fibre

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16
Q

Telomere

A
  • a compound structure at the end of a chromosome
  • region of repetitive nucleotide sequence at each end of a chromosome which protects it from deterioration of fusion with neighbouring chromosomes
  • equivalent to plastic piece on end of shoelace
17
Q

RNA polymerase

A
  • synthesizes RNA by following a strand of DNA
  • responsible for copying DNA sequence into an RNA sequence during transcription
  • RNA polymer synthesized in 5’ to 3’ direction
18
Q

Sense/antisense

A
  • antisense strand serves as the source for the protein code, because with bases complementary to the DNA sense strand it is used as a template for the mRNA
  • since transcription results in an RNA product complementary to the DNA template strand, the mRNA is complementary to the DNA antisense strand
19
Q

RNA splicing

A
  • editing of messenger RNA transcript to mature messenger RNA
  • introns are removes and exodus are joined together (ligated)
20
Q

Promoter

A
  • a region of DNA that initiates transcription of a particular gene
  • located near the transcription start sites of genes, on the same strand and upstream on the DNA (toward 5’ region of sense strand)
21
Q

RNA capping

A
  • 5’ cap is a specially altered nucleotide on the 5’ end of some primary transcripts such as pre-mRNA
  • enzyme catalyzes the reaction between the 5’ end of the RNA transcript and a guanine triphosphate (GTP)
22
Q

Poly-adenylation

A
  • addition of a polyA tail to a messenger RNA
  • consists of multiple adenosine monophosphates
  • a stretch of RNA that has only adenine bases
  • part of process that produces mature messenger RNA for translation
23
Q

Regulated gene expression

A

-

24
Q

Constitutive gene expression

A

-a gene that is transcribed at a relatively constant level regardless of cell environmental conditions

BIOC 2300 (16 decks)

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