Transcription and Translation Notes Flashcards
How is DNA different from RNA?
-RNA is a single strand
- An RNA Nucleotide has three parts:
Phosphate Group
Bases (Cytosine,
Guanine, Adenine or
URACIL)
Ribose Sugar
mRNA –
-Messenger RNA
Transmits information from DNA for use during protein
synthesis, serves as a template
Form is a characteristically long, single strand
Most common forms of RNA
mRNA, tRNA, rRNA
tRNA
Transfer RNA
Carries amino acids to ribosomes during protein synthesis
Form is a single stranded molecule folded back on itself
rRNA
Ribosomal RNA
Makes up the ribosomes
Form is characteristically globular
snRNA
Form of RNA found in the nucleus, important in splicing of RNA and maintaining telomeres
RNAi
(RNA Interfaces)– forms of RNA used in gene silencing, can turn genes on and off
Transcription
The process by which mRNA is copied
from DNA
- RNA polymerase: the enzyme that catalyzes the reaction of transcription
- Transcription continues until one entire gene has been copied into mRNA
Steps in Transcription
RNA polymerase initiates process by binding to
specific regions called promoters found at start
of gene sequences
2. Base pairing rules from replication are same, but
U A and the entire coding region is copied
3. Transcription continues until RNA polymerase
reads a terminal signal in the DNA sequence,
the RNA molecules detach and move to
cytoplasm for protein synthesis
Exons
Are regions of expressed DNA
Introns
Are regions of non-expressed DNA
Formally known as “junk” but now known to control protein synthesis
The Central Dogma:
DNA is transcribed to RNA which is translated to PROTEIN
Exeptions to Central Dogma
Retroviruses and Prions
Retroviruses
Are an exception to the Central Dogma where RNA makes DNA which then makes RNA and Proteins HIV is one of the most commonly known retroviruses
Prions
Diseases that appear to be spread through proteins only, without the process of the central dogma. Examples - Inherited: CJD, - Infectious: Mad Cow Disease, Kuru
Code chart thing
This codon chart shows
the amino acid-codon
combinations for all living
things.
-There are 64 possible codons, but only 20 different amino acids…why?
-The genetic code is universal – UUU codes of
Phenylalanine in virtually all organisms on earth.
The Transcript is the Template
mRNA (the transcript or code) consists of a long chains of
nucleotides copied from the DNA template strand
A specific group of three nucleotides on the mRNA is a codon
A codon specifies for a specific amino acids in the protein
The codon will match with an anticodon on the tRNA (which
transports in the amino acids)
Start Codons
-Tells the ribosome to begin protein synthesis. -Also codes for the amino acid methionine. -There is only one start codon: AUG
Stop Codons
- They tell the ribosome to stop protein synthesis.
- Does not code for any amino acids
- There are 3 of them:
1. UGA
2. UAA
3. UAG
Steps of Translation
Ribosome attaches to start codon on a mRNA molecule
2. The start codon will pair with the anticodon UAC on a
tRNA
3. The tRNA also carries the amino acid methionine.
4. As the ribosome moves along an mRNA transcript,
each mRNA codon is sequentially paired with its tRNA
anticodon
5. Amino acids are joined to a growing polypeptide chain
in the order specified by an mRNA transcript
6. When the ribosome reaches a stop codon, translation
ends
Gene Mutations
Changes to a single nucleotide , point mutations, make
changes inside a single gene
Frameshift Mutations: Type of point mutation that leads to
the misreading of the rest of the mRNA molecule
Chromosomal Mutations
A change in the entire chromosomes, changing an entire gene! A. Deletion: B. Duplication: C. Inversion: D. Translocation:
Epigenetics Regulation
The same set of genes but with expressions (structures) of those genes during different life stages
