CENTRAL DOGMA,
TRANSLATION AND
TRANSCRIPTION
GROUP 1
PREPARED BY:
Corpuz, Ana
De Arce, Pamela
Feliciano, Marvin
Gatchalian, Kristel
San Mateo, Patricia
Sumait, Angelene
Transcription
The goal of transcription is to make a copy of a
genes DNA sequence.
Transcription uses one of the two exposed DNA
strands as a template; this strand is called
the template strand. The RNA product is
complementary to the template strand and is
almost identical to the other DNA strand, called
the nontemplate (or coding) strand.
The site on the DNA from which the first RNA
nucleotide is transcribed is called the initiation
site. Nucleotides that come before the initiation
site are said to be upstream. Nucleotides that
come after the initiation site are said to
be downstream.
Base pairing refers to the fact that a
specific type of nitrogen base in the DNA
pairs up with only one specific type of
nitrogen base in the mRNA. The nucleotide
sequence of DNA determines the
nucleotide sequence of mRNA through
complementary base pairing.
But RNA doesn’t have thymine like DNA.
Instead it has Uracil U. So Uracil replaces
thymine as the partner to Adenine.
RNA BASE PAIRS
Adenine-----Uracil
Cytosine-----Guanine
Activity 2: Below each letter, type the
complementary mRNA strand.
1. G-C-G-A-T
C-G-C-U-A
2. T-T-A-A-G-C-T-G-C-G
A-A-U-U-C-G-A-C-G-C
Stages of Transcription
Stages of Transcription
1. Initiation
RNA polymerase
an enzyme that initiates
transcription by binding
to promoter at the 3'
end of DNA, unwinds
and unzips it.
Stages of Transcription
1. Initiation
RNA polymerase, binds
the RNA nucleotides
together to form the
mRNA polynucleotide.
RNA activated
nucleotides pair with the
complementary bases of
the DNA strand .
RNA polymerase
The main enzyme involved in transcription
is RNA polymerase, which uses a singlestranded DNA template to synthesize a
complementary strand of RNA
1. Initiation is the beginning or the first stage of transcription.
2. How does initiation occurs?
3. Initiation occurs when the enzyme RNA polymerase binds to a
region of a gene called the promoter. This signals the DNA to
unwind so the enzyme can ‘‘read’’ the bases in one of the DNA
strands. The enzyme is now ready to make a strand of mRNA with a
complementary sequence of bases.
Working along the DNA chain, the enzymes read the nitrogenous
bases and helps the RNA version of the nitrogenous bases floating
around the nucleus find their match. As it moves the RNA polymerase
rezips the DNA behind and let the new strand of DNA peel away.
Stages of Transcription
2. Elongation
.RNA polymerase initiates
mRNA synthesis at the
start codon and this moves
downstream along the
gene.
Stages of Transcription
Elongation is the addition of nucleotides to the
mRNA strand. RNA polymerase reads the unwound
DNA strand and builds the mRNA molecule, using
complementary base pairs. There is a brief time
during this process when the newly formed RNA is
bound to the unwound DNA. During this process,
an adenine (A) in the DNA binds to a uracil (U) in
the RNA.
Stages of Transcription
3. Termination
is the ending of transcription
occurs when RNA polymerase
crosses a stop (termination)
sequence in the gene.
Only one (1) strand of DNA in a
gene gets transcribed
Stages of Transcription
. The mRNA strand is complete, and it detaches from DNA. The
enzyme detaches from the gene and the DNA is returned to its
original state. But this time mrNA is produced. This carries the
information coded in the gene. After a quick modification during
mRNA processing it will leave the nucleus where all the genetic
material is and move into the cytoplasm where it will find a
ribosome to begin the process of translation.
Eukaryotic transcripts need to go through some processing
steps before translation into proteins which will be tackled by
the next discussant in our group. Maam Patricia San Mateo.
Take it away Maam Pat.
Codon
- Triplet of bases, codes for one
amino acid
64 Codons
- 1 start codon (AUG)
- 3 stop codons (UAG, UGA, UAA)
- 61 codes for amino acid
Functions of Proteins
The kind of protein our cells produced tells us what parts of our
bodies should be made of or what these parts can do.
REFERENCES
Video lesson 1: ”From DNA to Protein
– 3D”
(https://www.youtube.com/watch?v=g
G7uCskUOrA)
Jeff Hardin et al. - Becker’s World of
the Cell (8th ed.) - 2012