central dogma Flashcards
It outlines how DNA is transcribed into RNA, which is then translated into proteins, forming the basis for cellular function and heredity.
The Central Dogma of Molecular Biology
○ Process by which DNA makes a copy of itself before cell division.
○ Involves enzymes like DNA polymerase.
○ Ensures genetic information is passed to daughter cells.
DNA Replication
○ The process of synthesizing RNA from a DNA template.
○ RNA polymerase binds to the promoter region of a gene.
○ Produces messenger RNA (mRNA) that carries genetic information to
ribosomes.
Transcription
○ The process where ribosomes synthesize proteins using mRNA as a template.
○ Involves transfer RNA (tRNA) bringing amino acids to the ribosome.
○ Codons on mRNA correspond to specific amino acids, forming polypeptide
chains.
Translation
○ Includes folding, cleavage, phosphorylation, and glycosylation.
○ Essential for protein functionality and regulation.
Post-Translational Processing
Translation Process (5)
- initiation
- elongation
- translocation
- termination
- post-translation modifications
○ Ribosome assembly on mRNA.
○ Start codon recognition (AUG).
○ tRNA carrying methionine binds to the start codon.
Initiation
○ Sequential addition of amino acids to the growing polypeptide chain.
○ tRNA molecules bring specific amino acids to the ribosome based on
codon-anticodon pairing.
○ Peptide bonds form between adjacent amino acids.
Elongation
○ Movement of the ribosome along the mRNA strand.
○ The ribosome shifts to expose the next codon for tRNA binding.
○ This process requires GTP as an energy source.
Translocation
○ Occurs when a stop codon (UAA, UAG, UGA) is reached.
○ Release factors bind to the ribosome, prompting the release of the completed
polypeptide.
○ Ribosomal subunits disassemble from the mRNA
Termination
○ Chemical modifications of the newly synthesized protein.
○ Includes phosphorylation, glycosylation, methylation, and cleavage.
○ These modifications are crucial for protein functionality, stability, and
localization.
Post-Translation Modifications
Post-Translation Modifications (4)
- phosphorylation
- glycosylation
- methylation
- cleavage
- synthesizes proteins by translating messenger RNA (mRNA) into polypeptide chains
- It consists of two subunits, each made up of ribosomal RNA (rRNA) and proteins, which work together during protein synthesis
Ribosome Structure
In eukaryotes, the large subunit is ____ and the small subunit is ____; together
they form an ____ ribosome.
60S, 40S; 80S
In prokaryotes, the large subunit is ___ and the small subunit is ___; together
they form a ___ ribosome.
50S, 30S; 70S
○ The site where incoming aminoacyl-tRNA binds during translation.
○ Responsible for accepting new amino acids to be added to the growing
polypeptide chain.
A Site (Aminoacyl Site)
○ The site where the tRNA carrying the growing polypeptide chain is located.
○ Facilitates the formation of peptide bonds between amino acids.
P Site (Peptidyl Site)
○ The site where empty tRNA molecules exit the ribosome after their amino acid has been added to the polypeptide chain.
○ Plays a role in recycling tRNA for future rounds of translation.
E Site (Exit Site)
- first step in gene expression, where a specific segment of DNA is copied into RNA by the enzyme RNA polymerase.
- involves several key elements and steps that ensure accurate synthesis of messenger RNA (mRNA) from the DNA template.
Transcription Process
○ A specific DNA sequence located upstream of the gene.
○ Serves as the binding site for RNA polymerase and transcription factors.
○ Determines the start point for transcription.
Promoter Sequence
○ Proteins that bind to specific DNA sequences near the promoter.
○ Help recruit RNA polymerase to the promoter region.
○ Regulate the efficiency and rate of transcription initiation.
Transcription Factors
○ Formed when RNA polymerase binds to the promoter with the help of
transcription factors.
○ Marks the beginning of transcription.
○ Involves unwinding of the DNA double helix to expose the template strand.
Initiation Complex
○ Specific sequences in the DNA that signal the end of transcription.
○ Causes RNA polymerase to detach from the DNA and release the newly
synthesized RNA molecule.
○ Ensures proper length and integrity of the mRNA transcript
Termination Sequence
○ Modifications made to the primary RNA transcript before it becomes mature
mRNA.
○ Includes capping (addition of a 5’ cap), polyadenylation (addition of a poly-A
tail), and splicing (removal of introns).
○ Essential for stability, transport, and translation of mRNA.
Post-Transcriptional Processing
- the biological process of producing two identical replicas of DNA from one original DNA molecule.
- essential for cell division and occurs in a highly regulated manner to ensure genetic fidelity.
DNA Replication
Transcription Process (5)
- Promoter Sequence
- Transcription Factors
- Initiation Complex
- Termination Sequence
- Post-Transcriptional Processing
DNA Replication (6)
- Prereplication Complex
- Unwinding and Separation
- Replication Bubble
- Prevention of Tangling
- Priming and Creation
- Joining and Termination
○ Formation of a complex at the origin of replication.
○ Involves various proteins that prepare the DNA for unwinding.
Prereplication Complex
○ Helicase enzymes unwind the double helix structure.
○ Single-strand binding proteins stabilize separated strands to prevent
re-annealing.
Unwinding and Separation
○ The area where the DNA strands are separated, creating a bubble-like structure.
○ Allows for simultaneous replication on both strands
Replication Bubble
relieve torsional strain ahead of the replication fork
Topoisomerases
Prevents supercoiling and tangling of DNA strands during replication
Prevention of Tangling
○ RNA primers synthesized by primase provide starting points for DNA synthesis.
○ DNA polymerases extend the primers to create new DNA strands.
Priming and Creation
In joining and termination, ______ fragments on the lagging strand are joined by DNA ligase.
Okazaki
○ Replication terminates when the entire DNA molecule has been copied,
ensuring complete and accurate duplication
Joining and Termination
