Genes and Protein Synthesis Flashcards
Central Dogma of Biology
This principle explains the flow of genetic information within a biological system. It describes the sequential process: DNA -> RNA -> Protein.
DNA is transcribed into RNA, and RNA is translated into proteins.
Transcription
It occurs in the nucleus.
During transcription, RNA polymerase binds to a DNA template strand and synthesizes a complementary RNA molecule (mRNA) using nucleotides.
Translation
This takes place in the cytoplasm on ribosomes.
During translation, ribosomes read the mRNA sequence, and tRNA molecules bring amino acids to the ribosome according to the codons on the mRNA, creating a polypeptide chain that forms a protein.
mRNA (Messenger RNA)
Carries the genetic information from DNA to the cytoplasm/ribosome.
rRNA (Ribosomal RNA)
Forms the structure of ribosomes and facilitates protein synthesis.
tRNA (Transfer RNA)
Carries amino acids to the ribosome and matches them to the coded mRNA sequence during translation.
Initiation
RNA polymerase binds to the promoter region of DNA, and the DNA strands unwind.
Elongation
RNA polymerase moves along the DNA template, synthesizing mRNA by adding complementary RNA nucleotides.
Termination
RNA polymerase reaches a terminator sequence, and transcription stops. mRNA is released.
Processing
Pre-mRNA undergoes modifications like capping, splicing, and polyadenylation to form mature mRNA.
Direction of Transcription
DNA → RNA is read in the 3’ to 5’ direction
RNA → Protein is read in the 5’ to 3’ direction
Nucleotides
letters of the alphabet
Codons
words (made of three letters, always)
Ribosome Sites
Ribosomes move along mRNA, reading codons (sequences of three nucleotides). As the ribosome moves one codon, tRNA molecules bring amino acids corresponding to the codons.
Anticodon
It’s a sequence of three nucleotides on tRNA that pairs with the mRNA codon during translation.
Wobble Hypothesis
It suggests that the mRNA codon’s third base and the tRNA anticodon’s first base can exhibit some flexibility in base pairing, allowing one tRNA to recognize multiple codons.
Lac Operon
In the presence of lactose, the lac operon allows the transcription of genes responsible for lactose metabolism. This happens because the lac repressor protein cannot bind to the operator due to lactose.
Tryp Operon
It regulates the production of enzymes involved in tryptophan (amino acid) synthesis. When tryptophan levels are high, it binds to the repressor, activating it and preventing transcription.
Small-Scale Gene Mutation
Point mutations (substitution, insertion, deletion) affecting one or a few nucleotides. (codons are made of three nucleotides)
Large-Scale Gene Mutation
Deletions, duplications, inversions, or translocations affecting larger segments of DNA
Identification
Mutation diagrams/examples can reveal changes in nucleotide sequences or chromosomal structures.
Mutation Effects
Not all mutations are deleterious; some may be neutral or beneficial. However, mutations can lead to genetic disorders, cancers, or evolutionary changes.
