GENBIO: Lesson 1 - DNA Structure & Replication
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133 Terms
What does the central dogma of molecular biology describe?
Directional flow of genetic information
What processes are involved in the central dogma of molecular biology?
Transcription and Translation
What is gene expression?
Process where DNA directs protein synthesis
What is synthesis in biological terms?
Create something
What is hydrolysis?
Water breaks down chemical bonds
Where does protein synthesis occur?
In the nucleus
How does DNA dictate specific traits?
By dictating the synthesis of proteins
What are introns?
Noncoding genes that are not activated
What are exons?
Genes that code for active proteins
What role does RNA play in protein synthesis?
It acts as a bridge between genes and proteins
Why are proteins important?
They are crucial for transport, structure, and enzymes
What is the relationship between genotype and phenotype?
Proteins link genotype and phenotype
What is transcription?
DNA directed synthesis of mRNA
Where does transcription occur in eukaryotes?
Inside the nucleus
Where does transcription occur in prokaryotes?
In the cytoplasm
What happens to mRNA after transcription?
It moves out of the nucleus to the cytoplasm
What are the molecular components involved in transcription?
Promoters: Signal transcription start point
RNA Polymerase: Catalyzes RNA synthesis
Transcription Factors: Mediate RNA polymerase binding
Transcription Initiation Complex: Assembles transcription factors and RNA polymerase
Terminator: Signals end of transcription in bacteria
Transcription Unit: Stretch of DNA transcribed
Pre-mRNA: Initial RNA transcript in eukaryotes
What is the function of promoters in transcription?
Signal the transcription start point
What does RNA polymerase do during transcription?
Catalyzes RNA synthesis and joins nucleotides
What are transcription factors?
Proteins that mediate RNA polymerase binding
What is the transcription initiation complex?
Assembly of transcription factors and RNA polymerase
What is a terminator in bacteria?
Sequence signaling the end of transcription
What is a transcription unit?
Stretch of DNA transcribed
What is pre-mRNA?
Initial RNA transcript produced from DNA
What are the three stages of transcription?
Initiation: Promoter signals start, RNA polymerase binds
Elongation: RNA polymerase moves along DNA, adding nucleotides
Termination: Transcription ends at terminator sequence
What happens during the initiation stage of transcription?
Promoter signals start and RNA polymerase binds
What occurs during the elongation stage of transcription?
RNA polymerase moves along DNA, adding nucleotides
What is the direction of transcription?
Transcription happens in the 5’ -> 3’ direction
How does termination differ in bacteria and eukaryotes?
Termination is simpler in bacteria than eukaryotes
What happens to mRNA in eukaryotes after transcription?
It undergoes modifications before translation
What modifications occur to pre-mRNA in eukaryotic cells?
5’ end receives a modified guanine cap
3’ end gets a poly-A tail
Functions:
Produces mature mRNA
Facilitates export to cytoplasm
Protects from hydrolytic enzymes
Helps ribosomes attach for translation
What is the function of the 5’ cap on mRNA?
Helps ribosomes attach for translation
What is the function of the poly-A tail on mRNA?
Protects mRNA from hydrolytic enzymes
What is RNA splicing?
Process of removing introns and joining exons
What are introns?
Noncoding regions of RNA
What are exons?
Coding regions that are expressed
What are spliceosomes?
Complexes that carry out RNA splicing
What is translation?
RNA directed synthesis of proteins
Where does translation occur?
In the ribosomes
What is the role of ribosomes in translation?
They build proteins and attach mRNA
What does tRNA do during translation?
Transfers amino acids to the growing polypeptide
What is an anticodon?
Nucleotide triplet complementary to mRNA codon
What is the structure of tRNA?
One end carries amino acids, other carries anticodon
What happens in the cytoplasm during translation?
tRNA molecules bring amino acids to ribosomes
What are the molecular components involved in translation?
Ribosome: Builds protein and binds mRNA
mRNA: Directs tRNA for amino acids
tRNA: Transfers amino acids to ribosome
Small ribosomal subunit: Binds mRNA and initiator tRNA
Large ribosomal subunit: Joins small subunit and mRNA
Initiator tRNA: Carries first amino acid (methionine)
Release factors: Trigger release of finished polypeptideWhat is the function of release factors in translation?
What is the function of release factors in translation?
Trigger release of finished polypeptide
What is an amino acid?
Building block for proteins
How are amino acids transferred during translation?
Based on the genetic code from mRNA
What is the role of the small ribosomal subunit?
Binds mRNA and initiator tRNA
What is the role of the large ribosomal subunit?
Joins small subunit and mRNA
What is the function of the special initiator tRNA?
Carries the first amino acid (methionine)
How does tRNA read the mRNA codons?
By looking for complementary bases in triplets
What is the significance of the anticodon in tRNA?
It is complementary to the mRNA codon
What is the process of translation?
Synthesis of polypeptides using mRNA information
What is the role of ribosomes in the cell?
They are the protein factories of the cell
How does genetic information flow from mRNA to protein?
Through the process of translation
What does the large ribosomal subunit complete?
The translation initiation complex
What do release factors trigger during translation?
The release of the finished polypeptide
What is the monomer for proteins?
Amino acid
How are amino acids transferred by tRNA determined?
By the genetic code from mRNA
What is an anticodon?
A complementary nucleotide triplet to mRNA
What is the structure of tRNA?
Carries amino acids on one end
Carries an anticodon on the other end
3' A C C is the amino acid attachment site
What happens in the cytoplasm regarding tRNA molecules?
They bring amino acids for protein synthesis
What does the anticodon UAC carry when paired with AUG?
Methionine amino acid
What signifies the end of the translation process?
Stop codons UAG, UGA, UAA
What is the result of the translation process?
A chain of amino acids based on mRNA
What are the three stages of translation?
Initiation
Elongation
Termination
What signals the start of translation?
The start codon AUG
What do initiation factors do during translation?
They bring in the large ribosomal subunit
How does the small ribosomal subunit find the start codon?
It moves along the mRNA until AUG
What happens during the elongation stage of translation?
Each addition involves elongation factors
What is the first step in elongation?
Codon recognition by tRNA
What occurs during peptide bond formation?
Amino acids are joined together
What is translocation in the translation process?
Movement of tRNA and ribosome along mRNA
What happens when a stop codon reaches the A site?
A release factor is accepted
What does the release factor do during termination?
It adds a water molecule instead of an amino acid
vWhat are codons and their significance?
Triplet codons are three nucleotide words
Determine proteins synthesized from mRNA
Read in 5' to 3' direction
How many codons were deciphered in the early 1960s?
64 codons
How many codons code for amino acids?
61 codons
What are the three stop codons?
UAA, UAG, UGA
What does it mean that the genetic code is redundant?
More than one codon may specify an amino acid
Why must codons be read in the correct reading frame?
To produce the specified polypeptide correctly
What is the wobble position in codons?
Flexible pairing at the third base
Allows some tRNAs to bind to multiple codons
Only the third base differs among codons
What are the functions of ribosomes?
Facilitate coupling of tRNA and mRNA
Composed of large and small subunits
Targeted by specific antibiotic drugs
What do free ribosomes produce?
Proteins that stay inside the cell
What do bound ribosomes produce?
Proteins that are secreted or inserted into membranes
What are the three binding sites for tRNA on the ribosome?
A site: Holds tRNA with the next amino acid
P site: Holds tRNA with the growing polypeptide
E site: Where discharged tRNAs exit
What are mutations in genetic information?
Changes in the genetic information of a cell
What is a point mutation?
Change in one nucleotide pair of a gene
What is a silent mutation?
No effect on the amino acid produced
What is a missense mutation?
Codes for an incorrect amino acid
What is a nonsense mutation?
Changes an amino acid codon to a stop codon
What is a frameshift mutation?
Insertion or deletion alters the reading frame
What is a genetic disorder?
A mutation with an adverse effect on phenotype
How can a single nucleotide change affect protein production?
It can lead to an abnormal protein
A macromolecule made of monomers called nucleotides.
Nucleic acid
A type of nucleic acid where hereditary information is encoded.
Deoxyribonucleic acid
He developed the Chromosomal Inheritance Theory.
T.H. Morgan
It states that genes are located on chromosomes
Chromosomal Inheritance Theory
Components of a chromosome
DNA and histones