Bio Final cram session study boss level mode
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Key Figures in DNA Discovery
Key Contributors to DNA Structure:
Chargaff
Franklin
Watson and Crick
Griffith
Meselson and Stahl
Semiconservative DNA Replication
Semiconservative Replication Explanation:
Each new double helix consists of one old strand and one new strand.
The old double helix is degraded, and half of its nucleotides are used in the construction of two new double helices, but one of the double helices contains two old strands and the other contains two new strands.
Terminology and Key Concepts
Repetitive DNA Sequences in Chromosomes:
Telomeres: Protect the ends of chromosomes.
Centromeres: Region of a chromosome to which the microtubules of the spindle attach.
DNA Repair Mechanisms
Repair Process for Damage to DNA:
Nucleotide Excision Repair: Mechanism that removes damaged DNA.
Mismatch Repair: Fixes errors in replication.
Composition of Chromosomes
Chromosome Composition:
Made of DNA and proteins.
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DNA Characteristics During Interphase
DNA Structure During Interphase:
Exists as chromatin (not condensed) and is available for gene expression.
Genetics and Eye Color in Drosophila
Morgan's Eye Color Experiment:
The gene responsible for eye color is likely located on the X chromosome.
Chromosome Theory of Inheritance
Early 20th Century Understanding:
Mendelian genes exist at specific loci on chromosomes and segregate during meiosis.
Griffith's Transformational Experiments
Key Findings:
A substance transferred from pathogenic to non-pathogenic bacteria causing transformation.
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Griffith's Experiments Clarifications
Suggestions for Clarification:
Examining tissue from dead mice for pathogenic bacteria would better elucidate the findings.
Hershey and Chase's DNA Experiments
Key Determination on Genetic Material:
DNA contains phosphorus while proteins do not, which helped distinguish them.
Chargaff's Findings
Base Pairing Rule:
DNA contains equal amounts of adenine and thymine, and equal amounts of guanine and cytosine.
Experimental Shortcomings in DNA Labeling
Hershey and Chase's Experimental Modifications:
Using nitrogen could not distinguish between DNA and proteins since both contain nitrogen.
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Prokaryotic vs. Eukaryotic DNA Replication
Differences in DNA Replication:
Prokaryotes have a single origin of replication; eukaryotes have multiple origins.
Antiparallel DNA Strands
Definition:
A 5' to 3' DNA strand pairs with a 3' to 5' strand.
Mutation Effects in E. coli
DnaB Mutation Impact:
No replication fork will form due to the mutation.
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Importance of Low Error Rate in DNA Replication
Impacts on Evolution:
Rare errors serve as a source of genetic variation, critical for evolution.
E. coli DNA Polymerase III Functionality
Primary Function:
To add nucleotides to the growing DNA strand.
Leading vs. Lagging DNA Strands
Difference in Synthesis:
Leading strand is synthesized continuously, while the lagging strand is in fragments.
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Daughter DNA Products Post Replication
Semiconservative Replication Explanation:
Each daughter molecule consists of one original strand and one new strand.
Mutations and Replication Errors
Consequences of an Inactive Telomerase:
Chromosome length reduction in gametes and potential somatic cell cancer risks.
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Okazaki Fragments Discovery
Significance of the Discovery:
Evidence that DNA polymerases synthesize strands in one direction only.
DNA and Histone Interactions
Chromatin Structure:
DNA is negatively charged, forming ionic bonds with positively charged histones.
Flow of Genetic Information
Sequence of Genetic Information Flow:
From DNA to RNA to Protein.
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RNA Polymerase Functionality
Transcription Start:
Begins at a specific promoter sequence.
mRNA Processing Post-Transcription
Removal and Splicing Reactions:
Introns are removed, and exons are joined to form a continuous coding sequence.
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Initiation of Translation
Start of Translation:
mRNA's start codon directs the binding of tRNA.
Mutagens and Their Impact
Effect of Mutagens:
They induce changes in the sequence of DNA.
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Protein Synthesis Fundamentals
Process in Prokaryotes vs. Eukaryotes:
Simultaneous transcription and translation occurs in prokaryotes.
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Characteristics of mRNA
Codons Are Present In:
mRNA molecules, which specifies amino acids.
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RNA Properties and Functions
Unique Characteristics of RNA:
Single-stranded, functional in catalysis, and bonding with other nucleic acids.
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Role of Release Factor in Translation
Function in Eukaryotes:
Binds to the stop codon during translation, allowing termination.
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tRNA Binding Mechanism
tRNA Interaction:
Amino acids acutely bind at the tRNA's 3' end.
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Post-Translational Modifications of Proteins
Processes:
Include removal of introns and addition of carbohydrate groups to form glycoproteins.
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Cancer-Related Genes and Effects
Proto-oncogenes Role:
Normal role in promoting cell growth but can become oncogenic.
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Regulation of Gene Expression
How Master Regulatory Genes Function:
As transcription factors, they control related gene expressions.
Cancer Development Factors
What Can Lead to Cancer:
Changes in proto-oncogenes and tumor suppressor genes.
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Differences Between Heterochromatin and Euchromatin
Structural Differences:
Heterochromatin is denser and less accessible than euchromatin, influencing gene expression.
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E. coli Gene Regulation
Lactose Intolerance Predictions:
Likely impact on survival based on available nutrients and protein induction.
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Operon Control Mechanism
How CRP Affects the lac Operon:
Positively regulates transcription when bound to the operon.
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Enhancers versus Proximal Control Elements
Differences:
Enhancers are often located far from the promoter, whereas proximal elements are nearby.
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Characteristics of siRNA
Functionality:
Can bind and inactivate specific target mRNA sequences.
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Oncogene Development
How Proto-oncogenes Become Oncogenes:
Mutations can lead to oncogenic activity, affecting cell growth regulation.