Biology Chapter 16 Flashcards

Chemical Components of Chromosomes

• Chromosomes are composed of DNA and protein.

Genetic Material Discovery

• Initially, proteins were believed to be the genetic material due to their complexity and variety; little was known about nucleic acids.

Griffith's Experiment

• Distinction between virulent (disease-causing) and nonvirulent (harmless) strains of Streptococcus pneumoniae.
• Killed virulent strain could transform nonvirulent strain into a pathogenic form.

Transformation

• Transformation refers to a change in genotype and phenotype from external DNA uptake.

Avery's Experiment

• Avery identified DNA as the transforming factor by inactivating RNA, DNA, and protein in bacteria. Only active DNA caused transformation.

Bacteriophage Structure

• T2 bacteriophage is a virus specifically targeting bacteria.

Bacteriophage Infection Mechanism

• Bacteriophages destroy bacterial cells by injecting their own DNA into the host cell.

Hershey and Chase Experiment

• Used radioactive sulfur and phosphorus to distinguish between DNA and protein, concluding that DNA is the hereditary material.

Chargaff's Rules

• Adenine pairs with thymine; guanine pairs with cytosine.
• Base pair ratios are consistent within species, confirming the complementary base pairing.

Nucleotide Components

• Each nucleotide consists of a nitrogenous base, deoxyribose sugar, and a phosphate group.

Watson and Crick Model

• First DNA model constructed by James Watson and Francis Crick, contributing to the understanding of the double helix structure.

X-ray Diffraction

• Rosalind Franklin utilized X-ray diffraction to reveal DNA's double helix structure.

Purines vs. Pyrimidines

• Purines: Adenine and Guanine (double-ring structure).
• Pyrimidines: Cytosine and Thymine (single-ring structure).
• Adenine pairs with Thymine (2 hydrogen bonds); Guanine pairs with Cytosine (3 hydrogen bonds).

Structure of DNA

• DNA's backbone consists of sugar and phosphate groups, while nitrogenous bases form the rungs.

Antiparallel Strands

• DNA strands run in opposite directions; one has a 5' end facing the other’s 3' end.

Semiconservative Replication Model

• DNA replication results in two strands, each containing one old and one new strand.

Meselson and Stahl Experiment

• Used isotopes of nitrogen (15N and 14N) to demonstrate semiconservative replication through density differences in centrifuged samples.

Origins of Replication

• The sequence where DNA replication begins during the S phase of the cell cycle.

Leading vs. Lagging Strand

• Leading strand synthesized continuously towards the replication fork; lagging strand synthesized in short Okazaki fragments away from the fork.

DNA Synthesis Direction

• Nucleotide addition occurs at the 3' end of the new strand, starting at its 5' end.

Okazaki Fragments

• Short segments synthesized on the lagging strand, joined together by DNA ligase.

Role of Helicase

• Unwinds and separates the DNA strands for replication.

Single-Strand Binding Proteins

• Keep separated DNA strands apart during replication.

Primase Function

• Synthesizes RNA primers necessary for initiating DNA replication.

DNA Polymerase Role

• Adds nucleotides to the growing DNA strand and proofreads for accuracy.

Topoisomerase Function

• Relieves tension and strain ahead of the replication fork to prevent supercoiling.

Ligase Function

• Joins together DNA fragments, especially Okazaki fragments on the lagging strand.

DNA Polymerase I Role

• Replaces RNA primers with DNA nucleotides.

Proofreading and Repair Mechanisms

• DNA polymerase checks for accuracy; nuclease removes damaged segments; ligase fills gaps!

Thymine Dimers

• Covalent links between adjacent thymine bases caused by UV radiation, repaired by DNA repair enzymes.

Telomeres and Telomerase

• Telomeres shorten with each replication; telomerase restores their length in germ cells, preventing aging effects on DNA.

Immortality of Cancer Cells

• Cancer cells often retain active telomerase, allowing indefinite division.

Heterochromatin vs. Euchromatin

• Heterochromatin: tightly condensed, irregular clumps; Euchromatin: less compact and more accessible for transcription.

Griffith's Transfer of Pathogenicity

• Pathogenic substance transferred from dead harmful cells to live harmless cells, resulting in disease.

Lagging Strand Synthesis Direction

• Lagging strand elongates away from the replication fork.

Mismatch Repair

• Enzymes recognize and correct incorrectly paired nucleotides during DNA replication.

Telomere Functionality

• Telomeres act as protective buffers to prevent loss of important genetic information during DNA replication.

RNA Primers Necessity

• RNA primers are essential for DNA replication initiation, as DNA polymerases cannot start without them.

Prokaryotic DNA Structure

• Circular DNA structure allows prokaryotes to replicate without shortening effects during replication.

Explore the crucial concepts of the molecular basis of inheritance with these flashcards. Test your understanding of chromosomes, genetic material, and the distinctions between virulent and nonvirulent strains. Ideal for students studying genetics and molecular biology.