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Adenine (A)
A nitrogenous base found in DNA and RNA; pairs with with thymine (T) in DNA and uracil (U) in RNA
Bacteriophage
A virus that infects and replicates within bacteria
Chargaff’s Rules
The observation that in DNA, the amount of adenine (A) is equal to the amount of thymine (T), and the amount of guanine (G) is equal tot he amount of cytosine (C)
Chromosome
A thread-like structure of nucleic acids and protein that carries genetic information in the form of genes
Cytosine (C)
A nitrogenous base found in DNA and RNA; pairs with guanine (G)
Deoxyribonucleotide
A nucleotide containing deoxyribose as its sugar component, found in DNA
DNA (deoxyribonucleic Acid)
A double-stranded molecules that carries the genetic instructions for all known living organisms and many viruses
Euchromatin
A loosely packed form of chromatin that is rich in gene concentration and is often actively transcribed
Guanine (G)
A nitrogenous base found in DNA and RNA; pairs with cytosine (C)
Heterochromatin
A tightly packed form of chromatin that is generally transcriptionally inactive
Histones
Proteins around which DNA is wrapped to form nucleosomes. they help organize DNA into chromosomes and regulate gene activity
Nucleoside
A compound consisting consisting of a nitrogenous base linked to a sugar (ribose or deoxyribose)
Nucleotide
A building block of DNA and RNA, consisting of a nitrogenous base, a sugar (ribose or deoxyribose), and one or more phosphate groups
Repetitive DNA
DNA sequences that are present in multiple copies in the genome
RNA (ribonucleic acid)
A single-stranded molecule involved in various biological roles in coding, decoding, regulation, and expression of genes. Contains uracil instead of thymine
Supercoiled DNA
DNA that is twisted beyond its relaxed state. Can be positively or negatively supercoiled
Telomeres
Protective caps at the ends of eukaryotic chromosomes that prevent DNA degradation and chromosome fusion
Thymine (T)
A nitrogenous base found in DNA; pairs with adenine (A)
Tobacco Mosaic Virus (TMV)
An RNA virus that infects tobacco plants; used in experiments to determine the genetic material of viruses
Transforming substance
The substance capable of transforming non-virulent bacteria into virulent bacteria (identified as DNA by Avery, Macleod, and McCarty)
Uracil (U)
A nitrogenous base found in RNA; replaces thymine (T) and pairs with adenine (A)
What was the key question Griffith was attempting to answer in his experiment, and what was his conclusion?
Griffith wanted to determine if an extract from dead bacterial cells could genetically transform living cells. His conclusion was that a substance in heat killed virulent bacteria could genetically transform type IIR bacteria into living type IIIS bacteria
What was the significance of the Avery, MacLeod, and McCarty experiment in understanding the nature of genetic material?
These experiments sought to identify the chemical nature of the transforming substance discovered by Griffith. They concluded that DNA (not protein) was the transforming substance, proving that DNA carries genetic information
Describe the purpose and main finding of the Hershey-Chase experiment
The Hershey-Chase experiment aimed to determine whether DNA or protein serves as genetic material and is transmitted to progeny in bacteriophages. they found that DNA, not protein, was the genetic material transmitted
What did Heinz Fraenkel-Conrat’s experiment using the Tobacco Mosaic Virus demonstrate?
Heinz Fraenkel-Conrat’s experiment with TMV showed that RNA is the genetic material in the RNA virus, proving that RNA can also carry genetic information
State Chargaff’s rules and explain their importance to understanding DNA structure
Chargaff’s rules state that A=T and G=C. These rules were crucial in understanding the base pairing structure of DNA and helped Watson and Crick determine the double helix structure
Explain why RNA is NOT often found in a double-stranded state
RNA will take on its most thermodynamically stable state, but exists in an equilibrium. The presence of ribose sugar instead of deoxyribose in DNA, which makes RNA less stable and more prone to degradation
What is the key difference between the structure of ribose v.s. Deoxyribose
The key difference between ribose and deoxyribose sugars is that ribose has a hydroxyl group (-OH) attached to the 2' carbon atom, while deoxyribose lacks this hydroxyl group, meaning it has a hydrogen atom at that position instead; this makes deoxyribose slightly more stable than ribose, and consequently, ribose is found in RNA while deoxyribose is found in DNA.
What is meant by the term “supercoiled” DNA and why is it important in E. Coli?
Supercoiled DNA refers to DNA that is twisted beyond its relaxed state. It is functionally important in E. Coli because it allows the large chromosome to be packaged into the small cell, and plays a role in gene regulation and DNA replication
Describe the first step of DNA condensation in eukaryotic chromosomes
The 1st step of DNA condensation involves wrapping DNA around nucleosomes, which are made up of histones
What is the key difference between heterochromatin and euchromatin?
Heterochromatin is tightly packed DNA that is generally transcriptionally inactive, while euchromatin is less condensed and transcriptionally active
What is the role of telomeres in eukaryotic chromosomes?
Telomeres protect the ends of linear DNA molecules from deocyribonucleases, prevent fusion of chromosomes, and facilitate complete replication of the ends of linear DNA molecules
Describe the levels of DNA organization in eukaryotic chromosomes
Eukaryotic DNA is organized into chromosomes through multiple levels of compaction
DNA is wrapped around histone proteins to form nucleosomes
2. These nucleosomes are further organized into a 30 nm fiber
3. These fibers are then looped and attached to a protein scaffold, leading to further condensation and the final chromosome structure
Eukaryotic chromosomes also contain repetitive sequences, heterochromatin, and euchromatin regions, and are protected at their ends by telomeres
How does the structure of RNA typically differ from that of DNA?
RNA is single-stranded, although it can fold back on itself to form double-stranded regions. It contains the sugar ribose instead of deoxyribose, and it uses uracil (U) in place of thymine (T) as one of its nitrogenous bases. RNA also exists in an equilibrium with its thermodynamically stable state
What did Heinz Fraenkel-Conrat’s experiment with the Tobacco Mosaic Virus (TMV) demonstrate?
Fraenkel-Conrat’s work with TMV, an RNA virus, demonstrated that RNA can also serve as genetic material. He showed that by separating TMV into its RNA and protein components, then reconstituting hybrid viruses with different combinations, the infectivity of the reconstituted virus was determined by the source of the RNA, not the protein
What question did the Hershey-Chase experiment address, and what were its findings?
The Hershey-Chase experiment sought to determine whether DNA or protein was the genetic material transmitted by bacteriophages. By radioactively labeling either the DNA or protein of phages and then observing which label entered bacterial cells during infection, they concluded that DNA, not protein, was the genetic material passed on to progeny
What was the purpose and conclusion of the Avery, Macleod, and McCarty experiment?
This experiment aimed to identify the chemical nature of the “transforming substance” discovered by Griffith. Though a series of experiments that selectively eliminated different classes of molecules (proteins, RNA, etc), they concluded that DNA was the transforming substance, providing direct evidence that DNA carries genetic information
What was the significance of Griffth’s experiment?
Griffith’s experiment demonstarated that a substance from dead bacterial cells could genetically transform living cells. Specifically, he showed that non-virulent bacteria could become virulent after exposure to heat-killed virulent bacteria, indicating that genetic material could be transferred between cells
