Early Discoveries in DNA and Chromosomes

True (A)

bacteriophage

<p>protease, lipase, or RNase</p> Signup and view all the answers

<p>Griffith = Discovered bacterial transformation Avery = Identified DNA as the transforming principle Hershey and Chase = Confirmed DNA as the hereditary material using bacteriophages</p> Signup and view all the answers

<p>35S (B)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>nucleic acid</p> Signup and view all the answers

<p>enzymes</p> Signup and view all the answers

<p>Radioactive 32P = Found in the bacteria after infection Radioactive 35S = Found in the phages after infection DNA = Contains hereditary information Amino acids = Make up proteins</p> Signup and view all the answers

<p>DNA (A)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>chromosomes</p> Signup and view all the answers

<p>Nuclein (C)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>thread</p> Signup and view all the answers

<p>nucleic</p> Signup and view all the answers

<p>Sutton and Boveri (D)</p> Signup and view all the answers

<p>False (B)</p> Signup and view all the answers

<p>Johann Miescher = Isolated Nuclein from cell nuclei Walther Flemming = Observed and named Chromatin Albrecht Kossel = Identified Nuclein as a nucleic acid/DNA Walter Sutton &amp; Theodor Boveri = Concluded chromosomes carry hereditary material</p> Signup and view all the answers

<p>A vaccine (D)</p> Signup and view all the answers

<p>R</p> Signup and view all the answers

<p>The R strain was transformed into S strain</p> Signup and view all the answers

The process by which one type of bacteria (the harmless R strain) acquires genetic material from another type of bacteria (the deadly S strain), resulting in the R strain becoming deadly.

The experiment conducted by Oswald Avery in 1944 that aimed to identify the genetic material responsible for transformation in bacteria. Avery used enzymes to break down different components of the S-strain extract, discovering that only when DNA was destroyed did transformation fail.

A virus that infects bacteria. It consists of a DNA core surrounded by a protein coat.

The experiment conducted by Alfred Hershey and Martha Chase in 1952 using bacteriophages to definitively prove DNA as the genetic material. They labeled phage DNA with radioactive phosphorus and phage proteins with radioactive sulfur, finding that only the radioactive phosphorus entered the bacteria, confirming DNA's role in heredity.

The belief that proteins were the main carriers of genetic information. This viewpoint was challenged by the experiments of Avery and Hershey-Chase, which ultimately proved DNA as the genetic material.

Viruses cannot reproduce on their own and require a host cell to replicate.

Viruses use the host cell's enzymes and raw materials to create new viral particles.

A technique that uses radioactive isotopes to track the movement of specific molecules, demonstrating the genetic material's nature.

Hershey and Chase used sulfur-35 (35S) to label proteins and phosphorus-32 (32P) to label DNA to study phage infection.

In the Hershey-Chase experiment, phages containing radioactive sulfur (35S) did not transfer the radioactivity to bacteria, indicating that the phages' protein coats did not enter the bacteria.

In the Hershey-Chase experiment, phages containing radioactive phosphorus (32P) transferred the radioactivity to bacteria, indicating that the phages' DNA entered the bacteria.

The Hershey & Chase experiment demonstrated conclusively that DNA is the genetic material responsible for transmitting hereditary information.

The scientific community accepted DNA as the hereditary material after the conclusive evidence provided by the Hershey & Chase experiment.

Johann Miescher was a scientist who focused on the nucleus of cells. He collected cells with very little cytoplasm (such as fish sperm and white blood cells) - where he discovered a unique large acidic molecule that he called "Nuclein" - rich in nitrogen and phosphorus. This discovery challenged the long-held belief that protein was the primary carrier of genetic information, paving the way for the discovery of DNA.

In 1878, Walther Flemming identified thread-like structures in the nucleus. He called these structures 'Chromatin', which are highly absorbent of basophilic aniline dyes. They are often referred to as 'coloured bodies' and play a key role in cell division.

Albrecht Kossel was a scientist who discovered that 'Nuclein' is actually a nucleic acid, and further identified the five nucleotides. His work ultimately led to the discovery of DNA and RNA.

Walter Sutton and Theodor Boveri independently concluded that chromosomes are the carriers of hereditary material. Boveri used roundworms to show that chromosomes were essential for proper development. Sutton observed that chromosomes occur in matched pairs (one from the mother, one from the father) which separate during meiosis. This discovery was a crucial step in understanding how genetic information is passed down from parents to offspring.

Walter Sutton's 1902 paper summarized key insights about chromosomes and their role in heredity: 1) Chromosomes contain the genetic material. 2) Chromosomes are passed down from parents to their offspring. 3) Chromosomes are found in pairs in the nucleus of most cells. 4) During the formation of sperm and egg cells, chromosomes separate into their individual components. 5) Each parent contributes a set of chromosomes to their offspring. These conclusions established a foundational understanding of genetic transmission.

The 1918 Spanish flu pandemic caused by the H1N1 virus infected 30% of the world, leading to millions of deaths. The fear of another pandemic, particularly from Streptococcus pneumoniae, motivated Fred Griffith to research this bacteria and its potential for vaccine development.

Streptococcus pneumoniae cells exist in two main types: Rough (R) and Smooth (S). Rough (R) cells lack a capsule rendering them susceptible to the immune system and thus harmless. Smooth (S) cells are more virulent because their capsule prevents detection by the immune system. The difference in virulence makes these types of cells useful for studying hereditary material.

Fred Griffith conducted experiments to study the two strains of Streptococcus pneumoniae cells: Rough (R) and Smooth (S) cells. When mice were injected with the R cells, they survived as the R cells were harmless. When mice were injected with the S cells, they died because the S cells were deadly. This confirmed the virulence difference between the two strains.

Fred Griffith heated the deadly Smooth (S) strain of Streptococcus pneumoniae to kill it, and then injected it into mice. These mice survived, indicating successful inactivation of the deadly bacteria. This was the first step in experimenting with 'Transformation' in his research.

The most important experiment conducted by Fred Griffith involved injecting mice with both inactivated S strain and live R strain. To his surprise, the mice died! This experiment showed that the R cells had been "transformed" into S cells. This transformation process proved that the hereditary material from the S cells had been transferred to the R cells.