What is a gene?

What type of organism is Neurospora crassa?

Bread Mold

What was revealed by an autopsy of the mouse described in the previous question?

Living S-strain cells.

How did Mendel use a model organism?

Mendel used the common garden pea (Pistum sativum) as a model organism to investigate the nature of heredity.

What disrupts metabolic pathways ans caused certain phenotypes?

Missing or altered enzymes.

What is an "Auxotrophic" mutant?

Mutant may require a growth factor not required by the parent. -An "arg mutants" (Identification through indirect selection).

What happens to Neurospora crassa when it is subjected to the fungi of x-rays or ultraviolet radiation.

Mutation rate gets increased. These mutants unable to produce the amino acid arginine.

Purified S RNA + R cells=

No transformation

Purified S protein + R cells=

No transformation

What was Thomas Hunt Morgan's initial reaction to Sutton's chromosome theory of inheritance? Did his view ever change?

Noted that transmission of the white-eyed phenotype correlates with sex determination. (Males are more commonly affected). He also concluded that this gene is on the X-Chromosome.

What happened when Griffith injected heat-killed S-strain strep into a mouse?

The mouse survived.

What are Chargaff's Rules?

The number of A and T residues are always equal & The numbers of G and C residues are always equal.

What can Arg+ Cells produce?

Their own arginine

How was it demonstrated that the R and S phenotypes of Strep were genetically determined?

These phenotypes are HERITABLE- Thus determines by the genetic material.

Why are model organisms important for scientific study?

They are amenable to manipulation and study, and their findings can be applied to numerous other species.

-Non-enzyme proteins are also encoded by genes (One gene -> one protein). -Some proteins consist of different polypeptides (One gene -> one polypeptide). -Alternative splicing can occur (One gene -> one or more related polypeptides). -Some genes encode functional RNA molecules such as tRNAs or rRNAs (One gene -> one or more related polypeptides or a functional RNA molecule).

"one gene - one enzyme"

Enzymes are a subset of proteins; not all proteins are enzymes. (One gene one protein)

"one gene - one enzyme"

*Genes are units of DNA that direct the production or the activity of enzymes*

*

A gene is a unit of DNA that serves as a blueprint for:

-A protein, or -A polypeptide, or -A group of related polypeptides, or -A functional RNA molecule

Describe the symptoms of alkaptonuria.

-Characterized by urine that turns black after exposure to air -Urine contains excessive amounts of homogentisic acid -Ultimately leads to deposition of pigment in ears and eyes

Beadle and Tatum's results were consistent with the "one gene - one enzyme hypothesis"

-Did not know the specifics of this relationship, just that such a relationship is likely to exist -Beadle and Tatum received a Nobel Prize in Physiology or Medicine-1958. (Acknowledged Archibald Garrod when they received this award)

Fifteen independent arg- mutants identified factors: (3)

-None would grow on minimal media -All would grow on minimal media supplemented with the amino acid arginine -Could any of these classes grow if a molecule similar to arginine is added instead of arginine?

What basic biological concept was Beadle trying to uncover with is work on Drosophila eye color mutants?

-Numerous eye-color mutants. -Proposed that enzymes affect phenotypes. -Proposed that each of the mutations affecting eye color in Drosophila blocks pigment production at a specific step by preventing production of the enzyme that catalyzes that step.

What features make Neurospora crassa a useful model organism?

-Relatively easy to grow. - -Few nutritional requirements (Requires sugar, some salts, and the vitamin biotin) -Able to make all of its own amino acids -Sexual and asexual life cycles (Both cycles are relatively short).

What are the conclusions of Beadle and Tatum?

-The arg- phenotype is heritable (Genetic defect) -An enzyme is lacking in each mutant (Result of the genetic defect & Garrod's "inborn error of metabolism") -There is a relationship between a gene and an enzyme ("One gene - One enzyme")

Garrod quickly grasped the larger implications of his work. What are they?

-The effects of alkaptonuria are highly visible. -There are undoubtedly other metabolic disorders with more subtle appearances. -Those with this disorder lacked an enzyme important in this particular aspect of metabolism. -Those with a different genetic disorder lack a different enzyme important in a different aspect of metabolism.

Fifteen arg- mutants identified factors: (3)

-Unable to grow in the absence of arginine -All grew in the presence of arginine -Some grew when a similar molecule was substituted for arginine (Citrulline or ornithine).

What is Indirect Selection?

-Used when there is no medium on which the mutant can grow and the parent cell cannot. -Mutant may require a growth factor not required by the parent.

What were the two experiments Hershey & Chase conducted?

1. Infected E. Coli with radiolabeled phage - S-Labeled phage (Protein) - P-Labeled phage (DNA) 2. After establishing an infection, used a blender to remove phage parts loosely associated with the bacterial surface. 3. Separated cells from the liquid with a centrifuge -Portions of virus not inside cells remained in liquid -Cells were collected in pellet 4. Measured radioactivity in pellet and liquid -Radioactive sulfur found in LIQUID -Radioactive phosphorus found in PELLET

What were two key questions of significant importance to biology that were provoked by Mendel's chromosome theory of inheritance?

1. Of what substance are these genes comprised? 2. How does a gene confer a phenotype?

The indirect selection procedure requires what three things?

1. Replica plating 2. Minimal media 3. Various additions to minimal media

What are the percentages of human DNA?

19.5% G 30.3% A 30.3% T 19.9% C

What is natural theology?

A develop understanding of god through observations of nature rather than supposed "divine revelation".

The lack of a particular enzyme results in what?

A particular phenotype. This enzyme is lacking due to a genetic defect "Inborn error or metabolism".

What is "permissive media"?

A plate where both arg+ and arg- cells will grow.

What is "selective media"?

A plate where only Arg+ will grow.

What do alkaptonurics lack?

A specific enzyme. -Homogentisate 1,2-dioxygenase -This enzyme acts upon homogentisic acid -Without this enzyme, homogentisic acid accumulates.

Who preformed the "Blender Experiment"?

Alfred Hershey and Martha Chase

What did Garrod mean by an inborn error of metabolism?

Alkaptonurics lacked an enzyme necessary for protein breakdown & Resulted in the accumulation of a chemical that darkens urine

Archibald Garrod proposed that the genetic disorder was due to a metabolic defect. What did the genetic defect led too?

An "inborn error of metabolsim" (Genetically-determined lack of a specific enzyme).

Describe the nature of the DNA analyses performed by Erwin Chargaff.

Analyzed the base composition of DNA from a variety of organisms. He Found that the base composition is consistent within species, but differs between species (Molecular unity and diversity- This makes DNA a more credible candidate for the genetic material).

The two strands of DNA are termed what?

Antiparallel: Parallel but in opposite orientations

What do Arg- cells require?

Arginine in their growth medium.

Describe the relationship between biology and natural theology during the time of Gregor Mendel:

At this time, biology was mainly a descriptive science. The biological study was also governed by the concept of "natural theology".

What did Griffith conclude had occurred when he injected the mixture into the mouse? What term did he use to describe this phenomenon?

BACTERIAL TRANSFORMATION. He concluded, a heritable change resulting from the uptake of genetic material from a bacterium's surroundings.

Why do you think the importance of Mendel's work was not recognized during Mendel's lifetime?

Because it was not immediately understood. The behavior if chromosomes during cell division had not yet been studied- This provides a framework for our understanding of inheritance patterns.

What subfields of biology were George Beadle's specialty?

Biochemist and geneticist

What relevant and important changes and/or discoveries in biology had occurred between the time of Mendel's work and the rediscovery of his work? How were they important?

Biology had become a quantitative, experimental science. The behavior of chromosomes during cell division had been studied and was now understood.

In a single sentence, describe Walter Sutton's chromosome theory of inheritance.

Chromosomes contain the genetic material, and genes reside on the chromosomes. Diploid cells possess two sets of chromosomes. Meiosis produces gametes with a single chromosome set. Gametes then fuse to produce a zygote with two sets of chromosomes.

Was Maurice Wilkins recognized in any significant way for his exceedingly minimal contributions in elucidating the three-dimensional structure of DNA?

Crick and Watson accurately determined the three-dimensional structure of DNA Received a Nobel Prize in 1962 Shared this prize with Maurice Wilkins.

What did Crick and Watson correctly propose regarding the function of DNA's second strand?

Crick and Watson published an accurate model for the three-dimensional structure of DNA (1953)

What is the transforming agent in genetic material?

DNA

What is labeled phage in the presence of radioactive phosphorus?

DNA!! Not proteins.

What enzymes destroy DNA but nor protein contaminants?

DNAse

What was the primary focus of Frederick Griffith's research with strep?

He was attempting to develop a vaccine against pneumonia.

What features of DNA's three-dimensional structure did Rosalind Franklin infer from her X-ray crystallography images?

Determined various characteristics of DNA. -Phosphate groups are on the outside of the molecule -DNA is helical, and has two strands -Determined the shape and size of the double helix Could not yet determine how the bases paired

George Beadle studied the eye color in what?

Drosophila melanogaster

Who Analyzed DNA base composition from several species? Variation between species but constant within a species?

Erwin Chargaff

Who analyzed DNA base composition from several species? and what did he conclude?

Erwin Chargaff- He concluded that the variation between species but constant within a species.

How did Garrod establish that alkaptonuria was a genetic disorder?

Established alkaptonuria as a genetic disorder. -First human disorder established as genetic -How did he know? Rare in general population. Frequent in children of first-cousin marriages. Displayed pattern of recessive inheritance.

Who received a noble prize in 1962 for determining the 3-D structure of DNA?

Francis Crick and James Watson

What model organism did Morgan choose for his genetic studies?

Fruit Flies (Drosophila melanogaster).

Who helped to conclude that Genes act via enzymes?

Garrod, Beadle, and Tatum

Who helped to conclude that DNA is the genetic material?

Griffith, Avery, Hershey, and Chase

Three different classes of arg- mutants:

Grow when supplied with: -Class I: arginine, citrulline, or ornithine -Class II: arginine or citrulline -Class III: arginine only

Describe the asexual life cycle of Neurospora crassa.

Haploid asexual life cycle can make genetic analysis fairly straightforward

What observations did Walter Sutton make regarding chromosomes and traits?

He notes that the behavior of chromosomes paralleled the segregation of traits.

What specific traits was Morgan following when he demonstrated that genes did, in fact, reside upon chromosomes?

He was initially skeptical but ultimately verified Sutton's chromosomes theory of inheritance. He concluded, chromosomes contain the genetic material.

In a single sentence, describe Mendel's particulate nature of inheritance, focusing on the importance of the term particulate in his findings:

Heritable traits resulted from discrete physical particles, now called "genes". (Characteristics are passed from one generation to the next through the transmission of these genes.)

Who, in 1969, received a noble prize for the establishment of DNA?

Hershey (Male). Chase (who was a female did not.

Who radiolabeled the components of T2 bacteriophage?

Hershey and Chase

Who finally convinced he scientific community that DNA is the genetic material?

Hershey and Chase in (1952)

What acid is an intermediate in the breakdown of two amino acids.

Homogentisic acid (Phenylalanine and Tyrosine).

What was the second question from Gregor Mendel?

How does a gene confer a phenotype?

How is arginine synthesis possible?

If the product of this "broken" step is added (Adding ornithine or citrulline).

When was Mendel's work rediscovered?

In 1900

Where is sulfur present?

In proteins!! Not DNA.

During which century did Gregor Mendel live and perform his genetic experiments?

In the mid 1800s, he was among the first to treat biology as an experimental science.

Archibald Garrod proposed that genetic disorders resulted from what?

Inborn errors of metabolism.

-Very labor intensive process (Much more difficult than positive selection) -Beadle and Tatum identified fifteen independent arg- mutants -These mutants were then investigated further

Indirect selection for arg- mutants.

What is a bacteriophage?

It is a virus that infects E. Coli. Once E. Coli gets infected it gets reprogrammed. The cell is then converted into a virus-producing factory.

Did Mendel's discovery of the particulate nature of inheritance being humankind closer to knowing everything there is to know:

It provided the basis for our modern understanding of heredity.

What type of experiments did Hershey and Chase conduct?

Parallel experiments with the sets of labeled phage.

How was the batch of phage in the presence of radioactive sulfur labeled?

Phage PROTEINS, Not DNA.

Where (In the genetic material) is phosphorus found?

Phosphorus is abundant in DNA and not in proteins

What is the Metabolic pathway for arginine biosynthesis?

Precursor ->ornithine -> citrulline -> arginine (Each step is catalyzed by a specific enzyme & each mutant class lacks a different enzyme).

What was produced from purified DNA?

Produced thin fibers of purified DNA and subjected them to x-ray crystallographic analysis. Discovered A and B forms of DNA & Developed a method to separate these two forms. Separation was required to obtain useful x-ray crystallography data.

What enzymes destroy and protein contaminants?

Protease

Was Rosalind Franklin recognized in any significant way for her contributions in elucidating the three-dimensional structure of DNA?

Rosalind Franklin did not share the Nobel Prize with Crick and Watson.

Describe the key differences between the S stain and the R stain of Streptococcus:

S Strain: Smooth, possess a glycocalyx, pathongenic R Strain: Rough, lacks glycocalyx, non-pathogenic.

What type of Strep did Avery purify?

S- strain.

What was it about the mouse experiment that suggested that DNA was more likely candidate for the genetic material than protein?

Since the genetic material survived extreme heat, Griffith reasoned that DNA was a more likely candidate than protein. (Since heat irreversibly denatures most proteins & DNA tolerates heat much better.)

Together, Beadle and Tatum sought to better understand what?

Sought to better understand the connection between genes and phenotypes. -Developing experiments to unravel this connection was difficult in Drosophila due to the organism's complexity. -Focused their attention on the simpler organism Neurospora crassa.

What is the Pneumonia-causing bacterium?

Streptococcus pneumoniae

What subfields of biology were Archibald Garrod's specialty? How old were these fields?

Studied alkaptonuria

Describe the structure of T2 bacteriophage?

T2 bacteriophage is comprised exclusively of DNA and Protein.

Describe two hypothesis that would account for the type of bacteria found during the mouse's autopsy.

TRANSFORMED. He concluded, this transformation only occurred in the presence of dead S bacteria. & The transformation must have involved the uptake of genetic material from the dead S bacteria.

Does the second strand of a DNA molecule encode any information not already encoded by the first strand?

The base sequence of the first strand dictates the base sequence of the second strand. The second strand does not encode additional information

What model organism did Mendel choose for his genetic studies?

The common garden pea (Pisum sativum).

What is "One gene-one enzyme hypothesis"?

The connection between gene and phenotype that involves enzymes.

In one or two sentences, explain in a very simplistic way the mechanism of DNA replication.

The double-stranded nature of DNA is important in its replication. -The DNA double-helix unzips -The "missing" complementary bases are added -Two identical copies now exist -The hydrogen bonds connecting the two strands are relatively easily broken -Two daughter molecules are formed -Each consists of one "old" strand and one "new" strand

What is glycocalyx?

The glycocalyx is a glycoprotein-polysaccharide covering that surrounds the cell membranes of some bacteria, epithelia and other cells.

What happened when Giffith mixed live R-strain strep with heat-killes S-strain strep, and injected this mixture into a mouse?

The mouse died.

What happened when Griffith injected live S-strain strep into a mouse?

The mouse died.

What happened when Griffith injected the R-strain strep into a mouse?

The mouse lived.

What is the purpose of the blender experiment?

To identify the genetic material.

What did Oswald Avery set out to do?

To identify the transforming agents in Griffith's experiment. (He concluded the transforming agent was genetic material).

Purified S DNA + R cells=

Transformation

What was Rosalind Franklin's research focus?

Trying to discern DNA's three-dimensional structure

In a single sentence, describe in basic terms basics of the process of X-ray crystallography.

Used x-ray crystallography. -Purified DNA is crystallized. These crystals diffract x-rays, which form a pattern of exposure on x-ray film. Akin to the diffraction of light when passing through a prism

When was DNA established as a genetic material?

in 1952

How may experiments did Crick and Watson perform in their quest to determine DNA's three-dimensional structure?

Zero. (They didn't do any actuall experiments themselves.)

How many experiments did Crick and Watson do for the establishing the structure of DNA?

Zero. They relied heavily on the work of others.