AGRY 320 Lecture Notes and Exam Prep Unit 1

Why is genetics important?

Life depends on genetic information (life cycle).

How do mRNA vaccines work?

They introduce a piece of mRNA, that corresponds to a viral protein, usually a small piece of a protein found in the virus’s outer membrane.

True/False: Individuals that get an mRNA vaccine are exposed to the virus and can become infected by the vaccine. The mRNA gets incorporated into their genome.

False.

Using the mRNA blueprint from a mRNA vaccine, cells produce the viral ______.

Protein.

Why was the 2016/17 Flu vaccine largely ineffective (20%)?

The virus combination chosen to make it were not the predominant strains causing the fly in 2017.

The difference between the flu variants is all based on what?

Differences in the genetic material within the virus genome.

How many eukaryotic species are there globally?

~8.7 million (± 1.3 million SE)

What is genetics?

The study of genes, and inheritance and inherited traits.

Which statement best describes Porcine Epidemic Diarrhea Virus (PEDv) and its impact on the U.S. hog population?

PEDv is a virus that causes extreme diarrhea in piglets, killed at least 8 million pigs, and contributed to record-high pork prices.

What is a gene?

The fundamental physical and functional unit of heredity that carries information from one generation to the next.

What is a gene?

A segment of DNA composed of a transcribed region and regulatory sequences that control transcription.

What does this image represent?

Information transfer among biological molecules.

A _______ is a simple, idealized system that is easily manipulated.

Model system.

Which characteristic is NOT common to model organisms?

Large adult size.

Model organisms are ____ to control.

Easy.

The organism: Drosophila melanogaster (Fruit Fly) is useful as a model organism because:

• It is easy to raise in a lab.

• Has large, visible chromosomes.

• Has many observable mutations.

• Rapid life cycle (14 days).

The organism: Escherichia coli is useful as a model organism because:

• It is the most widely studied prokaryotic model organism.

• Showcases recombinant DNA techniques.

• Short life cycle (0.5 hour per generation).

The organism: Saccharomyces cerevisiae (Baker’s Yeast) is useful as a model organism because:

• It is a simple eukaryote.

• It has a rapid life cycle.

• Its genes are easy to work with.

The organism: Mus musculus (mouse) is useful as a model organism because:

It is closely related to humans, so most human genes have functional mouse counterparts, and the genome is organized in a very similar manner.

The organism: Arabidopsis thaliana is useful as a model organism because:

• It has a small genome (130 mB)

• Small plant size (20 - 25cm tall)

• It has a rapid life cycle (6 weeks)

The organism: Zea mays is useful as a model organism because:

• Large sized genome (1500 Mb)

• Large plant side (2M tall)

• 1 - 2 generations per year

• 100 - 200 seeds per pollination.

Agricultural applications of genetics include:

Plant breeding, animal breeding, diagnostics, and research.

Medicinal applications of genetics include:

Hereditary disease, diagnostics (virus detection, prosecution, and forensic science, and research/discovery.

Societal applications of genetics include:

Food safety and bioethics.

Science applications of genetics include:

Evolution and model organisms.

The central dogma of molecular genetics:

• DNA > DNA = Replication

• DNA > RNA = Transcription

• RNA > Protein = Translation

DNA > DNA =

Replication.

DNA > RNA =

Transcription.

RNA > Protein =

Translation.

In 1910, scientists understood that:

• Genes and mutations in genes affected phenotype.

• The one-gene-one-enzyme hypothesis.

• Genes reside on chromosomes.

• Chromosomes consist of DNA and protein.

True/False: Genetic material does not need to allow faithful replication.

False.

Genetic material must:

1. Allow faithful replication.

2. Must have informational content.

3. Must be able to occasionally change.

True/False: Genetic material does not have to change.

False.

What experiments determined DNA was the genetic material?

The Griffith Experiments (1928) using Streptococcus pneumoniae.

In the Griffith Experiments (1928) using Streptococcus pneumonia, what did the S-strain that was heat killed do to the mice?

The mice live.

In the Griffith Experiments (1928) using Streptococcus pneumonia, what did the S-strain that was heat killed do to the mice when paired with R-strain live cells?

The mice die.

Transformation:

The directed modification of a genome by the external application of DNA from a cell of a different genotype.

In Griffith’s experiments (1928), what was the identity of the “transforming” substance?

DNA.

In Griffith’s experiments (1928), the S-type strain was _______ and _______.

Smooth, virulent.

In Griffith’s experiments (1928), the R-type strain was _______ and _______.

Rough, a-virulent.

What did the Hershey–Chase experiment demonstrate?

DNA is the genetic material that carries instructions for making new viruses.

How did Hershey and Chase distinguish between viral DNA and protein?

They labeled DNA with phosphorus-32 and protein with sulfur-35.

Why were sulfur-35 and phosphorus-32 useful for identifying viral DNA and protein?

DNA contains phosphorus but no sulfur, while proteins contain sulfur but generally no phosphorus.

In the Hershey–Chase experiment, which viral component entered bacterial cells and directed the production of new viruses?

The viral DNA.

The structure of a nucleotide includes:

Phosphate, Sugar (deoxyribose), and a nitrogenous base.

The phosphate in a nucleotide gives DNA its _____ charge.

Negative.

Cleavage of triphosphate bonds provides what for DNA synthesis?

Energy.

Deoxyribose (sugar) is the link between ___________ and ___________.

Nitrogenous base, phosphate group.

In DNA, polymer 5’ and 3’ OH (hydroxyl) groups are used to:

Link adjacent bases.

Purines include:

Guanine, adenine.

Pyrimidines include:

Cytosine, Thymine, Uracil.

True/False: There are four types of DNA nucleotides.

True.

The primary structure of DNA is a:

Polymer of nucleotides joined by 5’ 3’ phosphodiester bonds.

The primary structure of DNA is a polymer of nucleotides joined by 5’ 3’ phosphodiester bonds, and have 5’-3’ polarity that is ________ charged.

Negatively.

Erwin Chargaff’s rules of base composition:

(T + C) = (A + G), A = T, G = C

True/False: In Erwin Chargaff’s rules of base composition, A + T = C +G

False.

Equivalence rule:

(A = T, G = C). There is a species-specific A +T/C+G ratio.

Rosalind Franklin’s DNA X-ray showed that DNA was:

Helical.

Who solved the structure of DNA?

Watson and Crick.

True/False: The genetic material must have informational content.

True.

In base pairing with DNA, a pyrimidine plus a pyrimidine meant that:

DNA was too thin.

In base pairing with DNA, a purine plus a purine meant that:

DNA was too thick.

In base pairing with DNA, a purine plus a pyrimidine meant that:

The thickness was compatible with X-ray data.

Which was not a conclusion of Watson and Crick?

DNA is a triple helix composed of three nucleotide chains held together by a complementary pairing of nitrogenous bases via hydrogen bonds.

The cell cycle:

Coordination of DNA replication with cell division.

In 1958, Meselson and Stahl developed methods to:

Differentially label and separate original DNA strands from newly synthesized strands.

DNA is copied by ________ replication.

Semiconservative.

This image shows:

A bacterial chromosome after one round of replication.

This image shows:

A bacterial chromosome after during the second round of replication.

DnaA protein:

Binds to DnaA boxes and begins to unwind DNA.

DnaB protein (helicase):

Unwinds DNA in both directions to form the replication fork.

Topoisomerase (gyrase):

Removes twists and supercoils.

Replication fork:

Point at which DNA unwinds to allow replication.

Prokaryotic and eukaryotic replication is ______.

Conserved.

In DNA replication, the parental strand is used as:

A template for deciding what nucleotides should be added next.

In DNA replication, the leading and lagging strand synthesis of complimentary strands ultimately results in:

Semiconservative replication.

The direction of DNA replication always proceeds in a 5’ to 3’ direction.

Template strands are the DNA that is to be:

Replicated.

In DNA replication, the leading strand gets replicated _________ in the 5’ to 3’ direction.

Continuously.

In DNA replication, the lagging strand gets replicated _________ in the 5’ to 3’ direction.

In segments.

Okazaki fragments:

Fragments of replicated DNA on the lagging strand.

Helicase:

Disrupts hydrogen bonds between the two (2) DNA strands.

SSB proteins:

Single-stranded binding proteins.

Primase:

Initiates a short strand of RNA complementary to DNA

DNA ligase:

Joins the DNA fragments after pol III replaces primer RNA sequence with DNA.

Topoisomerase:

Cuts and rotates DNA to remove coiling that is introduced as DNA unwinds.

True/False: DNA gyrase is a topoisomerase.

True.

DNA polymerase:

• Enzymes that link nucleotides in a specific order, using single-stranded DNA as a template.

• Pol III - replication function, 5’ to 3’ direction.

• Pol I - replication and repair function.

Pol III holoenzymes include:

• 2 pol III units.

• 2 B clamps.

• Accessory proteins.

How many DNA replication origins in humans?

Up to 100,000.

What is the main difference between the leading and lagging strands during DNA replication?

The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments.

Why must DNA unwind during replication?

To allow the template strands to become accessible so they can be copied.

Why must tension caused by DNA unwinding be relieved during replication?

To prevent excessive twisting and strain ahead of the replication fork.

Why is a free 3′ OH (hydroxyl) group necessary during DNA replication?

It provides the site where the next nucleotide is added to the growing DNA strand.

What is the origin of replication?

The location where DNA replication begins.

True/False: The ability of large genomes to rapidly replicate is due to the presence of thousands or origins of replication.

True.

True/False: Single nucleotide polymorphisms (SNPs) are used as a tool in molecular genetics for the genetic analysis of traits across a wide range of mammalian, plant, bacterial, and genetic studies.

True.

which of the following is true for RNA compared to DNA?

All answers are correct.

In DNA replication, replication of the leading strand takes place in a smooth, _______ manner, while replication of the lagging strand occurs in a discontinuous manner due to the need for RNA primers.

Continuous.