Chapter 3: Model organisms and their Genomes

Question 1

Saccharomyces cerevisiae

Answer 1

Yeast Integrating plasmids (YIp): These plasmids lack an ORI and must be integrated directly into the host chromosome via homologous recombination.

Yeast Replicating plasmids (YRp): These vectors contain an Autonomously Replicating Sequence (ARS) derived from the yeast chromosome. As the name suggests, these vectors can replicate independently of the yeast chromosome; however, they tend to be unstable and may be lost during budding.

Yeast Centromere plasmids (YCp): These are considered low copy vectors and incorporate part of an ARS along with part of a centromere sequence (CEN). These vectors replicate as though they are small independent chromosomes and are thus typically found as a single copy. Unlike the ARS vectors, CEN vectors are stable without integration.

Question 2

C. elegans

Answer 2

Non-hazardous, non-infectious, non-pathogenic, non-parasitic organism.

It is small, growing to about 1 mm in length, and lives in the soil—especially rotting vegetation

Survives by feeding on microbes such as bacteria.

Question 3

C. elegans: Life cycle

Answer 3

3 days - 4 months (depending on if Bauer development occurs due to extreme starvation/environment)

Question 4

C. elegans: Mating

Answer 4

Modes of reproduction in C. elegans. C. elegans can reproduce either by self-fertilization in a hermaphrodite or by cross- fertilization between a male and a hermaphrodite.

Question 5

C. elegans: Cell lineage, cell differentiation decision

Answer 5

The cell lineages that produce the vulva in C. elegans hermaphrodites.

The C. elegans vulva is a hermaphrodite-specific ectodermal organ that develops post-embryonically and functions to connect the internal reproductive system with the external environment.

The vulva is required for mating, as males inject sperm through it, and for deposition of embryos after internal fertilization

The C. eleganshermaphrodite vulva is an established model system to study mechanisms of cell fate specification and tissue morphogenesis.

Question 6

C. elegans: Transgenic worms and microinjection

Question 7

C. elegans vulval development

Answer 7

It is an intensively studied example of animal organogenesis.

Involves a network of intercellular signaling, signal transduction, and transcriptional regulation underlies the precise formation of this organ.

A single cell of the somatic gonad, the anchor cell, organizes the development of the vulva from epidermal precursors as well as the physical connection of the epidermis with the uterus.

Signaling pathway:
WNT signaling acting via the HOX gene.

Question 8

Drosophila melanogaster

Question 9

Drosophila melanogaster: Life cycle

Answer 9

~ 9 days

Question 10

Drosophila melanogaster: The imaginal discs

Answer 10

Organs and limb development is pre-meditated

Question 11

Drosophila melanogaster: Polytene chromosomes

Answer 11

Chromosomes have multiple arms, the closed the gene is to the chromocenter the more likely it is to be less active/

Question 12

Drosophila melanogaster: The P element

Answer 12

Transposons can mobilize DNA
Used as transformation vectors

Question 13

Aradopsis thaliana: The life cycle

Answer 13

Seed –> seedling –> mature sporophyte –> spores –> mature gametophytes (embryo sac and pollen grain) –> double fertilization –> seed

Question 14

Aradopsis thaliana: Mating

Answer 14

Cross-pollination and self-pollination

Question 15

Aradopsis thaliana: The Ti plasmid of Agrobacterium tumefaciens

Answer 15

vir genes, RB, T-DNA, LB

Question 16

Aradopsis thaliana: Transformation of Arabidopsis using modified Ti plasmids

Answer 16

Ti plasmid –> Remove T-DNA –> Replace with gene of interest –> Transform plasmid into Agrobacterium –> Infect plant cell with bacteria – Plasmid transferred –> Gene of interest is inserted into plant chromosome

Question 17

Aradopsis thaliana: Development of Glyphosate-Resistant Soybean Crops

Answer 17

N-(phosphonomethyl glycine) is a broad-spectrum systemic herbicide and crop desiccant.

It is an organophosphorus compound, specifically a phosphonate, which acts by inhibiting the plant enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSP synthase).

It is used to kill weeds, especially annual broadleaf weeds and grasses that compete with crops.

It was discovered to be an herbicide by Monsanto chemist John E. Franz in 1970. Monsanto brought it to market for agricultural use in 1974 under the trade name Roundup. Monsanto’s last commercially relevant United States patent expired in 2000.

Question 18

Mus musculus