2016 Genetics Midterm Terminology- Yeast – Flashcards

Simple fungi, but more-so refer to a life-style than to a phylogenic classification, specifically the unicellular phase of the life cycles of many different fungi. More commonly is used to term fungi that have only a unicellular phase. "Saccharomyces cerevisiae"

Yeast can indeed be germs. This type of yeast can be contracted in those who have a weakened immune response and can become infectious. Ex: Those who have AIDS (weak immune system) can create this type of infectious yeast.

Yeast has the ability to remain a haploid or a diploid and therefor undergo both vegetative and sexual reproduction.

To grow in the presence of oxygen. Under these conditions, yeast can support growth by oxidizing simple carbon sources such as ethanol, acetate, or glycerol.

To grow in the absence of oxygen. Deprived of oxygen, yeast can only convert sugars to carbon dioxide and ethanol, recovering less energy.

Organisms with one set of chromosomes. Mutations can be studied most easily in these type of yeast cells and most of these mutations are recessive nonlethal.

Organisms with two set of chromosomes. Mutations can be studied (not as easily) in these type of yeast cells and most of these mutations are dominant.

[Vegetative Reproduction] During this, when the nucleus divides, one of the nuclei is transferred to the bud, and then the two cells separate. Then the cycle begins again for both cells= an exponential increase in the number of cells.

[Vegetative Reproduction] Both haploid and diploid cells divide by this. When it is initiated, the chromosomes of the parent replicate.

[Sexual Reproduction] The diploid yeast will sporulate under deprivation of either a carbon or nitrogen source. The diploid goes through this, producing four haploid nuclei, which are incorporated into ascospores, encapsulated in ascus. Within each ascus, two spores are A type and two spores are alpha type and they interchange parts which are distributed into the haploid nuclei= new genetic trait combinations.

[Sexual Reproduction] When pairs of chromosomes separate to give new combinations of genetic traits.

[Sexual Reproduction] Diploid yeast will do this when its nucleus goes through meiosis, producing four haploid nuclei, which are then incorporated into ascospores.

The area on which diploid cells undergo (or don't undergo) meiosis to create four haploid cells.

[Sexual Reproduction] This is a packaging step for the four haploids produced from meiosis and are stress-resistant.

[Sexual Reproduction] This is a packaging step for the four haploids produced from meiosis in which the ascospores are encapsulated.

[Sexual Reproduction] Within each ascus (and within ascospores), two spores are this mating type, while the other two are the other mating type. Neither of the two are simply a mutant form of the other. Each is a functional gene and all cells have both, but normally each haploid only expresses one of the two.

These are mating type genes that, in yeast, are known as A and Alpha. These sequences encode regulators of the two different haploid mating types and of the diploids formed by their conjugation.

[Sexual Reproduction] During meiosis, these chromosomes in the diploid nucleus interchange parts and are distributed into the haploid nuclei yielding new combinations of genetic traits.

Sexual conjugation happens between these cells that are produced by each parent.

The exchange of genetic material between homologous chromosomes. This occurs during meiosis.

The condition in which genes are present on the same chromosome, causing them to be inherited as a unit, provided that they are not separated by crossing over during meiosis.

This type of gamete contains a new combination of alleles produced by crossing over during meiosis. Radiation produces sublethal chromosomal changes and stimulates genetic __________.

The type of mating between gametes that results in the transition from haploid to diploid. When spores are returned to a nutritionally adequate environment, they germinate and undergo vegetative growth in a stable haploid phase.

[Sexual Reproduction] When cells of the opposite mating type are mixed, each type of cell secretes this, and in turn responds to this produced by the opposite mating type. The cells stop dividing after this is secreted and change their shape.

[Sexual Reproduction] The elongated and pear-shaped gametes after pheromone is secreted. These distinctive cells are termed this because of their resemblance to the mythical "Li'l Abner" comic strip. These of opposite mating type formed together to make a "peanut" shape with a central constriction.

[Sexual Reproduction] The two haploid nuclei within each joined shmoo pair fuse into a diploid nucleus, forming this. The diploid promptly buds at the constriction, forming a "clover leaf".

The unit of genetic information, encoded in DNA (or RNA in the case of some viruses, including those that cause AIDS) that specifies the composition of a protein and/or functional RNA molecule.

Eukaryotic genetic information that is encoded in the cell's genes.

Prokaryotic genetic information that is encoded in the cell's genes.

The information coded in the total DNA of an organism.

This type of diploid is different from either of the two haploids. It has a dominant and recessive allele.

This is the type of each of the four haploids. It has a dominant and dominant or recessive and recessive allele composition.

An allele (one alternative forms of a gene) that expresses a phenotypic effect even when heterozygous. Often, but not always, the wild-type allele is dominant over the mutant allele.

If the phenotype of a heterozygous diploid- one that carries different alleles of a gene- is intermediate between the respective homozygous phenotypes, they can be called this.

An allele (one alternative forms of a gene) that only expresses a phenotypic effect when homozygous. In a hetero-zygote, the allele is overridden by the dominant allele.

The interaction of non-allelic genes, such that the one gene influences or interferes with the expression of another gene. Ex: If a cell carries the functional allele of the Y gene and a mutant allele of the Z gene, that cell will have the red phenotype (a characteristic of the mutant Z allele) rather than the white phenotype of the Y allele. *The mutant Z allele is __________ to the Y allele. (Not dominant).

A mutant strain that requires the addition of a nutrient to the media for growth. Once this mutant type of strain is isolated and characterized, the presence or absence of the mutant gene can be defined by whether or not the cell requires that nutrient in the growth medium. Ex: Mutants that require adenine and those that require tryptophan.

A wild-type strain that is able to produce the nutrient without supplementation.

Adenine is also a component of this, which plays a central role in energy metabolism.

An auxotrophic mutant requires this to grow. This compound is one of the bases that forms the building blocks of nucleic acids. These mutants develop a pink or red color due to a buildup of the precursor AIR, which is converted to from a red pigment. Ex: HA1 or HA2

The describable, heritable characteristics of an organism, such as the color of some part of it. Can use virtually any describable characteristic, but some are more useful than others.

An auxotrophic mutant requires this to grow. Ex: HB1 or HB2

Experimental organisms that differ by a small number of well-defined, single-gene traits. By using these, we generate strains that have alternative forms of a gene.

The functioning wild-type genes that have a white phenotype.

The first two adenine-requiring mutants discovered that have a red phenotype. Ex: HA1 and HB1 are one mating type, while HA2 and HB2 are the other mating type.

Agar plate that contains yeast extract, peptone, dextrose, and sugar. Both of the haploid strains, HB1 and HA2 (red phenotype), can grow on this medium because nutrients are provided and create a white phenotype diploid.

Agar plate that contains minimal media with only minerals and vitamins. Neither of the haploid strains, HB1or HA2 (red phenotype), can grow on this nutritionally poor medium due to the lack of adenine and tryptophan. However, the diploid formed (white phenotype) from these two strains can grow on this plate.

__ (400-315 nm) & __ (315-280 nm) ***Human and Yeast cells repair most of this damage. ***These cells are resistant to these in sunlight. __ (280-200 nm) ***Most damaging to DNA is filtered out of the sunlight by ozone.

________ breaks are disastrous to the cell by preventing the DNA molecule from replicating. ________ breaks are less serious.

This formation results from concentrated energy that breaks double-strands. In this reaction, two of these adjacent formations in the same chain (T-T, C-C, or T-C) become covalently bonded together. These _______ disrupt the local structure of the DNA double helix and prevent normal DNA replication.

A type of reparation for radiation damage. This is the most efficient system in yeast: When UV-damaged cells are exposed to sunlight that has the UV wavelengths filtered out, a specific enzyme in the cell uses the energy from the visible part of the solar spectrum to reverse the reaction that produces pyrimidine dimers. If the dimers are repaired before the DNA tries to replicate, no damage is done.

In yeast, mutation of PHR1 gene results in production of this defective enzyme, leading to increase in UV sensitivity. Photoreactivation is used to fix this usually.

Week 1: Mating 2 Haploid Strains & Observing Zygotes *Yeast Strain cross HA2 (ade2) and HBT (trp) on YED. Week 2: Selecting for Diploids *Previous mixture replicated on MV plate. Week 3: Presporulation *Transfer previous diploid cells on YED plate. Week 4: Sporulating the Diploids *Move diploid cells on YEKAC plate to induce meiosis. Week 5: Observation of Asci and Germination of Spores *Sporulated cells from YEKAC in "sack" with 4 spores.

Week 1: Mating 2 Haploid Strands ***HA1 (ade1), HA2 (ade2), HB1 (ade1), and HB2 (ade2). Week 2: Selecting for Diploids ***Previous mixture replicated on MV plate. Week 3: Results **HA1, HA2, HB1, HB2= Red Colonies **HA1xHB1 and HA2xHB2= Red Colonies **HA1xHB2 and HA2xHB1= White Colonies

Week 1: Effect of Adenine Conc. on Color Formation ** HA2 (ade2) in liquid form on both YED and MV plate. **Both plates have adenine-impregnated paper disk. Week 2: Results **YED: Almost fully covered with red colonies. **MV: Red colonies grow as far as the adenine disk can provide for them, creating an adenine gradient circle.

Week 1: Irradiating HBT and UVS with UV ***4 YED plates containing HBT (trp) strain. ***4 YED plates containing UVS (UV sensitive) strain. Week 2: Results **HBT- High % survival rate due to repairs. **UVS- Low % survival rate due to UV sensitivity.

***They have simple nutritional needs. ***They can be maintained as a haploid/diploid for vegetative/sexual reproduction. ***Easy observable life cycles allow simple, concrete, direct observations.