Genomes & Yeast

Module for CAPS

Intracellular Processes Studied

Meiosis, Mitosis, DNA Replication, Cell Cycle, Protein Synthesis, etc.

Yeast

Unicelullar eukaryotes that are classified as fungi. They are model organisms that can be applied across many complex organisms due to their basic genetic structure. They can be found in nature and can be grown in a liquid culture or an agar plate if growth requirements are defined.

Auxotrophic

A mutant organism that reqires a particular nutrient in order to survive.

Haploid

one copy each of chromosome. There are 2 mating types: a or α.

Diploid

two copies of each chromosome

Analysis on Cells

analysis is done on colonies of cells rather than individual cells.

Model Organisms

• Reducing complexity

• Functional conservation

• Universal properties

• Easy to manipulate

• Short lifespan

• Cost-effective

• Widely and abudantly available

• Specific properties

Simplified Yeast Cell Cycle

Haploid (n): Germination of Spores, Developing mating cells, Mating haploid cells, Shmoos
Diploid: Zygote, Budded zygote, Diploid colony (mitosis), Formation of Ascus and Spores (meiosis)

Yeast can live as..

Haploid or diploid.

Evolution

The change in heritable characteristics of populations over successive generations (Phenotype). The change in allele frequencies over successive generation (Genotype).

Genes

Functional unit of heredity; responsible for the characteristics of organisms

Alleles

Specific versions of genes that an individual possesses.

Allele Frequencies

The relative proportions of each allele in a gene pool. Represented by decimals.

Phenotype

Observable physical characteristics an individual shows

Genotypes

The genetic characteristics that an individual possesses. They are responsible for the phenotype of an organism.

Mutation

Deviations in DNA that stray from the alleles commonly found in a population. They can create new alleles.

Gene pool

all the alleles found in a population

Population

group of individuals that share similar genes

Genetic Drift

Change in allele frequencies in a population due to its size. It results in loss of alleles and reduces variation in a population, this is called fixation.

Fixation occurs

quickly when a population size is small; slowly when a population size is large

Examples of Genetic Drift

Founder effect, Bottleneck effect

Founder effect

when a smaller population migrates away from a larger population to a new environment. Results in less genetic variation and different allele frequencies.

Bottleneck Effect

when the original population is affected by outside factors resulting in high mortality strikes in the population. Reduces geenetic variability and change in allele frequencies.

Selection

differential fitness as a result of heritable variation in a trait; causes beneficial alleles to increase in frequency. Genetic drift can “help” or “hinder”.

Fitness

measurable success in survival and reproduction

Karyotype

A display of all chromosomes from a cell

Exons

coding sequences of DNA

Introns

noncoding sequences of DNA

Aneuploidy

Deviation from the normal karyotype. An abnormal amount of chromosomes.

Euploidy

Normal karyotype; there is an exact multiple of haploid number of chromosomes

Why aneuploid cells are better at drug resistance than euploid cells:

They have genetic heterogeneity and are susceptible to genetic changes. The diversity in the number of chromosomes in the population of cancer cells increases their likeliness to develop drug resistance.

Chromothripsis

the complex rearrangement of one or a few select chromosomes after they break apart.

Chromosomal Instability (CIN)

Persistent role of chromosome mis-segregation which results in losses and gains randomly.

Cancer

Common human disease due to somatic aneuploidy.

Aneuploidy occurs..

when there are errors in the precise mechanisms to replicate cells

Hardy-Weinberg Equilibrium

Requirements:

• Random mating

• No natural selection

• No migration

• No mutation

• Large population