Eukaryote exam qs Flashcards
What are clamp connections?
Clamp connections are in the sexual reproduction of basidomycetes. Clamp connections ensure that the nucleus from both mating strands are in the septated hyphae.
What is the role of cAMP in sexual cycle of dictyostelium?
In the sexual cycle, clumped cells of dictyostellium release cAMP attracting more cells, many of which are digested as a diploid zygote. This turns into multiple haploid amoebae
What is the role of cAMP in asexual cycle of dictyostelium?
When bacteria supply is low, amoeba emit cAMP pulses to attract other amoeba, they then join to create reaction centres, they get bigger and bigger and then form into slugs. This is amoeba aggregation
Describe how green algae move towards light
They contain eyespots. Eyespots contain photoreceptors and a reflected surface on the inside of the cell. When light is detected by eyespot this leads to opening of calcium channels and increase in calcium conc intracellularly. The high calcium makes the flagella away from the eyespot beat stronger and turn algae towards the light.
What are mating type loci?
Mating type loci contain genes which are required for mating. Mating loci prevent same mating strains to mate. The two strains that want to mate have to have the different mating type loci genes A and B. The A genes code for pheremone proteins and B genes encode for pheromone receptors. Formation of dikaryotic mycellium will only occur when pheromone receptors are bound.
What is the purpose of the dictyostelium enzymes that degrade cyclic AMP?
The cells degrade the cAMP because saturation of cAMP can result in loss of direction so cells cant connect with other cells
What are asci?
Asci are sacs which contain ascospores (4/8). They are formed in sexual reproduction. The ascospores are formed through meiosis and mitosis and the asci disperse them so they can grow elsewhere.
How did algae acquire photosynthesis
Cyanobacteria became first endosymionts and then evolved into chloroplasts. Eukaryotes ingest and then digest chloroplast containing eukaryotes and retain the chloroplasts. The chloroplasts adapt to the new life in host and become permanent organelles.
Describe importance of chemotaxis to dictyostellium
When amoeba are haploid, they feed on bacteria, positive chemotaxis towards folic acid allows amoeba to track bacteria. When sufficient bacteria is available, negative chemotaxi is used to repel amoeba away from eachother.
How do hyphae obtain resources when they grow on agar
Digestive enzymes are released from the hyphae tips into medium and these diffuse and break down nutrients and then absorbed through the hyphae tip, digested and converted into biomass and extended from tip (branching)
How do hyphae obtain resources when they grow upwards into the air
Evaporation of water at the tip of the aerial hyphae generates a water flow, carrying nutrients to their tips
What are contractile vacuoles
Contractile vacuoles are an alternative means of protection against osmotic pressure (to cell wall). Contractile vacuoles have a higher osmotic pressure than the cytoplasm so water is attracted to the higher osmotic pressure the contractile vacuole expands as it absorbs the water and then contracts and expels the water.
Describe the tetrad analysis for determining distance between genes
The more distant two loci are the more likely a crossing event will occur between them. This means that the frequency of recombination between pairs of genes can be used to determine the physical distance between genes.
What is the main function of ATPase in cytoplasmic membrane of fungi?
Helps with nutrient uptake as nutrient uptake is driven by the proton motive force which is generated through atpases through excrusion of protons.
What happens to the contractile vacuole when an amoeba is placed in a medium with high osmolarity and the medium osmolarity starts to decrease?
Decreasing osmolarity means increasing the water concentration extracellularly, and due to osmosis (water moves from high to low conc) this means water enters amoeba. This makes the contractile vacuole swell as it absorbs this excess water to prevent cell lysis and then contracts and expels the water.
