Question 2

The survival of organisms depends on regulatory mechanisms at various levels. Chose THREE from the following examples. Explain how each is regulated.

The expression of a gene The activity of an enzyme The density of a population

The cell cycle The internal water balance of a plant

Each regulatory mechanism must be explained

For each of the first three examples given, there is an internal maximum of four points.

Gene expression Dominant/recessive = no points

operon structure / concept

DNA binding proteins (repressor)

inducer/corepressor

promoter /RNA polymerase

positive control(cyclic AMP, CAP)

sigma factor

attenuation

regulation can result in differentiation

methylation of DNA

7-methyl-guanidine cap/ poly A tail

RNA processing (splicing, snRNP,

introns/exons)

hormonal control (steroids, etc.)

gene amplification

inducers, enhancers, transcription factors

polyribosome

initiation factors

heterochromatin/euchromatin (puffs,

X-chromosome inactivation,

Barr bodies)

acetylation of H 1 histone

Elaboration (max 1 point)

oncogenes

dosage compensation

demonstration of complete cycle

antisense RNA

Enzyme activity

pH/Temp.optima of enzymes = no pts

proenzyme/zymogen---> enzyme

environmental pH

environmental temperature

cofactor/coenzymes

competitive inhibition

non-competitive inhibition

allosteric (feedback) modulation

cooperativity

degradation rates of enzymes

covalent modification/phosphorylation

substrate concentration

Elaboration (max 1 point)

Cell cycle Phases of cell cycle = no points

surface: volume ratio (size)

genome: cytoplasmic ratio

temperature

age

differentiation

contact inhibition

cyclin-Cdk (Maturation Promoting Factor)

hormones/growth factors

chalones/FTS (prokaryotes)

oncogenes/tumor suppressor genes/cancer

apoptosis (programmed cell death)

checkpoints

Elaboration (max 1 point)

telomerase

Internal Water Balance
accomplished by transpiration rate regulation
stomata/ guard cell
K+ pump/ active transport
abscisic acid control
adaptations that regulate transpiration
(hairs, cuticle, stomatal crypts; folded stems, root hairs, CAM, C-4)
seasonal leaf drop
wilting/leaf curl
pattern of root growth
solute accumulation creating H20 potential

Elaboration (max 1 point)

Population Density

density size growth

mortality rate (survivorship)

predation (predator/prey)

parasites/disease

intraspecific competition

interspecific competition

birth rate (natality)

r and K strategies

migration (opens seasonal habitat)

immigration/ emigration

density independent factors (fire, etc.)

carrying capacity (determined by resource availability)

Elaboration (max 1 point)