Unit 14 - gene expression and water potential

gene expression

the mechanism that allows information in genes to have effects on phenotype (transcription —> translation —> protein function)

phenotype

the physical expression of genotype

promoters

sequences of DNA where RNA polymerase binds to begin transcription

enhancers

region where activator proteins bind, promoting transcription to occur

silencers

base sequences that inhibit transcription

transcription factors

proteins that influence transcription by either binding to the promoter or to the enhancers/silencers.

mRNA degradation in relation to gene expression

The presence of mRNA influences gene expression because if it is active within the cell, it is more likely to be translated.

forms of mRNA degradation

• shortening of poly-A-tail

• the activity of nucleases (enzymes that degrade mRNA)

• cellular stress

epigenesis

how cells and organisms differentiate through interactions between DNA and environmental factors.

epigenetic tags

chemical modifications that cause some genes to be expressed or not (it doesn’t edit the gene itself).

how do cells differentiate?

Not all genes are expressed in a cell. Cells ________ through the expression of certain genes.

genome

all of the DNA sequences in an individual

transcriptome

All of the transcribed RNA in an individual

proteome

all of the protein that is made in an individual

examples of epigenetic tags

1. methylation = methyl groups added to specific nucleic bases (ex. cytosine) in the promoter region of DNA. This represses transcription, reducing gene expression.

2. amino acids in histones can either be methylated or acetylated and this can either repress or activate transcription.

Epigenetic inheritance

The _______ of non-genetic information that can influence gene expression and phenotype traits.

what happens to epigenetic tags after fertilization?

most epigenetic tags are removed, resetting the epigenetics of the individual and this allows for new epigenetic modifications to occur.

Imprinted genes

only 1%of mammalian genes retain their epigenetic tags and are passed down to offspring. These can cause disruptions to typical genetic inheritance if a dominant allele is silenced by imprinting.

example of environmental effect on gene expression

Air pollution decreases methylation, which enhances the transcription of genes. This allows more genes to be expressed, but these genes can increase rates of asthma, heart attack, and disorders during gestation.

Solvation

the interaction between a solvent (often water) with a dissolved solute.

Solvent polarity

Determines how well a solvent dissolves a particular solute.

why is water a good solvent?

It is a ______ _________ because it is a polar molecule, therefore it dissolves polar/ionic solutes easily. The partial positive and negative sides of water are attracted to the positive and negative ions within the ionic compound, helping to breaking it up and fully dissolving.

Hydration shells

water forming a ring around an ionic particle from a solute in order to prevent the solute from reforming.

Osmosis

The passive movement of water across a semipermeable membrane towards areas of high [solute].

Isotonic

A solution that has the same solute concentration as the compared object.

Hypertonic

A solution that has a higher solute concentration than the compared object (water tends to leave that object and go towards the solution).

Hypotonic

A solution that has a lower concentration than the compared object (water tends to flow towards the object).

Osmolarity

The total solute concentration in a cell. This can be calculated by putting different types of tissues in solutions and calculate the %changes.

What happens when an animal cell is placed in a hypotonic solution?

The cell bursts because it doesn’t have a rigid cell wall or any other structure that prevents the intake of water.

What structure does paramecium have to prevent cell lysis?

The _______ have what is called a contractile vacuole that controls the intake of water and can remove excess water, preventing cell lysis.

Turgid

The amount of internal pressure that the cell (and the cell wall) feels due to the amount of water (happens when placed in hypotonic solutions).

Plasmolysis

The result of a plant cell being placed in a hypertonic solution and causes the cell membrane to shrink away from the cell wall and leads to cell/plant death.

medical applications of isotonic solutions

• saline used in medical procedures, such as bathing transplant organs

• IV drips containing saline solutions

• contact lense solutions

• eye drops

• nasal irrigations/washes

• keeps areas of damaged skin moistured prior to skin grafts

Water potential

the potential energy per unit volume relative to pure water. It is used to quantify the tendency of water to move from dilute to [ ] solutions due to osmosis.

Water potential formula

solute potential + pressure potential = water potential

Solute potential

The attraction of water molecules to solute particles, which, when present, reduces the number of free water molecules and limits the movement of water.

Dissolving a solute in water lowers the water potential.

The range is from zero downards.

Movement of water (in relation to W)

Water moves from areas of high water potential to areas of low water potential.

Pressure potential

The physical _____ exerted on systems. Hydrostatic _____ changes the potential energy of water.