Bio 241 Lecture 32: Organelles

Organelle chromosomes have mechanisms to ensure daughter cells inherit the correct number of what?

# of chromosomes

Do non-nuclear chromosomes obey mendelian genetics?

Nope

T/F Mitochondria produce energy through oxidative phosphorylation and contain their own small genome

T

Mitochondrial dysfunction is often linked to what kind of disorders? Give an example and its key biological characteristic.

Neurodegenerative

Parkinson's disease is caused by the loss of dopaminergic neurons

Mitochondria undergo (aerobic/anaerobic) metabolism

Aerobic

How many bp of DNA is in the human mitochondrial genome? How many genes?

~17,000 bp

37 genes

T/F Nearly 100% of the mitochondrial proteins are encoded by mitochondrial genes

F - mitochondrial proteins are mainly encoded by nuclear genes

Mitochondrial DNA is (linear/circular) and encoded what functions?

Circular

Only mitochondrial functions

Why would a cell have thousands of mitochondrial genomes?

It had thousands of mitochondria

What is the endosymbiotic theory?

An anaerobic bacteria engulfed a aerobic bacteria. Aerobic bacteria became the mitochondria/chloroplast.

What 4 things are similar enough in bacteria and mitochondria to support the endosymbiotic theory?

Lipid composition

Genome structure

Protein synthesis

rRNAs

What is unique about yeast mitochondria contribution compared to humans?

Yeast inherit mitochondria DNA from both parents because yeast don't have sperm

In humans, mitochondrial dysfunction is solely (maternal/paternal)

Maternal

T/F Yeast can either be haploid or diploid

T

Petite yeast mutants are due to defective what?

Defective mitochondrial function

Segregational yeast mutant is caused how and results in what?

Mutation in nuclear gene for mitochondrial function

2 petite, 2 normal yeast

Neutral yeast mutant is caused how and results in what?

Loss of function of mitochondrial gene

4 normal yeast

Suppressive yeast mutation is caused how and results in what?

Large deletion in mitochondrial genome

4 petite yeast

Sporulation meiosis from a diploid yeast zygote results in what?

4 haploid yeast ascospores

What is mtDNA

Mitochondrial DNA

Mitochondrial DNA is inherited how in humans

Maternally

What does MERRF stand for?

Symptoms?

Cause?

Myoclonic epilepsy and ragged red fiber disease

Ataxia, deafness, dementia, epileptic seizures

Muscle fibers have red patches from proliferation of abnormal mitochondria

T/F Mitochondrial genomes typically vary greatly within a single person

F - generally consistent within a person between mitochondria

What is homoplasmy?

Uniform population of organelle genotypes within cell/individual

What is heteroplasmy?

NON-uniform population of organelle genotypes within a cell/individual

What determines the severity of the MERRF phenotype?

Proportion of mutant mitochondria

Which tissues are least tolerant to mutant mitochondria?

Brain, heart

When would the skin or skeletal muscle be affected by mitochondrial dysfunction?

When the proportion of WT mitochondrial is greatly reduced

What is a maternal effect gene?

Made by the mother and required for egg development

What are the two components of a maternal effect gene?

Maternal component and embryonic component

If gene X is a maternal effect gene, describe the effect of the X-/X- genotype in a female?

How is this different from X-/X- in zygotic gene inheritance?

Sterile but viable female, her offspring would be lethal for lack of a functional egg

X-/X- would be recessive lethal and not viable at all

In the snail shell:

Right hand twist D for dextral is (dominant/recessive)

Left hand twist d for sinistral is (dominant/recessive)

Dominant

Recessive

What to remember about the maternal effect gene and snail shells

Offspring will have the phenotype of the mother regardless of their genotype

T/F a prion is a proteinaceous infectious particle that is highly resistant to inactivation

T

Mad cow disease is an example of what kind of disease?

A prion disease

Prions are resistant to what but sensitive to what?

Resistant to UV

Sensitive to proteases

If PrP^C is a normal protein and PrP^Sc is an infectious protein, how do they vary in genetic sequence and conformation

Same genetic sequence

PrP^Sc has disease folded conformation

What happens if you try to infect a mouse with a copy of a normal protein by inserting a prion copy?

The prion disease will spread to the mouse

What happens if you try to infect a mouse with a gene knockout by inserting a prion copy?

The mouse is resistant. A normal protein copy is required for prion infection

How does a prion protein propagate disease?

Prion protein converts normal protein into prion to propagate disease