Lecture 16 - Patterns of Genetic Variation Flashcards
Why is correct chromosomal segregation important?
To ensure accurate gene expression and proper cellular function, and to avoid pathological conditions and evolutionary drivers.
What is gene dosage?
The copy number of a gene influences the amount of corresponding RNA and protein, critical for maintaining proper cellular function.
What issues arise from unbalanced chromosomal segregation?
Pathological conditions, abnormal gene expression (e.g., 0.5× or 1.5× expression), and impacts on evolution.
How is expression on sex chromosomes compensated in XX or XY individuals?
Through epigenetic mechanisms like X-inactivation (e.g., DNA methylation and histone modifications) and dosage balancing.
Name a disease caused by chromosomal mis-segregation.
Down syndrome, caused by an extra copy of chromosome 21 (trisomy 21).
What are the impacts of chromosomal instability in cancer?
Aneuploidy, structural alterations, high mutation rates, and extensive dosage changes.
What is unique about chromosomal aneuploidy in plants?
Plants tolerate gene copy number variations better, facilitating evolution and adaptations.
What does “one-sided” inheritance refer to?
Mitochondrial DNA and Y chromosome inheritance are strictly maternal and paternal, respectively.
What are the mitochondrial Eve and Y-chromosomal Adam?
The most recent common ancestors for mitochondrial DNA and Y chromosomes in modern humans.
They are not the first humans but represent key lineage bottlenecks.
What are the three methods of DNA acquisition in bacteria?
Transduction (via viruses), conjugation (physical transfer), and transformation (uptake from the environment).
What are the main learning outcomes for understanding chromosomal segregation?
Describe key steps (and molecular players) involved in mitosis and meiosis.
Appraise the importance of correct chromosome segregation.
Identify the importance of crossovers and resulting recombination.
List differences in gametogenesis between sexes.
Compare mitosis and meiosis with fission and parasexual processes in bacteria.
Why is correct chromosomal segregation important?
Ensures proper gene expression.
Maintains balanced expression levels of genes.
Prevents unbalanced segregation, which can result in diseases or drive evolutionary change.
What is gene dosage, and why is it important?
Gene dosage refers to the copy number of a gene affecting RNA and protein production.
Proper dosage is critical for cellular function. Imbalances can cause disease or evolutionary changes.
What happens when chromosomal segregation goes wrong?
Mis-segregation can lead to conditions like cancer (chromosomal instability) or Down syndrome (trisomy 21).
It may also disrupt gene expression, metabolic pathways, and overall cellular function.
How do sex chromosomes achieve balanced gene expression?
Through epigenetic compensation mechanisms like X-inactivation in mammals, where one X chromosome in females is silenced.
Other strategies include adjusting expression from over- or under-represented chromosomes.
