Table of contents
- 1. Introduction to Genetics51m
- 2. Mendel's Laws of Inheritance3h 37m
- 3. Extensions to Mendelian Inheritance2h 41m
- 4. Genetic Mapping and Linkage2h 28m
- 5. Genetics of Bacteria and Viruses1h 21m
- 6. Chromosomal Variation1h 48m
- 7. DNA and Chromosome Structure56m
- 8. DNA Replication1h 10m
- 9. Mitosis and Meiosis1h 34m
- 10. Transcription1h 0m
- 11. Translation58m
- 12. Gene Regulation in Prokaryotes1h 19m
- 13. Gene Regulation in Eukaryotes44m
- 14. Genetic Control of Development44m
- 15. Genomes and Genomics1h 50m
- 16. Transposable Elements47m
- 17. Mutation, Repair, and Recombination1h 6m
- 18. Molecular Genetic Tools19m
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
2. Mendel's Laws of Inheritance
Pedigrees
3:51 minutes
Problem 19b
Textbook Question
Textbook QuestionResearchers examined a family with an interesting distribution of Leigh syndrome symptoms. In this disorder, individuals may show a progressive loss of motor function (ataxia, A) with peripheral neuropathy (PN, meaning impairment of the peripheral nerves). A mitochondrial DNA (mtDNA) mutation that reduces ATPase activity was identified in various tissues of affected individuals. The accompanying table summarizes the presence of symptoms in an extended family.
Person Condition Percent Mitochondria with
Mutation
Proband A and PN >90%
Brother A and PN >90%
Brother Asymptomatic 17%
Mother PN 86%
Maternal uncle PN 85%
Maternal cousin A and PN 90%
Maternal cousin A and PN 91%
Maternal Asymptomatic 56%
grandmother
In what way does a condition caused by mtDNA differ in expression and transmission from a mutation that causes albinism?
Verified Solution
This video solution was recommended by our tutors as helpful for the problem above
Video duration:
3mPlay a video:
Was this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Mitochondrial Inheritance
Mitochondrial inheritance refers to the transmission of genetic material found in mitochondria, which is passed exclusively from mother to offspring. This type of inheritance can lead to conditions like Leigh syndrome, where symptoms may vary among family members due to the proportion of mutated mtDNA in their cells. Unlike nuclear DNA, which follows Mendelian inheritance patterns, mitochondrial DNA mutations can result in variable expressivity and incomplete penetrance.
Recommended video:
Guided course
05:13
Organelle Inheritance
Variable Expressivity
Variable expressivity is a phenomenon where individuals with the same genetic mutation exhibit different symptoms or severity of a condition. In the case of Leigh syndrome, some family members may show significant symptoms like ataxia and peripheral neuropathy, while others may be asymptomatic despite carrying the same mtDNA mutation. This variability can be influenced by factors such as the percentage of mutated mitochondria in different tissues and environmental influences.
Recommended video:
Guided course
02:09
Penetrance and Expressivity
Albinism and Nuclear Inheritance
Albinism is typically caused by mutations in nuclear DNA that affect melanin production, and it follows Mendelian inheritance patterns. Unlike mitochondrial disorders, albinism can be inherited from either parent and usually presents consistently among affected individuals. This contrast highlights the differences in expression and transmission between conditions caused by mtDNA mutations, which can show variable symptoms and maternal inheritance, versus those caused by nuclear DNA mutations, which follow more predictable inheritance patterns.
Recommended video:
Guided course
05:13
Organelle Inheritance
Watch next
Master Pedigree Symbols with a bite sized video explanation from Kylia Goodner
Start learning