Mitochondrial DNA and Traits

Mitochondrial DNA

• Mitochondrial DNA (mtDNA) is a short genome found in mitochondria.
• It may have originated from a time when mitochondria were free-living organisms.
• mtDNA is identical between a mother and her child, allowing for tracing maternal lineages.
• Sperm contribute only nuclear DNA during fertilization.

Mitochondrial Traits

• Kearns-Sayre syndrome: Short stature and retinal degeneration.
• Leber optic atrophy (LHON): Vision loss in the center of the visual field, usually occurring in adulthood.
• MELAS syndrome: Episodes of vomiting, seizures, and stroke-like symptoms.
• MERRF syndrome: Deficiencies in enzyme complexes related to energy transfer.
• Oncocytoma: Benign kidney tumors.

Mutations

• Genomes are not constant; they change. Changes in DNA sequence can occur in people, across species, etc.
• Mutations happen from time to time.
• Mutations in body cells are called somatic mutations (non-sex cells).
• Only mutations in reproductive cells (germline mutations) are passed to offspring.

Causes of Mutations

• Some mutations occur naturally (spontaneous).
• These spontaneous mutations can arise from incorrect base pairings during DNA replication.
• Mutagens are substances that cause mutations.

Point/Base Substitutions and Frameshift Mutations

• Point mutations are changes in single DNA bases.
• Silent mutations do not affect the resulting amino acid.
• Missense mutations change an amino acid.
• Nonsense mutations create a premature stop codon, halting protein production.
• Frameshift mutations result from the insertion or deletion of a base pair, altering the reading frame.

Mutations and Variation

• Genetic variation is a result of mutations.
• DNA changes are the only source of inheritable variation.
• Variation may become an adaptation if environmental changes favor the variation.

Errors and Mutations

• Despite 3 billion base pairs in DNA, mistakes during replication are infrequent.
• "Proofreading" enzymes identify and repair mismatched base pairs.

Oncogenes

• Oncogenes are cancer-causing genes, typically inactive in normal cells.
• They become active when they mutate.
• Oncogenes can cause uncontrolled cell division.
• Ras is a common oncogene, found in various cancers.
• Oncogene activation can result from changes in regulator or structural genes.

Gene Recombination/DNA Tech

• Recombinant DNA technology manipulates genes across or within species.
• Restriction and ligase enzymes are used.
• Genes are inserted into small organisms (like bacteria or yeast) for study.

Restriction Enzymes

• Restriction enzymes, like EcoRI, cut DNA at specific sites.
• These sites have "sticky ends" which can bond with complementary sticky ends created by other restriction enzymes.

Explore the fascinating world of mitochondrial DNA and its implications in genetics. This quiz covers the origin of mtDNA, various mitochondrial traits, and the significance of mutations in DNA. Test your knowledge on conditions associated with mitochondrial dysfunction and inheritance patterns.