ANSCI 361 1st Edition Lecture 20 Outline of Last Lecture N/AOutline of Current Lecture I. Pedigree Diagramsa. Recessivei. X-Linkedb. Dominanti. X-LinkedII. mtDNAIII. Threshold EffectIV. WoodlandsCurrent Lecture- Male ☐- Affected Male - Female - Affected Female Characteristics of Recessive Phenotypes- Disorder may skip generations- All offspring of two affected parents are affected- ~Equal number of affected males & females- If rare disordero Most affected individuals have two normal parentso Frequency of affected offspring is 1/4 in such matingso Genetic relationship between normal parents of affected offspring is greater thanbetween normal parents without affected offspringCharacteristics of Dominant Phenotypes- Disorder does not skip generations- Every affected offspring has at least one affected parentThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Normal offspring from affected parents produce only normal offspring when mated with other normal’s- Approximately equal numbers of affected males & females- If disorder is lethal, it will be very rareCharacteristics of X-Linked Dominant- Affected males transmit disorder to all daughters and no sons- If disorder is infrequent, affected females transmit disorder to half of sons and daughters- If disorder is infrequent, there will be ~ 2X affected females vs males in population- Affected offspring have at least one affected parentCharacteristics of X-Linked Recessive- Disorder may skip generations- All offspring of two affected parents are affected- Incidence in females is lower than in maleso Incidence in males squared- If rare disordero Most affecteds are male and have two normal parentso Affected males mated to normal females will have no affected offspring, though all daughters are carrierso Affected females mated to normal males will have all affected sons and no affected daughters, all daughters will be carriersCharacteristics of mtDNA Disorder- Males and females affected- Sporadic, with different manifestations in affected individuals- Mothers may or may not show symptoms of disease- Pattern of transmission is non-Mendelian- Three differences distinguish diseases caused by mtDNA mutations from Mendelian diseaseso Maternal inheritanceo Heteroplasmy A combination of wild-type and mutant mitochondria at the level of a single cello Threshold effectHeteroplasmy- Single cell has a combination of mutant and wild-type mitochondria- Dividing cells unevenly distribute mutant mitochondria- A critical number of mutant mitochondria in a cell results in a disease phenotypeThreshold Effect- Different tissues have different energy requirements- Cell types consuming greater amounts of energy will be more sensitive to mutated mitochondriao Example: The brain is more sensitive to mitochondrial mutations than the liver because of the brain’s higher energy requirements The brain is said to have a lower thresholdWoodlands- X-linked- Maternally imprintedo Only expressed upon paternal inheritance from carrier males that were offspring of nonexpressing, carrier
View Full Document