Bio 141 - Lecture 11 - Pedigrees and probability

Describe and explain the autosomal recessive pattern of inheritance

• usually appears equally in males and females

• tends to skip generations due to carriers who do not express the trait

• requires both parents to pass on the recessive allele for the trait to be expressed in the offspring

Define and explain the autosomal dominant pattern of inheritance

• appears equally in males and females

• unaffected persons do no have the trait and cannot pass it on

• only one affected parent is needed to pass the dominant allele for the trait to be expressed in the offspring

Define and explain the X-linked recessive pattern of inheritance

• more commonly expressed in males due to the presence of only one X chromosome

• females can be carriers without expressing the trait if they have one normal X chromosome

• trait can skip generations, often appearing in sons of female carriers

Define and explain the X-linked dominant pattern of inheritance

• traits don’t skip generations

• affected males pass the trait on to all of their daughters and none of their sons

• affected females (if heterozygous) pass the trait on to around 50% of their offspring, regardless of sex

Define and explain the Y-linked pattern of inheritance

• traits transmitted in an exclusively male-to-male pattern

• mammals have less than 50 genes on the Y chromosome; those genes likely play roles in male sex determination or development

• genes of human Y chromosomes do not have a copy on the X chromosome

• all male offspring of an affected male are affected

Define and explain the mitochondrial pattern of inheritance

• only inherited from the mother

• if a female has a mitochondrial trait, all of her offspring inherit it

• if a male has a mitochondrial trait, none of his offspring inherit it

• only one allele is present in each individual, so dominance is not an issue

How do you construct and analyze a pedigree to determine the possible modes of inheritance?

You construct a pedigree by mapping out family relationships and noting the presence or absence of traits across generations. By analyzing patterns, such as affected individuals and their connections, you can infer the mode of inheritance

How would you explain why a mode was discluded?

You can explain the exclusion of a mode by examining the inheritance patterns observed in the pedigree. if a trait skips generations, is present in both sexes equally, or appears in male offspring only from affected fathers

How would you determine the most likely genotypes for individuals on a pedigree based on known information?

You analyze the inheritance patters of the traits and use known phenotypes to infer genotypes. consider factors such as dominant and recessive traits, the presence of affected or unaffected individuals, and the possibility of carriers to deduce the genetic makeup of individuals

How would you calculate the probability offspring will be affected for autosomal recessive traits?

First determine the genotypes of the parents. If both parents are carriers (heterozygous), there is a 25% chance for each child to inherit the recessive trait. If one parent is affected (homozygous recessive) and the other is a carrier, the likelihood is 50%

How would you calculate the probability offspring will be affected for autosomal dominant traits?

Consider the genotypes of the parents. If one parent is affected (heterozygous) and the other is unaffected (homozygous recessive), there is a 50% chance that the child will inherit the dominant allele and express the trait

How do you use pedigree analysis to determine the probability of an individual carrying or developing a certain issue?

Pedigree analysis allows you to track the inheritance patterns through generations, helping to assess the likelihood of an individual being a carrier or developing a specific genetic condition. By examining known affected and unaffected individuals, and considering the genetic contributions from ancestors, you can estimate probabilities for carriers and affected individuals