Genetic Inheritance Patterns Lecture 23

Lecture 23: The Patterns of Genetic Inheritance-1

• The lecture covers patterns of genetic inheritance, specifically pedigrees.
• A pedigree is a chart illustrating the genetic history of a family across several generations.
• Pedigrees are used to determine how traits are transmitted (including disease causes).
• Pedigrees predict the probability of offspring inheriting a trait.
• Pedigrees help identify whether a trait is dominant or recessive, and whether the gene is autosomal or X-linked.
• Pedigree construction involves symbols for males, females, mating, offspring (birth order), twins (monozygotic/dizygotic), pregnancies (affected/unaffected), marriage (consanguineous/normal), deceased individuals, and unknown sex.
• The proband (propositus) is the first person with a disease who seeks medical attention.

Types of Inheritance

• Mendelian inheritance patterns include: autosomal dominant, autosomal recessive, X-linked dominant, X-linked recessive, Y-linked.
• Non-Mendelian inheritance includes: imprinting, mitochondrial, multifactorial, sporadic, contiguous gene syndromes.

Complicating Factors

• Complicating factors influencing inheritance include: non-penetrance, new mutations, adult-onset conditions, consanguinity, and gene interactions.

Pedigree Evaluation

• Evaluate transmission patterns (vertical/horizontal).
• Analyze the ratio of affected males to females.
• Determine if the disease/gene is passed through unaffected individuals, and male to male transmissions.
• Calculate the percentage of affected children.

Vocabulary

• Character: heritable feature
• Trait: each variant for a character
• Monohybrid cross: inheritance of a single character
• P generation: parental generation
• F1 generation: first filial generation (offspring of P generation)
• F2 generation: second filial generation (offspring of F1 generation)
• Punnett square: illustrates how affected parents transmit normal/disease genes to offspring
• Allele: alternate version of a gene
• Dominant allele: expressed in heterozygotes
• Recessive allele: not expressed in heterozygotes
• Homozygote: pair of identical alleles
• Homozygous dominant: BB
• Homozygous recessive: bb
• Heterozygote: two different alleles (Bb)
• Genotype: genetic makeup
• Phenotype: appearance of an organism

Autosomal Dominant Inheritance

• One copy of a dominant allele expresses a trait.
• The gene is located on one of the 22 autosomes.
• Affected individuals typically have an affected parent.
• Both sexes are equally likely to be affected.
• Roughly 50% of offspring from an affected individual are also affected.
• Examples include Huntington's disease, achondroplastic dysplasia, and neurofibromatosis.
• This type of inheritance displays a vertical pattern of affected generations.

Autosomal Recessive Inheritance

• Two copies of a recessive allele are needed for the trait to be expressed.
• Both parents are carriers or heterozygous.
• Affected offspring may have unaffected parents.
• Trait can skip generations.
• Males and females are equally affected.

X-linked Recessive Inheritance

• Gene is located on the X chromosome.
• Men are more affected than women.

This quiz explores the patterns of genetic inheritance as covered in Lecture 23, focusing on the construction and interpretation of pedigrees. Learn how these charts help determine trait transmission, inheritance probabilities, and the type of genetic traits involved. Delve into Mendelian and non-Mendelian inheritance patterns to deepen your understanding of genetics.