Different modes of inheritance

Autosomal Dominant Inheritance

Mechanism

Autosomal dominant inheritance refers to conditions or traits for which having a mutation on one copy of the causative gene is sufficient to develop the phenotype. This is either because the amount of protein produced is insufficient for normal function, or the mutated gene produces a novel protein that has a new and deleterious function.

Pedigree

http://www.urdutehzeb.com/bssr/image...nant_small.jpg

Autosomal Recessive Inheritance

Mechanism

Autosomal recessive inheritance refers to conditions in which both copies of the gene must carry mutations to produce the phenotype. A person with only one mutation does not exhibit the trait, because enough normal protein is made by the normal copy to carry out needed functions. These individuals are called carriers.
Pedigree

http://www.urdutehzeb.com/bssr/image.../recessive.jpg

X- Linked Inheritance

Mechanism

X-linked inheritance refers to conditions or traits that are caused by changes in genes found on the X chromosome. The X and Y chromosomes determine an individual’s sex; males have one X chromosome and one Y chromosome, while females have two X chromosomes. The genes on the X and Y chromosome are different. This means that males have only one copy of each of the genes found on the X chromosome, while females have two copies. Women who carry one copy of an X-linked mutation are called carriers. In most females, having one normal copy of the gene may be sufficient to prevent symptoms altogether. Alternatively, a female may have such mild symptoms that she is never recognized as affected.
Pedigree

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Complex Inheritance

Mechanism

Complex inheritance means that many factors, usually a combination of genes and environment, are involved in causing a health problem or trait. These types of traits often occur in multiple family members because families share environmental and genetic factors. Most common, chronic diseases such as heart disease and diabetes are complex, as are many non-disease traits, including height. The chance of developing a complex trait depends on several factors, including:

• The number of relatives affected with a condition (or related conditions)
• How closely one is related to the affected individual(s)
• Similarity of the shared environment
• The location of disease or body system involved
• Severity of the condition in the affected relative
• The age at onset in the affected family member
• The sex of the affected family member

Pedigree

http://www.urdutehzeb.com/bssr/image...ifactorial.jpg