Lecture 44 – Lecture 45 Basic Patterns of Human Inheritance Ozgur Unal NIS - BIOLOGY Lecture 44 – Lecture 45 Basic Patterns of Human Inheritance Ozgur Unal

Basic Patterns of Human Inheritance How does the animal in the picture look? What is different in this animal from others of the same species? Do you find it beautiful? A genetic disorder is a disease that can pass from generation to generation. The animals in the pictures have a genetic disorder called albinism.

Recessive Genetic Disorders Remember recessive and dominant traits Example: Yellow seed color, Y, is dominant over green seed color, y. How about being homozygous and heterozygous for a trait? Example: Yy  heterozygous for seed color YY or yy  homozygous for seed color

Recessive Genetic Disorders Some genetic disorders exhibit themselves only if the individual is homozygous for that genetic disorder  recessive genetic disorder An individual who is heterozygous for a recessive disorder is called a carrier. Example: Albinism (A and a alleles) AA  Healthy individual Aa  Healthy individual who is a carrier aa  Albino

Recessive Genetic Disorders There are various recessive genetic disorders: Cystic Fibrosis Albinism Tay-Sachs Disease Galactosemia Cystic Fibrosis: Affects mucus producing glands, digestive enzymes and sweat glands Chloride ions are not absorbed into the cells of a person with cystic fibrosis, but are excreted in the sweat. Without sufficient Cl- in the cells, water does not diffuse from the cells  causes secretion of thick mucus that affects many areas in the body (pancreas, lung etc) Treatment: Physical therapy, medication, special diet etc.

Recessive Genetic Disorders Albinism: Absence of skin pigment melanin in the hair and eyes. A person with albinism has white hair, very pale skin, and pink pupils. The absence of pigment in eyes cause vision problems. Tay-Sachs Disease: Found on chromosome 15. Identified by a cherry red spot on the back of the eye. Seems to be predominant among Jews of the Eastern Europe descent. Absence of enzymes breaking down fatty acids called gangliosides. These fatty acids accumulate in the brain and cause mental deterioration.

Recessive Genetic Disorders Galactosemia: Inability to digest galactose. During the digestion of milk, lactose is broken down into glucose and galactose. Galactose is later broken into glucose by an enzyme called GALT. A person who lacks or has defective GALT cannot digest milk products.

Dominant Genetic Disorders Some genetic disorders are caused by dominant alleles  Dominant genetic disorder This means that those who do not have the disorder are homozygous for the recessive trait. Example: Huntington’s Disease Affects individuals between ages 30-50 (1 out of 10,000 people in the US) Symptoms include gradual loss of brain function, uncontrollable movements and emotional disturbances. H and h alleles: Hh and HH  Individuals that have the disease hh  healthy individuals

Dominant Genetic Disorders Another example of a dominant genetic disorder is achondroplasia  most common form of dwarfism A person with achondroplasia has a small body size and limbs that are comparatively short. Interestingly, 75 % of individuals with achondroplasia are born to parents with average size  indicates that the condition occured because of a new mutation ora genetic change. Why are recessive genetic disorders are more common than dominant genetic disorders?

Pedigrees A pedigree is a diagram that traces the inheritance of a particular trait through several generations. A pedigree uses symbols to illustrate inheritance of the trait. Males  squares Females  circles One who expresses the trait being studied is represented by a dark square/circle. One who does not express the trait is represented by an unfilled square/circle

Pedigrees A horizontal line between two symbols shows that these individuals are the parents of the offsprings listed below them. Offsprings are listen in descending order from left to right. A pedigree uses a numbering system: Roman numerals  generations Arabic numbers  individuals

Analyzing Pedigrees Check out and analyze Figure 11.2 Look at the figure below and analyze the phenotypes and genotypes. Check out and analyze Figure 11.3