Inheritance patterns

genetics

1. Inheritance patterns Recessive: expressed only when both chromosomes of a pair carry mutant alleles at a locus (2 mutant copies) Dominant: expressed when one chromosome of a pair carries a mutant allele at a locus (1 mutant copy)

2. Autosomal: on any of the other 22 chromosome pairs. Sex-linked: on the X or Y chromosomes

3. Autosomal Recessive Inheritance Autosomal recessive traits are only expressed in individuals who carry two mutant alleles inherited from each parent. Autosomal recessive traits usually arise in children of phenotypically normal parents.

4. Genotype and phenotype correlation with gene locus for an autosomal recessive trait

5. Segregation of an autosomal recessive trait in a pedigree

6. Autosomal recessive: increased incidence of parental consanguinity

7. Autosomal recessive inheritance Usually parents are heterozygous carriers Affected individuals are usually born to unaffected parents Affected children are homozygous for mutant gene In most autosomal recessive diseases males and females are equally likely to be affected Carrier couple has a 1 in 4 chance of having affected offspring There is an increased incidence of parental consanguinity

8. Oculocutaneous Albinism Lack of pigmentation Fair skin and hair Decreased visual acuity Lack of stereoscopic vision Mutations in the gene encoding Tyrosinase (lack of Melanin) on ch11q14.3 Long term sun exposure may predispose skin cancer known as melanoma.

9. Oculocutaneous Albinism This affects both male and female and is apparent from birth . Research indicates that OCA type1 occurs in 1 per 40,000 and OCA type2 1in 15,0000. OCA type 3 and OCA type 4 have not yet found. OCA type 2 is less severe than OCA type 1.

10. Cystic Fibrosis Cystic Fibrosis: a lethal autosomal recessive genetic disease Caused by deletion of 3 bases(delta F 504 phenylalanine ) on chromosome 7(CFTR gen on ch7q31.2). Common among Caucasians 1 in 20 are carriers One in 400 Caucasian couples will be both carriers of CF – 1 in 4 children will have it.

11. CF disease affects transport in tissues – mucus is accumulated in lungs, causing infections. Fluid in lung and potential respiration failure are common.

12. Cystic Fibrosis IF two parents carry the recessive gene of Cystic Fibrosis ( c ), that is, they are heterozygous (C c ), one in four of their children is expected to be homozygous for cf and have the disease: C C = normal C c = carrier, no symptoms c c = has cystic fibrosis

13. Gaucher Disease Gaucher Disease is a rare autosomal recessive genetic disease. It causes lipid-storage disorder (lipids accumulate in spleen, liver, kidney, brain and bone marrow) It is the most common genetic disease affecting Jewish people of Eastern European ancestry (1 in 500 incidence; rest of pop. 1 in 100,000)

14. Symptoms include: Hepatomegaly Spleenomegay Anemia Leucopenia Thrombocytopenia Neurological disorder Osteoporosis

15. Autosomal Dominant Inheritance Autosomal dominant traits are expressed in heterozygous or homozygous individuals. An affected person usually has at least one affected parent .

16. Genotype and phenotype correlation with gene locus for an autosomal dominant trait

17. Pedigree illustrating autosomal dominant transmission

18. Autosomal dominant Expressed in heterozygous or homozygous individuals Affects an individual of either sex Transmitted by either sex An affected person usually has at least one affected parent Transmitted to 50 % of offspring

19. Osteogenesis Imperfecta Type I Osteogenesis Imperfecta is an autosomal dominant genetic disorder that mainly causes d eficient production of the protein collagen leading to abnormal bone matrix. Muations in COL1A1on chromosome 17 (17q21.31) or COL1A2 on chromosome 7(7q22.1) lead to reduced amounts of normal collagen

20. Osteogenesis type I is a genetic disorders that mainly affect the bones. It results in bones that break easily.   The severity may be mild to severe. Other symptoms may include a blue tinge to the whites of the eye, short height, loose joints, hearing loss, breathing problems

21. Huntington Chorea The disease affects a person's ability to think, talk, and move (brain disorder). The disease destroys cells in the basal ganglia, the part of the brain that controls movement, emotion, and cognitive ability. HD is caused by a mutation in a gene on the short arm chromosome 4.

22. Most people who have the disease start to see symptoms between the ages of 30 and 50 (but symptoms can appear earlier or later in life). Symptoms include poor memory, depression mood swings, lack of coordination, twitching or other uncontrolled movements, and difficulty walking, speaking, and/or swallowing.