GENETIC DISORDERS Chapter 11 1 Genetic disorders Problem

GENETIC DISORDERS Chapter 11. 1

Genetic disorders • Problem caused by one or more abnormalities in the genome. • Usually present at birth (congenital) • Occur rarely

Recessive genetic disorders • Recessive traits can only be expressed when the individual is homozygous recessive for that trait • Individuals that are heterozygous for a trait are called carriers

Tay-Sachs • Occurrence – 1 in 2500 • Cause- absence of an enzyme to break down fats • Effect- Buildup of fatty deposits in the brain, mental disabilities • Treatment – no cure, management of symptoms. Death at age 5.

Albinism • Occurrence – 1 in 17, 000 • Cause- Genes do not produce normal amounts of pigment melanin • Effect- little to no color in hair skin and eyes. • Treatment – no cure. sunglasses and protective clothing.

Cystic fibrosis • Occurrence – 1 in 3500 • Cause- mutation in gene codes for membrane protein • Effect- Mucus builds up in respiratory and digestive systems. • Treatment -No cure, daily cleaning of mucus from lungs, mucus thinning drugs.

Galactosemia • Occurrence – 1 in 50, 000 • Cause- Absence of gene for enzyme that breaks down galactose sugar • Effect-mental disability, enlarged liver, kidney failure • Treatment – no cure. diet restrictions

Dominant genetic disorders • Not all disorders are caused by recessive alleles, some disorders are cause by dominant. • People without the disorder are homozygous recessive • People with the disorder are homozygous dominant or heterozygous.

Achondroplasia • Occurrence – 1 in 25, 000 • Cause – mutation in protein needed for bone growth • Effect- Short arms and legs, large head • Treatment – no cure or treatment

Huntingtons disease • Occurrence – 1 in 10, 000 • Cause –gene affecting neurological function • Effect – effects mental function and ability to move. • Treatment - No cure or treatment

What is a Pedigree? • A pedigree is a chart of the genetic history of a family over several generations. • Scientists or a genetic counselor would find out about your family history and make this chart to analyze.

Constructing a Pedigree • Female • Male

Constructing a pedigree • Affected • Unaffected • Carrier

Connecting Pedigree Symbols §Marriage §Generation §Siblings

Example • I 1 – • I 2 – • II 1 – • II 2 – • II 3 – • II 4 – Unaffected Male Female Carrier Unaffected female Male Carrier Unaffected Male Female Carrier

Recessive Disorder Pedigree • Neither parent has to have the disorder because they can be heterozygous.

Dominant Disorder pedigree • Dominant – one of the parents must have the disorder.

Example 1 1) Dominant or Recessive? Dominant 2)What is the Gender of III 3? Female I 1 2 3 4 II 1 2 3 4 5 III 1 2 3) What is the phenotype of I 3? Affected by disorder 4) What is the genotype of II 6? Homozygous recessive 3 6

Example 2 I 1) Dominant 1 2 3 Or Recessive? II Recessive 1 2 3 4 5 2) What is the III 1 2 3 Genotype of II 2? Homozygous recessive 3)What is the genotype of I 3? heterozygous 4) Who can you determine are Carriers? I 1, I 2, I 3, I 4, II 3, III 1, III 3 4 6

Example 3 I 1) Dominant or 1 2 3 II Recessive? 1 2 3 4 Recessive III 2) What is the 1 2 3 Genotype of I 1? Heterozygous 3) What is the phenotype of III 3? Affected by disorder 4) What’s the genotype of III 3? Homozygous recessive 4 5 6