CYTO 13 & 14

• GENETIC COUNSELORS - help people examine their families' histories
• PEDIGREE - one of the key steps in genetic counseling
• PROBAND - person whom the tree is initiated
• AFFECTED - person diagnosed with or having symptoms of a given disorder
• HETEROZYGOTE - person possesing one disease causing allele
• CARRIER - unaffected heterozygote in recessive disorders
• HOMOZYGOTE - person possesing 2 copies of disease causing alle
• COMPOUND HETEROZYGOTE - person possesing 2 different disease- causing allele
• MODE OF INHERITANCE - way in which human genetic disorders are passed down to later generations
• AUTOSOMAL INHERITANCE - genes located on autosomes
• DOMINANT TRAIT/ DISORDER - only one allele known to cause the trait
• AUTOSOMAL DOMINAT - when a gene is carried on an autosome
• EXAMPLES OF AUTOSOMAL DOMINANT DISORDERS: Achondroplasia, Huntington Disease & Marfan Syndrome
• ACHONDROPLASIA - form of dwarfism
• HUNTINGTON DISEASE - progressive & fatal disease affecting the brain & nervous system
• MARFAN SYNDROME - disorder affecting the skeletal system, heart & eyes
• The normal pattern of autosomal dominant inheritance has three exceptions
• THE THREE EXCEPTIONS TO NORMAL PATTERN OF AUTOSOMAL DOMINANT INHERITANCE ARE: New mutations, Incomplete penetrance & Variable expressivity
• PENETRANCE - percentage of individuals having a particular genotype
• EXPRESSION - degree to which an individual with a certain genotype exhibits the phenotypic effects of that genotype
• NEW MUTATIONS - occur in the egg & sperm of an individual, appears for the first time in single generation
• RECESSIVE TRAITS/DISORDER - both alleles of the associated gene need to have the necessary changes order to show related phenotype
• AUTOSOMAL RECESSIVE DISORDERS- caused by mutations in genes
• Both parents are heterozygous carriers - there is 25% chance of both parents passing o na disease - causing allele
• One parent is carrier & another is affected - each child has 50% of being a carrier
• One parent is carrier & another is affected - there is 50% chance og having an affected child
• One parent is affected & other is unaffected - there is 50% will be heterozygous carriers
• CONSANGUIENEOUS - meaning "same blood"
• SEX - LINKED GENES - actually located on the sex chromosomes themselves
• HEMOPHILIA is a x - linked while hairy ears are y - linked
• X - LINKED TRAITS & DISORDERS - result of sequence variants in genes
• X - linked recessive disorders express the traits fully in males
• X - INACTIVATION - most of the genes on one female's two X chromosome are turned off
• X - LINKED DOMINANT TRAITS show up more often in females
• HEMIZYGOUS - having only one copy of the chromosome
• Y - CHROMOSOME - is passed strictly from father to son
• SEX - LIMITED TRAITSS - inherited in the normal autosomal fashion but are not expressed in one sex
• SEX - INFLUENCED TRAIT - are coded by genes on autosomes
• DIAGNOSTIC TESTING - performed in an affected individual in order to establish a specific diagnosis
• PRENATAL TESTING- performed during pregnancy in order to diagnose the baby with a genetic condition