Introduction to genetic disease Flashcards
Genetic disorder
results from abnormalities in the genome and may or may not have been inherited
The human genome
22 pairs of autosomal chromosomes
and 1 pair of sex chromosomes giving a total of 46 chromosomes, Of a pair of chromo one pair is of paternal origin another from maternal origin. The sex chromosomes determine whether the individuals is make ( XY) or female ( XX)
Karyotype
chromosomal makeup of an individual
each chromosome of the karyotype is sorted and numbered according to size
Lyonization
Females have two X chromosomes. During early embryo development , one of the X chromosome in each cell is inactivated
Barr body
Inactivated chromosome excluded from the nucleus
Chromosomal disorders
occur when the entire chromosome is affected, Whole chromosome may be deleted or duplicated or there may be a large breakage, deletions and duplications within the chromosomes
Euploid vs aneuploid
Euploid person has 23 pairs of chromosome
Aneuploid does not have 23 pairs of chromosomes
Example of Aneuploid syndrome/ disease
Down syndrome, Trisomy 21- 3 copies of chromosome 21
Example of diseases caused by chromosome duplication or deletions
Klinefelter syndrome(47XXY) Turner syndrome (25X0)
Autosomal diseases
are due to a mutation in a single gene on an autosome. They may be either dominants (only one damaged allele) or recessive
Dominant autosomal disease
affects structural proteins disease occurs in heterozygotes non-uniform expression onset of disease may be delayed neither parent may have the disease When inherited, generations not skipped example Marfan syndrome- half building blocks are defective, cell cannot assemble structures properly
Recessive autosomal disease
affects chromosomes disease occurs in homozygotes more uniform expression onset of disease is early in life generally both parents have the disease or ae carries more common that autosomal dominant when inherited, generations may be skipped example Cystic fibrosis
X-linked disorders
inherited on X chromosome
most are recessive so disease will only be expressed if there is no normal X chromosome
A female will only be affected if she carries two abnormal X chromosomes, as Turner syndrome or as a result of lyonization
Generally only males are affected
X-linked disorders affect
Males- sons do not inherit the disease from their fathers
Heterozygous females will have no phenotypic expression and are called carriers
All the daughters of an affected male are carriers
Sex linked disorders include
hemophiliac A
red-green color blindness
Duchenne muscular dystrophy
Mitochondrial disorders
all inherited through female line therefore can only be passed on from mother to child
typically progressive and not obvious at birth and affect cells non-uniformly
Example is Leber’s hereditary optic atrophy which results in progressive visual impairment
