genetic disease Flashcards
Huntington’s Disease
Autosomal dominant disease
- Results in cell death in brain cells
- Normal alleles of the HTT gene encodes for a normal HTT protein
- Mutant alleles characterised by additional CAG repeats
Cystic fibrosis
Autosomal recessive disorder
* Defect in the protein, cystic fibrosis transmembrane conductance regulator (CFTR)
* Affects transport of chloride ions across plasma membranes
* Organ damage from thick and sticky mucus
Sickle cell disease
Autosomal recessive disorder
* Mutation in HBB gene resulting in abnormal haemoglobin S subunits
* Heterozygotes exhibit the sickle cell trait
* Half of haemoglobin is normal
* Incomplete dominance phenotype
X-linked dominant
- Affected females can have a homozygous or heterozygous genotype
- Affected males are hemizygous i.e. one abnormal allele is sufficient to cause the disorder
X-linked recessive
- Affected females have a homozygous recessive genotype
- Affected males are hemizygous
- Mostly occurs in males
- Females tend to be “carriers” i.e. heterozygous and do not exhibit the disorde
Y-linked
- Abnormal allele can only be passed down from father to son
Haemophilia
X-linked recessive disorder
* Clotting deficiency resulting from mutations of genes that code for protein coagulators
* Abnormal protein cannot participate effectively in blood clotting process
Haemophilia A
Deficiency of clotting factor VIII
Haemophilia B
Deficiency of clotting factor IX
Red-green colorblindness
X-linked recessive disorder
* Insensitivity to green light resulting from mutations in the OPN1LW or OPN1MW gene
* Abnormal opsin pigments in cone cells of retina
* Affected individuals have trouble distinguishing between some shades of red, yellow, and green.
Autosomal
Controlled by genes on chromosomes 1-22
* Autosomal dominant
* Autosomal recessive
Sex-linked
Controlled by genes on sex chromosomes
* X-linked dominant
* X-linked recessive
* Y-linked
