SAQ Disease Flashcards
1
Q
Human deafness + complementation
A
Many loci affect hearing pathway from outer ear to auditory nerve and brain
- Partial or total inability to hear, most commonly on both ears.
- Can be inherited by recessive genes (most common) , dominant genes + X-linked patterns
- 70% total registered cases are non syndromic, which means that there are no other signs or medical problems associated with the hearing loss.
- DFNA1 first gene mapped for non syndromic hearing loss
- Costa Rican family - single base change in the gene caused low frequency onset progressive hearing loss.
- Autosomal dominant inheritance pattern for that particular mutation.
- Penetrance age of 30.
2
Q
Phenylketonuria, PKU
A
Mutations in the PAH gene result in low levels of the enzyme phenylalanine hydroxylase.
- Build up of dietary phenylalanine to potentially toxic levels.
- gene-environment interaction, chemical
recessive
- can’t break down Phe -> special diet
- Untreated PKU can lead to intellectual disability, seizures, behavioral problems and mental disorder.
3
Q
Achondroplasia
A
- abnormal adult stature.
If both parents have the condition, a homozygous child is not likely to live. - 80% of cases of dwarfism caused by achondroplasia.
- Autosomal dominant inheritance.
4
Q
Cystic Fibrosis
A
- Disease affecting mainly the lungs, intestine, pancreas and kidneys.
- Failure in transmembrane conductance regulator (transport protein).
- Chloride ion transporter.
- Differences in amino acids account for the disfunction of the protein.
- Loss of phenylalanine in the sequence.
- Accumulation of mucus in respiratory and gastrointestinal tracts.
- Autosomal recessive. 1/25 allele incidence among populations of European ancestry.
- Prone to lung infections.
- No cure, only treatment for the symptoms.
- Males affected by the condition are infertile.
- Can be diagnosed by genetic screening.
5
Q
Albinism
A
- Absence of pigment in hair/skin. Recessive Mendelian Inheritance - Autosomal recessive
- Congenital disorder characterised by the complete or partial absence of melanin in the hair, skin and eyes.
- TYR gene for tyrosinase deficient, an important enzyme in the melanin-producing pathway
- Pleiotropic effects include vision and hearing impairments.
- Deletions and duplication of the gene coding for the enzyme
- Causes susceptibility to skin cancer and chronic sunburns.
6
Q
Autism
A
- Gene interaction and multiple loci involved
- Several genes affect one character (polygenic trait)
Autism Spectrum Disorders (ASD) are characterised by the autistic triad: - Impaired social communications and interactions.
- Restricted and obsessive interests and behavior.
- Language impairment.
- Neurodevelopmental disorder
- 1 locus alters phenotype produced by other locus.
7
Q
Lesch-Nyhan syndrome
A
- Characterised by the error in purine metabolism.
- Self-mutilation and death are common amongst affected individuals.
- Deficiency in hypoxanthine-guanine phosphoribosyltransferase.
- Gene located on the X chromosome (sex-linked)
- Buildup of uric acid in bodily fluids
- Neurological signs include poor muscle control and intellectual stability.
- Poor utilization of Vitamin B12
8
Q
Duchenne muscular dystrophy
A
- Severe type of X-linked (recessive) inherited muscular atrophy + X-chromsome inactivation
- Muscle loss predominantly in the upper legs and pelvis, followed by muscle loss along the arms.
- Detect age 3-5, fatal in 20’s - Most individuals affected are unable to walk by the age of 12.
- Carrier females may show some symptoms.
- Mutation in the protein dystrophin -> Protein important in the maintaining of muscle fibre cell membranes.
Individual will have high intravenous creatine kinase.
-> MZ twins 1 had DMD, the other didn’t
9
Q
Colourblindness
A
Daltonism; condition in which individual does not see a difference between certain colors (red-green being the most common manifestation).
- X-linked inherited condition
- More males affected than females. Males need only one copy (for their only X chromosome).
- Females would need to have a carrier mom and an affected father.
- > Heterozygous women can see in colour even though some retinal cells are colour blind due to x chromosome inactivation..
- Decreased visual acuity due to cone and rod dystrophy.
- Cones are color sensing cells in the retina, when impaired cannot distinguish certain colors accurately.
10
Q
Patau syndrome
A
- Chromosomal abnormality in which all or some of the cells trisomy 13 may be due to translocation
- Extra genetic material disrupts normal development
- Causes multiple and complex organ defects.
- Predominantly caused by nondisjunction.
- More than 80% of children with this condition die during their first year of life.
11
Q
Myeloid leukemia
A
Translocation 5-11/ 9-22 can be induced by chemical exposure and even radiation.
- > myeloid line of blood
- abnormal WBC in bone marrow or lack of creates susceptibility to infections
12
Q
Cri-du-chat
A
Chromsome deletion -> loss of tip of chr. 5
- Vocal cord abnormalities attribute a kitten sound to individuals voices, hence the name.
- Individuals have small head and jaws, wide eyes and unusual facial features.
- Growth retardation is a common symptom.
13
Q
Turner’s syndrome
A
XO, female
Aneuploidy
14
Q
Edward’s syndrome
A
Trisomy 18, aneuploidy
- Symptoms include a short and webbed neck, low-set ears, low hairline, and swollen feet and hands at birth.
- Kidney + Heart defects, diabetes and low thyroid hormone levels common in the condition.
- Infertility and lack of breasts and menstrual periods.
15
Q
Gynandromorphs
A
Half male half female - mosaic due to error in mitosis in early dip.
- Somatic aneuploidy
- Dm one red eye, one white
