Gene disorders Flashcards
Genetic Disorder
Diseases can be caused in three ways
Environmental, Genetic or both
What is a mutation?
A permanent change in Dna
Mutations can be divided into three categories
Genome, Chromosomal, Gene mutation
What is a Genome Mutation?
a change in the whole chromosome
Chromosome mutation
A visible change in the chromosome
Gene mutation
may result in a single base error
A gene can be altered in three ways. What are they?
Deletion, addition, substitution of a single base
what is translation
from mRNA to DNA
what are some of the effects on Gene Mutation
Interefere with protein synthesis, Abnormal proteins formed, produce abnormal mRNA, defects carried over into translation ( RNA to Proteiin)
HOw many genetic disorders are known currently?
4000
are most disorders common or rare?
Rare
some gene disorders can be an advantage to the patient. for example
Sickle Cell carriers, immunity to malaria.
three types of genetic disease
single gene mutation, including mendelian disorders and non- mendelian disorders, multifactorial and polygenic disorders.
Mendelian mode of inherence definition
he manner by which genes and traits are passed from parents to their children. The modes of Mendelian inheritance are autosomal dominant, autosomal recessive, X-linked dominant, and X-linked recessive. Also known as classical or simple genetics.
Karyotype
No. and appearance of chromosomes in the nucleus of a human cell.
how many chromosmes are in a karytope?
46 or 22 pairs
Autosome
any nuclear appearance other than the sex chromosomes
X linkage
Genes on the X chromosome
what type of karyotype is this?
Male
Disorders of Mendelian fashion may be
Disorder of mendelian fashion may be
autosomal or Xlinked
Autosomal Dominant.
th elocus is on an autosomal chromosome and only one mutant allele is required for expression of the phenotpye.
RecessiveThe locus is on an autosomal chromosome and both alles must be mutant alleles to express the phenotype.
The locus is on an autosomal chromosome and both alles must be mutant alleles to express the phenotype.
X linked
the locus is on the X chromosome and mutant allele/s is required for expression of the phenotype in females.
Disorder of non- mendelian fashion: mitochondrial inheritance
the locus is on the mitochondrial chromosome
Autosomal Dominant under single gene mutatution
- Mutated gene is located on autosome
- both genders affected
- presence of a single mutant is suffiecent to result in a mutant phenotype
- affected person are heterozygous
- multiple generations affected
- affected persons has 50% risk of transmitting disease to any offspring
this karytogram shows?
Autosomal Dominant Pedigree
Examples of autosomal Dominant disorders
- Familial Hypercholesterolamia ( high cholesterol, Cadiovasicular disease, atherosclerosis).
- achondrplasia ( dwarism)
- neurofibromatosis
- Hungtingtons’ disease
Autosomal Rescessive
- muatef gene located on autosome
- male and female affected\
- Ar Traits and disorder only mainfest whe the male allled show no feature of the disorder and are healty cariers
- The AR disorder must be inherited throug both parents ( carier heterozygotes)
- offspring allele person who are heterozygotes for the same autosomal recessive allele have 1 in 4 chance of being homozygous for that alled.
what is this pedigree showing?
Autosomal recessive
Example of Autosome Recessive
Sickel cell anaemia
thalassemia
Cystic fibrosis
phenylketonuria
X linked
- Genrally manifest in males
- affected fathers have no affect ed son and no normal daughters
- affected daughter are obligate carriers
- never transmitted directly from father to son
- son of the carieer females have a 50% chance of inheriting the disorder
- both males and females offspring of affected females have a 50% chance of inheriting th edisorder.
Examples of X linked
- Haemophilia A - Abnormal bledding
- Haemophilia B - abnormal bleeding
- Duchenne muscles dystrophy
- Fragile syndrome
Mitochondrial inheritance
- Maternal inheritance
- the father does not contribute
- all children of an affected female will inherit the mutated mDNA
Mt. Inheritance : Leber’s Hereditary optic neuropathy( LHON)
BIlateral loss of central vision doe to optic nerve atrophy in young adults,
affected persons matybe male or female
Multifactorial Disorder
Recur in families, without showing any characteristic
asscoaited with the effects of multiple genes in combination with lifestyle and environment factors
include a number of development disorder and many common disorder of adult life e.g.
Examples which can be multifactorial
- Cleft lip
- Neural tube defect
- Congenital heart disease
- gout
- alzeheimer degeneration
- hypertensions
Cytogenic Disorders
Alterations in the number or structure of chromosomes and may affect autosome or sex chromosomes.
Aneuploidy
Changes in the number of individual chromomes in a cells
monosomy
an autosomal cell with only 1 copy of a chromosome (lethal abnormality)
trisomy
a cell with 3 copies of a chromosome
nullisomy
a cell with no copies of chromosomes
What are the three well know defined autosomal chromosome trisomy disorders
21, 18, 13
What is this disease and its features
Edwards syndrome :Characteristic facial features, mental retardation, overlapping fingers, poor development and growth
what is this disease and its hallmark?
Patau Syndrome : sever sleft and lip, polydactyl. mental retardation, poor development
Sex chromosome disorders
- problems related to sexual development and fertility
- discovered at time puberty
- trisomic types are the most frequent ( XXY, XYY, XXX) are rare in spontaneous abortion
- retardation related to the number of X chromosome
- If you have at least one “Y” chromosome, you are male
Klinefelter’s Syndrome
- Hypogonadism
- # 1 cause of male infertility
- No retardation unless more X
- tall and thin males with long limbs, atrophic testes, small penis
- breast
Turner’s Syndrome
- failure of puberty
- neck webbing
- short stature and broast chest
- congenitial hear defects
true harmaphodrite have
ovaries and testes , often of the same side
What is Velocardiofacial syndrome?
Arises doe to deletion of segment of the long arm of chromosome 22.
