Genetic and chromosomal disorders in children Flashcards
It occurs when a mutation (a harmful change to a gene, also known as a pathogenic variant) affects your genes or when you have the wrong amount of genetic material.
Genetic Disorders
The basic physical and functional unit of heredity.
Gene
This is made of DNA (deoxyribonucleic acid), which contains instructions for cell functioning and the characteristics that make you unique.
Genes
It is the molecule that carries genetic information for the development and functioning of an organism
DNA
DNA is made of two linked strands that wind around each other to resemble a twisted ladder — a shape known as
Double Helix
They are a pair of genes in homologous chromosomes present at a specific locus (specific physical location of a gene or other DNA sequence on a chromosome, like a genetic street address).
Alleles
Condition where the paired genes are similar on homologous chromosomes for a character.
Homozygous
Condition where the paired genes are not similar on homologous chromosomes for a character.
Heterozygous
A hybrid organism is one that is heterozygous, which means that is carries two different alleles at a particular genetic position, or locus.
Hybrid
It is a gene which expresses itself in the presence of a contrasting gene.
Dominant Gene
It is a gene which fails to express itself in
the presence of a dominant gene.
Recessive Gene
It is a term used to denote the transmission of characters from parents to off springs?
Inheritance
The manner in which genes and traits are passed from parents to their children. Disorders are caused by a defect in a single gene that follows the patterns of inheritance by Mendel (1965).
Mendelian Inheritance
If a trait or disease manifests itself when the affected person carries only one copy of the gene responsible, along with one normal allele, the mode of inheritance of the trait is called
Dominant
If two copies of the defective gene are required for expression of the trait, the mode of inheritance is called
Recessive
Disease can be inherited from one parent also.
Can affect both males and females
Can be traced through many generations of a family.
Affected people are heterozygous for the abnormal allele and transmit the gene for the disease to half their offspring, whether male or female.
Autosomal Dominant
- Disease can appear only if both parents transmit it.
- Unaffected parents can transmit the trait to their offsprings(if both parents carry recessive gene)
- Siblings may be affected but parents usually are apparently normal
- Abnormal gene remains suppressed and does not manifest in a heterozygous individual.
The affected person is homozygous for the trait.
Autosomal Recessive
The gene is located on the X chromosome, but the gene acts in a dominant manner.
This means that both males and females can display the trait or disorder, by only having one copy of the gene.
X-Linked Dominant
This are expressed in females only if there are two copies of recessive gene (one on each X chromosome).
X-linked recessive genes
Refers to inheritance of a phenotypic characteristic (trait) that is attributable to two or more genes and their interaction with the environment.
Polygenic inheritance/multifactorial inheritance/ quantitative inheritance
Abnormal changes in the number and structure of chromosomes.
Chromosomal mutations
Numerical changes are known as
Ploidy Changes
Ploidy changes bring about abnormal alterations in the karyotype which causes serious _________.
Genetic Disorders
Extrachromosomal sets
Polyploidy
An extra or missing chromosome
Aneuploidy
One chromosome absent
Monosomy
One chromosome extra
Trisomy
Part of a chromosome missing
Deletion
Part of a chromosome present twice
Duplication
Two chromosomes join long arms or exchange parts
Translocation
Segment of chromosome reversed
Inversion
A chromosome with identical arms
Isochromosome
A chromosome forms a ring due to telomere deletions, which cause ends to adhere.
Ring Chromosome
Condition in sex chromosome aneuploids in female
Turner Syndrome
Who and when was it first reported Turner Syndrome?
Henry Turner in 1938
Turner Syndrome is also called the _____
Ovarian Dysgenesis
Abnormal female(sterile) condition
44A+X0
Caused by sex chromosomal monosomy, absence of an X chromosome(XO Syndrome)
Turner Syndrome
Turner’s Syndrome affects ___________ female births.
1 in 2,500
Clinical Manifestations of Turner’s Syndrome
Short Stature
Webbing of Neck
Low Posterior Hairline
Broad Chest and widely spaced nipples
Contraction of the aorta
Cubitus Valgus
Pigmented Nevi
Streak Ovaries, Infertile, Amenorrhea
Peripheral Lymphedema at birth
Cause of Turner’s Syndrome
Lack of Barr Body
Missing only part of an X chromosome
At birth: (looks normal) Clinical Manifestations
Puffy hands
Impaired Lymphflow in feet
At sexual maturity: Clinical Manifestations
sparse body hair develops
rudimentary / immature ovaries
very small uterus, normal cervix and vagina
intelligence is normal
turner neurocognitive phenotype
may cause memory deficits
What can be done if a person has Turner’s Syndrome?
Hormones (Progesterone and Estrogen)
Sex Chromosome Aneuploids: Male
Klinefelter’s Syndrome
Klinefelter’s Syndrome due to an extra X chromosome (47, XXY) caused by
Chromosomal Trisomy
What causes Klinefelter’s Syndrome?
Extra X chromosome (47, XXY) chromosomal trisomy
Klinefelter’s Syndrome is first reported by and on?
Klinefelter in 1942
Klinefelter’s Syndrome is observed in about ____________.
1 in 500 males
Clinical Manifestations of Klinefelter’s Syndrome
Frontal baldness absent
Poor Bread Growth
Tendency to grow fever
Chest Hairs
Narrow Shoulders
Breast Development
Female-type pubic hair pattern
Wipe hips
Small testicular size
long arms and legs
Symptoms of Klinefelter’s Syndrome
Immature testes and prostate glands
Sparse (thin and dispersed) pubic and facial hair
They have very long arms and legs, large hands and feet
may develop breast tissue( gynaecomastia)
genetic or chromosomal cause of male infertility.
Mental retardation in cases of more than 2 X chromosomes.
may be slow to learn
What can be done if a person has Klinefelter’s Syndrome?
Testosterone injections during adolescence can limit limb lengthening and stimulate development of secondary sexual characteristics.
Men with XXY syndrome have fathered children, with medical assistance.
Doctors select sperm that contain only one sex chromosome and use the sperm to fertilize oocytes.
A harmful change to a gene, also known as a pathogenic variant
Mutation
