Podcast
Questions and Answers
What is the main purpose of documenting the family's ethnic background in genetic disorders assessment?
What is the main purpose of documenting the family's ethnic background in genetic disorders assessment?
During physical assessment, what body areas should be given particular attention to identify potential genetic disorders?
During physical assessment, what body areas should be given particular attention to identify potential genetic disorders?
Why is careful inspection of newborns essential in genetic disorders assessment?
Why is careful inspection of newborns essential in genetic disorders assessment?
What is the purpose of karyotyping in genetic disorders assessment?
What is the purpose of karyotyping in genetic disorders assessment?
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Why should infants born less than 35 weeks' gestation and with multiple congenital anomalies receive close assessment?
Why should infants born less than 35 weeks' gestation and with multiple congenital anomalies receive close assessment?
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What is examined during the physical assessment of family members seeking genetic counseling?
What is examined during the physical assessment of family members seeking genetic counseling?
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Which part of the body should receive particular attention during inspection to identify genetic disorders?
Which part of the body should receive particular attention during inspection to identify genetic disorders?
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Why should a prenatal history be obtained for any affected family member in genetic disorders assessment?
Why should a prenatal history be obtained for any affected family member in genetic disorders assessment?
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What type of diagnostic testing involves analyzing cells under a microscope to identify chromosomal abnormalities?
What type of diagnostic testing involves analyzing cells under a microscope to identify chromosomal abnormalities?
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Why is it important to inspect abnormal features like fingerprints or palmar creases in genetic disorders assessment?
Why is it important to inspect abnormal features like fingerprints or palmar creases in genetic disorders assessment?
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Study Notes
Genetic Assessment and Counselling
- Genetic assessment and counselling are essential for patients at risk of inherited disorders to provide access to advice, resources, and support.
Nature of Inheritance
- Genes are the basic units of heredity that determine physical and cognitive characteristics of individuals.
- Genes are composed of DNA (Deoxyribonucleic acid).
- Genetics is the study of how and why chromosomal disorders occur.
- Cytogenetics is the study of chromosomes by light microscopy and the method by which chromosomal aberrations are identified.
Chromosomal Structure
- Humans have 46 chromosomes (22 pairs of autosomes and 1 pair of sex chromosomes) in each cell.
- Spermatozoa and ova each carry only half of the 23 chromosomes.
- Each chromosome in the sperm cell has a similar size and shape function (autosome, or homologous chromosome) in the ovum.
Genotype, Phenotype, and Genome
- A person's genotype is their actual gene composition.
- A person's phenotype is their outward appearance or expression of the genes.
- A person's genome is the complete set of genes present (approximately 50,000-100,000 genes).
Genetic Disorders
- Genetic disorders are defects in the structure or number of genes or chromosomes.
- Inherited or genetic disorders can be passed from one generation to the next.
- Genetic disorders occur when an ovum and sperm fuse in meiotic division or due to other genetic abnormalities.
Mendelian Inheritance: Dominant and Recessive Patterns
- Homozygous: a person has two healthy genes (one from each parent).
- Heterozygous: a person with different genes (a healthy gene from one parent and an unhealthy gene from the other parent).
- Autosomal Dominant Disorders:
- Either has two unhealthy genes (homozygous dominant) or heterozygous with a gene causing the disease.
- 50% chance of a child having the disorder or being a carrier, and 25% chance of a child being disease and carrier-free.
- Autosomal Recessive Inheritance:
- Diseases do not occur unless two genes for the disease are present.
- 25% chance a child will be disease and carrier-free, 50% chance a child will be like the parents (free of disease but carrying the gene), and 25% chance a child will have the disease.
Imprinting
- Imprinting refers to the differential expression of genetic material, allowing researchers to identify chromosomal material from the male or female parent.
Chromosomal Abnormalities (Cytogenic Disorders)
- Nondisjunction Abnormalities:
- Result from uneven division of chromosomes, leading to one new sperm cell or ovum with 24 chromosomes and the other with 22 chromosomes.
- If a spermatozoa or ovum with 24 or 22 chromosomes fuses with a normal spermatozoa or ovum, the zygote will have either 47 or 45 chromosomes.
- 45 chromosomes are not compatible with life, and the embryo or fetus will likely be aborted.
Genetic Disorders Assessment
- Physical Assessment:
- Assess family members with disorders, siblings, and couples seeking counseling.
- Pay attention to specific body areas (space between the eyes, height, contour, shape of ears, number of fingers and toes, presence of webbing).
- Diagnostic Testing:
- Karyotyping: a sample of peripheral venous blood or a scraping of cells from the buccal membrane.
- Cells are stained, placed under a microscope, photographed, and chromosomes are identified by size, shape, and stain, cut from the photograph, and arranged.
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Description
Test your knowledge on the inheritance patterns of autosomal dominant disorders, including the chances of having homozygous dominant, heterozygous, or disease-free offspring. Explore the probabilities of passing on genetic traits in families affected by autosomal dominant disorders.
