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What is the term for having an abnormal number of chromosomes?
What is the term for having an abnormal number of chromosomes?
What is the most common cause of Down syndrome?
What is the most common cause of Down syndrome?
What is the term for the fusion of two acrocentric chromosomes?
What is the term for the fusion of two acrocentric chromosomes?
What is the term for the absence of all or part of the X chromosome?
What is the term for the absence of all or part of the X chromosome?
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What is the term for a trisomy of chromosome 21?
What is the term for a trisomy of chromosome 21?
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What is the method used to diagnose Down syndrome in a fetus?
What is the method used to diagnose Down syndrome in a fetus?
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What heart condition is associated with Turner syndrome?
What heart condition is associated with Turner syndrome?
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What is the term for an error in cell division during meiosis?
What is the term for an error in cell division during meiosis?
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What is the total number of chromosomes in each daughter cell after meiosis?
What is the total number of chromosomes in each daughter cell after meiosis?
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What is the purpose of the drug colchicine in cytogenetics?
What is the purpose of the drug colchicine in cytogenetics?
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What is the term for the study of the structure and numeric characteristics of the cell's chromosomes?
What is the term for the study of the structure and numeric characteristics of the cell's chromosomes?
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What is the result of an error in meiosis that leads to an incorrect number of chromosomes?
What is the result of an error in meiosis that leads to an incorrect number of chromosomes?
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What is the term for a chromosomal abnormality where a part of a chromosome breaks off and attaches to a non-homologous chromosome?
What is the term for a chromosomal abnormality where a part of a chromosome breaks off and attaches to a non-homologous chromosome?
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What is the term for a condition where there is an extra copy of chromosome 21?
What is the term for a condition where there is an extra copy of chromosome 21?
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What is the term for a condition where there is a missing or partial deletion of a sex chromosome?
What is the term for a condition where there is a missing or partial deletion of a sex chromosome?
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What is the term for a condition where there is an extra copy of a chromosome, but not a complete extra set of chromosomes?
What is the term for a condition where there is an extra copy of a chromosome, but not a complete extra set of chromosomes?
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What is the approximate frequency of chromosomal anomalies in live births?
What is the approximate frequency of chromosomal anomalies in live births?
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What is the purpose of creating a family pedigree in genetic disorders?
What is the purpose of creating a family pedigree in genetic disorders?
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What is the likelihood of inheriting a dominant genetic disorder from an affected biological parent?
What is the likelihood of inheriting a dominant genetic disorder from an affected biological parent?
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What is the term for a chromosomal anomaly where an individual has an extra chromosome?
What is the term for a chromosomal anomaly where an individual has an extra chromosome?
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Which of the following is an example of a chromosomal anomaly caused by a trisomy?
Which of the following is an example of a chromosomal anomaly caused by a trisomy?
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What is the term for the exchange of genetic material between non-homologous chromosomes?
What is the term for the exchange of genetic material between non-homologous chromosomes?
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What is the purpose of mandatory newborn screening in many states?
What is the purpose of mandatory newborn screening in many states?
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What is the significance of autosomal dominant disorders in terms of reproduction?
What is the significance of autosomal dominant disorders in terms of reproduction?
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What is the typical karyotype of an individual with Klinefelter syndrome?
What is the typical karyotype of an individual with Klinefelter syndrome?
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Which of the following is a characteristic of congenital hypogonadism in Klinefelter syndrome?
Which of the following is a characteristic of congenital hypogonadism in Klinefelter syndrome?
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What is the primary function of the mitochondrial DNA?
What is the primary function of the mitochondrial DNA?
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What is the typical outcome of mitochondrial gene disorders?
What is the typical outcome of mitochondrial gene disorders?
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What is the number of genes encoded in mitochondrial DNA?
What is the number of genes encoded in mitochondrial DNA?
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What is the term for the presence of an extra X chromosome in a male?
What is the term for the presence of an extra X chromosome in a male?
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What is the term for a change in the number of chromosomes from the typical diploid number?
What is the term for a change in the number of chromosomes from the typical diploid number?
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What is the term for the transfer of a segment of DNA from one chromosome to a non-homologous chromosome?
What is the term for the transfer of a segment of DNA from one chromosome to a non-homologous chromosome?
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What determines the sex of a person?
What determines the sex of a person?
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What is the result of meiosis?
What is the result of meiosis?
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How many chromosomes are present in each cell undergoing meiosis?
How many chromosomes are present in each cell undergoing meiosis?
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What is the term for the organization of DNA into 23 pairs of chromosomes?
What is the term for the organization of DNA into 23 pairs of chromosomes?
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What is the process by which DNA is replicated to duplicate somatic cells?
What is the process by which DNA is replicated to duplicate somatic cells?
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What is the purpose of the Y chromosome?
What is the purpose of the Y chromosome?
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What determines the sex of a person?
What determines the sex of a person?
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What is the result of meiosis I?
What is the result of meiosis I?
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Study Notes
Chromosomal Abnormalities
- 5% of Down syndrome cases are caused by a Robertsonian translocation involving two acrocentric chromosomes, commonly chromosomes 13 and 14, or 14 and 21.
- Aneuploidy refers to having an abnormal number of chromosomes.
Down Syndrome
- Approximately 95% of Down syndrome cases are caused by nondisjunction or an error in cell division during meiosis, resulting in a trisomy of chromosome 21.
- A rare form of Down syndrome can occur in the offspring of people with a Robertsonian translocation.
Diagnosis of Down Syndrome
- Definitive diagnosis of Down syndrome in the fetus is through chromosome analysis using chorionic villus sampling, amniocentesis, or percutaneous umbilical blood sampling.
Turner Syndrome
- Turner syndrome is characterized by an absence of all or part of the X chromosome (45, X/0).
- It is associated with coarctation of the aorta and bicuspid aortic valve, which interfere with sufficient blood flow in the cardiovascular system.
Cell Division and Chromosomes
- There are 22 pairs of autosomes and one pair of sex chromosomes, with XX pairing in females and XY pairing in males.
- Duplication of chromosomes in a somatic cell line is completed by the process of mitosis, in which each daughter cell receives 46 total chromosomes, arranged in 23 pairs.
- Meiosis is limited to replicating germ cells and results in daughter cells that each have 23 total chromosomes.
Cytogenetics
- Cytogenetics is the study of the structure and numeric characteristics of the cell’s chromosomes.
- Chromosome studies can be done on any tissue or cell that grows and divides in culture, with white blood cells or buccal samples being frequently used.
Klinefelter Syndrome
- Klinefelter syndrome is a condition of testicular dysgenesis accompanied by the presence of one or more extra X chromosomes in excess of the usual male XY complement.
- Most males with Klinefelter syndrome have one extra X chromosome (47, XXY).
- Males with Klinefelter syndrome have congenital hypogonadism, resulting in an inability to produce normal amounts of testosterone.
Mitochondrial Gene Disorders
- Mitochondria contain their own DNA, distinct from the DNA contained in the cell nucleus.
- There are multiple disease-causing rearrangements and mutations that can occur in mitochondrial DNA (mtDNA).
- mtDNA mutations frequently affect the neuromuscular system and produce disorders such as encephalopathies, myopathies, retinal degeneration, loss of extraocular muscle function, and deafness.
Chromosomal Anomalies and Inheritance
- 1 in 150 live births has a chromosomal anomaly causing cognitive impairment and birth defects.
- Chromosomal abnormalities are even more prevalent among stillbirths and spontaneous abortions.
- Creation of a family pedigree can help to identify genetic disorders and is useful for genetic counseling.
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Description
This quiz covers the genetic causes of chromosomal abnormalities, including Down syndrome, and the different types of errors that can occur during cell division.
