Cytogenetics and molecular cytogenetics Flashcards
Chromosomal basis of inheritance • Karyotypes • Chromosomal abnormalities • Molecular cytogenetics approaches: FISH, CGH, molecular karyotyping
How can karyotyping help diagnose genetic disorders?
Karyotyping detects chromosomal abnormalities like aneuploidies (e.g., Down syndrome) and structural changes (e.g., translocations) by visualizing chromosome number and structure.
What is the difference between G-banding and Q-banding in chromosome analysis?
G-banding uses Giemsa stain to highlight AT-rich regions, while Q-banding uses fluorescent dyes to visualize chromosomes under UV light.
How does a Robertsonian translocation affect fertility?
It fuses two acrocentric chromosomes, leading to unbalanced gametes that can increase the risk of miscarriage or infertility.
Why are chromosomal abnormalities more common with increased maternal age?
Aging eggs are more prone to nondisjunction, leading to aneuploidies like Down syndrome.
How does X-inactivation contribute to genetic mosaicism in females?
One X chromosome is randomly inactivated in each cell, creating a mosaic pattern of gene expression (e.g., calico cats, Turner syndrome).
How does fluorescence in situ hybridization (FISH) improve chromosomal analysis?
FISH uses fluorescent DNA probes to detect chromosomal deletions, duplications, and translocations with higher precision than karyotyping.
What are whole chromosome paint probes, and how are they used in FISH?
They label entire chromosomes with fluorescent dyes, helping detect complex rearrangements like translocations.
How does spectral karyotyping (SKY) enhance cytogenetic analysis?
SKY assigns unique fluorescent colors to each chromosome, allowing for precise detection of chromosomal rearrangements.
What is comparative genomic hybridization (CGH), and how is it used in clinical genetics?
CGH compares patient and reference DNA to detect copy number variations (gains/losses), helping diagnose genetic syndromes.
Why is molecular cytogenetics important in cancer diagnostics?
Techniques like FISH and CGH identify chromosomal mutations in tumors, guiding personalized cancer treatments.
How does the chromosomal theory of inheritance explain Mendelian laws of segregation and independent assortment?
Genes are located on chromosomes, which segregate during meiosis (supporting Mendel’s law of segregation) and assort independently if on different chromosomes (supporting independent assortment).
Why do sex-linked disorders, such as hemophilia, occur more frequently in males than females?
Males have only one X chromosome, so a single recessive mutation is expressed, whereas females have two X chromosomes and can be carriers without being affected.
How is a karyotype prepared, and what information does it provide?
Cells are cultured, arrested in metaphase, stained, and analyzed under a microscope to detect aneuploidy, deletions, duplications, and translocations.
What is the significance of banding techniques (e.g., G-banding) in karyotype analysis?
G-banding highlights specific regions of chromosomes, aiding in identifying structural abnormalities such as deletions, duplications, and translocations.
What are the differences between aneuploidy and structural chromosomal abnormalities? Provide an example of each.
Aneuploidy refers to an abnormal chromosome number (e.g., trisomy 21 in Down syndrome), while structural abnormalities involve changes like translocations or deletions (e.g., Cri-du-chat syndrome).
How does nondisjunction lead to conditions such as Turner syndrome and Klinefelter syndrome?
Nondisjunction occurs when chromosomes fail to separate properly during meiosis, leading to monosomy X (Turner syndrome, 45,X) or XXY (Klinefelter syndrome, 47,XXY).
How does fluorescence in situ hybridization (FISH) improve chromosomal analysis compared to conventional karyotyping?
FISH uses fluorescent probes to detect specific DNA sequences, allowing identification of small deletions, duplications, or rearrangements that may be missed in traditional karyotyping.
What is comparative genomic hybridization (CGH), and how does it differ from karyotyping?
CGH compares patient and reference DNA to detect chromosomal gains/losses, offering higher resolution than karyotyping, which only detects large-scale changes.
How does molecular karyotyping using array CGH benefit clinical diagnostics?
Array CGH provides high-throughput detection of copy number variations (CNVs), making it valuable for diagnosing genetic syndromes and developmental disorders.
Why is spectral karyotyping (SKY) useful in cancer research?
SKY assigns unique fluorescent colors to each chromosome, allowing detection of complex chromosomal rearrangements seen in cancer cells.
