Chromosomal Abnormalities, Gene Mutations & Related Disorders

36 question-and-answer flashcards summarizing chromosomal abnormalities, gene mutation types, and the associated human disorders discussed in the lecture.

What is karyotyping?

A laboratory process that photographs and analyzes an individual’s chromosomes to determine number and structural abnormalities.

What term describes a numerical chromosome abnormality in which there is a missing or extra chromosome?

Aneuploidy.

What is trisomy?

The presence of three copies of a particular chromosome instead of the normal two.

What is monosomy?

The absence of one chromosome from a chromosome pair.

Which chromosomal abnormality causes Down syndrome?

Trisomy 21 (an extra copy of chromosome 21).

List three common physical features of Down syndrome.

Flattened facial profile, upward-slanting eyes, and short neck with excess skin at the back.

What is the usual genetic cause of Down syndrome?

Random nondisjunction during formation of the parents’ reproductive cells.

Which chromosomes are involved in the Philadelphia chromosome?

A reciprocal translocation between chromosome 9 and chromosome 22.

The Philadelphia chromosome is strongly associated with which cancer?

Chronic Myelogenous Leukemia (CML).

What genetic change causes Cri-du-chat syndrome?

Deletion of the short (p) arm of chromosome 5.

What hallmark cry characterizes infants with Cri-du-chat syndrome?

A high-pitched, cat-like (meowing) cry due to abnormal larynx and glottis development.

What is the karyotype and one key feature of Turner syndrome?

45,X (one X chromosome missing); features include webbed neck and short stature in females.

What is the karyotype of Klinefelter syndrome and a primary clinical feature?

47,XXY; primary feature is male infertility with small, poorly functioning testicles.

What causes Trisomy X and what is a typical physical trait?

An extra X chromosome in females (47,XXX); affected females are often taller than average.

Which trisomy results in Edwards syndrome and name one physical sign.

Trisomy 18; clenched fists with overlapping fingers.

Which trisomy causes Patau syndrome and cite one physical manifestation.

Trisomy 13; often presents with cleft lip or palate and polydactyly.

Define a chromosomal deletion.

Loss of a segment of a chromosome.

Define chromosomal duplication.

A segment of a chromosome is copied and present twice in tandem.

Define chromosomal translocation.

Movement of a chromosomal segment to a non-homologous chromosome.

Define chromosomal inversion.

A chromosome segment is rotated 180° and reinserted into the chromosome.

How does a paracentric inversion differ from a pericentric inversion?

Paracentric inversion does NOT include the centromere, whereas pericentric inversion does.

What is a gene mutation?

Any change in the DNA sequence that can alter gene function or expression.

What characterizes a silent mutation?

A nucleotide change that does not alter the encoded amino acid.

What is a missense mutation?

A point mutation that changes one amino acid to another in a protein.

What is a nonsense mutation?

A point mutation that converts an amino-acid codon into a stop codon, prematurely terminating protein synthesis.

Which missense mutation causes sickle cell anemia?

HBB gene change from GAG to GTG, substituting valine for glutamic acid in hemoglobin.

Marfan syndrome is commonly caused by what type of mutation in the FBN1 gene?

Various missense mutations affecting fibrillin-1.

Give an example of a disease produced by a nonsense mutation.

Duchenne Muscular Dystrophy caused by a nonsense mutation in the DMD gene.

Define an insertion mutation and name one disease example.

Addition of one or more bases; e.g., four-base insertion in HEXA causing Tay-Sachs disease.

How can a deletion mutation lead to cystic fibrosis?

Deletion of three bases (ΔF508) in the CFTR gene removes phenylalanine, impairing chloride channel function.

Which disease is linked to duplication of the PMP22 gene?

Charcot-Marie-Tooth (CMT) peripheral neuropathy.

Hemophilia A can arise from which type of chromosomal rearrangement in the F8 gene?

An inversion (often intrachromosomal).

Distinguish reciprocal from Robertsonian translocation.

Reciprocal: exchange of segments between two non-homologous chromosomes; Robertsonian: fusion of the long arms of two acrocentric chromosomes.

What form of Down syndrome results from a Robertsonian translocation?

Translocation Down syndrome, in which chromosome 21 material fuses to another acrocentric chromosome.

Why is regulation of the cell cycle important for the body’s normal functioning?

Proper regulation ensures accurate DNA replication and chromosome segregation; malfunction can lead to mutations, aneuploidy, and diseases such as cancer or genetic disorders.