Human Heredity: Principles & Issues

These flashcards cover key concepts and important details related to human heredity, cytogenetics, and chromosome abnormalities, aiding students in their exam preparation.

What are the two major types of translocations?

Reciprocal translocations and Robertsonian translocations.

What is triploidy, and how common is it?

A genetic condition where there are three copies of each chromosome, observed in 1% of all conceptions but often results in miscarriage.

What is aneuploidy?

Changes in chromosome numbers involving less than the duplication of a whole chromosome set, often the gain or loss of a single chromosome.

Describe the characteristics of Down syndrome (Trisomy 21).

Occurs in 1 in 800 live births; commonly associated with childhood intellectual disability and heart defects.

What are common risks for autosomal trisomy?

Genetic predisposition, exposure to radiation, viral infections, abnormal hormone levels, and advanced maternal age.

How are sex chromosome aneuploidies characterized?

Aneuploidies that involve variations in the number of X or Y chromosomes, with at least one copy of an X chromosome required for human survival.

What is the G-banding technique used for in karyotyping?

A method where metaphase spreads are treated with trypsin and stained with Giemsa to produce a distinctive banding pattern for identifying chromosomal abnormalities.

What is uniparental disomy (UPD)?

A condition where both copies of a chromosome are inherited from a single parent, associated with disorders like Prader-Willi syndrome and Angelman syndrome.

Describe the process of amniocentesis for chromosomal analysis.

A procedure to recover fetal cells from amniotic fluid around the 16th week of pregnancy, for karyotype preparation and metabolic disorder screening.

What is a karyotype?

An image of a complete set of chromosomes photographed from a metaphase cell, arranged in pairs by size and centromere location.

What are the two major types of translocations?

Reciprocal translocations and Robertsonian translocations.

What is triploidy, and how common is it?

A genetic condition where there are three copies of each chromosome, observed in 1% of all conceptions but often results in miscarriage.

What is aneuploidy?

Changes in chromosome numbers involving less than the duplication of a whole chromosome set, often the gain or loss of a single chromosome.

Describe the characteristics of Down syndrome (Trisomy 21).

Occurs in 1 in 800 live births; commonly associated with childhood intellectual disability and heart defects.

What are common risks for autosomal trisomy?

Genetic predisposition, exposure to radiation, viral infections, abnormal hormone levels, and advanced maternal age.

How are sex chromosome aneuploidies characterized?

Aneuploidies that involve variations in the number of X or Y chromosomes, with at least one copy of an X chromosome required for human survival.

What is the G-banding technique used for in karyotyping?

A method where metaphase spreads are treated with trypsin and stained with Giemsa to produce a distinctive banding pattern for identifying chromosomal abnormalities.

What is uniparental disomy (UPD)?

A condition where both copies of a chromosome are inherited from a single parent, associated with disorders like Prader-Willi syndrome and Angelman syndrome.

Describe the process of amniocentesis for chromosomal analysis.

A procedure to recover fetal cells from amniotic fluid around the 16th week of pregnancy, for karyotype preparation and metabolic disorder screening.

What is nondisjunction?

The failure of homologous chromosomes or sister chromatids to separate properly during cell division, leading to aneuploidy.

What is a reciprocal translocation?

A rearrangement where two different chromosomes exchange segments of genetic material.

What is a Robertsonian translocation?

A specific type of translocation that occurs between two acrocentric

What is a karyotype?

An image of a complete set of chromosomes photographed from a metaphase cell, arranged in pairs by size and centromere location.

What are the two major types of translocations?

Reciprocal translocations and Robertsonian translocations.

What is triploidy, and how common is it?

A genetic condition where there are three copies of each chromosome, observed in 1% of all conceptions but often results in miscarriage.

What is aneuploidy?

Changes in chromosome numbers involving less than the duplication of a whole chromosome set, often the gain or loss of a single chromosome.

Describe the characteristics of Down syndrome (Trisomy 21).

Occurs in 1 in 800 live births; commonly associated with childhood intellectual disability and heart defects.

What are common risks for autosomal trisomy?

Genetic predisposition, exposure to radiation, viral infections, abnormal hormone levels, and advanced maternal age.

How are sex chromosome aneuploidies characterized?

Aneuploidies that involve variations in the number of X or Y chromosomes, with at least one copy of an X chromosome required for human survival.

What is the G-banding technique used for in karyotyping?

A method where metaphase spreads are treated with trypsin and stained with Giemsa to produce a distinctive banding pattern for identifying chromosomal abnormalities.

What is uniparental disomy (UPD)?

A condition where both copies of a chromosome are inherited from a single parent, associated with disorders like Prader-Willi syndrome and Angelman syndrome.

Describe the process of amniocentesis for chromosomal analysis.

A procedure to recover fetal cells from amniotic fluid around the 16th week of pregnancy, for karyotype preparation and metabolic disorder screening.

What is nondisjunction?

The failure of homologous chromosomes or sister chromatids to separate properly during cell division, leading to aneuploidy.

What is a reciprocal translocation?

A rearrangement where two different chromosomes exchange segments of genetic material.

What is a Robertsonian translocation?

A specific type of translocation that occurs between two acrocentric chromosomes, involving the fusion of their long arms and the loss of the short arms.

What specific chromosomal abnormality causes Down syndrome?

Down syndrome is caused by Trisomy 21, meaning there are three copies of chromosome 21 instead of the usual two.

What are acrocentric chromosomes?

Chromosomes where the centromere is located very close to one end, resulting in a very short p arm and a long q arm. In humans, chromosomes 13, 14, 15, 21, and 22 are acrocentric.

Name two common sex chromosome aneuploidies and their chromosomal complements.

• **Klinefelter syndrome:** XXY (extra X chromosome in males)
• **Turner syndrome:** XO (missing an X chromosome in females)

What is the primary diagnostic purpose of karyotyping?

Karyotyping is primarily used to detect chromosomal abnormalities, such as aneuploidies, translocations, deletions, and duplications, which can cause genetic disorders.