Chromosome Structure and Functions

Study Notes

Chromosome Structure and Functions

Human body contains 46 chromosomes organized into 23 pairs (diploid).
Homologous chromosomes are pairs of chromosomes of the same length and appearance, inherited from each parent.
Two main types of chromosomes:
- Autosomes: Chromosomes 1-22 (non-sex chromosomes).
- Sex Chromosomes: The 23rd pair, determining the biological sex of an individual.

Sex Chromosomes

Female sex chromosomes: XX.
Male sex chromosomes: XY.
X is the largest sex chromosome, while Y is the smallest.

Karyotyping

Karyotyping is a technique used to visualize a complete set of chromosomes.
Chromosomes are grouped in pairs and arranged from largest to smallest, resulting in a karyogram.

Meiosis and Chromosomal Abnormalities

Expected chromosome number after meiosis is 23.
Errors during meiosis can lead to abnormal chromosome counts, resulting in chromosomal abnormalities.
Nondisjunction occurs when homologous chromosomes or sister chromatids fail to separate during meiosis, leading to various forms of aneuploidy.

Ploidy Levels

Euploidy: Normal number of chromosome sets in a cell.
Aneuploidy: Abnormal number of chromosomes, which can be due to missing or extra chromosomes.
Types of aneuploidy include:
- Monosomy: Presence of only one chromosome from a pair.
- Trisomy: Presence of three copies of a chromosome.

Examples of Chromosomal Abnormalities

Turner Syndrome (45, XO):
- Affects females with a single X chromosome.
- Symptoms include underdeveloped reproductive organs, short stature, webbed neck, and swelling of hands/feet.
Down Syndrome (Trisomy 21):
- Caused by three copies of chromosome 21.
Klinefelter Syndrome (47, XXY):
- Males with one or more extra chromosomes (can be 48, XXXY or 49, XXXXY).
- Symptoms include underdeveloped reproductive organs, delayed puberty, and language-based learning disabilities.
Jacob Syndrome (47, XYY):
- Males with an extra Y chromosome; sometimes referred to as Supermale or Criminal Syndrome.
Trisomy X (47, XXX):
- Females with an extra X chromosome, typically normal in appearance but may struggle with speech, learning, and experience infertility.

Key Terms

Nondisjunction: Failure of chromosomes to separate during meiosis.
Karyotyping: Method to view the complete set of chromosomes.
Karyogram: The resulting visual output from karyotyping.
Chromosomal abnormalities arise from errors in cell division or duplications/deletions of chromosome segments.

Description

Explore the intricate world of chromosomes with this quiz. Understand the differences between autosomes and sex chromosomes, the role of karyotyping, and the implications of errors in meiosis. Test your knowledge on how these factors influence human biology.