Question

Define these pairs of terms, and distinguish between them. aneuploidy/euploidy monosomy/trisomy Patau syndrome/Edwards syndrome autopolyploidy/allopolyploidy autotetraploid/amphidiploid paracentric inversion/pericentric inversion

Short answer

Answer: Aneuploidy refers to a chromosomal number that is not an exact multiple of the haploid number, resulting from the loss or gain of one or more chromosomes. Euploidy, on the other hand, is when an organism's chromosomes exist in exact multiples of the haploid number.

Step-by-step solution

Aneuploidy vs Euploidy

Aneuploidy refers to a chromosomal number that is not an exact multiple of the haploid number, resulting from the loss or gain of one or more chromosomes. Euploidy, on the other hand, is when an organism's chromosomes exist in exact multiples of the haploid number.

Monosomy vs Trisomy

Monosomy is a type of aneuploidy in which an organism has a single copy of a chromosome instead of the usual two copies (2n - 1). Trisomy is the presence of an extra chromosome in an organism, resulting in three copies instead of the usual two (2n + 1).

Patau Syndrome vs Edwards Syndrome

Patau Syndrome (also known as Trisomy 13) is a chromosomal abnormality characterized by the presence of an extra copy of chromosome 13. It often results in severe physical and developmental disorders. Edwards Syndrome (also known as Trisomy 18) is a chromosomal abnormality where there is an extra copy of chromosome 18, which also results in severe physical and developmental disorders.

Autopolyploidy vs Allopolyploidy

Autopolyploidy is a type of polyploidy in which an organism has multiple sets of chromosomes that are identical and derived from the same species. Allopolyploidy occurs when an organism has multiple sets of chromosomes derived from different species due to hybridization.

Autotetraploid vs Amphidiploid

Autotetraploid refers to an organism with four sets of chromosomes derived from the same species (4n), which is a type of autopolyploidy. Amphidiploid (also known as allopolyploid) refers to an organism that has two complete sets of chromosomes derived from two different species (2n + 2n).

Paracentric Inversion vs Pericentric Inversion

Paracentric inversion is a chromosomal abnormality in which a segment of chromosome is inverted and does not include the centromere. Pericentric inversion, on the other hand, is a chromosomal inversion that includes the centromere and the inverted segment changes the position of the centromere within the chromosome.

Key concepts

Aneuploidy

Aneuploidy is a condition in which an organism has an abnormal number of chromosomes. Unlike euploidy, where chromosomes are a complete set and multiples of the haploid number, aneuploidy results from a discrepancy. This discrepancy occurs due to the addition or loss of chromosomes, often during cell division.

Common forms of aneuploidy include:

• Monosomy: Missing one chromosome, leading to a 2n-1 condition.
• Trisomy: Having an extra chromosome, resulting in a 2n+1 situation.

Aneuploidy can lead to significant developmental and health issues. It plays a crucial role in conditions like Down syndrome, where there is an extra chromosome 21. Understanding these anomalies is essential because they can give insights into syndromes and disorders, influencing medical diagnosis and treatment approaches.

Polyploidy

Polyploidy occurs when an organism has more than two complete sets of chromosomes. It’s common in plants and rarely found in animals. Polyploidy can result from errors during cell division or hybridization of two species.

Key types of polyploidy include:

• Autopolyploidy: Multiple chromosome sets come from the same species, such as in autotetraploids (4n).
• Allopolyploidy: Multiple chromosome sets come from different species due to hybridization. Commonly seen in crops like wheat, which is an amphidiploid.

In agriculture, polyploidy is an asset. Many crops are polyploid because it can lead to more vigorous growth and improved traits. Ploidy manipulation often results in enhanced plant qualities such as larger fruits and increased resistance to diseases.

Inversion Mutations

Inversion mutations happen when a section of a chromosome is reversed end to end. These mutations can significantly impact an organism by altering gene expression or disrupting important genetic sequences.

Two main types exist:

• Paracentric Inversions: The inverted section does not include the centromere. As a result, these inversions can form loops during meiosis, leading to further chromosomal abnormalities.
• Pericentric Inversions: The inverted section includes the centromere. This type changes the chromosome's overall structure and can impact genetic relationships by adjusting linkage between genes.

Inversion mutations often don’t alter gene content but impact how genes' positions relate to each other on the chromosome. Although they don't typically cause diseases by themselves, they can predispose organisms to certain disorders by affecting genetic stability.