Pedigree

Pictorial representation of a family history outlining the inheritance of one or more traits or diseases.

TLS Online TPP Program

#Id: 6969

#Unit 8. Inheritance Biology

Aneuploidy

TLS Online TPP Program

#Id: 6970

#Unit 8. Inheritance Biology

Aneuploidy can arise in several ways

Chromosome may be lost during mitosis or meiosis.

The small chromosome generated by a Robertsonian translocation may be lost in mitosis or meiosis.

Aneuploidy may arise through nondisjunction.

TLS Online TPP Program

#Id: 6971

#Unit 8. Inheritance Biology

Types of Aneuploidy

Nullisomy is the loss of both members of a homologous pair of chromosomes. It is represented as 2n-2.

Monosomy is the loss of a single chromosome, represented as 2n-1. 

Trisomy is the gain of a single chromosome, represented as 2n+1. 

Tetrasomy is the gain of two homologous chromosomes, represented as 2n+2. 

TLS Online TPP Program

#Id: 6972

#Unit 8. Inheritance Biology

Nondisjunction

TLS Online TPP Program

#Id: 6973

#Unit 8. Inheritance Biology

SEX-CHROMOSOME ANEUPLOIDIES 

The most common aneuploidies seen in living humans.

Aneuploidy of the human sex chromosomes is better tolerated than aneuploidy of autosomes.

AUTOSOMAL ANEUPLOIDIES

There is no mechanism of dosage compensation for autosomes.

TLS Online TPP Program

#Id: 6974

#Unit 8. Inheritance Biology

DOWN SYNDROME Also known as trisomy 21, is the most common autosomal aneuploidy in humans About 75% of the nondisjunction events that cause Down syndrome are maternal in origin, most arising in meiosis I.