Hox genes & synpolydactyly

王鈞立 B9902003

林孟萱 B9902025

Homeotic genes

• Homeotic genes are genes that control pattern formatoin.

• For example, homeotic genes are involved in determining where, when, and how body segments develop in flies.

• in the case of plants, flowers with abnormal numbers of parts.

Hox genes

• are a group of regulatory genes that control the timing and route of development.

• Contain a DNA sequence known as the homeobox

• their location in gene clusters on the genome

• Hox genes are highly conserved in evolution, suggesting that they are of ancient origin.

Hox gene(homeobox-containing genes)

Homeobox 180-nucleotide sequences

Homeodomain(transcription regulator)

Contain 60 amino acid

Homeotic?

homeodomain

• The protein products of Hox genes

• Transcription factor which can bind to any DNA segment. But it cannot determine which genes it regular.

• Proteins with homeodomains switch the development genes on or off.

homeobox

• A homeobox is a DNA sequence found within genes that are involved in the regulation of patterns of anatomical development (morphogenesis) in animals, fungi and plants.

• a 180 nucleotide long DNA sequence that encodes a 60 amino acid long protein domain known as the homeodomain.

Mutation of homeotic genes cause homeotic transformations, in which one segment or part of the body is replaced by another or duplicated.

Mutatoin

Synpolydactyly (Type II syndactyly )

• Mutations in human Hox genes result in limb development defects

• Many digits joined together

• a joint presentation of syndactyly and polydactyly

• have been designated as SPD1, SPD2 and SPD3

• Both polyalanine tract expansions and frameshifting deletions in HOXD13 cause similar forms of this condition

• webbing between 3/4 fingers and between 4/5 toes with partial or complete digit duplication.

• a large Pakistani and an Indian family with SPD.

• Three loci have been identified at chromosomes 2q31, 22q13.31 and 14q11.2-q12, and have been designated as SPD1, SPD2 and SPD3, respectively

• Unique expansion mutations in a poly alanine repeat