Chapter 21: Sex Chromosome Haplotyping and Gender Identification

Patrilineage

The Y chromosome is inherited from the father and is passed on to all male offspring.

Pseudoautosomal Regions (PARs)

Homologous nucleotide sequences that are present on the X and Y chromosomes.

PAR1

It is located on the terminal region of the short arm. It comprises 2.6 Mb. Twenty-four genes have been identified within the PAR1.

PAR2

It is located at the tip of the long arm. It comprises 320 kb, with only four genes identified so far.

Male-Specific Y Region

The remainder of the Y chromosome.

DYF155S1

The first characterized VNTR at the human Y chromosome. It consists of an array of AT-rich repeats at 25 bp per unit repeat.

X-chromosomal STR (X-STR) profiling

is a useful tool in kinship testing in forensic investigations.

homologous PARs

Homologous recombination between the X and Y chromosomes is restricted to the _______.

paternal X chromosome

The _________ is inherited by daughters as haplotypes.

Recombination Fraction

The percentage of recombinants resulting from chromosomal crossover between two loci during meiosis among all the offspring.

Amelogenesis Imperfecta

A disorder that causes abnormal formation of tooth enamel in both primary and permanent teeth.

AMEL X

AMEL locus which is located on the human X chromosome.

AMEL Y

AMEL locus which is located on the human Y chromosome.

Sex-determining region Y (SRY) gene

Encodes a transcription factor that plays a role in the regulation of sex determination toward male development.

HMG box

The SRY protein contains a DNA-binding domain known as the _____.

SOX3

An SRY-related HMG box-containing gene, has been identified at Xq27.1 of the X chromosome, which shares sequence homology with SRY.

TSPY Locus

It encodes the testis-specific protein Y-encoded gene that is only expressed in the testis and may play a role in spermatogenesis.

DYS14

A marker utilized for the characterization of the TSPY locus.

TSPY-like (TSPYL) gene

It has been identified on the short arm of the X chromosome and is designated as TSPYL2.

TSPYL2

A single-copy gene per X chromosome and is 6.3 kb in length, consisting of 7 exons and 6 introns.

DXYS156

A polymorphic pentanucleotide STR. It is located at the pseudoautosomal region of both X and Y chromosomes, is another candidate marker used for sex typing.

DXYS156 Y

Alleles that have an additional adenine insertion in the repeat units of STR.

Steroid sulfatase (STS) gene

Encodes an enzyme that catalyzes the conversion of sulfated steroid precursors to biologically active steroids such as estrogens and androgens.