sex chromosome


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sex chromosome

n.
Either of a pair of chromosomes in diploid cells, or a single chromosome in haploid cells, carrying genes that determine the sex and sex-linked characteristics of an organism. Most mammals, including humans, have one pair of sex chromosomes in diploid cells, designated XX in females and XY in males.

sex chromosome

a chromosome that determines the sex of individuals; it carries genes that transmit sex-linked traits and conditions. In humans and other mammals there are two distinct sex chromosomes, designated X and Y, which appear in females as XX and in males as XY. Compare autosome.

sex chromosome

or

heterosome

one of a pair of chromosomes that is different in the two sexes and is involved in SEX DETERMINATION. All remaining chromosomes in a KARYOTYPE are called AUTOSOMES. In most organisms, such as mammals and DIOECIOUS plants, the female contains two identical X-chromosomes and is the HOMOGAMETIC SEX while the male contains one X and one Y-chromosome and is the HETEROGAMETIC SEX. In birds, butterflies and moths, some fish and certain plants, the situation is reversed in the two sexes. Genes located on sex chromosomes are described as showing SEX LINKAGE.

chromosome 

One of the thread-like structures located within the cell nucleus composed of an extremely long, double-stranded DNA (deoxyribonucleic acid) helix tightly folded around proteins called histones. Each chromosome carries genes that contain the hereditary material that controls the growth and characteristics of the body. There are 46 chromosomes in each human somatic cell organized in 23 pairs, of which 22 pairs are similar in appearance but differ at the molecular level. They are called autosomal chromosomes or autosomes and are designated by a number (with chromosome 1 being the longest, followed by chromosome 2, etc.). The other pair, the sex chromosomes determines the sex of the individual. In mammals the two sex chromosomes of females are alike (homologous) and are referred to as X chromosomes. Males carry one X chromosome along with a much shorter chromosome, the Y chromosome. Each chromosome has a centromere that divides it into two arms, the short arm 'p' and the long arm 'q'. Disorders of chromosome number in which the number of chromosomes is above or below the normal (46) are called aneuploidy. Common forms of aneuploidy are trisomy in which there is one extra chromosome and monosomy in which there is one less, than the normal 46. They rarely cause specific eye diseases but affected individuals present ocular manifestations. Examples: Down's syndrome (trisomy of chromosome 21), Edwards' syndrome (trisomy 18), Turner's syndrome (monosomy 45 XO). There are other chromosome abnormalities such as translocation (one segment of a chromosome is transferred to another chromosome) as may occur in congenital anterior polar cataract, deletion (a loss of a piece of chromosome) as in aniridia, choroideremia, retinoblastoma, etc. Other cases involve damage of a chromosome (e.g. fragile X syndrome). See defective colour vision; gene; mitosis; mutation.
References in periodicals archive ?
8%), all 3 sex chromosome aneuploidies were called correctly, and there was 1 false-negative sex chromosome result called (63).
40) Also, commercially available cfDNA-based NIPT tests that utilize counting methodologies typically do not routinely report X and Y chromosome copy number, but will report sex chromosome anomalies when detected.
There are certain aspects to the composition of these sex chromosomes that have intrigued evolutionary biologists for a long time," Karr said.
Of the four pesticide studies that investigated aneuploidy in the sex chromosomes (Recio et al.
Multiple sex chromosomes in the genus Hoplias (Pisces, Erythrinidae).
Along with trisomy 21, sex chromosome aneuploidies account for the majority of aneuploidies in children who survive.
This means that even lab mice with odd numbers of sex chromosomes - for instance males with two X's or females that have a Y - still developed normally; they had normal genitalia and sexual behaviours for their gender.
Topics addressed include germline stem cells, molecular regulation of the mitosis/meiosis decision in multicellular organisms, sex chromosome function in mammalian fertility, transcription regulation in male germ cells, translation control in oocyte development, RNA granules in germ cells, germ cell intercellular bridges, small noncoding RNAs in the germline, mammalian genomic imprinting, and nuclear transfer to eggs and oocytes.
We classified the individuals with sex chromosome aneuploidy or mosaicism as carriers and individuals with chromosomal polymorphism (Table 1).
Only one study has investigated associations between benzene exposure and sex chromosome aneuploidy (Liu et al.
Among the topics are silkworm genetics and genomics, the rise and fall of the W chromosome, the sex chromosome and sex determination in Bombyx mori, molecular and physiological innovations of butterfly eyes, circadian clocks, lepidopteran chemoreceptors, genetics and molecular biology of the major crop pest genus Helicoverpa, innate immune responses of Manduca sexta, lepidopterans as model mini-hosts for human pathogens and as a resource for peptide antibiotics, and the interactions between polydnavirus-carrying parasitoids and their lepidopteran hosts.