Sex chromosomes

In most species of animals the sex of individuals is determined decisively at the time of fertilization of the egg, by means of chromosomal distribution. This process is the most clear-cut form of sex determination. When any cell in the body divides, except… Individuals having two X chromosomes XX are female; individuals having one X chromosome and one Y chromosome XY are male. The X chromosome resembles a large autosomal chromosome with a long and a short arm.

Sex chromosomes

Sexual differentiation in humans All diploid organisms with allosome-determined sex get half of their allosomes from each of their parents. Sex chromosomes a mammal to be chromosomally female, the individual must receive an X chromosome from both parents, whereas to be chromosomally male, the individual must receive a X chromosome from their mother and a Y chromosome from their father.

However, a small percentage of humans have a divergent sexual development, known as intersex.

Sex Chromosome | Definition of Sex Chromosome by Merriam-Webster

This can result from allosomes that are neither XX nor XY. It can also occur when two fertilized embryo fuse, producing a chimera that might contain two different sets of DNA one XX and the other XY.

It could also result from exposure, often in utero, to chemicals that disrupt the normal conversion of the allosomes into sex hormones and further into the development of either ambiguous outer genetilia or internal organs. Genes that are carried by either sex chromosome are said to be sex linked.

Sex linked diseases are passed down Sex chromosomes families through one of the X or Y chromosomes. Since only men inherit Y chromosomes, they are the only ones to inherit Y-linked traits.

Sex chromosomes

Men and women can get the X-linked ones since both inherit X chromosomes. Dominant inheritance occurs when an abnormal gene from one parent causes disease even though the matching gene from the other parent is normal. The abnormal allele dominates. Recessive inheritance is when both matching genes must be abnormal to cause disease.

If only one gene in the pair is abnormal, the disease does not occur, or is mild. Someone who has one abnormal gene but no symptoms is called a carrier. A carrier can pass this abnormal gene to his or her children.

Most of them code for something other than female anatomical traits. Many of the non-sex determining X-linked genes are responsible for abnormal conditions. The Y chromosome carries about 78 genes. Most of the Y chromosome genes are involved with essential cell house-keeping activities and sperm production.

Only one of the Y chromosome genes, the SRY gene, is responsible for male anatomical traits. When any of the 9 genes involved in sperm production are missing or defective the result is usually very low sperm counts and infertility.

Color blindness or color vision deficiency is the inability or decreased ability to see color, or perceive color differences, under normal lighting conditions. Color blindness affects many individuals in the population. There is no actual blindness, but there is a deficiency of color vision.

The most usual cause is a fault in the development of one or more sets of retinal cones that perceive color in light and transmit that information to the optic nerve. This type of color blindness is usually a sex-linked condition.

The genes that produce photopigments are carried on the X chromosome; if some of these genes are missing or damaged, color blindness will be expressed in males with a higher probability than in females because males only have one X chromosome.

Hemophilia refers to a group of bleeding disorders in which it takes a long time for the blood to clot. This is referred to as X-Linked recessive.

They only have one copy of the gene in question and therefore express the trait when they inherit one mutant allele. In contrast, a female must inherit two mutant alleles, a less frequent event since the mutant allele is rare in the population.

X-linked traits are maternally inherited from carrier mothers or from an affected father. Queen Victoria was a carrier of the gene for hemophilia.

She passed on the harmful allele to one of her four sons and at least two of her five daughters.Chromosomal basis of sex determination. X and Y chromosomes, X-linkage. The XX/XY sex-determination system is the most familiar, as it is found in humans.

The XX/XY system is found in most other mammals, as well as some this system, most females have two of the same kind of sex chromosome (XX), while most males have two distinct sex chromosomes (XY).

May 31,  · In the human body, every cell that has a nucleus also carries 23 pairs of chromosomes except the germ cells/ gametes which carry a combination of 22+ X or 22 + Y (only 23 chromosomes)depending on the gender.

Sex chromosomes & X-linked inheritance (article) | Khan Academy

mature RBCs do not have a nucleus and hence lack chromosomes as well. Sex chromosome, either of a pair of chromosomes that determine whether an individual is male or sex chromosomes of human beings and other mammals are designated by scientists as X and humans the sex chromosomes comprise one pair of the total of 23 pairs of chromosomes.

The other 22 pairs of chromosomes are called autosomes. sex chromosome or heterosome one of a pair of chromosomes that is different in the two sexes and is involved in SEX remaining chromosomes in a KARYOTYPE are called 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 .

Supplement. A somatic cell contains a genome comprised of paired chromosomes: the autosomes and sex chromosomes. A sex chromosome is a type of chromosome responsible for the chromosomal determination of the sex of an individual, e.g.

whether a female or a male.

sex chromosome | Definition, Examples, & Facts |