Nondisjunction:An accident of meiosis or mitosis, in which both members of a pair of homologous chromosomes or both sister chromatids fail to move apart properly.

Recessive Genes:A gene that is expressed only when it is present in two copies or if theother copy is missing.

Dominant Genes: (Of, or pertaining to) An allele or a gene that is expressed in an organism’s phenotype, masking the effect of the recessive allele or gene when present.

Somatic Cell any cell of a living organism other than the reproductive cells.

Germ cell Either the egg or the sperm cell; a reproductive cell. Each mature germ cell is haploid, meaning that it has a single set of 23 chromosomes containing half the usual amount of DNA and half the usual number of genes. Except for the egg and the sperm, most cells in the human body contain the entire human genome. Also known as a gamete.

Tell me about a Karyotype and how the genotype can change the phenotype.

Why is genotype not the only factor that affects phenotype? Because the environment can cause changes to ones appearance.

a karyotype is the number and visual appearance of the chromosomes in the cell nuclei of an organism or species.


Kleinfetter's syndrome- Klinefelter syndrome is a genetic disorder that affects males. Klinefelter syndrome occurs when a boy is born with one or more extra X chromosomes. Most males have one Y and one X chromosome. Having extra X chromosomes can cause a male to have some physical traits unusual for males.

Down Syndrome- congenital disorder, caused by the presence of an extra 21st chromosome, in which the affected person has mild to moderate mental retardation, short stature, and a flattened facial profile. Also called trisomy 21, trisomy 21 syndrome.

Colorblindness a sex-linked inherited condition where there is an inability to distinguish colours. Very few women are colour blind, but up to 10% of all men have some degree of colour blindness. The most common for is red-green colour blindness. The second most common is blue-yellow.

Turner's disease A rare genetic disorder (1 in 3,000 births) in women that is characterised by the absence of an x chromosome. This disorder inhibits normal sexual development and causes infertility.


Created with images by Simon Strandgaard - "deuteranopia - colorblind simulation"

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