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Human genetics. Human genetics is the study of inheritance as it occurs in human beings. Human genetics encompasses a variety of overlapping fields including: classical genetics, cytogenetics, molecular genetics, biochemical genetics, genomics, population genetics, developmental genetics, clinical genetics, and genetic counseling.
A variety of human hair colors; from top left, clockwise: black, brown, blonde, white, red. Human hair color is the pigmentation of human hair follicles and shafts due to two types of melanin: eumelanin and pheomelanin. Generally, the more melanin present, the darker the hair. Its tone depends on the ratio of black or brown eumelanin to yellow ...
Mendelian traits in humans. A 50/50 chance of inheritance. Sickle-cell disease is inherited in the autosomal recessive pattern. When both parents have sickle-cell trait (carrier), a child has a 25% chance of sickle-cell disease (red icon), 25% do not carry any sickle-cell alleles (blue icon), and 50% have the heterozygous (carrier) condition. [1]
Red hair, also known as ginger hair, is a human hair color found in 2–6% of people of Northern or Northwestern European ancestry and lesser frequency in other populations. It is most common in individuals homozygous for a recessive allele on chromosome 16 that produces an altered version of the MC1R protein. [ 1 ]
A rex rabbit. The rex mutation is a genetic variation in mammals that results in soft curly fur. These effects are due to changes in the structure of groups of hairs and cross-section of individual hairs. The rexed coats are unusual but occur (and have been preserved) in cats, rats, rabbits, horses, and dogs.
Analysis of the pedigree using the principles of Mendelian inheritance can determine whether a trait has a dominant or recessive pattern of inheritance. Pedigrees are often constructed after a family member afflicted with a genetic disorder has been identified. This individual, known as the proband, is indicated on the pedigree by an arrow. [6]
In a dominant-recessive inheritance, an average of 25% are homozygous with the dominant trait, 50% are heterozygous showing the dominant trait in the phenotype (genetic carriers), 25% are homozygous with the recessive trait and therefore express the recessive trait in the phenotype. The genotypic ratio is 1: 2 : 1, and the phenotypic ratio is 3: 1.
Menkes disease. Menkes disease (MNK), also known as Menkes syndrome, [ 1 ][ 2 ] is an X-linked recessive disorder caused by mutations in genes coding for the copper-transport protein ATP7A, [ 3 ] leading to copper deficiency. [ 4 ][ 5 ] Characteristic findings include kinky hair, growth failure, and nervous system deterioration.