A widow’s peak is a V-shaped point in the hairline in the center of the forehead. Hair growth on the forehead is suppressed in a bilateral pair of periorbital fields. Normally, these fields join in the middle of the forehead so as to give a hairline that runs straight across. Widow’s peak results when the point of intersection on the forehead of the upper perimeters of these fields is lower than usual.
Hypertrichosis (also called Adams syndrome) is an abnormal amount of hair growth on the body;[1][2] extensive cases of hypertrichosis have informally been called werewolf syndrome.[3] The two distinct types of hypertrichosis are generalized hypertrichosis, which occurs over the entire body, and localized hypertrichosis, which is restricted to a certain area.[1] Hypertrichosis can be either congenital (present at birth) or acquired later in life.[3][4] The excess growth of hair occurs in areas of the skin with the exception of androgen-dependent hair of the pubic area, face, and axillary regions.[5]
Hitchhiker’s thumb is a recessive trait, which means that people must inherit the gene from both parents for it to manifest. People can also carry the gene without exhibiting the trait, by inheriting the gene from one parent only.
The human earlobe is composed of tough areolar and adipose connective tissues, lacking the firmness and elasticity of the rest of the pinna. Since the earlobe does not contain cartilage it has a large blood supply and may help to warm the ears and maintain balance. However earlobes are not generally considered to have any major biological function.[
The Essay on Gene Therapy 2
Gene therapy is the use of genes and the techniques of genetic engineering in the treatment of a genetic disorder or chronic disease. Most of the techniques are still being experimented and are awaiting government approval (Concise Columbia Electronics Encyclopedia). Some 2000 to 3000 diseases have been determined as genetic or hereditary (Access Excellence). With the perfection of gene therapy ...
a pattern of inheritance in which the transmission of traits depends on the presence or absence of certain alleles on the autosomes. The pattern may be dominant or recessive, and males and females are usually affected with equal frequency. The majority of hereditary disorders are the result of a defective gene on an autosome. Kinds of autosomal inheritance are autosomal-dominant inheritance and autosomal-recessive inheritance.
Autosomal Inheritance
Autosomal inheritance describes the patterns of genetic transmission related to genes located on autosomal chromosomes. Accordingly, autosomal dominant or autosomal recessive inheritance patterns are based upon transmission of genes found on chromosomes other than the sex chromosomes. Autosomal inheritance patterns account for approximately half of genetic diseases and abnormalities.
All chromosomes found in human cells, except the X and Y sex chromosomes, are autosomes. Human cells carry 22 pairs of homologous autosomal chromosomes. Autosome pairs are numbered, largest to smallest, from 1 to 22. In normal human cells, one of the homologous chromosomes in each pair comes from the mother, the other is donated by the father. Homologous autosomal chromosomes contain similar, but not identical genes. Although normal homologous autosomes contain the same genes (e.g., the gene for a particular trait) each may carry a different form of the gene (allele).
Autosomal dominant inheritance occurs when an allele of one the chromosomes of a homologous pair (i.e., derived from one parent) of autosomal chromosomes is able to express itself regardless of what allele is present on the homologous chromosome. With autosomal dominant inheritance, if an abnormal gene located on an autosomal chromosome is a dominant gene, it is able to cause the expression of a trait or disease even though the corresponding gene on the homologous chromosome is normal.
Autosomal recessive inheritance occurs when an allele of one the chromosomes of a homologous pair (i.e., derived from one parent) of autosomal chromosomes is incapable of expressing the trait or disease it codes for unless another copy of the recessive gene is present on the homologous chromosome. With autosomal recessive inheritance, if an abnormal gene located on an autosomal chromosome is a recessive gene, it is only able to cause the expression of a trait or disease if a copy of the abnormal gene is also present on the homologous autosomal chromosome.
The Term Paper on Gene Expression
We need to know how the elements in the DNA sequence or the words on a list work together to make the masterpiece. In cell biology, the question comes down to gene expression. Even the simplest single-celled bacterium can use its genes selectively—for example, switching genes on and off to make the enzymes needed to digest whatever food sources are available. And, in multicellular plants and ...
When homologous pairs carry a dominant and a recessive gene (heterozygosity), the dominant gene is expressed. Such heterozygous individuals are, however, capable as acting as carriers of the disease or trait because they may pass on the abnormal allele to their children. With autosomal recessive inheritance, if both parents are heterozygous carriers of an abnormal recessive gene located on an autosome, there is 25% statistical chance (.25 statistical probability) that they will have a child that inherits both abnormal recessive genes. Because both parents contribute one chromosome to a pair of homologous autosomal chromosomes, there is a 50% chance that a child will inherit at least one of the abnormal genes and become a carrier of the recessive gene or trait.
The gene for cystic fibrosis, a disease that can result in chronic or lethal obstructions of the airway, are passed from parents to children by autosomal recessive inheritance. Both parents must carry the cystic fibrosis genes for a child to be affected with the disease. At present, more than 400 genes are associated with cystic fibrosis transmission, all located on autosomal chromosome seven.
Although the presence of a dominant autosomal gene results in the expression of an often adverse (deleterious) trait such genes are maintained in a population due to variable expressivity, high mutation rates, onset of the trait after the reproductive years have passed (late onset), and incomplete penetrance. Variable expressivity results when individuals exhibit only a portion of the range of symptoms associated with a particular disease or when the severity of such expression is variable. High mutation rates, such as those associated with Achondroplasia, persist in reintroducing the same deleterious alleles into a population, even when strongly selected against at the phenotypic level (e.g., fetal death).
The Term Paper on Cystic Fibrosis Gene Patients Disease
... an autosomal recessive gene. That means that it may, but does not always skip generations. In order to get this disease, ... alone carry the defective gene and are not aware of it because the dominant gene masks the recessive gene (2). Consequently, it ... became overwhelmed with dehydrated CF children (4). These children became dehydrated much quicker than children without the disorder. Thus eventually ...
Late onset diseases, such as Huntington disease, do not usually produce adverse symptoms until after the reproductive years have passed (i.e., an individual has an opportunity to pass on deleterious genes before being adversely affected. Incomplete penetrance (along with variable expressivity, relevant only in cases of autosomal dominant inheritance), allows an individual to carry an unexpressed dominant gene that may once again be expressed as a dominant gene in his or her children.
During meiosis in organisms with a full set of chromosomes (diploid organisms), the homologous autosomal chromosomes align and allow a crossing over of genetic material that causes a reassortment of maternal and paternal genes (genes from the mother and father).
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