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Over 100 years of theoretical and experimental genetics studies, and the more recent sequencing and annotation of the human genome, have helped scientists to develop a better understanding of how an individual’s genotype is expressed as their phenotype. This body of knowledge can help scientists and medical professionals to predict, or at least estimate, some of the features that an offspring will inherit by examining the genotypes or phenotypes of the parents. One important application of this knowledge is to identify an individual’s risk for certain heritable genetic disorders. However, most diseases have a multigenic pattern of inheritance and can also be affected by the environment, so examining the genotypes or phenotypes of a person’s parents will provide only limited information about the risk of inheriting a disease. Only for a handful of single-gene disorders can genetic testing allow clinicians to calculate the probability with which a child born to the two parents tested may inherit a specific disease.

Mendel’s theory of inheritance

Our contemporary understanding of genetics rests on the work of a nineteenth-century monk. Working in the mid-1800s, long before anyone knew about genes or chromosomes, Gregor Mendel discovered that garden peas transmit their physical characteristics to subsequent generations in a discrete and predictable fashion. When he mated, or crossed, two pure-breeding pea plants that differed by a certain characteristic, the first-generation offspring all looked like one of the parents. For instance, when he crossed tall and dwarf pure-breeding pea plants, all of the offspring were tall. Mendel called tallness dominant    because it was expressed in offspring when it was present in a purebred parent. He called dwarfism recessive    because it was masked in the offspring if one of the purebred parents possessed the dominant characteristic. Note that tallness and dwarfism are variations on the characteristic of height. Mendel called such a variation a trait    . We now know that these traits are the expression of different alleles of the gene encoding height.

Mendel performed thousands of crosses in pea plants with differing traits for a variety of characteristics. And he repeatedly came up with the same results—among the traits he studied, one was always dominant, and the other was always recessive. (Remember, however, that this dominant–recessive relationship between alleles is not always the case; some alleles are codominant, and sometimes dominance is incomplete.)

Using his understanding of dominant and recessive traits, Mendel tested whether a recessive trait could be lost altogether in a pea lineage or whether it would resurface in a later generation. By crossing the second-generation offspring of purebred parents with each other, he showed that the latter was true: recessive traits reappeared in third-generation plants in a ratio of 3:1 (three offspring having the dominant trait and one having the recessive trait). Mendel then proposed that characteristics such as height were determined by heritable “factors” that were transmitted, one from each parent, and inherited in pairs by offspring.

Questions & Answers

5. Discuss thoroughly the renal regulation of acid-base balance in the body with the illustration of conservation of bicarbonate ion in the kidney
Jonathan Reply
What is anatomy
Tiamiyu Reply
anatomy is the study of the different organs of the body being internal and external organ
Cyrille
is't possible for non-identical twins to have different father ? ?
Cyrille
ANATOMY is the scientific study of the structure of human or animal bodies.
jagriti
Anatomy is the branch of science concerned with the bodily structure of humans, animals, and other living organisms, especially as revealed by dissection and the separation of parts.
Brightone
anatomy is the branch of science that duty with the study structure of the human and living organisms.
Masiame
examples of lymph nodes
Arimpa Reply
Clusters of lymph nodes are found in the neck, axilla (underarm), chest, abdomen, and groin. For example, there are about 20-40 lymph nodes in the axilla. Also called lymph gland. Anatomy of the lymph system, showing the lymph vessels and lymph organs including lymph nodes, tonsils, thymus, spleen,
Adnan
Excellent 😊
Sharon
in part of body where did we get medulla
Olawale Reply
Are you referring to the medulla oblongata? In which case, this is a part of the brain, located at the brain stem. It controls a lot of our unconscious behaviors such as motor coordination, breathing, etc.. But medulla generally refers to an innermost structure, so it can be found in hair or kidneys
Elliot
How does blood circulate in the upper limbs
Mary Reply
From the aortic arch, blood is supplied to the brain via the R and L carotid arteries. To supply the upper limbs, blood goes to the R and L subclavian arteries, axillary, radial/ulnar, palmar and carpal arteries.
Elliot
describe the muscles found in the heart
Atotwe Reply
myocardial
Kenndy
thank you very much
Atotwe
asalamu aleikum
Cabdala
waalekum salam
Tifu
types of connective tissues?
Tifu
the muscle found in the body is myocardial muscles
Freeman
what is a muscular system and details about it
Jackson Reply
what is the type of homones responseble for blenking of eyes
Moses Reply
what are the functions of cell?
Keyirangzile Reply
how does the femur act as a lever?
Mutoni Reply
what is stumac
Abdussalam Reply
What is phagocytosis
Mohamed Reply
Phagocytosis, process by which certain living cells called phagocyte
Sadashiv
It is the process that is carried out by the immune system of the body, that certain specialized immune cells (macrophages, Nks, dendritic cells, etc) that engulf and neutralize the foreign substances that invades the body.
Wesley
So that they can be predicate out of the body.
Wesley
phagocytosis is the process by which living cell or yh plasma membrane engulf large molecules into it internal environment ... it also known as food feeding
Boateng
all that you are say what does it mean?
Dzah
simply is the way the immune system fights foreign bodies by engulfing them..
Dzah
by the help of the immune cells...
Dzah
The process by which a cell engulfs particles such as bacteria, other microorganisms, debris of dead cell.e.g: neutrophils and monocytes (types of white blood cells)
Tifu
what are the six types of connective tissues
Athieno Reply
loose and dense , cartilage and bone , blood and lymph
Queen
describe the structure of the liver
Atwebembeire Reply
what is specific name for spinal cord
Stanley Reply
what is the best description for skeletal muscular
Stanley
what is the best description for skeletal muscular
Stanley
costs of bones of skeleton, their joint s and voluntary
grace
what are examples of long bones
grace
example of long bones will be the femur tibia and humerus and even radius
Nina
so basically long bones are mostly in you hands and feets
Nina
skeletal muscular are voluntary and are attached to the bone by tendon which help maintain the posture and position of the body and it also protects internal organs in the abdominal region
Nina
The specific name for spinal cord is coccygeal segment
Sandra
what are the hormones responseble for blenking of eyes.
Moses
vertebral column
SRIPRIYADHARSHINI

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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