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Chromosomes : threadlike structures made up of deoxyribonucleic acid, or DNA

Genes: units of hereditary information composed of DNA that help cells to reproduce themselves and manufacture the proteins that maintain life

Gametes: sperm or ova.

The male gametes are produced in the testes through a process called spermatogenesis, which begins at about 12 years of age.

The female gametes, which are stored in the ovaries, are present at birth but are immature.

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Twenty-two of those chromosomes from each parent are similar in length to a corresponding chromosome from the other parent.

However, the remaining chromosome looks like an X or a Y. Half of the male's sperm contain a Y chromosome and half contain an X.

All of the ova contain X chromosomes. If the child receives the combination of XY, the child will be genetically male. If it receives the XX combination, the child will be genetically female.

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Monozygotic: occur when a single zygote or fertilized egg splits apart in the first two weeks of development.

Dizygotic: Sometimes two eggs or ova are released and fertilized by two separate sperm.

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Genetic Disorders and Chromosomal Abnormalities

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Genetic Disorders and Chromosomal Abnormalities

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Genetic disorders are conditions caused by abnormalities in an individual's DNA or chromosomes.

These abnormalities can arise spontaneously or be inherited from one or both parents. Genetic disorders can affect various aspects of health, including physical traits, development, metabolism, and susceptibility to certain diseases.

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Trisomy 21 occurs when there are three rather than two chromosomes on #21.

A person with Down syndrome has distinct facial features, intellectual disability, and oftentimes heart and gastrointestinal disorders.

Symptoms vary from person to person and can range from mild to severe.

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germinal, embryonic, and fetal periods of development.

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germinal, embryonic, and fetal periods of development.

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1. The Germinal Period

Conception occurs when a sperm fertilizes an egg and forms a zygote, which begins as a one-cell structure.

The mother and father’s DNA is passed on to the child at the moment of conception.

2. The Embryonic Period

The embryonic period begins once the zygote is implanted in the uterine wall.

It lasts from the third through the eighth week after conception.

Upon implantation, this multi-cellular organism is called an embryo.

3. The Fetal Period

When the organism is about nine weeks old, the embryo is called a fetus.

At this stage, the fetus is about the size of a kidney bean and begins to take on the recognizable form of a human being as the “tail” begins to disappear.

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Teratogens are usually discovered after an increased prevalence of a particular birth defect. For example, in the early 1960’s, a drug known as thalidomide was used to treat morning sickness.

Exposure of the fetus during this early stage of development resulted in cases of phocomelia, a congenital malformation in which the hands and feet are attached to abbreviated arms and legs.

Alcohol consumption, particularly during the second month of prenatal development, but at any point during pregnancy, may lead to neurocognitive and behavioral difficulties that can last a lifetime.

There is no acceptable safe limit for alcohol use during pregnancy, but binge drinking (5 or more drinks on a single occasion) or having 7 or more drinks during a single week places a child at particularly high risk.

Environmental chemicals can include an exposure to a wide array of agents including pollution, organic mercury compounds, herbicides, and industrial solvents.

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Maternal mortality is unacceptably high. About 830 women die from pregnancy or childbirth-related complications around the world every day.

It was estimated that in 2015, roughly 303,000 women died during and following pregnancy and childbirth.

Almost all of these deaths occurred in low-resource settings, and most could have been prevented.

The high number of maternal deaths in some areas of the world reflects inequities in access to health services and highlights the gap between rich and poor.

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The APGAR is conducted one minute and five minutes after birth. This is a very quick way to assess the newborn's overall condition.

Five measures are assessed: the heart rate, respiration, muscle tone (quickly assessed by a skilled nurse when the baby is handed to them or by touching the baby's palm), reflex response (the Babinski reflex is tested), and color.

A score of 0 to 2 is given on each feature examined. An APGAR of 5 or less is cause for concern.