Heredity and Genes

Heredity

• Heredity helps shape human development.
• Genes and chromosomes affect development.
• Nature is the contribution of genetics to development.
• Genes are sequences of nucleotides that are recipes for proteins.
• Proteins influence cell structure and function.
• Genes are located on chromosomes; there are an estimated 20,500 genes for humans.
• Normal human cells contain 46 chromosomes (23 pairs) in the nucleus.
• Most body cells are created through mitosis, where the nucleus makes an exact copy of chromosomes.
• Gametes (sperm or ova) are formed through meiosis.
• During meiosis, gamete chromosomes duplicate and divide twice, resulting in four cells with half the original genetic material.
• Each sperm and egg possesses 23 chromosomes, combining to produce the normal 46 chromosomes.
• The likelihood of having genetically identical offspring (excluding twins) is one in trillions due to the amount of genes and meiosis unpredictability.
• Of the 23 chromosome pairs, 22 are similar in length and called autosomes.
• The remaining pair, or sex chromosomes, may differ in length, with XY indicating a male and XX indicating a female.

Genotypes and Phenotypes

• Genotype is the total sum of genes a person inherits.
• Phenotype is the features that are actually expressed in a person.
• Genes are inherited in pairs on the chromosomes.
  • Homozygous means receiving the same version of a gene from both parents for a characteristic.
  • Heterozygous means receiving a different version of a gene from each parent.
• Dominant genes express themselves in the phenotype even when paired with a different version of the gene.
• Recessive genes express themselves only when paired with a similar version gene.
• Alleles are different versions of a gene.
• Most characteristics result from multiple genes; this is called polygenic.
• Incomplete dominance is when a dominant gene does not completely suppress the recessive gene.
• Sickle cell disease is an example of incomplete dominance, where carriers may experience mild symptoms under oxygen deprivation.
• Monozygotic twins occur when a fertilized egg splits in the first two weeks of development, resulting in genetically identical offspring.
• Dizygotic twins occur when two eggs are fertilized by two separate sperm, resulting in siblings with different genotypes and phenotypes .

Genetic Disorders

• Most known genetic disorders are dominant gene-linked.
• The majority of dominant gene-linked disorders are not serious or debilitating.
  • Huntington's Disease is an exception and is a fatal, dominant gene-linked disorder affecting the nervous system that appears in midlife.
• Recessive gene disorders are less common but may claim more lives as people may be unaware they are carriers.
• In sex-linked disorders, defective genes are found on the X-chromosome.
• Males are at greater risk for recessive sex-linked disorders as they only have one X chromosome.
• Females need to inherit the recessive gene on both X chromosomes to be affected, but can be equally at risk if the defective gene is dominant.
• In Recessive Disorders (Homozygous), the individual inherits a gene change from both parents, and if inherited from just one parent, the person is a carrier.
  • Sickle Cell Disease (SCD) affects oxygen transport by shaping red blood cells like a sickle; 1 in 500 Black and 1 in 36,000 Hispanic births.
  • Cystic Fibrosis (CF) affects breathing and digestion with thick mucus; 1 in 3500 births.
  • Phenylketonuria (PKU) is a metabolic disorder causing intellectual deficits if untreated; 1 in 10,000 births, detected and treated with a special diet.
• Tay Sachs Disease is due to enzyme deficiency, causing brain lipid build-up, cognitive and physical decline, death by age five; 1 in 4000 in 30 American Jews and 1 in 20 French Canadians are carriers.
• In Autosomal Dominant Disorders (Heterozygous), the individual only needs to inherit the gene change from one parent in order to have the disorder.
  • Huntington's Disease damages the nervous system, causing deteriorating movement, behavior, and cognition; fatal and occurs at midlife; 1 in 10,000.
• In Sex-Linked Disorders, X chromosome carries the mutated gene, males are more affected as they possess only one X chromosome.
  • Fragile X Syndrome affects brain development and causes learning and behavioral problems; 1 in 4000 males and 1 in 8000 females.
  • Hemophilia causes blood clotting problems; 1 in 10,000 males.
• A chromosomal abnormality occurs when a child too many or too few chromosomes.
  • The most common cause of chromosomal abnormalities is the age of the mother due to longer exposure to environmental factors.
  • Trisomy 21 or Down syndrome occurs causing an intellectual disability and certain physical features.
• If the abnormality is on 23rd pair the result is a sex-linked chromosomal abnormality; Two of the more common sex-linked chromosomal.
  • Turner syndrome occurs when part/all of one X chromosome is lost. 1 in 2,500 live female births result in affected cognitive function and sexual maturation, but the external genitalia appear normal but the woman can't menstruate.
  • Klinefelter syndrome occurs when an extra X chromosome is present in males; 1 in 650 live male births cause causes small testes, some breast development, infertility and low levels of testosterone.

Chromosomal Disorders

• Autosomal disorders involve too many/few chromosomes inherited.
  • Down Syndrome/Trisomy 21 is caused by an extra chromosome 21. The affected individuals have birth defects,intellectual disability, facial features, heart defects, variations in severity
  • Trisomy 13 and 18 are caused by extra chromosomes 13 and 18; respectively, causing multiple birth defects and early death; 1 in 7,906 and 1 in 3,762 births; respectively.
• Sex-linked disorders occur on chromosome pair #23.
  • Turner Syndrome happens if all/part of one X chromosome is lost and infertility and/or short stature may be noted, occurs in 1 in 2500 females.
  • Klinefelter Syndrome occurs when an extra X chromosome is present , the male still has male genitalia but may have some breast development, infertility and low levels of testosterone occuring in 1 in 650 males,.

Genetic Counseling

• Genetic counseling assists individuals in identifying, testing for, and explaining potential genetic conditions.
• Reasons for seeking genetic counseling include: family history, ethnic group membership, result information from genetic testing, chances of having a baby with a genetic condition.

Behavioral Genetics

• Behavioral genetics studies the interplay between genetics and environment regarding behavior.
• Gottlieb's analytic framework recognizes the interplay between environment, behavior, and genetic expression.
• Environmental circumstances can trigger genetic disorder symptoms.
• Genotype-Environment Correlations refer to genetic factors that contribute to variations in the environment.
• Passive genotype-environment correlation when children inherit genes and environments from their family.
  • Athletically inclined children inherit genes and encouragement, and have environmental success.
• Evocative genotype-environment correlation refers to the social environment reacting to an individuals inherited characteristics.
  • Temperament will affect how he or she is treated by others.
  • Active genotype-environment correlation occurs when individuals seek niche picking environments that support their genetic tendencies; children seek music instruction.
• Genotype-Environment Interactions involve genetic susceptibility to the environment; evident from adoption studies where environmental effects on behavior differ based on the genotype.
• Epigenetics studies modifications in DNA that affect gene expression and are passed on when cells divide.
• Environmental factors can change gene expression by switching genes on and off; identical twins may increasingly differ in gene expression with age.

Human Genome Project (HGP)

• in 1990 , the HGP began sequencing the 3 billion base pairs of the human genome.
• The project gave us the blue print for building a human in April of 2003.
• Information from the HGP also discovered the genes involved in over 1000 diseases.
• HGP amassed a data base called HapMap in 2005.
• Future directions for for the HGP include; identifying the genetic markers for all 50 major forms of cancer and examining the legal, social and ethical implications of genetic knowledge.

Prenatal Development

• Prenatal development is divided into the germinal period, the embryonic period, and the fetal period.

Germinal Period

• The germinal period lasts about 14 days, from conception to implantation.
• Millions of sperm are released into the vagina, but only a few reach and fertilize the egg.
• Once a sperm has entered the egg, the egg wall becomes hard and prevents others from entering.
• The sperm containing the genetic information from the father, unites with the nucleus of the egg.
• A new cell, a zygote is formed.
• The organism begins cell division through mitosis.
• After five days there are 100 cells, now called a blastocyst that consists of inner and outer groups of cells.
• The inner group of cells, or embryonic disk will become the embryo.
• The outer group, or trophoblast, becomes the support system.
• The stage ends when the blastocyst fully implants into the uterine wall
• Mitosis is a fragile process, with fewer than half of all zygotes surviving beyond the first two weeks

Embryonic Period

• Starting the third week the blastocyst has implanted in the uterine wall, now called the embryo.
• Now blood vessels grow and form the placenta.
• The placenta is a structure connected to the uterus and provides nourishment and oxygen from the mother to the developing embryo.
• During this period, cells continue to differentiate.
• Growth during prenatal development occurs in two major directions; cephalocaudal, proximodistal development.
• The head develops in the fourth week and the precursor to the heart begins to pulse.
• Gills and a tail are apparent but disappear.
• The embryo is approximately 1 inch in length and weighs about 8 grams at the end of eight weeks, responding to touch.

Fetal Period

• From the ninth week until birth, the organism is referred to as a fetus.
• By the third month, the fetus has all its body parts including external genitalia.
• The fetus will develop hair, nails, teeth and the excretory and digestive systems will continue to develop, weighing about 28 grams.
• During the 4th - 6th months, the eyes become more sensitive to light and hearing develops.
  • The respiratory system continues to develop
  • Reflexes such as sucking, swallowing and hiccupping, develop during the 5th month.
• The first chance of survival outside the womb, known as the age of viability is reached at about 24 weeks.
• Between the 7th - 9th months, the fetus gains about 5 pounds and 7 inches, a layer of fat develops under the skin for insulation and body temperature regulation.
  • At around 36 weeks the fetus is almost ready for birth, weighing about 6 pounds and about 18.5 inches long.
  • By week 37 all of the fetus's organ systems are developed to survive outside the mother's uterus.

Brain Development

• The prenatal brain development begins in the third gestational week with the differentiation of stem cells in the neural plate.
• By the end of the third week, the formation of the neural groove and the neural tube occurs.
• By the end of the embryonic period, or week eight, the neural tube has further differentiated into the forebrain, midbrain, and hindbrain.
• Brain development during the fetal period involves neuron production, migration, and differentiation.
• From the early fetal period until midgestation, most of the 85 billion neurons have been generated and have migrated to their brain positions.
• Neurogenesis is largely completed after five months of gestation, except in the hippocampus.
• Neural migration is mostly completed in the cerebral cortex by 24 weeks.
• Neurons begin to produce dendrites and axons that form the neural networks responsible for information processing.
• Regions that contain the cell bodies are referred to as the gray matter.
• The axons that form the neural pathways make up the white matter because they are covered in myelin.
• Although cell differentiation is complete at birth, the growth of dendrites, axons, and synapses continue for years.

Teratogens

• The developing child is most at risk for problems during the first three months of development.
• Teratology is the study of factors that contribute to birth defects.
• Teratogens are environmental factors that can contribute to birth defects and include maternal diseases, pollutants, drugs and alcohol.
• Structures are vulnerable to the most severe damage when they are forming.
• Factors influencing prenatal risks include; the timing of amount/number, genetics, and being male/female.
• If a substance is introduced during a structure's critical period, the damage to that structure may be greater.
• Males are more likely to experience damage to teratogens than are females, believed that the Y chromosome may have an impact.
• Factors influencing prenatal risks are factors influencing prenatal risks.
• Alcohol consumption during pregnancy can lead to neurocognitive and behavioral difficulties, resulting in Fetal Alcohol Spectrum Disorders (FASD),
  • The most severe form of FASD is Fetal Alcohol Syndrome (FAS) which includes physical, cognitive features and have poor judgement, higher rates of ADHD, learning issues and lower IQ scores.
• When a pregnant woman smokes, the fetus is exposed to nicotine, carbon monoxide and tar, lessening the amount of oxygen available to the fetus.
• Smoking is associated with low birth weight, ecotopic pregnancy, the placenta lies low in the uterus and preterm still birth.
• About 70% of pregnant women take at least one prescription drug.
• Prescription drugs can cause birth defects as well as problems to the fetus and should women should not take any during pregnancy unless medically ordered.
• Common illicit drugs include cocaine , marijuana and prescription drugs that are abused.
• Illicit drug Mothers that use have other unhealthy behaviors such as; smoking and not eating healthy meals Illicit complications from illicit drug use include, premature birth, smaller head size, birth heart and infections.

Pollutants

• An environmental pollutant of significant concern is lead poisoning because it has also been linked to fertility problems, high blood pressure, low birth weight, prematurity, miscarriage, and slowed neurological development.
• Prenatal exposure to bisphenol A (BPA), a chemical commonly used in plastics, which may disrupt the action of certain genes contributing to certain birth defects
• If a mother is exposed to radiation, it can get into the bloodstream and pass through the umbilical cord to the baby. Exposure to radiation can slow the baby's growth, cause birth defects
• Mecury, a heavy metal, can cause brain damage and affect the baby's hearing and vision, this is why women are cautioned about the amount and type of fish.
• The tiny parasite, toxoplasma gondii can cause premature birth and stillbirth with defects to eyes and brain

Sexually Transmitted Diseases/HIV

• Gonorrhea, syphilis, and chlamydia are sexually transmitted infections that are passed to the fetus by an infected mother that can cause premature birth, miscarriage, and still births. -Mothers should be tested as early as possible to minimize the risk of spreading these infections to their unborn child
• .HIV is a leading cause of illness and death. This is through mother-to-child transmission of the virus prenatally, or by breastfeeding so antiviral medication is recommended.

Maternal Factors

• Women over 35 are at increased risk of fertility problems, pregnancy problems and is is shown that environmental teratogens can affect the eggs.
• This can affect quality of eggs.
• A teenage mother at risk for complications including anemia, high blood pressure.
• Infants from teenage mom are a risk for low birth weight or health conditions.
• Those with higher risk are under 15.
• Gestational Diabetes is where body has too much glucose and will go away but might indicate risk for developing more.
• High Blood Pressure (Hypertension) which is the pressure against arteries that can result as a premature and low birth weight.
• Rh is a found in the blood in which some might no exist in which positive mean exist and negative mean absent, results in a anlemia disease

Weight Gain/Prenatal Assessment

• Weight Gain during Pregnancy needs only 300 calories but can be harmful.
• stress increases babies born early or small which are is needed stress from infection and premature birth
• Assessment are routine to find the test for test in a blood analysis for the mother and to find the birth tests. -Ultrasounds: are to check for problems defects and find information about the location of the placenta.

Infertility/Reproductive Complications

• Reproductive Technology is needed due problems of lack of production for men and ovulate for women.
• Fertility Majority are created by drug to increase ovulation/surgery.

Minor Copmlications/Child Birth

• Are considered minor but can be side effects such as. nausea, heart burns, hemorrhids, etc.
• Major Complications are Ectopic Preeclampsia that can occurs where the zygote is not reaching the uterus
• Maternal Morality CDC states that 700 women do die from complications related to the baby. Spontaneous Abortion happens at 20-40 percent of underdiagnosed in 10 prcent
• Abnormalities that can happen.
• Preparation is to to help provide a healthy environment and accept them to be new parents.

Stages of Birth

• 1st stage begins with uterine contractions and 15-20 minute with increase duration to a minute.
• It starts with bleeding or fluid
• Doctors have said call in at every 5 minutes 2nd involves the passage of the baby (2-3 mi) and relax and listen to direction of medical staff. 3rd stage its is painless it when you deliver the baby and it takes about 20 minutes.

Cesarean Section

• A C-Section is done to deliver the baby surgery to be removed through the mothers abdomen. -Problems that can occur are; The baby has stopped growing.
• The birth of both and the test comes a very quick way to determine the babies overal situation being the 5 measures.
  • Heart rate, respiration all the 5 and it would cause concern if you scores 5.

Problems

• Anoxia us a temperature oxygen to the brain and can result in damage or death.
• A baby can considered a Low birth weight is they way less than 5 pounds.

Postpartum Maternal Concerns

• After pregnancy women experience emotions like baby blues but can be also more than blue like postpartum symptoms etc.
• Symptoms are include sadness and sleeplessness. Changing Hormones can be a factor for this and this can happen by substance abuse.