II: Prenatal & Childbirth

• Fertilization: The fusion of the male and female gametes to form a zygote
• Zygote: a diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.
• Ovulation: Rupture of a mature follicle in either ovary and expulsion of its ovum—occurs about once every 28 days until menopause.
• Ovum: The female gamete, or egg, which is produced by the ovaries.
• Dizygotic twins

  • develop from two separate eggs fertilized by two different sperm,
  • can be of different sexes, and differ physically.
  • (INHERIT 50% SIMILAR GENES)
  • can be same or different sex
  • may have genetic basis
• Monozygotic Twins

  • develop from the same egg fertilized by a single sperm
  • have identical genetic makeup
  • are always of the same sex.
  • (INHERIT 100% SIMILAR GENES)
• Genetic Code: The sequence of bases in a gene that codes for a specific amino acid.
• Chromosome: A threadlike structure of DNA that carries genetic information.
• DNA: a polymer of nucleotides that carries genetic information in the form of genes
• Genes: Small segments of DNA located in definite positions on particular chromosomes; functional units of heredity. 
• Bases: The “letters” of the genetic code.

  • adenine (A), thymine (T), cytosine (C), and guanine (G).
• Human Genome: The entire genetic makeup of a human being.
• Mitosis: A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent cell
• Meiosis: The sex cells undergo when they are developing, each sex cell ends up with only 23 chromosomes— one from each pair.
• Sex Chromosomes: X and Y, determine the sex of an individual.
• Gregor Mendel:  crossbred pea plants that produced only yellow seeds with pea plants that produced only green seeds.

  • Father of Genetics
• Alleles: Two or more alternative forms of a gene that occupy the same position on paired chromosomes and affect the same trait.
• Homozygous: Having two identical alleles of a particular gene.
• Heterozygous: Having two different alleles for a particular gene.
• Dominant Inheritance: Pattern of inheritance in which,

  when a child receives different alleles, only the dominant one is expressed
• Recessive Inheritance: Pattern of inheritance in which a child receives identical recessive alleles, resulting in expression of a nondominant trait.
• Polygenic Inheritance: A trait that is controlled by multiple genes.
• Multifactorial Transmission: Combination of genetic and environmental factors to produce certain complex traits.
• Phenotype: The physical expression of a gene.
• Genotype: The genetic makeup of an organism, including the alleles it carries.
• Epigenesis: Mechanism when the genes are turned off or on as they are needed by the developing body or when triggered by the environment
• Incomplete Dominance: Pattern of inheritance in which a child receives two different alleles, resulting in partial expression of a trait.
• Sex-linked Inheritance of defects: A pattern of inheritance in which certain characteristics carried on the X chromosome inherited from the mother are transmitted differently to her male and female offspring.
• carriers:

  • Heterozygote females who carry one “bad” copy of a recessive gene and one “good” one.
• Sex-Linked Recessive Disorders

  • More common in males than in females.
  • Eg. red-green color blindness, hemophilia, and Duchenne muscular dystrophy.
• XYY Syndrome:  is a genetic condition that affects males with an extra Y chromosome.
• Down syndrome (trisomy 21) : is caused by the presence of all or part of a third copy of chromosome 21. It can happen either during the sperm or egg formation or as a result of abnormal cell division after conception.
• Turner syndrome (XO) : is a rare genetic disorder that mainly affects females and causes them to be shorter than average at birth and have webbed necks, among other problems.
• Prader–Willi syndrome: is a complex neurodevelopmental disorder associated with intellectual disability, short stature, and behavioral problems such as hyperphagia (insatiable appetite).
• Fragile X

  • is a common inherited disorder that affects the X chromosome and causes learning and behavioral challenges.
  • more prevalent and severe in males than females, as males have only one X chromosome and females have two.
• Klinefelter syndrome (XXY)

  • is a genetic condition that results when a boy is born with an extra copy of the X chromosome.
  • it often isn't diagnosed until adulthood
  • may adversely affect testicular growth = infertility
  • reduced muscle mass
  • reduced body and facial hair
  • enlarged breast tissue
• Sickle Cell Anemia: is a group of inherited red blood cell disorders. People who have this disease were born with abnormal hemoglobin, called hemoglobin S. Hemoglobin carries oxygen throughout your body. If you inherit two genes for beta thalassemia — one from each parent — you will develop this type of anemia.
• Cystic fibrosis (CF): is a life-shortening disease affecting multiple organ systems. In people with CF, a defective gene leads the body to produce unusually thick, sticky mucus that clogs the lungs and leads to life-threatening lung infections; it also obstructs the pancreas and stops natural enzymes from helping the body absorb food.
• Phenylketonuria (PKU): is an autosomal recessive metabolic disorder characterized by the deficiency of phenylalanine hydroxylase enzyme activity. The accumulation of phenylalanine in the brain may cause mental retardation if not treated early enough.
• Alpha Antitrypsin Deficiency: enzyme deficiency that can lead to cirrhosis of the liver in early infancy and emphysema and degenerative lung disease in middle age