chapter 7 genetic and developmental diseases. review of structure and function fertilization is the...

Chapter 7Genetic and

Developmental Diseases

Review of Structure and Function

• Fertilization is the uniting of a sperm and ovum resulting in 23 pairs of chromosomes

• Diseases can result from abnormalities in the make-up of the 23 pairs

• Abnormalities may be caused by duplication or deletion of parts of a chromosome


• Every genetic trait is influenced by two alleles

• One allele may either be dominant or recessive– A dominant allele results in how the genetic

trait is expressed– A recessive allele trait will only be

expressed if both are defective


• Genotype– The genetic makeup of individuals– Even though this describes exactly what

genes an individual has, it cannot predict how genes are expressed

• Non-penetrance

• Variable expressivity


• Phenotype– The physical and functional manifestation of

genetic traits– In other words, the end result after taking

into account non-penetrance and variable expressivity

Definitions

• Genetic disease– Caused by an abnormal gene, these are not

necessarily familial

• Chromosomal disease– Microscopically visible structural changes in

chromosomes

Definitions

• Familial disease– Several family members have the same

genetic or chromosome based disease

Frequency and Significance of Developmental Abnormalities

• Monogenetic disease– Classified by whether the abnormal gene is

located on an autosome or sex chromosome, and whether it is dominant or recessive

– Autosomal disease is much more common than sex-linked disease


• Dominant disorders– The presence of the disease identifies those

with the gene– Offspring has a 50% chance of inheriting the

defective gene


• Recessive disorders– These appear sporadically– Offspring has a 25% chance of inheriting the

defective gene—because they must inherit one defective gene from each parent


• Sex-linked recessive disorders– Appear in every other generation– Females with the abnormal gene on the “x”

chromosome will not express signs of disease, because they have one normal “x”

– However, males will express signs of disease, because they only have one “x”


• Inborn errors of metabolism– Enzyme defects that effect the metabolism

of carbohydrates, proteins, lipids, or minerals.

• Mitochondrial disease– Affects the energy-producing apparatus– Can result in deficiencies of the brain,

muscles and nerves


• Environmental Factors– Teratogens

• Known toxins or infectious agents that cause defects in the developing embryo or fetus

• an agent that interrupts or alters the normal development of a fetus, with results that are evident at birth, e.g. a chemical, virus, or ionizing radiation


• Environmental Factors– TORCH

• Diseases that cause mild disease in the mother, but devastating disease in the newborn

• Toxoplasmosis, Other (usually syphilis), Rubella, Cytomegalovirus, and Herpes simplex virus


• Embryonic Anomalies– Congenital heart defects are the most

common– Abnormalities of the kidney and urinary

tract


• Fetal Diseases– Erythroblastosis fetalis– Chorioamnionitis – Nutritional deficiencies in the mother, affect

the growth and development of the fetus


• Perinatal disease– Prematurity


• Most common diseases of infancy– Congenital and chromosome abnormalities– Prematurity and low birth weight– Sudden Infant Death Syndrome– Complications of maternal illness– Diseases of the placenta, cord, and

membranes

Symptoms, Signs, and Tests

• Genetic disease– This will be highly individualized depending

on where the defect is located– Some diseases will present at birth, while

others will not present until later


• Genetic disease– Laboratory studies or genetic testing can be

diagnostic– Some diseases can be diagnosed before

birth, while others are tested for at birth, thus providing early treatment to minimize complications


• Chromosomal disease– Often suspected by physical exam– Karyotyping provides accurate diagnosis

and counseling

• Embryonic anomalies and fetal diseases– The method of diagnosis depends on the

nature of the disease

Specific Diseases

• Genetic disease– Often have a racial predilection

• Sickle Cell Anemia—African or Mediterranean

• Cystic Fibrosis—northern European

Specific Diseases

• Chromosomal Disease– Caused by increases or decreases in the

normal complement of chromosomes or changes to parts of one or more arms of chromosomes• Down syndrome• Klinefelter syndrome• Turner syndrome• Fragile X syndrome

chapter 7 genetic and developmental diseases. review of structure and function fertilization is the...

Documents

abnormal gene

mild disease

devastating disease

recessiveautosomal disease

functionevery genetic

express signs of disease

chromosomereview of

defectivereview of structure