Genetics Study Guide PDF

Definitions: - Genetics The study of genes and their role in inheritance. Determines the way that certain traits or conditions are passed down through genes. They have an impact on health and disease. - Genomics The study of all a person's genes (the genome). → The interactions of these gene...

Definitions: - Genetics The study of genes and their role in inheritance. Determines the way that certain traits or conditions are passed down through genes. They have an impact on health and disease. - Genomics The study of all a person's genes (the genome). → The interactions of these genes with each other and the person's environment. → The study of complex diseases is typically caused by a combination of genetic and environmental factors rather than a single gene. - Genetic mutation They can be inherited from a parent (germline mutation) or acquired (somatic mutation) during a person's lifetime. A mutation is any change in the usual DNA sequence. Mutations range in size from a single DNA base (building block) to a large segment of a chromosome. The change in gene structure may change the type and/or amount of protein made. The protein may not work at all, or it may work incorrectly. - Germline mutations Pass from parent to child. These mutations are present in the oocyte and sperm cells. This type of mutation is present throughout a person's life in virtually every cell in the body. - Acquired (somatic) mutations Occur in the DNA of a cell at some time during a person's life. An acquired mutation passes on to all cells that develop from that single cell. These mutations in somatic cells cannot be passed on to the next generation. Acquired mutations can occur if (1) a mistake occurs as DNA replicates during cell division or (2) environmental factors alter the DNA. - Autosomal dominant Are caused by a mutation of a *[single gene pair (heterozygous)]* on a chromosome. A dominant allele prevails over a normal allele. - Autosomal recessive Are caused by mutations of *[2 gene pairs (homozygous)]* on a chromosome. A person who inherits 1 copy of the recessive allele does not develop the disease because the normal allele predominates. However, this person is a carrier. - X-linked recessive Are caused by a mutation on the X chromosome. They can severely affect men because they have only 1 X chromosome. Women who carry the mutated gene on 1 X chromosome have another X chromosome to compensate for the mutation. Women who carry the mutated gene can transmit it to their offspring. - Epigenetics is the study of inheritable changes in gene expression that do not involve changes in the DNA sequence. - [Heter]ozygous Having 2 [different] alleles for 1 given gene, 1 inherited from each parent. - [Homo]zygous Having 2 [identical] alleles for 1 given gene, 1 inherited from each parent. - Chromosome Microscopic structures in the cell nucleus composed of chromatin, which contain genetic information. Each cell normally has 46 chromosomes in 23 pairs (22 autosome pairs and 2 sex chromosomes). - Autosome A chromosome other than X or Y. The human genome has 44 autosomes (22 pairs of autosomes). - Locus Position of a gene on a chromosome. - Allele One of a series of alternative forms (genotypes) at a specific region (locus) of a chromosome. - Gene Functional unit of heredity. A gene is a unit of DNA sequence that encodes for a specific functional product, such as RNA. - Genotype Genetic identity of a person, comprised of the entire complex of genes inherited from both parents. - Phenotype Observable characteristics of a person. Measured categorically or quantitatively. - DNA Stores genetic information and encodes the instructions for producing specific proteins needed to maintain life. - Pharmacogenomics Study of variability of drug metabolism in relation to variations in and interactions of *[multiple genes or the person's genome.]* - Pharmacogenetics Study of variability of drug metabolism related to variations in *[single genes.]* **Genetic disorders can be caused by** (page 203) 1\. mutation in 1 gene (single gene disorder). 2\. mutations in multiple genes (multifactorial inheritance disorder), which are often related to environmental factors. 3\. damage to chromosomes (changes in the number or structure of chromosomes). **Genetic Testing** (page 205) Genetic Information Non-discrimination Act (GINA) An act to protect a person's test results as their medical records might not be private, and there is the potential for discrimination by employers and insurance companies. **Interpreting Genetic Test Results** (page 205) A positive test result means → that the laboratory found a change in a particular gene, chromosome, or protein that was being tested. → may confirm a diagnosis (like a disease), show that a person is a carrier of a particular genetic mutation (like cystic fibrosis), identify an increased risk for developing a disease, or suggest a need for further testing. A negative test result means → that the laboratory did not find an altered form of the gene, chromosome, or protein under consideration. Predictive genetic testing; can be used to identify mutations that increase a person's risk for developing certain disorders like breast and ovarian cancer. Diagnostic genetic testing; can be used to diagnose, rule out, or confirm a specific genetic or chromosomal condition such as sickle cell disease, polycystic kidney disease, and hemophilia. Hemophilia; an X-linked recessive disorder and are caused by a mutation on the X chromosome. Women who carry it can transmit it to their offspring. **Technology Used for Genetic Testing** (page 206) DNA fingerprinting → extracting DNA from the cells in a sample of blood, saliva, semen, or other appropriate fluid or tissue. Polymerase chain reaction (PCR) → is a quick, easy method to provide unlimited copies of a DNA or RNA sequence using only a small sample. Important for genetic fingerprinting and used in forensic medicine. DNA microarray (DNA chip) → can identify changes in gene sequences or if certain genes are turned off in cells and tissues. **Genome-Wide Association Study** (GWAS) (page 207) Is an approach that involves rapidly scanning complete sets of DNA, or genomes, of many people to find genetic variations associated with the development or progression of a specific disease. **Gene Therapy** (page 208) experimental technique used to treat the underlying cause of a disease. may be able to supply a missing gene, provide the missing gene's role, or enhance the treatment of a disease. **Stem Cells** (page 209) are unspecialized cells in the body that have the ability to (1) remain in their unspecialized state and divide or (2) differentiate and develop into specialized cells. Types: → Totipotent cells can produce all the cell types of the developing organism. → Pluripotent cells can make any body cell because they make all cells of the embryo. → Multipotent cells only make cells within a specific germ layer. → Unipotent cells make a single cell type. **Nursing Management: Genetics and Genomics** (page 209) The nurse needs to: - **understand the influence that genetics has on health and illness.** - **help the patient and family in making critical decisions related to genetic issues, such as genetic testing.** - **provide resources and education in response to questions.** - **collaborate with other health care team members, including genetics nurses and genetics counselors.** **Cystic Fibrosis** (CF) (McKinney page 1074) What is cystic fibrosis? The mucus produced by the exocrine glands (particularly those of the bronchioles, small intestine, and pancreatic and bile ducts) is abnormally thick causing obstruction of the small passageways. Etiology: Autosomal recessive trait → both parents must carry the gene for the child to be affected → 25% chance. Manifestations: Depends on the extent of specific organ system involvement. Respiratory system: - wheezing - dry, nonproductive cough (early sign) - repeated bouts of bronchiolitis, pneumonia, bronchitis - chronic bacterial infections As the disease progresses... - crackles, wheezes, diminished breath sounds, accessory muscle use, retractions, hypoxia, and cyanosis. - Cough increases and, dyspnea and tachypnea occur. - Emphysema and atelectasis may develop as the airways become increasingly obstructed with secretions Later stages... - pulmonale and congestive heart failure resulting from fibrotic lung changes - Spontaneous pneumothorax or hemoptysis (blood-stained sputum) - Nasal polyps, sinusitis, [digital clubbing (can be due to hypoxia)], and a barrel chest (increased anteroposterior chest diameter) Digestive system: - steatorrhea (frothy, foul-smelling stools two to three times bulkier than normal) - flatus - Malnutrition and growth failure (despite normal caloric intake) - → deficiencies in the fat-soluble vitamins A, D, E, and K are caused by an inability to absorb fats - Vitamin A deficiency can lead to xerophthalmia (abnormal thickening of eye tissue) - Vitamin K deficiency can result in bleeding, especially in infants. - high concentrations of sodium and chloride in sweat are an early sign of CF (mothers often report that their infants taste salty when kissed) - infants prone to developing hyponatremia and hypochloremia, as well as dehydration - Many children complain of a dry mouth and have an increased susceptibility to infection - 2-year delay in secondary sex characteristics - Females -- have a thicken cervical mucus → *may be* difficult to become pregnant along with poor nutrition depending on how mild the CF is - Sterility caused by the lack of sperm is noted in approximately 95% of male patients with CF; otherwise, sexual function is normal Diagnostic evaluation: Genetic defect → abnormally thick secretions → obstruction → inflammation, bronchospasm, hyperinflation, chronic infection ↙ ↘ Impaired gas exchange ↓ ↓ Hypoxia, hypercapnia, acidosis Atelectasis, fibrosis, destruction of pulmonary tissue ↓ ↙ ↘ (can lead to both outcomes) Pulmonary vasoconstriction Pulmonary complications → pulmonary vascular resistance → spontaneous pneumothorax hemoptysis → enlargement of R. ventricle → respiratory failure **→ [congestive heart failure ]** **[→ death]** Therapeutic management: treatment goals are to relieve airway obstruction by mobilizing secretions, to decrease the number of bacteria by removing secretions, and to treat infections by administering antibiotics. Medications: Mucolytic (dornase) Bronchodilators (albuterol) CFTR potentiator (ivacaftor) Pancreatic enzymes Are important for cystic fibrosis patients because the pancreas is often not able to make the enzymes needed to digest food → a failure to gain weight and thrive (which come as enteric-coated capsules containing the enzyme beads) as ordered within 30 minutes of eating all meals and snacks. The child should not mix the enzymes with hot foods because enzymes are inactivated by heat Advise the family to note the color, consistency, and frequency of the child's stools because enzyme replacement correlates with the child's bowel elimination pattern (e.g., an acceptable pattern is one or two stools daily in older children and more often in infancy). Vitamins A, D, E, K Because CF causes malabsorption of fat-soluble vitamins, supplementation with A, D, E, K is required