Module 3: Genetic Disorders

Learning Objectives

Understand the biological basis of genetic disorders, encompassing chromosomal abnormalities and single-gene variations
Learn how to integrate knowledge of genetic inheritance and genetic testing into your nursing assessment
Understand the pattern of single gene inheritance

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Glossary

Alleles: Alternative forms of a gene that form from any genetic variation and are found at the same locus or place on a chromosome.

Allosomes: Sex chromosomes. Autosomal Dominant Inheritance (?): A pattern of genetic inheritance in which an individual requires one copy of an altered gene and one normal gene on a pair of autosomal or non-sex-linked chromosomes to exhibit the traits of the genetic disorder. At least one parent of the offspring must possess one copy of the altered gene.

Apoptosis: A form of programmed cell death which helps control growth and development in multicellular organisms.

Autosomal Recessive Inheritance: A pattern of genetic inheritance in which an individual needs two copies of the altered gene to manifest the genetic disorder. The parents of the offspring with an autosomal recessive inheritance must each carry at least one copy of the altered gene.

Autosomes: Any of the non-sex chromosomes in an organism; they contain several different genes, but these genes are not able to determine sex.

Cancer: A disease caused by uncontrolled growth of cells which can spread throughout the body.

Caspases: Caspases are a family of cysteine proteases that are activated during apoptosis and cleave damaged proteins, ultimately leading to cell death.

Cell Cycle: The stages that take place in a cell leading to duplication of its DNA (DNA replication) and division of cytoplasm and organelles to produce new cells.

Central Dogma: The two-step process of transcription and translation which converts gene information into proteins.

Checkpoint: A stage in the eukaryotic cell cycle at which the cell is examined to check for any cell damage, viral infection, or cancerous cell. The checkpoints induce a cell cycle arrest until the defects are repaired. These checkpoints occur near the end of G1, at the G2/M transition, and during metaphase.

Chromosomes: Structures of nucleic acids and proteins found in the nucleus of most living cells, which contain genetic information.

Codon: A sequence of three DNA or RNA nucleotides that are specific to an amino acid or stop signal during protein synthesis.

Congenital Abnormalities: Structural or functional disorders which occur prenatally or at birth; they can be detected later during infancy as well. Some examples include Down syndrome, cleft palate, and spina bifida.

Gene: The basic unit of heredity, which is passed on from parents to offspring and determines specific traits for individuals.

Genetics: The study of the effects of individual genes and their influence on relatively rare single-gene disorders.

Genome: The entire sequence of our genes or genetic information contained in a cell.

Genomics: The study of all the genes in the genome, including interactions between genes, interactions between genes and environmental factors, and the impact of other psychosocial and cultural factors.

Genotype: The genetic makeup of an individual organism that determines its traits.

Germline Variations: Any alteration that occurs in gametes or germ cells which affects every cell of the body and can be passed onto the offspring.

Hereditary Variation: Genetic alterations that are inherited from parents and present in every cell of an organism. The variations are present in the germ cells (sperm and egg) of the parents and are passed on to their offspring through reproduction.

Homologous Pairs: Sets of chromosomes, one inherited from each parent, that possess the same genes but with different versions, or alleles, of those genes. These pairs go through genetic recombination during meiosis, which contributes to genetic diversity in the offspring.

Meiosis: The cell division process of making egg and sperm cells.

Missense Variation: A change in the DNA base sequence that results in a different amino acid than the previous one, altering protein synthesis.

Mitosis: The cell division process of making somatic cells.

Monogenic Inheritance: The inheritance of a specific trait from a parent to their offspring, which is determined by the expression of a single gene or allele rather than by multiple genes.

Pharmacogenetics: The study of how single gene information or variations among a group of individuals affects drug response.

Pharmacogenomics: The study of pharmacology (the science of drugs) and genomics (the study of genes and their functions) to identify variants that together, will determine variability in drug response.

Phenotype: The observable characteristics of an individual that are determined by the genetic expression of a genotype and the environment.

Sex Chromosomes: Identified as X and Y chromosomes in humans and most mammals, which determine the sex-linked characteristics of an organism. Females have two X chromosomes in their cells, while males have both X and Y chromosomes in their cells. The combination of these chromosomes gives an organism their different sex characteristics.

Single Gene Inheritance: A pattern of genetic inheritance in which a specific trait is determined by the expression of a single gene pair alone, which consists of two alleles. The offspring inherits one paternal allele, and one maternal allele.

Somatic Cell: Any cell of a living organism other than the reproductive germ cells such as the sperm and egg.

Somatic Variation: Genetic alterations that occur in the cells of an organism’s body often due to environmental factors or random errors in DNA replication. Somatic variations are only present in certain cells, and they do not affect the entire organism. Note that a large portion of an organism’s cells may contain the variation if the alteration occurs early on in development.

Sporadic Cancer: Cancer that occurs in individuals who do not have any family history of cancer or an inherited gene(s) which increases their risk of cancer.

Telomeres: A sequence of repetitive nucleotides at each end of a chromosome. They mainly protect the ends of the chromosomes from weakening or from fusing with other neighboring chromosomes.

Tumor Suppressor Genes: These genes normally function to slow down cell division, repair any DNA impairments, or tell damaged cells to induce apoptosis. When tumor suppressor genes are altered, cells may grow out of control, which can lead to cancer.

Learning Objectives

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