Module 2: Introduction to Genetics II
Learning Objectives
- Explain additional fundamental genetic concepts of inheritance (including building pedigrees), phenotype vs genotype, variations and polymorphisms
- Describe how to incorporate assessment of genetic red flags in nursing assessments
- Describe the implications of understanding genetic inheritance to nursing practice
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Glossary
Acetylation: A process which typically “opens” chromatin, increasing gene expression
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.
Amino Acid: Fundamental building blocks of proteins.
Apoptosis: A form of programmed cell death which helps control growth and development in multicellular organisms.
Autosomal Dominant: An autosomal dominant trait or disorder is a genetic condition that occurs when only one copy of an altered gene, located on a non-sex chromosome, is inherited. This is needed to cause the trait or disease.
Autosomal Recessive: An autosomal recessive trait or disorder is a genetic condition that occurs only when two copies of an altered gene, located on a non-sex chromosome, are inherited — one from each parent. Offspring that inherit one copy of an altered gene with an autosomal recessive inheritance pattern are carriers of the trait or disorder.
Base Pair: Two complementary nucleotide bases.
Cancer: A disease caused by uncontrolled growth of cells which can spread throughout the body.
Carrier: An individual that carries one copy of a recessive gene that can cause a genetic disorder when two copies are present.
Cascade Testing: A diagnostic genetic test for family members of an individual with a known pathogenic variant. It helps identify relatives who may also carry the variant and are at risk for developing the same condition.
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.
Cell differentiation: Process by which a young (unspecialized) cell changes into a differentiated (specialized) cell (such as a brain cell).
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.
Chromosomal microarray analysis (CMA): Is used to look for copy number variants and duplications/deletions smaller than those detectable through a karyotype (as small as 100kb).
Chromosome rearrangements: Changes in the order of genes on the DNA strand.
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.
Daughter cell: A new cell produced by the division of pre-existing (parent) cell.
Deletion Variation: A change in DNA sequence due to the removal of a base pair.
Direct-to-consumer genetic testing: Allows individuals to seek out genetic testing without the oversight of a healthcare provider.
DNA (Deoxyribonucleic Acid): The hereditary material in humans and almost all other organisms. DNA carries the instructions for cells to construct proteins.
DNA replication: The creation of two identical strands of DNA during the process of cell division.
Dominant Alleles: One copy of a dominant allele is sufficient for expression of a trait. Dominant alleles mask recessive alleles.
Duplication: A change in DNA sequence due to the production of one or more copies of a gene.
Epigenetic: Related to external or environmental factors that modify gene function, but do not alter the DNA sequence.
Epigenetics: The study of how environmental factors and lifestyle behaviors can modify or alter the function of genes without changing the DNA sequence.
Epigenome: All the epigenetic changes in the genome.
Epigenomics: The study of the collection of all epigenetic marks (chemical modifications) on the genome that influence gene activity.
Expressivity: Variation in the expression of the phenotypes expressed by a specific genotype at an individual level.
Extensive metabolizers: Responds to a drug as expected.
Familial or multifactorial cancer: Cancers resulting from a combination of genetic variations and shared environmental risk factors within a family, all contributing to an increased risk of cancer.
Fluorescence in-situ hybridization (FISH): Used to detect small duplications or deletions of particular genes.
Frameshift Variation: A change in the DNA sequence due to an insertion or deletion of a base pair. This alters the grouping of bases and changes the code for amino acids which usually creates a non-functional protein.
Gene: The basic unit of heredity, which is passed on from parents to offspring and determines specific traits for individuals.
Gene panel: Is used to detect variants across multiple genes. It is commonly employed when a mutation in any one of several genes could cause a genetic disorder, or when symptoms are broad and may match multiple conditions.
Gene silencing: Mechanism that inhibits or shuts down the expression of a gene but does not change the underlying DNA sequence.
Genetic: Related to genes and DNA.
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.
Genomic: Related to the whole genome.
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 Cancer: Is caused by variations in the germ cells (sperm and egg).
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.
Heterozygous: Both alleles are different.
Histone: A protein that chromosomes wind around that provides structural support and modifies gene expression.
Histone Modification: A process which alters gene expression by adding acetyl or methyl groups to histone tails.
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.
Homozygous: Both alleles are identical.
Insertion Variation: A change in DNA sequence due to the addition of a base pair. This may alter the number of amino acids in a protein and its functionality.
Intermediate metabolizers: Slightly reduced response to a drug. May have unintended effects.
Karyotype: Used to detect changes in the number of chromosomes.
Macrophage: White blood cell that removes pathogens and cellular debris. They also promote an immune response from other cells.
Meiosis: The cell division process of making egg and sperm cells.
Mendelian genetics: the predictable pattern of single gene inheritance as described by Gregor Mendel.
Methylation: A process that can either activate or repress genes, depending on the location and type of modification.
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.
Multifactorial: Caused by the interaction of multiple genes and environmental factors.
Nonsense Variation: A change in the DNA base sequence that causes the DNA sequence to change into a stop codon. This signals the cell to stop building the protein, and it results in a shortened protein which may or may not function effectively.
Normal metabolizers: Responds to a drug as expected.
Nucleotide: Fundamental building block made up of a nitrogenous base plus a sugar and phosphate molecule.
Nucleus: The central organelle of a eukaryotic cell, which usually contains the cell’s DNA.
Oncogenes: Genes that function to allow normal cell growth. When oncogenes are activated, they inhibit cell apoptosis and cause cells to grow out of control which leads to cancer.
Pedigree: Symbolic diagram and representation of family members over generations, social and biological relationships, and lines of descent.
Penetrance: How often someone with a genotype expresses the corresponding phenotype (at the population level).
Pharmacodynamics: What the drug does to the body.
Pharmacogenetics: The study of how single gene information or variations among a group of individuals affects drug response.
Pharmacokinetics: What the body does to the drug.
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.
Pluripotent: Embryonic stem cells are able to develop all cell types in the human body (except extra-embryonic tissues, like the placenta).
Polymerase chain reaction (PCR): A specific DNA sequence is copied many times to yield large quantities of a particular DNA sequence. It is also known as “molecular photocopying.”
Polymorphism: Genetic polymorphisms are also known as multiple forms of a gene. Polymorphisms are more common than variants. Polymorphisms must occur in a population at a frequency of greater than 1%.
Poor metabolizers: Greatly reduced response to a drug. Likely to have high drug plasma levels affecting response and unintended effects.
Predictive: Someone with no current symptoms who has a family history of a genetic condition.
Promoter: Non-coding region of DNA where proteins bind to initiate transcription.
Proto-oncogene: Genes that help normal body cells function and grow.
Recessive Alleles: An allele that leads to expression of a trait only when paired with another recessive allele. It will be masked if a dominant allele is present.
Red Flags: Genetic red flags are features of personal and family medical history which suggest a higher than average chance of the presence of a genetic condition.
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.
Single gene tests: Are used to look for genetic changes in one gene to confirm a specific diagnosis.
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.
Star alleles: Simplified labels (haplotypes) for specific variants.
Targeted single variant tests: Are used to look for a specific genetic variant within one gene known to cause a disorder. It can detect a specific variant in family members when someone in the family is known to have that variant.
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.
Transcription: Process of making messenger RNA (mRNA) from DNA.
Translation: Process of making proteins from messenger RNA (mRNA).
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.
Ultrarapid metabolizers: Greatly increased response to a drug. Likely to have low drug plasma levels which affects response and may cause unintended effects.
Variant/Variations: Permanent alterations in the DNA sequence which can be due to environmental factors or changes during the cell division process.
Whole-exome sequencing: Sequencing of all the exons or protein-coding regions.
Whole-Genome Sequencing (WGS): Whole-genome sequencing (WGS) is the process of determining the complete DNA sequence of an organism’s genome in a single, comprehensive analysis. It is capable of detecting nearly all DNA variations in a genome.
X-linked: An X-linked trait or disorder is a genetic condition caused by an altered gene located exclusively on the X chromosome (one of the two sex chromosomes). One altered X chromosome is sufficient to cause the disorder in males since they only have one X chromosome. In females (who have two X chromosomes), the alterations would have to occur in both chromosomes in order for them to inherit the disorder.