mcn (genetics and genetic counseling)

• genetics: the study of heredity and the variation of inherited characteristics.
• genomics: the branch of molecular biology concerned with the structure, function, evolution, and mapping of genomes.
• karyotyping


  -examine chromosomes.

  -the determination of a karyotype, e.g. to detect chromosomal abnormalities.
• genetic testing is used to identify genetic disorders, determine the risk of developing a disease, and predict the likelihood of developing a disease
• genetic screening 


  applies to testing of populations or groups independent of positive family history or symptom manifestation
• genes: the basic unit of heredity, consisting of a segment of DNA that codes for a particular protein
• genome: entire set of genetic instruction found in a cell.
• chromosome: a long, coiled DNA molecule that carries genetic information
• Deoxyribonucleic acid (DNA): primary genetic material in humans consisting of nitrogenous gases, sugar group, phosphate. Combined into double helix.
• allele: variant form of a gene.
• single-gene disorder testing: testing for a single gene that is associated with a particular disorder
• carrier screening test: a test that screens for a genetic disorder that can be passed on to offspring (do not show symptoms) (autosomal recessive condition)
• predictive testing: testing for a specific disease to determine if a person is at risk of developing it (asymptomatic family members)
• population-based screening: screening of the whole population, not just those with risk factors
• mitosis: the process of cell division that results in two identical daughter cells
• meiosis: is the reduction division of diploid egg or sperm resulting in haploid gametes.
• gene mutations: heritable alteration in genetic material
• genetic variation: variation in degree to which trait is manifested; clinical severity.
• chromosomal differences 


  • chromosome number, chromosome shape, chromosome size
  • major cause of birth defects, mental retardation, malignancies.
  • extra or missing chromosome or structural arrangement of chromosome.
• sex chromosomes: XY (male) XX(female)
• homologous: same number and arrangement of genes
• homozygous

  • having two identical alleles of a particular gene, e.g. BB
  • two copies of same trait
• heterozygous: having two different alleles of a particular gene or genes
• karyotype: the number and visual appearance of the chromosomes in the cell nuclei of an organism or species.
• genotype: genetic makeup of an individual
• phenotype: observable expression of an individuals genotype
• Genotype: The specific combination of alleles in an organism's DNA for a particular gene, such as having the alleles AA, Aa, or aa for a gene determining eye color.
• dominant expression: the trait is expressed when only one copy of the gene is present.
• aneuploidy

  • an abnormal number of chromosomes in a cell
  • when the numeric deviation is not an exact multiple of the haploid set (23).
• monosomy: missing a chromosome
• trisomy: contain an extra chromosome
• 46 - total chromosome number
• trisomy 21 also referred to as down syndrome.

  • a genetic condition caused by an extra chromosome.
• trisomy 18 also referred to as edwards syndrome

  •  a disorder in which babies are born with 3 copies of chromosome 18 instead of 2.
  • Overlapping fingers and/or clubfeet. Small physical size (head, mouth and jaw).
• trisomy 13 also referred to as patau syndrome.

  •  a severe chromosomal condition, with multiple malformations due to an additional copy of all or part of chromosome 13.
  • It is characterized by cleft lip, cleft palate, cerebral defects, anophthalmia, simian creases, polydactyly, trigger thumbs, and capillary hemangiomata.
• genetic counseling: is a process o communication between two or more persons who meet to solve a problem.
• Sheldon Reed proposed the terminology "Genetic Counseling in 1947"
• Smith (1955) defines counseling as "a process in which the counselor assists the counselee to make interpretations of facts relating to a choice, plan, or adjustments which he needs to make.
• the American Society of Human Genetics defines Genetic counseling as a communication process, which deals with human problems associated with the risk of occurrence of a genetic disorder in a family.
• XY = sex determination (male)