Patho Study Guide Module 1

Study Guide Module 1 1. Differentiate genotype and phenotype. Are there any situations where a person’s genotype and phenotype are the same?(Beery & Workman, p.19-20; Pathophysiology, p. 135; 151) Genotype- the exact gene allele composition a person has for a specific single-gene trait is the person’s GENOTYPE for that trait. The composition of genes at a given locus. (Has the Brown hair gene). (having the PKU gene). Phenotype- is the person’s observed expression of any given single-gene trait. The outward appearance of an individual, which is the result of both genotype & environment. (Actually HAS brown hair). (Showing mental retardation from PKU). Genotype AO blood & Phenotype AA blood: both express phenotype of type A blood even though genotypes are different. Genotype & Phenotype are the SAME when homozygous gene alleles are present for a single-gene trait & for recessive traits & for dominant traits(but don’t have to be). 2. Determine the gender and ploidy of a person based on his or her karyotype.(Beery & Workman, p. 16-19) Karyotype- an organized arrangement of all the chromosomes within one cell during the metaphase section of mitosis. Technician organizes the chromosomes into pairs then arranges them by # according to size & centromere position. Determine Gender X is longer than Y XX - female XY - male Euploid (diploid 2N) - having chromosomes that are normal for number & appear normal in structure… Euploid is good! No obvious mutations or deletions or additions. Ploidy- the number of sets of chromosomes in a cell… Tetraploidy = 4 sets of every chromosome (very rare) = 92 chromosomes (Which term describes a cell that contains a multiple of 23 chromosomes = prac quiz question) 3. Explain how dominant gene alleles and recessive gene alleles determine expression of single gene traits.(Beery & Workman, p.18-19; Pathophysiology, p. 151) Single gene trait - one gene controls the expression of a specific structure, protein, or function. Dominant trait - expressed even when the 2 gene alleles for that trait are different. (which term describes an allele with an observable effect - prac quiz question) Recessive trait - single gene trait that is expressed only when BOTH alleles are the same. 4. Compare the processes in spermatogenesis and oogenesis.(Beery & Workman, p.55-63, Table 3-1) Spermatogenesis Oogenesis Converts diploid precursor germ cells into mature haploid sperm Converts diploid precursor germ cells into mature haploid ova Requires the process of meiosis Requires the process of meiosis Begins at puberty & continues through the lifespan Begins in fetal life & stops when menstruation stops Is a continuous process Is a cyclical process Completion of meiosis I & II takes days - weeks Completion of meiosis I & II takes years & isn’t complete until after fertilization Prophase I is hours- days long Prophase I is years long One diploid precursor cell can ultimately result in the formation of 4 haploid sperm capable of fertilizing a mature ovum. One diploid precursor cell can result in the formation of 1 haploid ovum capable of being fertilized by a mature sperm & up to 3 haploid polar bodies. 5. Differentiate the mode of inheritance of autosomal dominant, autosomal recessive, and sex-linked recessive patterns of inheritance for monogenic traits.(Beery & Workman, p.68-78; Pathophysiology, p. 152-158) Autosomal Dominant - ● Equal distribution between males & females ● Has no carrier status (The person with even 1 dominant allele expresses the trait) ● Appears in every generation ● The risk for an infected person who is heterozygous for the dominant allele to pass the trait to their child is 50% (practice quiz question) ● The risk for an infected person who is homozygous for the dominant allele to pass the trait to their child is 100% ● Unaffected people do not have the allele & have essentially ZERO risk transmitting it to their children Autosomal Recessive - ● Expressed only when BOTH alleles are present ● Equal distribution between male & female ● Trait often appears first in siblings rather than in the parents of affected child ● May not appear in all generations of any one branch of a family ● Risk for children of 2 affected parents to also be affected is close to 100% ● About 25% of the members of a family with an Autosomal Recessive trait will express the trait/disorder ● Happens often with consanguinity (ie marriage of first cousins) ● On average, the 4th of the offspring of carrier parents is affected ● AR traits DO have a carrier status in which those individuals who only have one affected allele may not express any level of the trait ● Unaffected carriers of AR traits CAN transmit to their kids if their partner is an affected carrier (check this wording from book) ● An AR allele may be present in a family for many generations without overt expression Sex-Linked Recessive