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Genetic Counseling in Assisted Reproductive Technology
Published in Carlos Simón, Carmen Rubio, Handbook of Genetic Diagnostic Technologies in Reproductive Medicine, 2022
Autosomal recessive inheritance is when mutation in both alleles of an autosomal disease is necessary to cause disease. An affected individual has two non-functional alleles, one inherited from each carrier parent. An individual carrying a single variant in a recessive gene is unaffected with the condition, but when two individuals are carriers, there is a 25% chance that both variants will be passed on, resulting in an affected child. There may be no family history of a recessive condition when a child is found to be affected. The variant can be passed down generation to generation without ever causing disease until, by random chance, both members of a reproductive couple are carriers, and future offspring are at risk of being affected. Carrier screening can therefore be an effective tool in detecting such carrier couples.
An Approach to Inherited Pulmonary Disease
Published in Stephen D. Litwin, Genetic Determinants of Pulmonary Disease, 2020
One result of the Lyon phenomenon is that each human female is a mosaic of two kinds of cells that are different because they have different genetically active X chromosomes. By this mechanism some females who are heterozygous for an X-linked gene causing a recessive phenotype may manifest some or, rarely, all of the phenotype. When by random chance most of the cells in a heterozygous female contain an inactive X chromosome with the allele for the normal phenotype, and an active X chromosome with the allele for the recessive phenotype, that phenotype may be expressed in a manner similar to the expression in males who have only one X chromosome with the recessive gene. Females in whom a smaller number of cells contain an active X chromosome with the gene for the recessive phenotype may show various partial or mosaic phenotypes.
Basal Cell Nevus Syndrome
Published in Dongyou Liu, Handbook of Tumor Syndromes, 2020
Priyanka Chhadva, Pete Setabutr
If a dominant gene located on one of the 22 nonsex chromosomes (autosomes) is mutated in a parent, there is a 50% chance for a child to inherit the mutated gene (dominant gene) from this parent along with a normal gene (recessive gene) from the other parent and become affected. There is also is a 50% chance for a child to inherit two normal genes (recessive genes) from parents and remain unaffected. In autosomal dominant disorder, inheritance (or transfer) of one copy of the altered gene in each cell is sufficient for the disease to occur.
Early flowering, good grain quality mutants through gamma rays and EMS for enhancing per day productivity in rice (Oryza sativa L.)
Published in International Journal of Radiation Biology, 2021
Vinithashri Gautam, Manonmani Swaminathan, Manoharan Akilan, Anand Gurusamy, Meena Suresh, Bhuvaneswari Kaithamalai, A. John Joel
Both genotypic differences and modes of action of different mutagens contribute to variation in the spectrum of mutants generated. Kharkwal (2000) quoted the differences in frequency and spectrum of viable mutations induced by various mutagens due to genetic differences in varieties. Putting forth in a theoretical way, any gene responsible for an agronomic trait is mutable, hence a wide spectrum of viable mutations can be generated in a mutation experiment. The occurrence of these macro-mutations can be attributed to chromosomal aberrations. Mutations in recessive genes occur when there are deficiency, duplications, or point mutations due to mutagens. Chlorophyll mutants and morphological mutants show up in M2 generation while they are not observed in M1 generation and this explains the recessive nature of those mutations. Mutagenic effectiveness and efficiency represent the features of mutagens and sheds light on their utility in crop improvement. Mutagenic effectiveness gives the measure of the frequency of mutations induced by a unit dose of mutagen and efficiency gives the info on biological damage (Konzak, 1965; Nilan, 1965). The results of gamma rays and combination treatments in M2 and M3 generation revealed that the combination treatments were found more effective and efficient in causing variability than gamma rays alone.
UK guidelines for the medical and laboratory procurement and use of sperm, oocyte and embryo donors (2019)
Published in Human Fertility, 2021
Helen Clarke, Shona Harrison, Marta Jansa Perez, Jackson Kirkman-Brown
Furthermore, the potential donor should ordinarily not be heterozygous for an autosomal recessive gene known to be prevalent in the donor’s ethnic background. This includes: (i) cystic fibrosis in Caucasian populations; (ii) glucose-6-phosphate dehydrogenase deficiency or ∝0 or β-Thalassaemia in Mediterranean populations; (iii) sickle cell disease in African & Afro-Caribbean populations; and (iv) Tay-Sachs disease in Jews of Eastern European descent. However, in exceptional circumstances (e.g. in cases of known donation) the presence of a recessive gene disorder may not necessarily be a contraindication to donation provided that, when the donation is used, all parties are fully informed, the view of an appropriately qualified clinical geneticist is obtained and full records are kept. The decision whether or not to proceed should consider the type of treatment being offered as well as the genetic profile of the donor and recipient couple.
The Moral Choices on CRISPR Babies
Published in The American Journal of Bioethics, 2019
In favor: healthy children. In cases where a woman’s eggs have a heritable genetic abnormality, as in mitochondrial mutations, a dominant allele associated with a disease, or both she and her husband have recessive genes linked to a disease, which could give rise to a genetically abnormal child, gene editing could in theory result in a healthy offspring. In such circumstances, where all of a woman’s eggs are defective, preimplantation genetic screening (PGS) is unlikely to resolve the problem. For parents who wish to have a healthy child with their nuclear DNA, gene editing may be the only choice. Considering the interests of the parents and the limited use of gene editing purely for therapeutic purposes, an argument can be made that it is the ethical thing to do once the procedure can be proven safe and effective. This argument is implicit in the plan by Russian scientists to use CRISPR on the embryos of deaf couples who do not want deaf children (Le Page 2019).