add to this text (if possible) the duration of gene expression in humans and in tailed/cat-eared animals. For example: TBXT expression is shorter in time than in an animal with a tail, etc.

text to redact:
Genes play a pivotal role in determining the physical attributes of an organism, including the formation of ears and tails. With genetic modification, it is possible to construct these structures in humans, even though they are not naturally present. There are various genes and their functions that could be useful in constructing cat ears and tails in humans. The following genes are beneficial in such tasks, ranked in descending order of importance:

Ear Formation:
1. SHH (Sonic Hedgehog) - Responsible for the development of the midline of the embryo, including the formation of the ear. Mutations in this gene can lead to anomalies such as cyclopia and abnormal ear development. [Reference: Ingham and McMahon (2001)]
2. PAX8 - Regulates the expression of other genes during ear formation, including the differentiation of sensory cells in the inner ear. [Reference: Bhattacharyya et al. (2014)]
3. SOX9 - Necessary for the development of the ear’s cartilage and the maturation of its sensory cells. [Reference: Wright et al. (2003)]
4. FGF (Fibroblast Growth Factors) - Regulate the growth, differentiation, and migration of cells during ear development. [Reference: Hartsock et al. (2014)]
5. NOTCH - Plays a role in ear development by regulating cell fate decisions, including determining the number and type of cells in the inner ear. [Reference: Kiernan et al. (2011)]
6. HOX genes - Responsible for the anterior-posterior patterning of the embryo and involved in the formation of the ear’s shape. [Reference: Izpisua-Belmonte et al. (1991)]

Tail Formation:
1. Wnt - Regulates the growth and development of the dorsal (top) and ventral (bottom) sides of the embryo, including the formation of the tail. [Reference: De Robertis and Kuroda (2004)]
2. BMP (Bone Morphogenetic Protein) - Plays a significant role in determining embryonic development and is responsible for the creation of limbs, the spinal cord, and the tail. [Reference: De Robertis and Kuroda (2004)]
3. CDX (Caudal-Related Transcription Factor) - Controls the expression of other genes involved in hindgut and tail development. This gene is also expressed in the tail bud and is critical for tail elongation. [Reference: Kim et al. (2011)]
4. TBXT (T-box transcription factor T) - This essential gene helps regulate the development of embryonic germ layers, including the formation of tail structures in the embryo. [Reference: Micallef et al. (2007)]
5. WNT3A - This gene contributes to tail elongation and dorsoventral patterning, inducing the expression of Hox genes in the tail bud that are critical to proper tail elongation and patterning. [Reference: ten Berge et al. (2008)]

While these genes provide essential information related to the molecular events responsible for the formation of specialized organs in developing organisms, caution is necessary concerning genetic modification on humans due to ethical and safety concerns. The possibility of constructing cat ears and tails in humans is purely hypothetical and requires ethical and scientific considerations.


Bibliography:
- Bhattacharyya, S., Bailey, A. P., Bronner-Fraser, M., & Streit, A. (2014). PAX8 and the Development of the Inner Ear Epithelium. Advances in Experimental Medicine and Biology, 801, 659-667.
- De Robertis, E. M., & Kuroda, H. (2004). Dorsal-Ventral Patterning and Neural Induction in Xenopus Embryos. Annual Review of Cell and Developmental Biology, 20, 285-308.
- Hartsock, A., Lee, C. M., & Arnold, S. J. (2014). Fibroblast growth factor signaling in ear development and regeneration: One gene to rule them all. Developmental Biology, 392(2), 67-82.
- Ingham, P. W., & McMahon, A. P. (2001). Hedgehog signaling in animal development: paradigms and principles. Genes & Development, 15(23), 3059-3087.
- Izpisua-Belmonte, J. C., Tickle, C., Dolle, P., & Wolpert, L. (1991). Expression of Hox-4 genes in the chick wing links pattern formation to the generation of neural crest. Nature, 350(6316), 585-589.
- Kim, S. H., Park, H. C., Yeo, S. Y., Hong, S. K., Gong, Z., & Kim, C. H. (2011). Cdx-Hox code controls competence for responding to Fgfs and retinoic acid in zebrafish neural tissue. Developmental Cell, 20(1), 118-129.
- Kiernan, A. E., Cordes, R., Kopan, R., Gossler, A., & Gridley, T. (2011). Notch signaling during ear development. Seminars in Cell & Developmental Biology, 22(5), 480-489.
- Micallef, L., Bel-Vialar, S., & Lambert, A. (2007). The Spatial and Temporal Distribution of Two T-box Transcription Factor, Tbx21 And Tbx3, During Chick Embryonic Development. International Journal of Developmental Biology, 51(5), 315-321.
- ten Berge, D., Koole, W., Fuerer, C., Fish, M., Eroglu, E., & Nusse, R. (2008). Wnt signaling mediates self-organization and axis formation in embryoid bodies. Cell Stem Cell, 3(5), 508-518.
- Wright, T. J., Mansour, S. L., & Fgf, W. G. (2003). SOX9 expression and action in the auditory rosette apparatus during avian cochlea development. Developmental Biology, 255(1), 207-218.