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A germline mutation in the reproductive cells of an individual gives rise to a constitutional mutation in the offspring, that is, a mutation that is present in every cell. A constitutional mutation can also occur very soon after fertilization , or continue from a previous constitutional mutation in a parent. [ 90 ]
During differentiation, stem cells change their gene expression profiles. Recent studies have implicated a role for nucleosome positioning and histone modifications during this process. [38] There are two components of this process: turning off the expression of embryonic stem cell (ESC) genes, and the activation of cell fate genes.
This process of the second bacterial cell taking up new genetic material is called transformation. In molecular biology and genetics, transformation is the genetic alteration of a cell resulting from the direct uptake and incorporation of exogenous genetic material from its surroundings through the cell membrane(s).
The cause of Tay–Sachs disease is a genetic defect that is passed from parent to child. This genetic defect is located in the HEXA gene, which is found on chromosome 15. The HEXA gene makes part of an enzyme called beta-hexosaminidase A, which plays a critical role in the nervous system.
Sickle cell disease: In a healthy individual, the HBB gene is responsible for encoding hemoglobin which carries oxygen throughout the body. [16] However, when a person has this disease due to inheriting two mutated copies of the HBB gene due to a base pair point mutation, their red blood cells are shaped differently. [16]
Genetic variation can be identified at many levels. Identifying genetic variation is possible from observations of phenotypic variation in either quantitative traits (traits that vary continuously and are coded for by many genes, e.g., leg length in dogs) or discrete traits (traits that fall into discrete categories and are coded for by one or a few genes, e.g., white, pink, or red petal color ...
Epigenetic mechanisms. In biology, epigenetics is the study of heritable traits, or a stable change of cell function, that happen without changes to the DNA sequence. [1] The Greek prefix epi-(ἐπι-"over, outside of, around") in epigenetics implies features that are "on top of" or "in addition to" the traditional (DNA sequence based) genetic mechanism of inheritance. [2]
In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA damage, resulting in tens of thousands of individual molecular lesions per cell per day. [2] Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell's ability to transcribe the gene that the ...