6. In our body skin cells and muscle cells share the same DNA. Which of the following
is true
a. Although they share the same DNA, both have a different genetic code so the
proteins expressed are different.
b. The statement is incorrect, they are different tissues so there is a difference in
their DNA.
c. The statement is true, they differ though in the genes they transcribe and
translate.
d. The statement is true, the skin cells and muscle cells differ in how many copies
of DNA they have.
Skin cells and muscle cells in the human body contain identical DNA but express different proteins due to selective gene transcription and translation, making option c the correct answer.
Option Analysis
a. Although they share the same DNA, both have a different genetic code so the proteins expressed are different.
This is incorrect because the genetic code—the mapping of codons to amino acids—remains universal across all cell types in the body and nearly all organisms. Differences arise not from code variation but from which genes are activated.
b. The statement is incorrect, they are different tissues so there is a difference in their DNA.
False; somatic cells like skin keratinocytes and muscle myocytes derive from the same zygote and retain the full diploid genome. DNA sequence identity enables organism-wide consistency despite tissue specialization.
c. The statement is true, they differ though in the genes they transcribe and translate.
Correct; differential gene expression regulates cell fate. Muscle cells express genes like MYH for myosin via transcription factors such as MyoD, while skin cells prioritize keratins for barrier function. Epigenetic marks like histone acetylation further control this.
d. The statement is true, the skin cells and muscle cells differ in how many copies of DNA they have.
Incorrect for diploid somatic cells, which maintain two DNA copies per cell (2n=46 chromosomes). Exceptions like polyploidy in some muscle fibers or aneuploidy in cancers do not apply here.
Gene Expression in Cell Differentiation
All nucleated body cells share the ~3 billion base pair human genome, yet over 200 cell types exist due to regulated gene expression. During development, signals trigger transcription factors to activate tissue-specific genes while repressing others via promoters, enhancers, and silencers. For CSIR NET aspirants, note that RNA polymerase II transcribes mRNA selectively, followed by translation into proteins defining cell identity—e.g., actin in muscle vs. collagen in skin.
This principle underlies cellular differentiation, crucial for topics like developmental biology and epigenetics in exams. Muscle differentiation involves MyoD binding chromatin modifiers, contrasting skin’s KLF4-driven pathways.
