What controls the way in which a zygote differentiates? Selective genes are turn
ID: 88267 • Letter: W
Question
What controls the way in which a zygote differentiates?
Selective genes are turned on and off, depending on the fate of the cell.
Operons mature and control gene expression.
All the genes that will be expressed in the adult are made in the zygote.
The DNA of genes that will not be expressed is degraded.
When are DNA molecules the least tightly coiled?
metaphaseS phase of interphasetelophaseG2 phase of interphase
Alternative RNA splicing has revealed inaccuracies in the one gene:one polypeptide hypothesis. Why?
It really should be the one exon: one polypeptide hypothesis.
It shows that it takes more than one gene to code for most polypeptides.
Transcription of the same gene can lead to the production of different mRNAs and therefore different proteins.
It really should be the one intron: one polypeptide hypothesis.
A mutation in the ras gene can
inhibit cell division
control cell division
alter the number of copies of the ras gene
stimulate cell division
Cells become specialized by a process known as
differentiation
apoptosis
signal transduction
divergence
Histones are
groups of genes that respond to environmental changes
proteins around which DNA is coiled
portions of genes that are transcribed
master genes that affect development
In eukaryotes, gene expression is regulated mostly by
controlling the translation of mRNA into protein
selectively breaking down certain proteins so they cannot function
controlling the transcription of genes
controlling gene packing and unpacking
Proto-oncogenes have the potential to become oncogenes. Which of the following is most likely to lead to cancer?
a mutation that causes the proto-oncogene to become overactive
a mutation in a gamete
a viral infection
a tissue injury
Embryonic stem cells differ from adult stem cells because they
can differentiate into all cell types
are capable of being fertilized
are capable of many cell divisions
can differentiate into many cell types
In eukaryotic cells, signal transduction pathways involve
signal molecules that bind with transcription factors embedded in the plasma membrane
relay proteins that initiate transcription in the nucleus
signal molecules that are released from the nucleus of the target cell
a series of relay molecules, of which the last activates a transcription factor
Explanation / Answer
1. Option first is correct. The process of differentiation involves the activation (turning on) of some genes and the inactivation (turning off) of other genes, in order to get the specific collection of proteins that characterizes that cell type.
2. S phase of interphase. S-phase (synthesis phase) is the part of the cell cycle in which DNA is replicated, occurring between G1 phase and G2 phase.
3.Option 3rd is correct. Transcription of the same gene can lead to the production of different mRNAs and therefore different proteins; the same strand of mRNA can be spliced in different ways so that different polypeptides are coded.
4. Stimulate cell division. All Ras protein family members belong to a class of protein called small GTPase, and are involved in transmitting signals within cells (cellular signal transduction). Because these signals result in cell growth and division, overactive Ras signaling can ultimately lead to stimulation of cell division.
5. Differentiation. Cell differentiation is the process by which cells become specialized in order to perform different functions.
6. Proteins around which DNA is coiled. Histones are highly alkaline proteinsfound in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, acting as spools around which DNA winds, and playing a role in gene regulation.
7. Controlling the transcription of genes. Transcription is the process of synthesis of mRNA from DNA molecule and this is the stage where gene expression is regulated mostly.
8. A mutation that causes the proto-oncogene to become overactive; an overactive proto oncogene could become an oncogene.
9. Can differenciate into all cell types. Embryonic stem cells can become all cell types of the body because they are pluripotent. Adult stem cells are thought to be limited to differentiating into different cell types of their tissue of origin.
10. A series of relay molecules, of which the last activates a transcription factorSignal transduction pathway is a set of chemical reactions in a cell that occurs when a molecule, such as a hormone, attaches to a receptor on the cell membrane. The pathway is actually a cascade of biochemical reactions inside the cell that eventually reach the target molecule or reaction.
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