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These are the answers to the quiz. |
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1) DNA replication is carried out in the endoplasmic reticulum. | ||
| Not answered. It is false. DNA replication is performed within the nucleus or nucleoplasm. In the endoplasmic reticulum membranes, mRNA is translated to proteins. | ||
2) Eukaryote cells are characterized by having just one nucleus. | ||
| Not answered. It is false. Containing at least one nucleus is the feature that defines eukaryote cells. Most eukaryote cells contain one nucleus. However, many other eukaryote cells contain more than one. For example, macrophages contain several nuclei, and skeletal muscle cells contain many of them. | ||
3) The nucleus is composed of nucleplasm and nuclear envelope. | ||
| Not answered. It is true. The nuclear envelope is made up of the outer and inner membranes, and the perinuclear cisterns in between. Nuclear pore complexes are inserted in the nuclear envelope. The nucleoplasm is enclosed by the nuclear envelope. DNA and all the molecular machinery for maintaining, expressing and regulating the DNA constitute the nucleoplasm. | ||
4) The nuclear envelope separates the nucleoplasm from the cytoplasm. | ||
| No answered Iti s true. | ||
5) The nuclear envelope is composed of one membrane where nuclear pore complexes are inserted. | ||
| Not answered. It is false. The nuclear envelope is made up of an outer and an inner membrane, with a perinuclear space in between. Nuclear pore complexes are found in the spaces where the two membranes are connected and continuous, and only a few proteins of the nuclear pore complex are transmembrane proteins. | ||
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6) Protein synthesis happens in the nuclear envelope. | ||
| No answered It is true. The outer membrane of the nuclear envelope physically continues with the endoplasmic reticulum membrane. There are attached ribosomes to the outer membrane doing translation of proteins. Actually, the nuclear envelope is regarded as an endoplasmic reticulum domain. | ||
7) Molecular composition of the outer and inner membranes are similar. | ||
| Not answered It is false. Different molecules of the nuclear envelope are segregated between the outer and inner membranes, even if they are physically continuous. This makes sense since the functions of both membranes are different, one facing the cytosol and the other the basal lamina and nucleoplasm. | ||
8) The basal lámina maintains the integrity of the nuclear envelope. | ||
| Not answered. It is true. The basal lámina is composed of laminas, proteins that are assembled in a scaffold just below the inner membrane of the nuclear envelope. This lattice allows to maintain the nuclear envelope integrity. When a cell enters mitosis, and the nuclear envelope needs to be disorganized, lamina proteins are phosphorylated and the basal lamina and nuclear envelope are disassembled, letting microtubules to contact with chromosomes. | ||
9) Gene expression of eukaryote cells couldn't be regulated without the nuclear envelope. | ||
| Not answered. It is true. For example, transcription factors are proteins that regulate gen expression. They are synthesized in the cytosol and must cross the nuclear envelope to come inside the nucleus and be in contact with the DNA. Transcription factors cannot freely cross the nuclear envelope but through the nuclear pore complexes. So, the molecular system that enters and gets molecules out of the nucleus, together with the nuclear pore complexes, regulate the transfer of transcription factors and therefore the gene expression. | ||
10) DNA is also known as chromatin. | ||
| Not answered. It is false. Chromatin consists of DNA plus associated proteins, mostly histones. | ||
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11) Chromatin is found in the cytoplasm. | ||
| Noat answered It is false. Chromatin is found inside the nucleus. It is a component of the nucleoplasm. | ||
12) Euchromatin is a type of chromatin loosely condensed. | ||
| Not answered It is true. Morphologically, chromatin is divided in euchromatin, which is less condensed and more clear, and in heterochromatin, more condensed and dark. They can be distinguished with both light and electron microscopy. | ||
13) Facultative heterochromatin is a type of chromatin that does not decondensate during interphase. | ||
| Not answered. It is false. In fact, facultative means that this type of heterochromatin may change between the condensed and decondensed states during interphase (cell cycle period between mitosis). | ||
14) Nucleolus cannot be observed with the light microscope but with the electron microscopy. | ||
| Not answered. It is false. The nucleolus is bigger enough to be seen the optical microscopes. Actually, it can be larger than mitochondria. | ||
15) The nucleolus is involved in the syntehsis of ribosomes. | ||
| Not answered. It is true. Ribosomal RNA is synthesized in the nucleolus, excepting ribosomal 5S RNA. Ribosomal subunits are assembled in the nucleolus as well. Assembling means that ribosomal RNA and proteins are joined together to form the ribosomal subunits, that are eventually exported to the cytosol. | ||
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16) The fibrilar center is the region of the nucleolus where most ribosomal RNA is transcribed and processed. | ||
| Not answered. It is true. The long ribosomal RNA is transcribed and processed in the fibrillar center of the nucleolus. The 5S ribosomal RNA is transcribed in other place of the nucleoplasm. The other nucleolar regions are involved in the ribosomal subunit assembling. | ||
17) There are many copies of the gen that code for ribosomal RNA. | ||
| Not answered. It is true. Many copies make possible to produce many ribosomal ARN molecules in a short period of time. Cells need to produce many functional ribosomes with the proper amount of ribosomal RNA to translate all the proteins that carried out the cell functions. | ||
Quiz results
Right answers = 0
Wrong answers = 0
Not answered = 17
Unusefull answers = 0
The score of the quiz (range between 0 and 10) = 0,0 Do you need to read the descriptive pages again ?