MCAT Biology assist » biological » cabinet Biology, molecule Biology, and Genetics » cellular Processes and Functions » Mitosis and also Meiosis
Explanation:

DNA is stored in loosely wound euchromatin prior to mitosis. Throughout mitosis, the DNA condenses into chromosomes, which are made the heterochromatin. It becomes an ext dense throughout prophase, and also stays that means until the end of mitosis. Euchromatin is more lightly packed than heterochromatin.

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Mitosis follows the following sequence: prophase, metaphase, anaphase, telophase, cytokinesis. Interphase refers to the time duration between mitotic divisions. During interphase, most DNA is euchromatin, yet some areas remain together heterochromatin to protect against unwanted transcription; thus DNA exists together both types of chromatin throughout interphase, yet only as heterochromatin throughout mitosis. Equivalent euchromatin come telophase is the answer, together this is a false statement.


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Example concern #12 : Mitosis and Meiosis


Something walk wrong throughout meiosis in a male and also the 4 daughter sperm cells that are produced all have actually the dorn amount that chromosomes. 2 of the sperm have actually one extra chromosome and also the other two have actually one missing chromosome. At what action did the problem most most likely occur, and also what was it?


Possible Answers:

Telophase I—deletion


Prophase I—trisomy


Metaphase I—nondisjunction


Telophase II—translocation


Anaphase I—inversion


Correct answer:

Metaphase I—nondisjunction


Explanation:

If nondisjunction wake up in Metaphase I, then one extra chromosome created of 2 tetrads would enter one that the cells beginning metaphase II while the various other would have actually one less. This extra chromosome would then experience the rest of meiosis normally, leave an extra chromosome, written of one tetrad in two of the daughter sperm. These are the two that are absent from the other daughter sperm. 


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Example concern #11 : Mitosis and also Meiosis


When does genetic crossover take place during meiosis? 


Possible Answers:

Prophase I


Telophase II


Anaphase I


Metaphase I


Correct answer:

Prophase I


Explanation:

This is a straightforward memorization problem. Crossover occurs as soon as the cell nucleus decondenses. The chromosomes space able come crossover throughout prophase I once chromosome pairs are aligned alongside one another. Crossover cannot happen later in meiosis, together the chromosomes have already been separated.


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Example question #14 : Mitosis and also Meiosis


The concept of genomic imprinting is crucial in person genetics. In genomic imprinting, a certain region of DNA is just expressed by among the two chromosomes that comprise a usual homologous pair. In healthy individuals, genomic imprinting outcomes in the silencing of gene in a particular section that the maternal chromosome 15. The DNA in this component of the chromosome is "turned off" through the addition of methyl groups to the DNA molecule. Healthy people will hence only have actually expression that this ar of chromosome 15 native paternally-derived DNA.

The two standard human illness that highlight defects in genomic imprinting are Prader-Willi and Angelman Syndromes. In Prader-Willi Syndrome, the section of head chromosome 15 that is normally expressed is disrupted, such together by a chromosomal deletion. In Angelman Syndrome, maternal gene in this section are deleted, while paternal genes space silenced. Prader-Willi Syndrome is thus closely linked to paternal inheritance, if Angelman Syndrome is linked to maternal inheritance.

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Figure 1 shows the chromosome 15 homologous pair for a kid with Prader-Willi Syndrome. The parental chromosomes are likewise shown. The gene on the mother’s chromosomes are silenced normally, as represented by the black color boxes. At once, over there is also a chromosomal deletion on among the paternal chromosomes. The result is the the child does not have any type of genes express that room normally uncovered on that region of this chromosome.

 

 

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A scientist is investigate a cabinet undergoing division, and notes the chromosome 15 is aligned with the various other chromosomes in the center of the cell, as if follow me a line. Every of the 23 bag of chromosomes is arranged together a tetrad follow me this plate. Which phase of cell department is this cell most most likely undergoing?