Explanation:
During the process of prophase I, the nuclear envelope containing chromosomes has only partly broken down homologous chromosomes are joined together by proteins and a complex or pairing call synapsis- corresponding genes on sister chromatids are aligned precisely.
The syanapsis allows for crossing over which is the exchange of segments of chromosome, between non-sister homologous or similar chromatids crossing over happens at chiasmata, the point where non-sister chromosomes are joined.
Further Explanation:
All the genetic information within the eukaryotic cell is stored within the nucleus as helical DNA. This DNA is tightly wound around histones as chromosomes. In meiosis, the number of chromosomes (2n) is halved to 23 chromosomes (haploid number)through meiotic divisions, producing 4 haploid (n) germ cells or gametes (sperm or eggs), each containing half the number of chromosomes as its parent cell.
In Meiosis I
- homologs pair off into bivalents
- At crossing over: the exchange of segments of chromosome, between non-sister homologous or similar chromatids crossing over happens at chiasmata, the point where non-sister chromosomes are joined in prophase I forming bivalents; tetrads are formed.
- Spindle fibers from centrioles join sister chromatids together at their centromeres in metaphase I, pulling them to the equator of the cell;
- then, in anaphase I, while joined, they are pulled to opposite sides of the cell; the cell body splits and the nuclear envelope reforms in telophase I
In Meiosis II...
- Later, in prophase II, the nuclear envelope disintegrates and mitotic spindle fibers are formed
- independent assortment occurs. in metaphase II of meiosis: spindle fibers attach to centromeres, chromatids align independently at the equator. Genes segregate independently into new combinations as sister chromatids are pulled apart by their centromeres in anaphase II
- in telophase II the cells' nuclei and membrane are then formed with each containing the haploid number (n)
- Following the formation of gametes in the last stage, randomized fertilization occurs in sexual reproduction sperm cells fertilize an ovum to form a zygote. This occurs randomly by chance, to result in a complete set of chromosomes 2n, that is a novel combination of half each parent's number of chromosomes
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14 should be B if I can remember correctly, 15 is C
Answer:
carbon based molecules + oxygen = water + carbon dioxide
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A time when I have resented feeling enclosed was : When I was trapped in an elevator due to power outage.
<h3 /><h3>What is the fear of enclosure </h3>
The fear of enclosure is known as Claustrophobia ( an anxiety disorder ) and this disorder is present in individuals scared of being in enclosures such as elevators and in crowded rooms. Someone with such disorder ( Claustrophobia ) will tend to avoid enclosures. when I resented feeling enclosed I was assured of getting me out of the enclosure ( elevators ) as power was returned almost immediately and this improved my outlook.
In conclusion A time when I have resented feeling enclosed was : When I was trapped in an elevator due to power outage
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In biology, a mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements. Mutations result from errors during DNA replication or other types of damage to DNA, which then may undergo error-prone repair, or cause an error during other forms of repair, or else may cause an error during replication. Mutations may also result from insertion or deletion of segments of DNA due to mobile genetic elements. Mutations may or may not produce discernible changes in the observable characteristics of an organism.