Explanation:
Crossing over, or genetic recombination contributes to genetic variation and diversity.
In early Prophase I of meiosis, crossing over occurs. This 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. The chromosome pairs form tetrads held together at chiasmata.
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. To produce daughter cells, the chromosomes (total number of chromosomes (2n)) are copied before the cell splits into two daughter cells. This process is known as mitosis, and occurs in cell division and growth processes. Two new nuclei are formed, along with identical cells. These are the same as the parent cell and the chromosome number (2n) is maintained. Conversely in meiosis, the number of chromosomes (2n) is halved through meiotic divisions, producing 4 (n) germ cells (sperm or eggs), each containing half the number of chromosomes as its parent cell.
During the process of prophase I one 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 chromatids are aligned precisely. The syanpsis 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.
Crossing over contributes to genetic variation and diversity; novel gene combinations in gametes are formed, which are not present in parent chromosomes. Genetic diversity describes all the genetic characteristics or traits within a species.
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Answer:
(a) crossing over: Meiosis I, Recombination
(b) chromatids separate at their centromeres and migrate to opposite poles: Meiosis II, Anaphase II
(c) chromosomes become aligned in pairs at the equator: Meiosis II, Metaphase II
Explanation:
Homologous recombination is a type of genetic recombination that occurs during meiosis (formation of ovum and sperm cells). The paired chromosomes of the male and female parents are aligned so that similar DNA sequences intersect. This crossing over produces an exchange of genetic material, which is an important cause of the genetic variability observed in the offspring.
Meiosis II: Anaphase II. The centromeres separate and the daughter chromatids - now individual chromosomes - move to the opposite poles of the cell. The centromeres separate, and the two chromatids of each chromosome move toward the opposite poles in the spindle.
Meiosis II: Metaphase II. Chromosomes are accommodated in the equatorial plate of metaphase, similar to what happens in mitosis. They are attached to the already fully formed meiotic spindle. Each chromosome is aligned in the equatorial plate of the metaphase, as it happens in mitosis.
Answer
The key markers for the identification of bacteria are special RNA polymerase, peptidoglycan in cell walls. ester-linked fatty acids.
Explanation:
Answer:
I would start on Evaporation. I will then have to go through condensation, then precipitation, then a surface runoff then into groundwater which will start the evaporation process all over again :)
