Respuesta :
The appropriate matching for the above; is I) Random fertilization-The formation of a zygote from an egg and a sperm is an unpredictable event;
II) Independent orientation; Random combinations of paternal and maternal chromosomes end up in gametes;
III) Crossing over.An allele on the paternal chromosome 18 ends up on the maternal chromosome 18;
Random fertilization indicates that the collection of genes with one gamete do not give that gamete a lesser or better chance than any of the other gamete cells of fusing with an egg to produce a zygote. Independent orientation or assortment involves the formation of random combinations of chromosomes in meiosis and of genes on different pairs of homologous chromosomes by the passage according to the laws of probability of one of each diploid pair of homologous chromosomes into each gamete independently of each other pair. Cross over occurs in prophase I of meiosis where homologous chromosomes exchange genetic materials.
II) Independent orientation; Random combinations of paternal and maternal chromosomes end up in gametes;
III) Crossing over.An allele on the paternal chromosome 18 ends up on the maternal chromosome 18;
Random fertilization indicates that the collection of genes with one gamete do not give that gamete a lesser or better chance than any of the other gamete cells of fusing with an egg to produce a zygote. Independent orientation or assortment involves the formation of random combinations of chromosomes in meiosis and of genes on different pairs of homologous chromosomes by the passage according to the laws of probability of one of each diploid pair of homologous chromosomes into each gamete independently of each other pair. Cross over occurs in prophase I of meiosis where homologous chromosomes exchange genetic materials.
Answer:
I) Random Fertilization
II) Independent Orientation
III) Crossing-over
Explanation:
I) Fertilization is a phenomenon that occurs in sexually-reproducing organisms only. It is the process whereby the male gamete (sperm cell) fuses with the female gamete (egg cell) to produce a ZYGOTE. Both sperm and egg cells are usually haploid in chromosomal number. The sperm randomly fertilizes the egg. This process is described as unpredictable in the question because, no one knows which sperm will fertilize which egg. It occurs by chance.
II) During Metaphase I of the meiotic process, homologous chromosomes from maternal and paternal parent aligns at the equator of the cell in a random orientation. This random orientation determines which maternal or paternal chromosome ends up in which cell. According to the law of independent assortment, each gamete will randomly contain one allele of each gene. Note that, each of the two alleles of a gene comes from each parent. Hence, based on the example, the combination of maternal and paternal chromosomes that are present in each gamete occurs randomly during the orientation in Metaphase I of meiosis.
III) Crossing-over also called Recombination is a unique process that occurs only during meiosis. It occurs during the Prophase stage of meiosis specifically. It involves the exchange of chromosomal segment between non-sister chromatids of homologous chromosomes ( similar but non-identical chromosomes from each parent). In the example given in the question, the chromosome involved is Chromosome 18. The homologous chromosomes from each parent (male and female) lie side by side to form a TETRAD structure during prophase, after which a chromosomal segment containing alleles is exchanged between non-sister chromatids of maternal and paternal chromosome 18.
