Explanation:
In the majority of cases, the extra copy of chromosome 21 comes from the mother in the egg.
In a small percentage (less than 5%) of cases, the extra copy of chromosome 21 comes from the father through the sperm.
In the remaining cases, the error occurs after fertilization, as the embryo grows.
Answer:
He examined covered and uncovered meat to determine that maggots came from eggs.
Explanation:
Prior to Redi's experiment and other supporting experiments, it was formerly believed that life could emanate from non-living things, for example, the generation of maggots from rotting meat.
In 1668, a scientist called Francesco Redi disproved the idea of spontaneous generation. He did this when he experimented that the maggots from meats are only as a result of eggs laid by flies when they perched on the meat.
He placed the meat in two jars; an uncovered jar and another in a covered jar with a cloth, after several days, the uncovered jar had maggots on the meat, while the covered jar had no maggot on the meat, but on the cloth. With this experiment, he was able to demonstrate that the maggot arose from the eggs of the flies, not the meat itself which is nonliving and hence, disproved the idea of spontaneous generation.
Explanation:
(X3+8)+( 2X2+ 4X)
(X+2)(X2-2X +4) + 2X(X+2)
(X+2)(X2-2X+4+2X)
(X+2)( X2+4)
Answer:
Option C, shared DNA sequences
Explanation:
Complete question -
What evidence suggests that vertebrates are more closely related to echinoderms than are any other invertebrate phyla?
- shared patterns of development
- shared morphology
- shared DNA sequences
Solution
Vertebrates have true backbone while invertebrates lack true backbone. Among the invertebrates, the echinoderm phylum is closely related to vertebrates as the echinoderm possesses notochord (similar to backbone) during their early stage development which disappears later.
Through the genomic sequence studies it has been found that echinoderms are similar to vertebrates in many ways. Echinoderms have diverged from deuterostomes along with human and hence pose some genetic similarity which can be devised through study of common DNA sequences
Hence, option C is correct
