Answer:
Crossing-over between homologous chromosomes (prophase 1), the random lining of homologous chromosomes (metaphase 1), and random fertilization are the mechanisms involved in genetic variation.
Explanation:
Crossing-over between homologous chromosomes (prophase 1), the random lining of homologous chromosomes (metaphase 1), and random fertilization are the mechanisms involved in genetic variation.
The Crossing-over events occur between two homologous chromosomes in the equatorial plane and make the daughter cells genetically different from the original one. The Chiasma is the position where two homologous chromatids interchange genetic information, giving a place for new genetic material or information to be provided to descendants. After crossing over, homologous chromosomes get separated again.
On the equatorial plane, homologous paired together, randomly aline with their kinetochores facing opposite poles. The random arrangement of tetrads is different in every cell going through the meiosis process. There is no equal alinement between two cells. When tetrads aline in the equatorial plane, there is no predetermined order for each of the homologous chromosomes of each tetrad to face one of the poles and then migrate to it while separating. Chromosomes of the homologous pair arrange to face any of the poles to migrate forward to it. Each of the chromosomes has two possibilities for orientation at the plane. When the new haploid cells are formed, the number of variations in each cell is also different and depends on the chromosomes that form that cell. The order in the equatorial plane is what introduces variation into the gametes, being almost impossible for two gametes to have the same genetic charge.
Independent assortment occurs when the alleles from two or more different genes distribute in gametes independently from each other. In other words, a gamete receives an allele from a gene that does not depend on nor influence the allele of another gene in the same gamete. This can only be applied to independent genes. An organism gets only one of the members of the chromatids pair of each parent.
Answer:
A. Ancient bacteria
Explanation:
From the salt of the earth, researchers have isolated and revived a Bacillus strain, which they believe is >250 million years old. If correct, Russell Vreeland and his colleagues from West Chester University, Pennsylvania, have discovered the oldest living organism in the world.
"These" should be referring to Alkali Metals.
They include metals such as Lithium, Sodium, Potassium etc.
They're classified as Group I elements because they all have one outmost shell electrons. This is why these metals are so reactive because they only need to lose one electron in order to achieve the octet of electrons (or duplet for Lithium), which means complete outmost shell electrons (2 or the 1st shell, others are 8).
The reason why they're especially reactive to Halogens (Group VII) elements are that Halogens have 7 outmost shell electrons, which only needs one more electron in order to get to the octet of electrons. So, if an Alkali metal reacts with a Halogen, the metal would give one of their electrons to the Halogen, that way, both of the elements can have an octet of electrons (or duplet).
The answer would be Biology and Chemistry. Although they do use a little bit of physics, it's mostly chemistry and biology.
Answer:
Option B,
Explanation:
Proper restraint and handling techniques are used while dealing with animals in laboratory. These techniques ease the process of dealing with animals and must be practiced on regular basis even when there is no procedure being performed.
Unlike other animals cat is the most co-operative animals and it is usually dealt by restraining the body be one hand and head by other hand. Cats can also be restrained by holding the scruff with one hand and then gently holding the hind limbs followed by stretching it.
Hence, option B is correct.
