Answer:
The answer is option "B"
Explanation:
DNA is comprised of a set of genes that dictates a given trait. The genes themselves are comprised of alleles that allow for variations and differences in the trait that the concerned gene is responsible for. In the case of D. Melanogaster, there is an allele that allows for resistance to pesticides such as DDT. The two samples that are referred to in the question are differentiated on the basis of the amount of time that has lapsed since the start of significant DDT usage. So at the time when widespread DDT usage was not in place, the sample showed no DDT resistant alleles. With the passage of time in which DDT usage grew, the resultant effect as evidenced from the later sample indicated a significantly higher percentage of DDT resistant allele. This means that the ability of this species of fruit flies to survive, referred to as their evolutionary fitness, increased only after use of DDT increased. This means that DDT resistance trait changed as a natural response to the introduction of a different climate thereby allowing subsequent offspring of fruit flies to boast of higher numbers of alleles that have DDT resistance capacities thus allowing them to survive.
Meiosis is a cellular division that produces four haploid daughter cells from a parent cell. It is observed in gametes/sex cells. The process of meiosis undergoes two consecutive divisions. Each division has five phases: prophase, metaphase, anaphase, telophase, and cytokinesis.
In Meiosis I, the chromosomes of the parent cells are multiplied. Each chromatid of the chromosomes exchanges genetic information, or <em>recombination</em>. The number of chromosomes at the end of Meiosis I is haploid but the chromatids of the chromosomes are still attached to each other. Due to recombination, the sister chromatids may not be identical to each other.
In Meiosis II, the chromosomes are separated and produce four daughter cells. It is shorter compared to Meiosis I because it no longer replicates the DNA or exchanges genetic information, and just separates the prepared chromatids from Meiosis I. It is similar to mitosis since it begins with a haploid cell and ends with a haploid cell.
The correct answer would be D
DNA replication has such accuracy varies. There are many DNA polymerases/repair enzymes that synthesize/repair DNA. Some are more frequent than others. The error frequency ranges between 1 to per 10,000 base pairs to 1 to per 10,000,000 base pairs, depends on the enzyme
Answer:
phép lai cho tỉ lệ kiểu hình 1:1 là Aa x aa => 1Aa:1aa