Question

how many chromosomes are in a cell during prophase I of meiosis?

how many chromosomes are in a cell during prophase of mitosis?

are the chromosomes considered uncondensed at the end of telophase?

where do tetrads come from? are they from your mom and dad? if so, how does that work since we’re preparing gametes to be fertilized which have not yet received the partners 23 chromosomes?

Answer 1

The answer to your query is as follows:

Q1. There are 46 chromosomes in a cell during the Prophase I of Meiosis I. It is because replication of the DNA occurs in the S phase of interphase before the Prophase I.

Humans have 23 pairs of the chromosomes or 46 chromosomes. The set of 23 chromosomes is inherited from mother and a set of 23 chromosomes is inherited from the father. After the duplication of the genetic material in the S phase of the interphase , the chromosomes condenses during the prophase I of the meiosis I. But, there are still only 46 chromosomes. It is because they are found in a X- shaped structure. It means that after duplication they contain two chromatids attached to the centromere of the chromosome.

Thus, the humans will have 46 chromosomes and 92 chromatids in a cell during prophase I of meiosis I.

Q2. There are 46 chromosomes in a cell during the Prophase of Mitosis. It is because replication of the DNA occurs in the S phase of interphase before the Prophase stage of the mitosis.

Humans have 23 pairs of the chromosomes or 46 chromosomes. The set of 23 chromosomes is inherited from mother and a set of 23 chromosomes is inherited from the father. After the duplication of the genetic material in the S phase of the interphase , the chromosomes condenses during the prophase of the mitosis. But, there are still only 46 chromosomes. It is because they are found in a X- shaped structure. It means that after duplication they contain two chromatids attached to the centromere of the chromosome.

Thus, the humans will have 46 chromosomes and 92 chromatids in a cell during prophase of mitosis just like the prophase I of meiosis I.

Q3. Chromosomes are considered as decondensed at the end of the telophase. In late telophase, the nuclear membrane reappears. The chromosomes decondense back to their interphase conformations.Chromosome decondensation can be defined as the relaxation or decompaction of the chromosomes back into their expanded chromatin form. It is necessary so that the cells can resume back to their interphase processes.

Q4. We know that humans are diploid (2n) in nature. It means that most of their chromosomes occur in matched sets. These sets are called as homologous pairs. The two members of each 23 pairs of the chromosomes or 46 chromosomes are said to be homologues to one another. The only one difference is found in the sex chromosomes or X and Y chromosomes.

The gametes which are human sperm and eggs have only one homologous chromosome from each 23 pair.Thus, they are haploid (1n) in nature. The fusion of a sperm and a egg leads to the formation of one diploid set of chromosomes. This, proves that one of the homologues comes from the mother and the other comes from the father for each homologous pair of chromosomes in the genome of the offspring.

Thus, a tetrad is the structure formed during the prophase I of the meiosis I made by two homologous chromosomes. These have already been replicated into a pair of sister chromatids in the S phase.

Hope it helps!