What happens in prophase 1 of mitosis?
During prophase I, homologous chromosomes pair and form synapses, a step unique to meiosis. The paired chromosomes are called bivalents, and the formation of chiasmata caused by genetic recombination becomes apparent. Chromosomal condensation allows these to be viewed in the microscope.
What happens to the cell during prophase I?
During prophase, the complex of DNA and proteins contained in the nucleus, known as chromatin, condenses. The chromatin coils and becomes increasingly compact, resulting in the formation of visible chromosomes. The sister chromatids are pairs of identical copies of DNA joined at a point called the centromere.
What happens at prophase 1 of meiosis?
During prophase I, the complex of DNA and protein known as chromatin condenses to form chromosomes. A large structure called the meiotic spindle also forms from long proteins called microtubules on each side, or pole, of the cell. Between prophase I and metaphase I, the pairs of homologous chromosome form tetrads.
How does prophase 1 in meiosis differ from prophase in mitosis?
In mitosis, prophase, metaphase, anaphase and telophase occur once. Chromosomes condense and the centrosomes begin to form an early spindle. Meiotic prophase I is much longer that mitotic prophase. During prophase I homologous chromosomes make contacts with each other called chiasmata and “crossing over” occurs.
What is the result of prophase 1?
At the end of prophase I, the pairs are held together only at the chiasmata; they are called tetrads because the four sister chromatids of each pair of homologous chromosomes are now visible. The result is an exchange of genetic material between homologous chromosomes.
What is the definition of prophase 1?
1 : the initial stage of mitosis and of the mitotic division of meiosis characterized by the condensation of chromosomes consisting of two chromatids, disappearance of the nucleolus and nuclear membrane, and formation of mitotic spindle.
How is prophase I different from prophase of mitosis?
During prophase I, the chromosomes condense, as in mitosis. Unlike in mitosis, the sister chromosomes stay together through meiosis I, but the homologous chromosomes are separated. Each homologous chromosome carries different alleles for each gene.
How many chromosomes are in prophase?
For humans, this means that during prophase and metaphase of mitosis, a human will have 46 chromosomes, but 92 chromatids (again, remember that there are 92 chromatids because the original 46 chromosomes were duplicated during S phase of interphase).
What is the function of prophase?
B is correct. The purpose of prophase is to condense the DNA, and prepare the cellular machinery to move chromosomes and organelles around the cell. Without chromosomes or organelles, bacteria do not need to go through prophase in order to divide.
Definition of prophase 1 : the initial stage of mitosis and of the mitotic division of meiosis characterized by the condensation of chromosomes consisting of two chromatids, disappearance of the nucleolus and nuclear membrane, and formation of mitotic spindle
What happens to chromosomes during prophase?
During prophase, the identical chromatids of each chromosome are pulled apart. They are pulled to opposite poles of the nucleus by the microtubules attached to each centromere . After each chromosome has been split, the cell divides producing two identical cells with the identical DNA in each.