mutations that arise during meiosis are not transmitted to the next generation,yes,no,explanation?
Answers
Answer:
Organisms that reproduce sexually are thought to have an advantage over organisms that reproduce asexually, because novel combinations of genes are possible in each generation. Furthermore, with few exceptions, each individual in a population of sexually reproducing organisms has a distinct genetic composition. We have meiosis to thank for this variety.
Meiosis, from the Greek word meioun, meaning "to make small," refers to the specialized process by which germ cells divide to produce gametes. Because the chromosome number of a species remains the same from one generation to the next, the chromosome number of germ cells must be reduced by half during meiosis. To accomplish this feat, meiosis, unlike mitosis, involves a single round of DNA replication followed by two rounds of cell division (Figure 1). Meiosis also differs from mitosis in that it involves a process known as recombination, during which chromosomes exchange segments with one another. As a result, the gametes produced during meiosis are genetically unique.
Researchers' initial understanding of meiosis was based upon careful observations of chromosome behavior using light microscopes. Then, in the 1950s, electron microscopy provided scientists with a glimpse of the intricate structures formed when chromosomes recombine. More recently, researchers have been able to identify some of the molecular players in meiosis from biochemical analyses of meiotic chromosomes and from genetic studies of meiosis-specific mutants.
Meiosis Is a Highly Regulated Process
A schematic diagram shows key events in mitosis and meiosis during the development cycles of male and female sex cells in humans. During fetal development, cells undergo a period of mitotic proliferation. In females, the cells enter meiosis, followed by meiotic arrest. Cells exit meiotic arrest and are either lost before birth or undergo follicle formation after birth. After puberty, these cells are either ovulated each month, one at a time, or becomes atretic. During fetal development in males, proliferating cells enter mitotic arrest. After birth, they enter a second period of mitotic proliferation. After puberty, the cells undergo meiotic divisions to produce sperm cells.
View Full-Size ImageFigure 2
Figure Detail
Meiosis represents a survival mechanism for some simple eukaryotes such as yeast. When conditions are favorable, yeast reproduce asexually by mitosis. When nutrients become limited, however, yeast enter meiosis. The commitment to meiosis enhances the probability that the next generation will survive, because genetic recombination during meiosis generates four reproductive spores per cell, each of which has a novel genotype. The entry of yeast into meiosis is a highly regulated process that involves significant changes in gene transcription (Lopez-Maury et al., 2008). By analyzing yeast mutants that are unable to complete the various events of meiosis, investigators have been able to identify some of the molecules involved in this complex process. These controls have been strongly conserved during evolution, so such yeast experiments have provided valuable insight into meiosis in multicellular organisms as well.
In most multicellular organisms, meiosis is restricted to germ cells that are set aside in early development. The germ cells reside in specialized environments provided by the gonads, or sex organs. Within the gonads, the germ cells proliferate by mitosis until they receive the right signals to enter meiosis.
In mammals, the timing of meiosis differs greatly between males and females (Figure 2). Male germ cells, or spermatogonia, do not enter meiosis until after puberty. Even then, only limited numbers of spermatogonia enter meiosis at any one time, such that adult males retain a pool of actively dividing spermatogonia that acts as a stem cell population. On the other hand, meiosis occurs with quite different kinetics in mammalian females. Female germ cells, or oogonia, stop dividing and enter meiosis within the fetal ovary. Those germ cells that enter meiosis become oocytes, the source of future eggs. Consequently, females are born with a finite number of oocytes arrested in the first meiotic prophase. Within
Answer:
Organisms that reproduce sexually are thought to have an advantage over organisms that reproduce asexually, because novel combinations of genes are possible in each generation. Furthermore, with few exceptions, each individual in a population of sexually reproducing organisms has a distinct genetic composition. We have meiosis to thank for this variety.
Meiosis, from the Greek word meioun, meaning "to make small," refers to the specialized process by which germ cells divide to produce gametes. Because the chromosome number of a species remains the same from one generation to the next, the chromosome number of germ cells must be reduced by half during meiosis. To accomplish this feat, meiosis, unlike mitosis, involves a single round of DNA replication followed by two rounds of cell division (Figure 1). Meiosis also differs from mitosis in that it involves a process known as recombination, during which chromosomes exchange segments with one another. As a result, the gametes produced during meiosis are genetically unique.
Researchers' initial understanding of meiosis was based upon careful observations of chromosome behavior using light microscopes. Then, in the 1950s, electron microscopy provided scientists with a glimpse of the intricate structures formed when chromosomes recombine. More recently, researchers have been able to identify some of the molecular players in meiosis from biochemical analyses of meiotic chromosomes and from genetic studies of meiosis-specific mutants.
Meiosis Is a Highly Regulated Process
A schematic diagram shows key events in mitosis and meiosis during the development cycles of male and female sex cells in humans. During fetal development, cells undergo a period of mitotic proliferation. In females, the cells enter meiosis, followed by meiotic arrest. Cells exit meiotic arrest and are either lost before birth or undergo follicle formation after birth. After puberty, these cells are either ovulated each month, one at a time, or becomes atretic. During fetal development in males, proliferating cells enter mitotic arrest. After birth, they enter a second period of mitotic proliferation. After puberty, the cells undergo meiotic divisions to produce sperm cells.
View Full-Size ImageFigure 2
Figure Detail
Meiosis represents a survival mechanism for some simple eukaryotes such as yeast. When conditions are favorable, yeast reproduce asexually by mitosis. When nutrients become limited, however, yeast enter meiosis. The commitment to meiosis enhances the probability that the next generation will survive, because genetic recombination during meiosis generates four reproductive spores per cell, each of which has a novel genotype. The entry of yeast into meiosis is a highly regulated process that involves significant changes in gene transcription (Lopez-Maury et al., 2008). By analyzing yeast mutants that are unable to complete the various events of meiosis, investigators have been able to identify some of the molecules involved in this complex process. These controls have been strongly conserved during evolution, so such yeast experiments have provided valuable insight into meiosis in multicellular organisms as well.
In most multicellular organisms, meiosis is restricted to germ cells that are set aside in early development. The germ cells reside in specialized environments provided by the gonads, or sex organs. Within the gonads, the germ cells proliferate by mitosis until they receive the right signals to enter meiosis.
In mammals, the timing of meiosis differs greatly between males and females (Figure 2). Male germ cells, or spermatogonia, do not enter meiosis until after puberty. Even then, only limited numbers of spermatogonia enter meiosis at any one time, such that adult males retain a pool of actively dividing spermatogonia that acts as a stem cell population. On the other hand, meiosis occurs with quite different kinetics in mammalian females. Female germ cells, or oogonia, stop dividing and enter meiosis within the fetal ovary. Those germ cells that enter meiosis become oocytes, the source of future eggs. Consequently, females are born with a finite number of oocytes arrested in the first meiotic prophase. Within
Explanation: