Unit 6 Target 1: Meiosis

A trisomy of chromosome 21 causes Down syndrome. Down syndrome is a genetic disorder that occurs when there is an extra copy of chromosome 21. This additional genetic material leads to developmental delays, intellectual disabilities, and characteristic physical features such as a flat facial profile, upward slanting eyes, and a single deep crease across the palm. Albinism, dwarfism, and color blindness are caused by different genetic abnormalities and are not related to trisomy of chromosome 21.

The diagram is showing crossing-over. Crossing-over is a process that occurs during meiosis where genetic material is exchanged between homologous chromosomes. This process leads to genetic variation and the production of gametes with unique combinations of alleles.

The process shown in the illustration is meiosis. Meiosis is a type of cell division that occurs in sexually reproducing organisms to produce gametes (sperm and eggs). It involves two rounds of division, resulting in the formation of four haploid cells with half the number of chromosomes as the parent cell. This process is crucial for maintaining the correct number of chromosomes in the offspring and for genetic diversity.

Meiosis is the correct answer because it is the cell process specifically designed for sexual reproduction, allowing parents to contribute their genes to their offspring. During meiosis, the DNA in the parent cells is divided into half, resulting in the formation of gametes (sperm and eggs) with a unique combination of genes. This process ensures genetic diversity in offspring and is essential for evolution and adaptation. Mitosis is a cell process involved in growth and repair, while protein synthesis and diffusion are not directly related to the transfer of genes from parents to offspring.

Meiosis is a type of cell division that occurs in sexually reproducing organisms. It involves two rounds of division, resulting in the formation of four daughter cells. These daughter cells are genetically different from the parent cell and are haploid, meaning they contain half the number of chromosomes as the parent cell. These haploid cells are known as sex cells or gametes, such as sperm and eggs, which are involved in sexual reproduction. Therefore, the correct answer is haploid sex cells.

The diploid number of an organism represents the total number of chromosomes in its cells, which is typically double the haploid number. Since the diploid number is given as 12, the haploid number can be calculated by dividing the diploid number by 2, resulting in 6. Therefore, the correct answer is 6.

Meiosis is a type of cell division that occurs in sexually reproducing organisms. It involves two rounds of division, resulting in the formation of four haploid cells. These cells are genetically different from each other and from the parent cell. This genetic diversity is achieved through processes like crossing over and independent assortment, which shuffle and recombine genetic material. Therefore, the correct answer is four genetically different cells.

Gametes are the specialized reproductive cells that are involved in sexual reproduction. The process responsible for producing gametes is meiosis. Meiosis is a type of cell division that reduces the chromosome number by half, resulting in the formation of haploid cells. This is important for sexual reproduction because when two gametes fuse during fertilization, the resulting zygote will have the correct number of chromosomes. Mitosis, on the other hand, is the process of cell division that produces identical copies of cells for growth and repair. Replication refers to the process of DNA duplication. Crossing-over is a genetic phenomenon that occurs during meiosis, leading to the exchange of genetic material between homologous chromosomes.

Nondisjunction is the failure of chromosomes to separate properly during cell division. It can lead to abnormal chromosome numbers in the resulting cells. Anaphase I and II are the phases of meiosis where chromosome separation occurs. In Anaphase I, homologous chromosomes fail to separate, while in Anaphase II, sister chromatids fail to separate. Therefore, nondisjunction can occur in both Anaphase I and II, leading to the formation of cells with abnormal chromosome numbers.

Gametes have half the number of chromosomes compared to the parent cell. This is because during the process of meiosis, the parent cell undergoes two rounds of cell division, resulting in the formation of four gametes, each with half the number of chromosomes. This reduction in chromosome number is important for sexual reproduction as it ensures that when gametes combine during fertilization, the resulting zygote will have the correct number of chromosomes for the species.

During metaphase I of meiosis, paired homologous chromosomes line up along the cell's equator. This is known as the metaphase plate. This alignment is crucial for the proper separation of homologous chromosomes during anaphase I. Each pair of homologous chromosomes consists of one chromosome from the mother and one from the father, and they align in a random orientation, contributing to genetic diversity in the resulting gametes. The centromeres of replicated chromosomes do not line up along the equator until metaphase II, and sister chromatids do not separate until anaphase II.

Human gametes, which are sperm and egg cells, contain half the number of chromosomes compared to other cells in the body. This is because during the process of meiosis, the chromosomes in the gametes undergo a reduction division, resulting in the formation of cells with only one set of chromosomes. In humans, the diploid number of chromosomes is 46, so the correct answer is 23 chromosomes in human gametes.

During meiosis, there are indeed 2 divisions, and homologous chromosomes do pair up during Prophase I. Additionally, Anaphase I separates homologous chromosomes, while Anaphase II separates sister chromatids. However, interphase (DNA replication) only occurs once before the start of meiosis, not twice. This is because DNA replication occurs during the S phase of interphase in the cell cycle, and meiosis involves two rounds of division without an additional round of DNA replication.

Spermatogenesis is the process of producing sperm cells in males, and it results in the production of four viable sperm cells. On the other hand, oogenesis is the process of producing egg cells in females, and it results in the production of one viable egg cell and three polar bodies. Therefore, the statement "Oogenesis results in 1 viable egg cell and 3 polar bodies" is true, while the other statements are not.

During meiosis, the process of cell division that produces gametes, a female gamete is called an ovum. The term "ovum" refers to the mature egg cell that is released from the ovary during ovulation. This female gamete carries half of the genetic material required for reproduction and is capable of being fertilized by a male gamete, such as a sperm, to form a zygote. The other options listed, such as sperm, spermatogonium, and oogonium, are not correct as they refer to male gametes or precursor cells involved in the production of gametes.

Prophase I is the stage in meiosis where chromosomes condense and pair up, forming structures called tetrads. This process occurs during the first meiotic division and is essential for genetic recombination. During prophase I, crossing over between homologous chromosomes can also occur, further increasing genetic diversity. Therefore, the process depicted in the diagram is most likely happening during Prophase I.

Crossing over occurs during meiosis but not during mitosis because homologous chromosomes do not pair up during mitosis. In meiosis, homologous chromosomes pair up during prophase I and undergo crossing over, which is the exchange of genetic material between non-sister chromatids. This results in genetic recombination and increased genetic diversity. However, in mitosis, homologous chromosomes do not pair up. Instead, the sister chromatids separate and are distributed equally to the daughter cells. Therefore, crossing over does not occur during mitosis.

During cytokinesis in the female, the cytoplasm divides unequally. Cytokinesis is the final stage of cell division, where the cytoplasm is divided into two separate daughter cells. In the female, this process occurs during the formation of the egg or ovum. The unequal division of cytoplasm ensures that one daughter cell receives most of the cytoplasmic components necessary for the development of the egg, while the other daughter cell, called the polar body, receives a minimal amount of cytoplasm and eventually disintegrates. This mechanism ensures that the majority of resources are allocated to the developing egg for successful fertilization and embryonic development.

Gametes are reproductive cells that contain half the number of chromosomes as compared to other cells in the body. Each gene in the gametes has only one allele, which is a variant form of a gene. This is because during the formation of gametes through a process called meiosis, the homologous chromosomes separate and only one of each pair is passed on to the gamete. Therefore, gametes have one allele for each gene, ensuring genetic diversity when they combine during fertilization.