All in the Family

The family members photo in figure (PageIndex1) illustrates critical point. Kids in a household resemble your parents and also each other, yet the kids are never specifically the very same unless they are similar twins. Each of the youngsters in the picture inherited a unique combination of traits native the parents. In this concept, you will learn just how this happens. The all starts with sex — sex-related reproduction, that is.

You are watching: If the sperm gamete that fertilizes an egg has a(n) _____ chromosome, it will form male offspring.



Figure (PageIndex3): summary of Meiosis. During meiosis, homologous chromosomes separate and go to different daughter cells. This diagram shows simply the nuclei the the cells. An alert the exchange of genetic material that occurs prior to the very first cell division.

The process that produces haploid gametes is referred to as meiosis. Meiosis is a type of cell department in which the number of chromosomes is diminished by half. It occurs just in specific special cell of one organism. In mammals, Meiosis occurs only in gamete creating cells within the gonads. Throughout meiosis, homologous (paired) chromosomes separate, and haploid cells type that have actually only one chromosome from each pair. Figure (PageIndex3) gives review of meiosis.

As you have the right to see native the meiosis diagram, two cell departments occur during the overall process, so a full of 4 haploid cells room produced. The two cell departments are referred to as meiosis I and also meiosis II. Meiosis I begins after DNA replicates during interphase. Meiosis II complies with meiosis ns without DNA replicating again. Both meiosis I and also meiosis II occur in four phases, called prophase, metaphase, anaphase, and also telophase. You may recognize these four phases from mitosis, the department of the nucleus that takes place throughout routine cell department of eukaryotic cells.

api/deki/files/18053/Sperm-egg.jpg?revision=1&size=bestfit&width=291&height=197" />Figure (PageIndex5): A human being sperm is a small cell through a tail. A human being egg is lot larger. Both cells space mature haploid gametes the are qualified of fertilization. What procedure is presented in this photograph?

At the finish of meiosis, 4 haploid cells have actually been produced, but the cells room not however gametes. The cells have to develop before they become mature gametes qualified of fertilization. The advancement of diploid cells into gametes is called gametogenesis. It differs in between males and females.

A gamete created by a masculine is dubbed a sperm, and the procedure that produces a tires sperm is referred to as spermatogenesis. During this process, a sperm cabinet grows a tail and also gains the ability to “swim,” prefer the human sperm cell shown in the number below. A gamete produced by a woman is dubbed an egg, and also the procedure that produce a mature egg is called oogenesis. Simply one egg is produced from the four haploid cell that result from meiosis. The single egg is a very big cell, together you can see from the person egg also shown in figure (PageIndex5).

Spermatogenesis occurs in the wall surface of the seminiferous tubules, with stem cells at the periphery of the tube and also the spermatozoa at the lumen of the tube. Instantly under the capsule of the tubule room diploid, regardless of cells. These stem cells, called spermatogonia (singular: spermatagonium), go with mitosis v one offspring walk on to distinguish into a sperm cell, if the other offers rise come the next generation of sperm.

api/deki/files/15863/Figure_43_03_06.jpg?revision=1" />Figure (PageIndex7): Oogenesis The procedure of oogenesis wake up in the ovary"s outermost layer. A major oocyte begins the first meiotic division but then arrests until later in life as soon as it will finish this division in a arising follicle. This outcomes in a second oocyte, i m sorry will complete meiosis if that is fertilized.

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The cell beginning meiosis is called a primary oocyte. This cell will start the first meiotic division, however be arrested in its progress in the very first prophase stage. At the moment of birth, all future eggs space in the prophase stage. In ~ adolescence, anterior pituitary hormones cause the advancement of a variety of follicles in one ovary. This results in the primary oocyte finishing the an initial meiotic division. The cell divides unequally, with many of the moving material and organelles going come one cell, called a an additional oocyte, and also only one set of chromosomes and a tiny amount that cytoplasm going come the other cell. This second cell is called a polar body and also usually dies. A an additional meiotic arrest occurs, this time in ~ the metaphase II stage. At ovulation, this second oocyte will be released and also travel toward the uterus with the oviduct. If the second oocyte is fertilized, the cell continues through the meiosis II, perfect meiosis, producing a 2nd polar body and a fertilized egg containing every 46 chromosomes the a person being, fifty percent of them comes from the sperm.