prophase

American  

[proh-feyz] / ˈproʊˌfeɪz /

noun

1. Cell Biology. the first stage of mitosis or meiosis in eukaryotic cell division, during which the nuclear envelope breaks down and strands of chromatin form into chromosomes.

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prophase British  

/ ˈprəʊˌfeɪz /

noun

1. the first stage of mitosis, during which the nuclear membrane disappears and the nuclear material resolves itself into chromosomes See also metaphase anaphase telophase

2. the first stage of meiosis, divided into leptotene, zygotene, pachytene, diplotene, and diakinesis phases

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prophase Scientific  

/ prō′fāz′ /

1. The first stage in the process of mitosis. Before prophase begins, the chromosomes duplicate to form two long, thin strands called chromatids. During prophase itself, the chromatids condense and thicken to form distinct bodies. Chromatids making up a single chromosome are joined at the middle in an area called the centromere. The membrane surrounding the nucleus disappears, and the spindle begins to form. In prophase and the later stages of mitosis until separation of the individual chromatids during anaphase, each chromosome consists of two chromatids, and each chromatid contains a complete copy of the genetic information belonging to the chromosome. For example, human beings have 23 pairs of chromosomes in all somatic cells, or 46 chromosomes in total. At the end of prophase, each of these 46 chromosomes contains two identical chromatids.

2. One of the two stages in meiosis that resemble prophase in mitosis. However, there are important distinctions between prophase of mitosis and prophase of meiosis. The prophase of meiosis occurring during the first meiotic division of the cell is usually called prophase I. In prophase I of meiosis, pairs of homologous chromosomes intertwine and the process called crossing over occurs as chromatids from homologous pairs of chromosomes swap genetic information. This process creates genetic diversity among the gametes formed through meiosis. In mitosis, by contrast, pairs of homologous chromosomes remain separate and there is no crossing over, since the purpose of mitosis is to produce cells with identical genetic material rather than gametes. At the beginning of prophase II of meiosis, which occurs after telophase during the first meiotic division, the chromosomes of each daughter cell are grouped together in a mass. During prophase II, the individual chromosomes of the daughter cells become distinct again and begin to prepare for the second meiotic division. If a membrane has formed around the chromosomes at the end of the first division, it disappears during prophase II.

3. See more at meiosis mitosis

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Etymology

Origin of prophase

First recorded in 1880–85; pro- ¹ + phase

Explanation

In biology, the very first stage of cell division is known as prophase. During prophase, the cell prepares itself in various ways for the division that occurs in later stages. If you take a biology class, you'll learn all about mitosis, when cells divide and duplicate their DNA. This process takes place over five phases (sometimes grouped into four), the first of which is prophase. During prophase, the nucleolus and nuclear membrane break down, and chromosomes coil more tightly. This is all in preparation for when the cell splits into two daughter cells. The word prophase comes from Greek roots meaning "before stage."

Example Sentences

JQ1 works by disrupting meiosis during prophase 1, causing developing cells to die at that stage.

From Science Daily • Apr. 7, 2026

Surprisingly, different from other HSFs responding to stress, the study showed that HSF5 plays an essential role in the meiotic prophase progression in male germ cells under non-stress conditions.

From Science Daily • May 1, 2024

All these findings underscore HSF5's atypical role in gene expression during meiotic prophase in males.

From Science Daily • May 1, 2024

At the time of birth, all future eggs are in prophase I. This situation is in contrast with the male reproductive system in which sperm are produced continuously throughout the life of the individual.

From Textbooks • Apr. 25, 2013

Figure 208 a and b shows two sections of an oögonium in the prophase of mitosis.

From Studies in Spermatogenesis Part I by Stevens, Nettie Maria