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Which is the correct term haploid daughter cells or haploid parent cells?

Which is the correct term haploid daughter cells or haploid parent cells?


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Meiosis 2 begins with 2 haploid parent cells and ends with 4 haploid daughter cells (gametes). Gametes from the opposite sex can now merge together and fertilize.

If I were to refer to a specific haploid daughter cell merging with another to produce a zygote; are these daughter cells from Meiosis 2 still called 'daughter' cells or are they now called parent cells?


"Parent" and "daughter" terminology is indeed relative. Any parent cell has been a daughter at some point. However, in the case of the zygote there is no "parent" strictly speaking since it is the result of a fusion between two cells, that you may call "daughter cells" only if you are referring to the previous meiosis event.

In this particular case, there is no cell division, so no "daughter" is formed, so no point in calling the haploid cells from M2 "parents" either.


All About Haploid Cells in Microbiology

In microbiology, a haploid cell is the result of a diploid cell replicating and dividing twice through meiosis. Haploid means "half." Each daughter cell produced from this division is haploid, meaning that it contains half the number of chromosomes as its parent cell.


Contents

Chromosomes are linear arrangements of condensed deoxyribonucleic acid (DNA) and histone proteins, which form a complex called chromatin. [2] Homologous chromosomes are made up of chromosome pairs of approximately the same length, centromere position, and staining pattern, for genes with the same corresponding loci. One homologous chromosome is inherited from the organism's mother the other is inherited from the organism's father. After mitosis occurs within the daughter cells, they have the correct number of genes which are a mix of the two parents' genes. In diploid (2n) organisms, the genome is composed of one set of each homologous chromosome pair, as compared to tetraploid organisms which may have two sets of each homologous chromosome pair. The alleles on the homologous chromosomes may be different, resulting in different phenotypes of the same genes. This mixing of maternal and paternal traits is enhanced by crossing over during meiosis, wherein lengths of chromosomal arms and the DNA they contain within a homologous chromosome pair are exchanged with one another. [3]

Early in the 1900s William Bateson and Reginald Punnett were studying genetic inheritance and they noted that some combinations of alleles appeared more frequently than others. That data and information was further explored by Thomas Morgan. Using test cross experiments, he revealed that, for a single parent, the alleles of genes near to one another along the length of the chromosome move together. Using this logic he concluded that the two genes he was studying were located on homologous chromosomes. Later on during the 1930s Harriet Creighton and Barbara McClintock were studying meiosis in corn cells and examining gene loci on corn chromosomes. [2] Creighton and McClintock discovered that the new allele combinations present in the offspring and the event of crossing over were directly related. [2] This proved interchromosomal genetic recombination. [2]

Homologous chromosomes are chromosomes which contain the same genes in the same order along their chromosomal arms. There are two main properties of homologous chromosomes: the length of chromosomal arms and the placement of the centromere. [4]

The actual length of the arm, in accordance with the gene locations, is critically important for proper alignment. Centromere placement can be characterized by four main arrangements, consisting of being either metacentric, submetacentric, acrocentric, or telocentric. Both <of these properties are the main factors for creating structural homology between chromosomes. Therefore, when two chromosomes of the exact structure [ clarification needed ] exist, they are able to pair together to form homologous chromosomes. [5]

Since homologous chromosomes are not identical and do not originate from the same organism, they are different from sister chromatids. Sister chromatids result after DNA replication has occurred, and thus are identical, side-by-side duplicates of each other. [6]

In humans Edit

Humans have a total of 46 chromosomes, but there are only 22 pairs of homologous autosomal chromosomes. The additional 23rd pair is the sex chromosomes, X and Y.The 22 pairs of homologous chromosomes contain the same genes but code for different traits in their allelic forms since one was inherited from the mother and one from the father. [7] So humans have two homologous chromosome sets in each cell, meaning humans are diploid organisms. [2]

Homologous chromosomes are important in the processes of meiosis and mitosis. They allow for the recombination and random segregation of genetic material from the mother and father into new cells. [8]

In meiosis Edit

Meiosis is a round of two cell divisions that results in four haploid daughter cells that each contain half the number of chromosomes as the parent cell. [9] It reduces the chromosome number in a germ cell by half by first separating the homologous chromosomes in meiosis I and then the sister chromatids in meiosis II. The process of meiosis I is generally longer than meiosis II because it takes more time for the chromatin to replicate and for the homologous chromosomes to be properly oriented and segregated by the processes of pairing and synapsis in meiosis I. [6] During meiosis, genetic recombination (by random segregation) and crossing over produces daughter cells that each contain different combinations of maternally and paternally coded genes. [9] This recombination of genes allows for the introduction of new allele pairings and genetic variation. [2] Genetic variation among organisms helps make a population more stable by providing a wider range of genetic traits for natural selection to act on. [2]

Prophase I Edit

In prophase I of meiosis I, each chromosome is aligned with its homologous partner and pairs completely. In prophase I, the DNA has already undergone replication so each chromosome consists of two identical chromatids connected by a common centromere. [9] During the zygotene stage of prophase I, the homologous chromosomes pair up with each other. [9] This pairing occurs by a synapsis process where the synaptonemal complex - a protein scaffold - is assembled and joins the homologous chromosomes along their lengths. [6] Cohesin crosslinking occurs between the homologous chromosomes and helps them resist being pulled apart until anaphase. [7] Genetic crossing-over, a type of recombination, occurs during the pachytene stage of prophase I. [9] In addition, another type of recombination referred to as synthesis-dependent strand annealing (SDSA) frequently occurs. SDSA recombination involves information exchange between paired homologous chromatids, but not physical exchange. SDSA recombination does not cause crossing-over.

In the process of crossing-over, genes are exchanged by the breaking and union of homologous portions of the chromosomes’ lengths. [6] Structures called chiasmata are the site of the exchange. Chiasmata physically link the homologous chromosomes once crossing over occurs and throughout the process of chromosomal segregation during meiosis. [6] Both the non-crossover and crossover types of recombination function as processes for repairing DNA damage, particularly double-strand breaks. At the diplotene stage of prophase I the synaptonemal complex disassembles before which will allow the homologous chromosomes to separate, while the sister chromatids stay associated by their centromeres. [6]

Metaphase I Edit

In metaphase I of meiosis I, the pairs of homologous chromosomes, also known as bivalents or tetrads, line up in a random order along the metaphase plate. [9] The random orientation is another way for cells to introduce genetic variation. Meiotic spindles emanating from opposite spindle poles attach to each of the homologs (each pair of sister chromatids) at the kinetochore. [7]

Anaphase I Edit

In anaphase I of meiosis I the homologous chromosomes are pulled apart from each other. The homologs are cleaved by the enzyme separase to release the cohesin that held the homologous chromosome arms together. [7] This allows the chiasmata to release and the homologs to move to opposite poles of the cell. [7] The homologous chromosomes are now randomly segregated into two daughter cells that will undergo meiosis II to produce four haploid daughter germ cells. [2]

Meiosis II Edit

After the tetrads of homologous chromosomes are separated in meiosis I, the sister chromatids from each pair are separated. The two haploid(because the chromosome no. has reduced to half. Earlier two sets of chromosomes were present, but now each set exists in two different daughter cells that have arisen from the single diploid parent cell by meiosis I) daughter cells resulting from meiosis I undergo another cell division in meiosis II but without another round of chromosomal replication. The sister chromatids in the two daughter cells are pulled apart during anaphase II by nuclear spindle fibers, resulting in four haploid daughter cells. [2]

In mitosis Edit

Homologous chromosomes do not function the same in mitosis as they do in meiosis. Prior to every single mitotic division a cell undergoes, the chromosomes in the parent cell replicate themselves. The homologous chromosomes within the cell will ordinarily not pair up and undergo genetic recombination with each other. [9] Instead, the replicants, or sister chromatids, will line up along the metaphase plate and then separate in the same way as meiosis II - by being pulled apart at their centromeres by nuclear mitotic spindles. [10] If any crossing over does occur between sister chromatids during mitosis, it does not produce any new recombinant genotypes. [2]

In somatic cells Edit

Homologous pairing in most contexts will refer to germline cells, however also takes place in somatic cells. For example, in humans, somatic cells have very tightly regulated homologous pairing (separated into chromosomal territories, and pairing at specific loci under control of developmental signalling). Other species however (notably Drosophila) exhibit homologous pairing much more frequently. In Drosophila the homologous pairing supports a gene regulatory phenomenon called transvection in which an allele on one chromosome affects the expression of the homologous allele on the homologous chromosome. [11] One notable function of this is the sexually dimorphic regulation of X-linked genes. [12]

There are severe repercussions when chromosomes do not segregate properly. Faulty segregation can lead to fertility problems, embryo death, birth defects, and cancer. [13] Though the mechanisms for pairing and adhering homologous chromosomes vary among organisms, proper functioning of those mechanisms is imperative in order for the final genetic material to be sorted correctly. [13]

Nondisjunction Edit

Proper homologous chromosome separation in meiosis I is crucial for sister chromatid separation in meiosis II. [13] A failure to separate properly is known as nondisjunction. There are two main types of nondisjunction that occur: trisomy and monosomy. Trisomy is caused by the presence of one additional chromosome in the zygote as compared to the normal number, and monosomy is characterized by the presence of one fewer chromosome in the zygote as compared to the normal number. If this uneven division occurs in meiosis I, then none of the daughter cells will have proper chromosomal distribution and non-typical effects can ensue, including Down’s syndrome. [14] Unequal division can also occur during the second meiotic division. Nondisjunction which occurs at this stage can result in normal daughter cells and deformed cells. [4]

While the main function of homologous chromosomes is their use in nuclear division, they are also used in repairing double-strand breaks of DNA. [15] These double-stranded breaks may occur in replicating DNA and are most often the result of interaction of DNA with naturally occurring damaging molecules such as reactive oxygen species. Homologous chromosomes can repair this damage by aligning themselves with chromosomes of the same genetic sequence. [15] Once the base pairs have been matched and oriented correctly between the two strands, the homologous chromosomes perform a process that is very similar to recombination, or crossing over as seen in meiosis. Part of the intact DNA sequence overlaps with that of the damaged chromosome's sequence. Replication proteins and complexes are then recruited to the site of damage, allowing for repair and proper replication to occur. Through this functioning, double-strand breaks can be repaired and DNA can function normally. [15]

Current and future research on the subject of homologous chromosome is heavily focused on the roles of various proteins during recombination or during DNA repair. In a recently published article by Pezza et al. [ which? ] the protein known as HOP2 is responsible for both homologous chromosome synapsis as well as double-strand break repair via homologous recombination. The deletion of HOP2 in mice has large repercussions in meiosis. [16] Other current studies focus on specific proteins involved in homologous recombination as well.

There is ongoing research concerning the ability of homologous chromosomes to repair double-strand DNA breaks. Researchers are investigating the possibility of exploiting this capability for regenerative medicine. [17] This medicine could be very prevalent in relation to cancer, as DNA damage is thought to be contributor to carcinogenesis. Manipulating the repair function of homologous chromosomes might allow for bettering a cell’s damage response system. While research has not yet confirmed the effectiveness of such treatment, it may become a useful therapy for cancer. [18]


How Daughter Cells Are Created

In the broadest overview of cell division, the process is simple. Every substance, structure, and particle in the cell must be accumulated, copied, and divided. This means that before any cell division or daughter cells, the original parent cell must grow. The cell’s machinery have evolved to take nutrients and atoms from the environment, and incorporate them into the cell. When the cell reaches a certain size, a genetic switch gets thrown, and kicks the cell into division mode.

The cell first goes through the process of DNA replication. The DNA is “unzipped” by special proteins, which break the hydrogen bonds between nucleotides. When each single strand is exposed, an opposing strand is created. When this process is complete, the cell contains 2 copies of the DNA. Now, it can start to create daughter cells.

The end of cell division, telophase and cytokinesis, includes the actual separation of the cellular membrane, marking the creation of the new daughter cells. Thus, unlike during the creation of offspring, in the creation of cells the “parent” cell is directly divided into the new cells. This is in contrast to a parent producing an offspring and staying intact. While the term is a little confusing, it is simply a way to track which cells were derived from which cellular lines.


Ploidy

Ploidy is the complete set of chromosomes in a cell. In humans most somatic cells are in a diploid state and only switch to a haploid state in gametes or sex cells. In algae and fungi cells switch between a haploid and diploid state over the length of their life cycle (known as alternation of generation), and are in a haploid state during the principle stage of their life cycle.

Polyploidy refers to a state where multiple sets of chromosomes are present. This is commonly seen in plant cells but not in animal cells.


13.1. Asexual Reproduction

Asexual Reproduction

Although nearly all multicellular organsims have sexual reproduction, some plants and animals will also engage in asexual reproduction, producing identical copies of the parent, usually the mother. There are several types of asexual reproduction, we will consider two of these, vegetative propagation and parthenogenesis.

Figure 13.2. The Kalanchoe plant, sometimes called mother-of-thousands, with plantlets that will eventually drop off and grow independantly.

During vegetative propagation, plants develop miniature versions of themselves, usually on specialized leaves. The Kalanchoe leaf above has several plantlets that are developing asexually. Note that only one leaf of the plant has plantlets. When large enough, these plantlets will drop of and continue growing independently of the parent plant.

Other plants such as the tulip, will develop bulbs asexually by vegetative propagation. Many grasses and several species of trees also propagate asexually, often through the roots. The famous Pando, a clonal colony of quaking aspen trees in Utah, has grown from 1 male tree to 47,000 through asexual reproduction through the roots. This tree system is estimated to be 80,000 years old and is among the oldest known living organisms.

Parthenogenesis is another way in which organisms can reproduce asexually, usually through an unfertilized egg, so only females can asexually reproduce this way. Plants, invertebrates including insects often undergo parthenogenesis, along with a few species of lizards will reproduce parthenogenically. There are a number of different methods by which the egg is diploid and is stimulated to develop, depending on the species. In some organisms haploid eggs fuse to become diploid in others there is doubling of the chromosomes without cytoplasmic division either before or after meiosis. Regardless of the method, all organisms which are produced by parthenogenesis are identical clones of their mother, as is the aphid being born from an unfertilized egg in Figure 13.3.

Figure 13.3. Female aphid giving birth to a clone derived from an unfertilized egg by parthenogenesis.

Asexual reproduction is less common than sexual reproduction in flowering plants and rare in vertebrates, making sexual reproduction much more common among these organisms. Yet sexual reproduction is often very risky business for the individuals involved by involving large outlays of energy. Take the peacock for example (Figure 13.4) This impressive display of tail feathers with their distinctive eyes, require a lot of energy to produce each spring. In addition, having such a large and cumbersome tail makes it difficult for the peacock to fly away from predators and even to capture food. Yet the peacock flaunts its feathers with great pride, shaking them at nearby pea hens to get the female’s attention.

Why would the peacock invest so much energy at so much risk of injury or even death to attract a female? The answer, of course, is sexual reproduction. There is among nearly all sexually reproductive organisms a competition for reproductive success. In many species, males are driven to want to produce as many offspring as he can from as many females as possible, hence the annual fights for females among such diverse species as deer, frogs, and even round worms. The better the peacock is at acquiring food the more extensive his display and the more likely he will be to fertilize her eggs.

The female, however, is looking for the fittest male to fertilize her eggs, thereby helping to ensure their survival. Studies have shown that the peahen, for example, counts the number of eyes on the feathers of the peacock’s tail. The male with the most eyes, and therefore the most healthy, will usually win the female.

Figure 13.4. The peacock in full springtime display

Populations that reproduce asexually are at the whim of a variable environment. Since they are clones of each other, they are equally suseptable to environment factors such as disease or changing climate conditions, and could easily become extinct. Populations that reproduce sexually are much more diverse and so are more likely to have at least some in the population who will survive environmental changes. This “drive to survive” is at the heart of why the large investment of energy in sexual reproduction is worth the effort.

Exercises

  1. The female tiger shark has occasionally produced offspring from unfertilized eggs. What type of asexual reproduction is this?
  1. Sexual reproduction involves fewer steps.
  2. There is a lower chance of using up the resources in a given environment.
  3. Sexual reproduction is more cost-effective in terms of energy utilization.
  4. Sexual reproduction results in variation in the offspring.

Difference Between Meiosis I and Meiosis II

Meiosis is the type of cell division, which happens only once in the lifetime of a eukaryote. This process is essential for the eukaryotic organisms as in this gametes, or sex cells are formed after the genetic material is mixed or rearranged. In the process of meiosis, the number of chromosomes in the parent cell are reduced to half, and four gamete cells are produced. Meiosis produces the eggs and sperm cells, which are used by the organism for sexual reproduction. The whole process of meiosis can be mainly divided into two smaller processes, Meiosis I and Meiosis II. In Meiosis I, the diploid parent cell forms haploid daughter cells, and the number of chromosomes in this process are reduced to half, whereas in Meiosis II the two haploid parent cells produce four haploid daughter cells, and the number of chromosomes remains the same.

Comparison Chart

BasisMeiosis IMeiosis II
Number of chromosomesIn meiosis I, the number of chromosomes are reduced to half.In meiosis II, the number of chromosomes remains the same
ProductionHaploid daughter cells are formed from the diploid parent cellHaploid daughter cells are formed from the haploid parent cell.
Complicated and Longer processYesNo
Crossing over of chromosomesYesNo

What is Meiosis I?

It is the process of cell division in which the number of chromosomes is reduced to half, and the haploid daughter cells are formed from the diploid parent cell. This cell division process commences with one cell and ends with two cell where the number of chromosomes also reduced to the half. As compare to the meiosis II, it is a more complicated and longer type of cell division. In this process of cell division, the homologous chromosomes underwent the separation, resulting in the formation of two gametes. Meiosis I starts with the shrinkage of the chromosome in the nucleus of the only diploid cell. In meiosis I, recombination or mixing of chromosome pairs happens which end as reducing the number of chromosomes, whereas such kind of process is absent in the meiosis II. Meiosis I and Meiosis II undergo the same five stages prophase, prometaphase, metaphase, anaphase, and telophase. The main difference comes in the prophase of meiosis I, which is longer and more complicated than it is in the process of meiosis II.

What is Meiosis II?

It is the process of cell division in which the number of chromosomes remains the same, and four haploid daughter cells are formed from the haploid parent cell. It is simpler, and a shorter process as compared to the meiosis I and in this the two chromatids of replicated chromosome are separated. Meiosis II resembles the process of mitosis, which is an asexual process of cell division that happens in every of the organism. Apart from the close resemblance with the process of mitosis, the difference it possesses is the presence of two parent cells instead of the only one parent cell. The process of meiosis II, which ends up with four daughter cells is the short duration process in which the crossing over of chromosomes doesn’t happen and furthermore, the sister chromatids are separated in this process.


Meiosis vs Mitosis [ edit | edit source ]

The main differences is in the metaphase and the anaphase. During mitosis the chromosomes line up at the equatorial line. All of them lie just in one line. Then in the anaphase they are separate into the individual sister chromatids. The parent cell has 4N (92 chromosomes) and two daughter cells have 2n (46 chromosomes).

Meiosis differs in that during metaphase the chromosomes lie side by side. Then in the anaphase there is no division of the chromatid. The whole chromosome is pulled to the one pole of the cell. The parent cells have 4N (92 chromosomes) and the daughter cells have 2N (46 chromosomes). But that is just the first meiotic division. The second one takes place directly after - without replication of the DNA. It means that the daughter cell becomes "parent" and divides again. The result is a pair of the sex cell with 1N (23 chromosome). This we call the second meiotic division.


Meiosis Is The Process By Which_______ (Sex cells) are produced that contain half the number of chromosomes as the parent body cell(haploid) ?

Meiosis is he process by which gametes (Sex cells) are produced, that contain half the number of gametes.

Explanation:

The question is not very clear what one wants to ask.

Meiosis is reduction division in which the daughter cells produced contain half the number of chromosomes of parental cell.

The daughter cells (haploid) produced as a consequence of meiosis are not always sex cells or gametes. In flowering plants, haploid cells produced by meiosis develop into meiospores , which are of two types, i.e. microspores and megspores.

Microspore and megaspore develop into male and female gametophyte, respectively , which are haploid.

The male and female gametophytes produce male and female gametes (sex cells) by mitosis.


Watch the video: Fertilization terminology: gametes, zygotes, haploid, diploid. MCAT. Khan Academy (November 2022).