During Which Phase Of The Cell Cycle Does The Law Of Independent Assortment Occur?

During Which Phase Of The Cell Cycle Does The Law Of Independent Assortment Occur
The reason for independent assortment – To see why independent assortment happens, we need to fast-forward half a century and discover that genes are physically located on chromosomes. To be exact, the two copies of a gene carried by an organism (such as a Y and a y allele) are located at the same spot on the two chromosomes of a homologous pair,

Homologous chromosomes are similar but non-identical, and an organism gets one member of the pair from each of its two parents. The physical basis for the law of independent assortment lies in meiosis I of gamete formation, when homologous pairs line up in random orientations at the middle of the cell as they prepare to separate.

We can get gametes with different combos of “mom” and “dad” homologues (and thus, the alleles on those homologues) because the orientation of each pair is random. To see what this means, compare chromosome arrangement 1 (top) and chromosome arrangement 2 (bottom) at the stage of metaphase I in the diagram below.

In one case, the red “mom” chromosomes go together, while in the other, they split up and mix with the blue “dad” chromosomes. If meiosis happens many times, as it does in a pea plant, we will get both arrangements—and thus RY, Ry, rY, and ry classes of gametes—with equal frequency. Genes that are on different chromosomes (like the Y and R genes) assort independently.

The seed color and seed shape genes are on chromosomes 1 and 7 of the pea genome, respectively, in real life, Genes that are far apart on the same chromosome also assort independently thanks to the crossing over, or exchange of homologous chromosome bits, that occurs early in meiosis I.

In which phase is the law of Independent Assortment occurring?

Independent Assortment Examples – Gregor Mandel carried out several experiments on pea plants. as a result, he was able to identify the way by which the units of heredity work, which are now known as genes after the discovery of DNA and genetic information.

How does independent assortment occur? Independent assortment occurs spontaneously when alleles of at least two genes are assorted independently into gametes. Consequently, the allele inherited by one gamete does not affect the allele inherited by other gametes. Mendel noted that the transmission of different genes appeared to be independent events.

In independent events, the probability of a particular combination of traits can be predicted by multiplying the individual probabilities of each trait. In independent events, the inheritance pattern of one trait will not affect the inheritance pattern of another.

  1. For example, when Mendel crossed plants with round yellow peas to plants with wrinkled green peas, all of the F1 peas expressed the dominant traits round and yellow.
  2. In the F2, along with round yellow and wrinkled green peas, he observed round green and wrinkled yellow peas.
  3. Each of the dominant traits was present in ¾ of the progeny and each of the recessive traits was present in ¼ of the progeny.

The four possible combinations of color and shape appeared in the ratio of 9:3:3:1, which represents the independent assortment of the genes for the two pairs of traits into the gametes. If you have ¾ yellow and ¾ round then independent events predict that ¾ x ¾ = 9/16 will be both yellow and round. During Which Phase Of The Cell Cycle Does The Law Of Independent Assortment Occur Figure 2: Using Punnett square for calculating the genetic ratios in a dihybrid cross. The filled-in squares of a Punnett square represent a specific allele combination that is used for calculating genotypic ratio. Image Credit: OpenStax Biology Later, after the discovery of chromosomes, and of their behavior in meiosis, it was possible to explain independent assortment as a consequence of the independent movement of each pair of homologous chromosomes during meiosis. During Which Phase Of The Cell Cycle Does The Law Of Independent Assortment Occur Figure 3: Independent assortment of different alleles in pea plant according to shape and color. Credit: LadyofHats, public domain. The development of the law of independent assortment was based on Mendel’s breeding of pea plants having different characteristics: garden pea plants that produced wrinkled green peas and another garden pea plant that produced rounded yellow peas.

  1. Yellow and round characters were more dominant; therefore, all offspring of the first generation were yellow and rounded peas.
  2. However, the second generation showed marked variation after breeding the first generation with each other.
  3. The experiment proved the independent inheritance of homologous traits on different alleles in yellow and green peas as the produced offspring were not only yellow and round or green and wrinkled as their parents.

What is independent assortment as explained with a suitable example? Let’s take for example a random population of cats and track two traits: eye color (brown or green) and fur color (white or grey). The dominant allele for the eye color, for example, is brown eyes ( B ), and the recessive allele, green eye color ( b ).

As for the color of the fur, let’s say that the white fur ( W ) allele is dominant over the gray fur allele ( w ). Heterozygous cats with dominant traits, brown eyes and white fur, will produce gametes at sexual maturity. During gamete production, the alleles for eye color will be sorted independent of the alleles for the fur color, if we are to base it on the law of segregation.

The resulting gamete after meiosis will contain random alleles such that when two heterozygous cats are crossed, their offspring will likely have mixed traits. One of the kitten, for example, could have brown eye color ( BB or Bb ) and grey fur color ( ww ).

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Another kitten might have green eyes ( bb ) and grey fur ( ww ). Others still could have brown eyes and white fur (thus, possible genotypes could be BBWW, BBWw, BbWW, BbWw). Now, this is just an illustrative example. In nature, the eye and fur color traits are polygenic, meaning several alleles are involved in determining the phenotype of the offspring.

The independent assortment is now explained according to the behavior of chromosomes during meiosis and the random movement of each homologous pair of chromosomes during meiosis. Independent assortment is an important process for the production of new genetic combinations that contribute to the genetic diversity among individuals that reproduce sexually. How do you know if a chromosome is homologous? Get insights here: Difference Between Homologous Chromosomes and Sister Chromatids, Join our Forum now! Try to answer the quiz below to check what you have learned so far about Independent assortment.

When during the cell cycle does independent assortment of chromosomes occur?

Answer and Explanation: The independent assortment of chromosomes occurs during meiosis I. First, during prophase I, the homologous chromosomes exchange genes during a process called ‘crossing over’. Then, during metaphase I the homologous pairs are lined up along the midline of the cell.

Is independent assortment during metaphase?

Answer and Explanation: The stage of meiosis where independent assortment occurs is metaphase I. Metaphase I is the first metaphase that occurs in meiosis where the tetrads of homologous chromosomes align at the middle of the cell.

Is independent assortment in prophase?

Law of Independent Assortment – This law says inheriting an allele has nothing to do with inheriting an allele for any other trait. The alleles from parents are passed on independently to the offspring. After fertilization, the resulting zygote(s) can end up with any combination of chromosomes from the parents and all the possible combinations occur with equal frequency.

Like segregation, independent assortment occurs during meiosis, specifically in prophase I when the chromosomes line up in random orientation along the metaphase plate. Crossing over, the exchange and recombination of genetic information between chromosomes also occurs in prophase I and adds to the genetic diversity of the offspring.

The image above illustrates the laws of Mendelian inheritance. The segregation of gametes and the independent assortment of traits occurs in meiosis. As a result, each offspring ends up with the full number of chromosomes containing randomly assorted alleles from each parent.

Does independent assortment occur in metaphase 1 or 2?

Metaphase I – During metaphase I, the homologous chromosomes are arranged in the center of the cell with the kinetochores facing opposite poles. The homologous pairs orient themselves randomly at the equator. For example, if the two homologous members of chromosome 1 are labeled a and b, then the chromosomes could line up a-b, or b-a.

This is important in determining the genes carried by a gamete, as each will only receive one of the two homologous chromosomes. This is called Independent Assortment, Recall that homologous chromosomes are not identical, they contain slight differences in their genetic information, causing each gamete to have a unique genetic makeup.

This randomness is the physical basis for the creation of the second form of genetic variation in offspring. Consider that the homologous chromosomes of a sexually reproducing organism are originally inherited as two separate sets, one from each parent.

Using humans as an example, one set of 23 chromosomes is present in the egg donated by the mother. The father provides the other set of 23 chromosomes in the sperm that fertilizes the egg. Every cell of the multicellular offspring has copies of the original two sets of homologous chromosomes. In prophase I of meiosis, the homologous chromosomes form the tetrads.

In metaphase I, these pairs line up at the midway point between the two poles of the cell to form the metaphase plate. Because there is an equal chance that a microtubule fiber will encounter a maternally or paternally inherited chromosome, the arrangement of the tetrads at the metaphase plate is random.

  1. Any maternally inherited chromosome may face either pole.
  2. Any paternally inherited chromosome may also face either pole.
  3. The orientation of each tetrad is independent of the orientation of the other 22 tetrads.
  4. This event—the random (or independent) assortment of homologous chromosomes at the metaphase plate—is the second mechanism that introduces variation into the gametes or spores.

In each cell that undergoes meiosis, the arrangement of the tetrads is different. The number of variations is dependent on the number of chromosomes making up a set. There are two possibilities for orientation at the metaphase plate; the possible number of alignments therefore equals 2 n, where n is the number of chromosomes per set.

  • Humans have 23 chromosome pairs, which results in over eight million (2 23 ) possible genetically-distinct gametes.
  • This number does not include the variability that was previously created in the sister chromatids by crossover.
  • Given these two mechanisms, it is highly unlikely that any two haploid cells resulting from meiosis will have the same genetic composition (see figure below).

To summarize the genetic consequences of meiosis I, the maternal and paternal genes are recombined by crossover events that occur between each homologous pair during prophase I. In addition, the random assortment of tetrads on the metaphase plate produces a unique combination of maternal and paternal chromosomes that will make their way into the gametes. During Which Phase Of The Cell Cycle Does The Law Of Independent Assortment Occur Random, independent assortment during metaphase I can be demonstrated by considering a cell with a set of two chromosomes (n = 2). In this case, there are two possible arrangements at the equatorial plane in metaphase I. The total possible number of different gametes is 2n, where n equals the number of chromosomes in a set.

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Does independent assortment occur in anaphase 1 or 2?

When cells divide during meiosis, homologous chromosomes are randomly distributed during anaphase I, separating and segregating independently of each other. This is called independent assortment.

Which of the following occurs during G1 of the cell cycle?

What Happens in G1 of the Cell Cycle? – In some instances, such as starvation or when the tissue under generation has reached its targeted size the cells will exit the cell cycle and stay in stasis called G0 (figure 1). Most of these cells are capable of re-entering the cell cycle at G1 should the need ever arise.

Nerve cells do not normally regenerate; they remain in stasis. In G1, cells accomplish most of their growth; they get bigger in size and make proteins and organelles needed for normal functions of DNA synthesis. Here, proteins and RNAs are synthesized, and, more especially the centromere and the other components of the centrosomes are made.

The cells are fully functional; in addition to being on a dividing mission they can also perform their normal functions. In vertebrates and diploid yeasts the chromosome number is 2n at this phase, while in haploid yeasts the chromosome number is 1n. In short, the first growth phase is the time when just after birth ( in mitosis ) the cell is preparing for DNA synthesis (in S phase).

What occurs during anaphase I?

During anaphase I, the homologous chromosomes are pulled toward opposite poles of the cell. During anaphase I, the homologous chromosomes are pulled toward opposite poles of the cell.

During which phase of meiosis does independent assortment occur quizlet?

Independent assortment is random and occurs during Metaphase I of meiosis.

What happens during metaphase 1 of meiosis?

meiosis Meiosis is a type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells. This process is required to produce egg and sperm cells for sexual reproduction. During reproduction, when the sperm and egg unite to form a single cell, the number of chromosomes is restored in the offspring.

Meiosis begins with a parent cell that is diploid, meaning it has two copies of each chromosome. The parent cell undergoes one round of DNA replication followed by two separate cycles of nuclear division. The process results in four daughter cells that are haploid, which means they contain half the number of chromosomes of the diploid parent cell.

Meiosis has both similarities to and differences from mitosis, which is a cell division process in which a parent cell produces two identical daughter cells. Meiosis begins following one round of DNA replication in cells in the male or female sex organs.

The process is split into meiosis I and meiosis II, and both meiotic divisions have multiple phases. Meiosis I is a type of cell division unique to germ cells, while meiosis II is similar to mitosis. Meiosis I, the first meiotic division, begins with prophase I. During prophase I, the complex of DNA and protein known as chromatin condenses to form chromosomes.

The pairs of replicated chromosomes are known as sister chromatids, and they remain joined at a central point called the centromere. A large structure called the meiotic spindle also forms from long proteins called microtubules on each side, or pole, of the cell.

  • Between prophase I and metaphase I, the pairs of homologous chromosome form tetrads.
  • Within the tetrad, any pair of chromatid arms can overlap and fuse in a process called crossing-over or recombination.
  • Recombination is a process that breaks, recombines and rejoins sections of DNA to produce new combinations of genes.

In metaphase I, the homologous pairs of chromosomes align on either side of the equatorial plate. Then, in anaphase I, the spindle fibers contract and pull the homologous pairs, each with two chromatids, away from each other and toward each pole of the cell.

  • During telophase I, the chromosomes are enclosed in nuclei.
  • The cell now undergoes a process called cytokinesis that divides the cytoplasm of the original cell into two daughter cells.
  • Each daughter cell is haploid and has only one set of chromosomes, or half the total number of chromosomes of the original cell.

Meiosis II is a mitotic division of each of the haploid cells produced in meiosis I. During prophase II, the chromosomes condense, and a new set of spindle fibers forms. The chromosomes begin moving toward the equator of the cell. During metaphase II, the centromeres of the paired chromatids align along the equatorial plate in both cells.

  • Then in anaphase II, the chromosomes separate at the centromeres.
  • The spindle fibers pull the separated chromosomes toward each pole of the cell.
  • Finally, during telophase II, the chromosomes are enclosed in nuclear membranes.
  • Cytokinesis follows, dividing the cytoplasm of the two cells.
  • At the conclusion of meiosis, there are four haploid daughter cells that go on to develop into either sperm or egg cells.

: meiosis

At what stage is the independent assortment of chromosomes determined quizlet?

Germ-line cells are haploid but gametes are diploid. Independent assortment occurs in prophase I.

Which event during meiosis is responsible for the principle of independent assortment quizlet?

The principle of independent assortment is best illustrated by events that take place during metaphase I, during which nonhomologous chromosomes segregate independently of each other.

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What involves independent assortment?

The idea behind independent assortment is that genes are inherited independently of one another. In other words, the genetic factors that control crest and sex are physically separate. Because the genetic factors are physically separate, they segregate independently during gamete (egg and sperm) formation.

Why crossing over and independent assortment occur in meiosis but not mitosis?

Crossing over occurs in meiosis but not mitosis because meiosis creates genetically unique cells and mitosis creates genetically identical cells. During meiosis in prophase I, crossing over occurs where homologous chromosomes exchange corresponding sections of DNA.

What happens in metaphase 1 and metaphase 2 in meiosis?

During meiosis I, metaphase I takes place and pairs of chromosomes line up in the middle of the cell. During meiosis II, metaphase II takes place and chromosomes line up in the middle of the cell. The major difference is that in metaphase I, it is pairs of chromosomes and in metaphase II the chromosomes are not paired.

What happens in each stage of meiosis 1 and 2?

There are two divisions in meiosis; the first division is meiosis I: the number of cells is doubled but the number of chromosomes is not. This results in 1/2 as many chromosomes per cell. The second division is meiosis II: this division is like mitosis; the number of chromosomes does not get reduced.

During which phases of meiosis 1 and meiosis 2 can genetic variation occur?

Genetic variation is increased by meiosis – During fertilisation, 1 gamete from each parent combines to form a zygote. Because of recombination and independent assortment in meiosis, each gamete contains a different set of DNA. This produces a unique combination of genes in the resulting zygote.

Recombination or crossing over occurs during prophase I. Homologous chromosomes – 1 inherited from each parent – pair along their lengths, gene by gene. Breaks occur along the chromosomes, and they rejoin, trading some of their genes. The chromosomes now have genes in a unique combination. Independent assortment is the process where the chromosomes move randomly to separate poles during meiosis.

A gamete will end up with 23 chromosomes after meiosis, but independent assortment means that each gamete will have 1 of many different combinations of chromosomes. This reshuffling of genes into unique combinations increases the genetic variation in a population and explains the variation we see between siblings with the same parents.

What happens at anaphase II?

During anaphase II, microtubules from each spindle attach to each sister chromatid at the kinetochore. The sister chromatids then separate, and the microtubules pull them to opposite poles of the cell. As in mitosis, each chromatid is now considered a separate chromosome (Figure 6).

What is meiosis prophase 1?

What is the sub stages prophase 1 of meiosis 1? Explain briefly. Answer Verified Hint: Meiosis takes place only in sexually reproducing organisms. Prophase 1 of meiosis is essentially the crossing over and recombination of genetic material between non sister chromatids which results in the genetically identical, haploid daughter chromatid cells.

  • Complete answer: To answer this question, first, we need to know about meiosis.
  • The process that decreases the chromosomes number from diploid to haploid in cell division in sexually reproducing species is known as meiosis.
  • Meiosis requires two consecutive nucleus divisions and contributes to the development of animal reproductive cells (gametes) and to the development of spores in fungi, plants, and most algae.

The prophase 1 of meiosis occurs in 5 stages given below-Leptotene – In this stage the chromosomes start to condense and are attached to the nuclear membrane via their telomeres.Zygotene – Here Synapsis begins with a synaptonemal complex developing between homologous chromosomes.Pachytene – In this stage crossing over of genetic material takes places between non-sister chromatids.Diplotene – In this stage synapsis ends with the disappearance of synaptonemal complex; homologous pairs remain linked at chiasmata.Diakinesis – At last, chromosomes become fully condensed and the nuclear membrane disintegrates prior to metaphase 1.

What happens in prophase?

prophase Prophase is the first phase of mitosis, the process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells. During prophase, the complex of DNA and proteins contained in the nucleus, known as chromatin, condenses.

The chromatin coils and becomes increasingly compact, resulting in the formation of visible chromosomes. Chromosomes are made of a single piece of DNA that is highly organized. The replicated chromosomes have an X shape and are called sister chromatids. The sister chromatids are pairs of identical copies of DNA joined at a point called the centromere.

Then, a structure called the mitotic spindle begins to form. The mitotic spindle is made of long proteins called microtubules that begin forming at opposite ends of the cell. The spindle will be responsible for separating the sister chromatids into two cells.

During which phase of meiosis does independent assortment occur quizlet?

Independent assortment is random and occurs during Metaphase I of meiosis.

How and at what stage is independent assortment accomplished quizlet?

Independent assortment occurs when tetrads randomly align at metaphase plate. Then the chromosomes separate during anaphase I and II; each gamete receives one of each type of chromosome. During prophase I, Crossing over occurs with tetrads at chiasmata resulting in genetic variation.

At what stage is the independent assortment of chromosomes determined quizlet?

Germ-line cells are haploid but gametes are diploid. Independent assortment occurs in prophase I.