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FAQ: What causes nondisjunction during meiosis II?

Nondisjunction in meiosis II results from the failure of the sister chromatids to separate during anaphase II. Since meiosis I proceeded without error, 2 of the 4 daughter cells will have a normal complement of 23 chromosomes. The other 2 daughter cells will be aneuploid, one with n+1 and the other with n-1.

What causes nondisjunction in meiosis?

Nondisjunction occurs when homologous chromosomes or sister chromatids fail to separate during meiosis, resulting in an abnormal chromosome number. Nondisjunction may occur during meiosis I or meiosis II.

What is the result of a nondisjunction during meiosis II quizlet?

What happens if nondisjunction occurs during meiosis II? If nondisjunction occurs during meiosis II, sister chromatids fail to separate. In this case, 50% of the gametes that are produced are normal haploid gametes, 25% of gametes have an extra chromosome, and 25% are missing a chromosome.

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What are the two conditions that are caused by nondisjunction?

Nondisjunction causes errors in chromosome number, such as trisomy 21 (Down syndrome) and monosomy X (Turner syndrome). It is also a common cause of early spontaneous abortions.

What happens in meiosis 2 of meiosis?

During meiosis II, the sister chromatids within the two daughter cells separate, forming four new haploid gametes. Therefore, each cell has half the number of sister chromatids to separate out as a diploid cell undergoing mitosis.

How does nondisjunction appear in meiosis I and II?

Nondisjunction in meiosis I occurs when the tetrads fail to separate during anaphase I. Nondisjunction in meiosis II results from the failure of the sister chromatids to separate during anaphase II. Since meiosis I proceeded without error, 2 of the 4 daughter cells will have a normal complement of 23 chromosomes.

How does nondisjunction during meiosis I differ from nondisjunction in meiosis II?

-Nondisjunction during meiosis I results in only two gametes, while nondisjunction during meiosis II gives four gametes, half of which have extra or missing chromosomes.

Which process would cause nondisjunction if it occurred during meiosis quizlet?

Nondisjunction can occur during anaphase of meiosis I or meiosis II. If it happens during meiosis I, an entire bivalent migrates to one pole (Figure 8.22a). Following the completion of meiosis, the four resulting haploid cells produced from this event are abnormal.

Which of the following would be the result if nondisjunction occurred in meiosis II?

If nondisjunction occurs during anaphase II of meiosis II, it means that at least one pair of sister chromatids did not separate. In this scenario, two cells will have the normal haploid number of chromosomes. Additionally, one cell will have an extra chromosome (n + 1) and one will be missing a chromosome (n – 1).

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What causes nondisjunction quizlet?

nondisjunction. failure of one or more chromosome pairs of chromatids of a single chromasome to properly move to opposite poles during meiosis or mitosis. tay sachs disease. caused by nucleotide insertion and causes the lysosomes to lack the functional enzyme that breaks down certain fats. You just studied 9 terms!

Is Down syndrome caused by nondisjunction in meiosis 1 or 2?

Trisomy 21 or Down syndrome (DS) is one of the most common chromosomal abnormalities. The majority of full trisomy 21 is caused by chromosomal nondisjunction occurring during maternal meiotic division (∼90%). Errors occur more frequently in the first maternal meiotic division than the second (73% vs.

Is nondisjunction more common in meiosis I or II?

Among the 188 maternal cases, nondisjunction occurred in meiosis I in 128 cases and in meiosis II in 38 cases; in 22 cases the DNA markers used were uninformative. Therefore meiosis I was responsible for 77.1% and meiosis II for 22.9% of maternal nondisjunction.

What are the effects of nondisjunction?

Nondisjunction in meiosis can result in pregnancy loss or birth of a child with an extra chromosome in all cells, whereas nondisjunction in mitosis will result in mosaicism with two or more cell lines. Aneuploidy may also result from anaphase lag.

What events occur during meiosis I and meiosis II?

In meiosis I, homologous chromosomes separate, while in meiosis II, sister chromatids separate. Meiosis II produces 4 haploid daughter cells, whereas meiosis I produces 2 diploid daughter cells. Genetic recombination (crossing over) only occurs in meiosis I.

Which event occurs during meiosis II but not during meiosis?

In meiosis II, these chromosomes are further separated into sister chromatids. Meiosis I includes crossing over or recombination of genetic material between chromosome pairs, while meiosis II does not.

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Which of the following occurs during meiosis 2?

In meiosis II, the sister chromatids separate, making haploid cells with non-duplicated chromosomes. Prophase II: Starting cells are the haploid cells made in meiosis I. Chromosomes condense. Metaphase II: Chromosomes line up at the metaphase plate. Anaphase II: Sister chromatids separate to opposite ends of the cell.

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