Which process would cause nondisjunction if it occurred during meiosis?
Figure 7.8 Following meiosis, each gamete has one copy of each chromosome. Nondisjunction occurs when homologous chromosomes (meiosis I) or sister chromatids (meiosis II) fail to separate during meiosis.
What happens if nondisjunction occurs in meiosis 1?
Nondisjunction Produces Abnormal Gametes
If nondisjunction occurs during anaphase I of meiosis I, this means that at least one pair of homologous chromosomes did not separate. The end result is two cells that have an extra copy of one chromosome and two cells that are missing that chromosome.
What is nondisjunction and when in meiosis can it occur quizlet?
nondisjunction: the occurrence where chromosomes fail to separate normally during meiosis, the resulting gamete will either lack a chromosome or carry an extra copy. -can occur during mitosis, meiosis I and meiosis II.
How does nondisjunction cause chromosomal abnormality?
Nondisjunction is the failure of homologous chromosomes to disjoin correctly during meiosis. This results in the production of gametes containing a greater or lesser chromosomal amount than normal ones. Consequently the individual may develop a trisomal or monosomal syndrome.
Why does aneuploidy in animals generally result in phenotypic abnormalities?
Why does aneuploidy in animals generally result in phenotypic abnormalities? … It results in an imbalance of gene products from affected chromosomes, which alters normal development. It results in an imbalance of gene products from affected chromosomes, which alters normal development. You just studied 10 terms!
What occurs during nondisjunction and the effect of the resulting cells?
There are three forms of nondisjunction: failure of a pair of homologous chromosomes to separate in meiosis I, failure of sister chromatids to separate during meiosis II, and failure of sister chromatids to separate during mitosis. Nondisjunction results in daughter cells with abnormal chromosome numbers (aneuploidy).
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.
Which describes the cells at the end of meiosis 1 when nondisjunction occurs during meiosis 2?
One cell with extra homologous chromosomes and one cell missing a homologous chromosome. Which describes the cells at the end of meiosis I when nondisjunction occurs in meiosis II? The homologous pairs are in separate cells. The cells are haploid.
What happens during meiosis to produce an aneuploid?
What happens during meiosis to produce an polyploid? DNA replicates, but is not apportioned into daughter cells, forming a diploid gamete. … Crossing over in the male yields unbalanced gametes, which can fertilize oocytes, but too much or too little genetic material halts development.
How do non disjunction errors occur?
Nondisjunction occurs when chromosomes fail to segregate during meiosis; when this happens, gametes with an abnormal number of chromosomes are produced.
When can a Nondisjunction occur?
Nondisjunction can occur during anaphase of mitosis, meiosis I, or meiosis II. During anaphase, sister chromatids (or homologous chromosomes for meiosis I), will separate and move to opposite poles of the cell, pulled by microtubules.
What occurs during Nondisjunction quizlet?
What happens if nondisjunction occurs during meiosis I? If nondisjunction occurs during meiosis I, homologous chromosomes fail to separate. This produces abnormal gametes that contain two members of the affected chromosome or none at all. … If nondisjunction occurs during meiosis II, sister chromatids fail to separate.
What kind of chromosomal abnormalities can occur?
Some chromosomal abnormalities occur when there is an extra chromosome, while others occur when a section of a chromosome is deleted or duplicated. Examples of chromosomal abnormalities include Down syndrome, Trisomy 18, Trisomy 13, Klinefelter syndrome, XYY syndrome, Turner syndrome and triple X syndrome.
What events during meiosis produces trisomies and Monosomies?
If a gamete with two copies of the chromosome combines with a normal gamete during fertilization, the result is trisomy; if a gamete with no copies of the chromosomes combines with a normal gamete during fertilization, the result is monosomy.
What are some examples of Nondisjunction disorders?
Conditions that arise from non-disjunction events include:
- Patau’s Syndrome (trisomy 13)
- Edwards Syndrome (trisomy 18)
- Down Syndrome (trisomy 21)
- Klinefelter Syndrome (XXY)
- Turner’s Syndrome / Fragile X (monosomy X)