Table of Contents
What are the results 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 happens during nondisjunction in meiosis?
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.
Is Down syndrome caused by nondisjunction?
Down syndrome is caused by a random error in cell division that results in the presence of an extra copy of chromosome 21. The type of error is called nondisjunction (pronounced non-dis-JUHNGK-shuhn).
What are 3 types of nondisjunction?
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.
Which of the following can result from nondisjunction Mcq?
Explanation: The non-disjunction results in the production of XXY.
What happens when nondisjunction occur in mitosis?
Nondisjunction, in which chromosomes fail to separate equally, can occur in meiosis I (first row), meiosis II (second row), and mitosis (third row). These unequal separations can produce daughter cells with unexpected chromosome numbers, called aneuploids.
Is nondisjunction more common in meiosis I or II?
meiosis I
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 is the outcome of nondisjunction in meiosis I quizlet?
Nondisjunction in meiosis I results from failure of homologs to separate; the gametes produced are either n+1 or N-1.
What type of nondisjunction is Turner’s syndrome?
Turner syndrome (TS) is a complex phenotype associated with complete or partial monosomy of the X chromosome, usually the result of a sporadic chromosomal nondisjunction.
How is Down’s syndrome caused?
Down’s syndrome is when you’re born with an extra chromosome. You usually get an extra chromosome by chance, because of a change in the sperm or egg before you’re born. This change does not happen because of anything anyone did before or during pregnancy.
What type of mutation causes Down syndrome?
Typically, a baby is born with 46 chromosomes. Babies with Down syndrome have an extra copy of one of these chromosomes, chromosome 21. A medical term for having an extra copy of a chromosome is ‘trisomy. ‘ Down syndrome is also referred to as Trisomy 21.
What is a possible result of nondisjunction quizlet?
Result of nondisjunction in meiosis II. Half of gametes have normal number of chromosomes, other half have abnormal number. Aneuploidy. Having an abnormal number of chromosomes. Chromosomal losses are more detrimental than chromosome gains.
What gametes result from nondisjunction in meiosis II quizlet?
If one chromosome undergoes nondisjunction in meiosis II, half the gametes will have the normal haploid number of chromosomes (n), one-quarter will have an extra chromosome (n +1), and one-quarter will be missing a chromosome (n – 1).
What genetic mutation causes Turner syndrome?
Turner syndrome, a condition that affects only females, results when one of the X chromosomes (sex chromosomes) is missing or partially missing. Turner syndrome can cause a variety of medical and developmental problems, including short height, failure of the ovaries to develop and heart defects.