a. nondisjunction during meiosis b. c. d an inversion a chromosomal deletion X-l
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a. nondisjunction during meiosis b. c. d an inversion a chromosomal deletion X-linked dominance 22. What is nondisjunction? a. failure of chromosomes to duplicate before mitosis or meiosis b. failure of homologous chromosomes or sister chromatids to separate c an extra duplication of all the chromosomes before mitosis or meiosis d. failure of cells to divide by cytokinesis after telophase 23. Which of the following statements is not true regarding Down syndrome? a. Affected individuals usually have three copies of chromosome 21 b. Most Down syndrome children are born to women 35 years of age or older c. The condition is usually caused by nondisjunction in egg formation. d. Approximately 0.1 percent of all live births are children with Down syndrome. 24. Which of the following conditions is NOT an outcome of nondisjunction? a. It can cause Down syndrome. b. It can cause color blindness c. It can take place in meiotic division. d. It can take place in mitotic division. 25 When chromosomes recombane with others that are not homologous, what is the result? a. deletion b. duplication c. inversion d. translocation 26. Karyotyping was done for a patient of suspected blood cancer. Chromosomal analysis indicated that there was an extra-long chromosome 9 and a shorter chromosome 22, called the Philadelphia chromosome. It is a diagnosis of chronic myeloid leukemia, a form of blood cancer in which a big portion of chromosome 22 is transferred to chromosome 9 and a small portion of chromosome 9 is transferred to chromosome 22. What is this form of chromosomal abnormality called? a. deletion b. duplication c. inversion d. translocation 27. A female employee was accidentally exposed to a small dose of radiation while at work. Some of the radiation penetrated her body and struck the developing ega cell in her ovary, causing one arm on the replicated chromosome 10 and one arm on the replicated chromosome 15 pieces switched places, so that the broken piece of chromosome 10 became attached to chromosome 15 and vic versa. This type of chromosomal aberration is considered a/an to break off. Before reconnecting, the two broke a. deletion b. duplication c. inversion d. translocationExplanation / Answer
Q21) Which causes Down's syndrome-
Answer- A - Non-disjunction during meiosis.
Explanation- Down syndrome is usually caused due to an error during cell division called non-disjunction. Non-disjunction occurs in an embryo having three copies of chromosome 21, instead of two copies which is normally found. Before or during conception, a pair of 21st chromosome either in sperm or the egg fails to separate. So when the embryo develops, the extra chromosome is replicated in every cell of the body. It is usually found in 95% of cases, rest occurs due to translocation.
Q22) What is Non-disjunction?
Answer- B- failure of homologous chromosomes or sister chromatids to separate.
Explanation:- Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division. There are three types of nondisjunction, they are the 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.Due to nondisjuction there is abnormal chromosome numbers in caugter cells.
Q23) Which is not true about Down's syndrome ?
Answer- C- condition caused by nondisjuction in egg formation.
Explanation- Down syndrome is usually caused by an error in cell division called nondisjunction. Nondisjunction occurs in an embryo with three copies of chromosome 21 instead of two. Before or during conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate. As the embryo develops, the extra chromosome is replicated in every cell of the body.so non disjunction in egg is only not responsible for the syndrome.
Q24) Which of the following is not an outcome of non-disjunction?
Answer- B- It can cause color blindness.
Explanation- Colorblindness is a X-linked recessive inheritance pattern, not related to nondisjuction,
Down's syndrome caused by nondisjunction, it can take place during meiotic and mitotic division , when the sister chromatids fail to separate.
Q25) when chromosomes recombine with others that are not homologous, what is the result?
Answer- D- Translocation.
Explanation- In case of recombination between two non-homologous chromosomes it is called Translocation. Deletion and duplication takes place in homologous chromosomes. In chromosomal duplications, extra copies of a chromosomal region is formed, in deletion there is loss of DNA sequences. Inversion is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. An inversion occurs when a single chromosome undergoes breakage and gets rearranged within itself.
Q26) karyotyping done for a patient suspected with blood cancer. Chromosomal analysis indicates there was an extra-long chromosome-9 and a shorter chromosome at 22 called Philadelphia chromosome. It is a diagnosis of chronic myeloid leukemia, a form of blood cancer in which a big portion of chromosome 22 is transferred to chromosome 9 and a small portion of chromosome 9 is transferred to chromosome 22. What is the form of chromosomal abnormality?
Answer- D- Translocation.
Explanation- Chromosome translocation is a chromosomal abnormality caused due to rearrangement of parts between non-homologous chromosomes. Translocation can be balanced when there is equal exchange of genetic materials and imbalanced when there is unequal exchange of chromosome materials.
In this case chromosome 22 and chromosome 9 are non-homologous chromosomes and there is unequal distribution of materials between them causing mutation leading to chronic myeloid leukemia. This is a type of reciprocal translocation in which parts of chr-9 and chr-22 exchange their places.
Q27) A female employee was accidentally exposed to a small dose of radiation, while at work, some of the radiation penetrated her body and struck the developing egg cells in her ovary. Causing one arm on the replicated chromosome 10 and one arm on the replicated chromosome 15 to break off. Before reconnecting the two broken parts switched places, so that the broken pieces of chromosome 10 becomes attached to chromosome 15 and vice versa. The type of chromosomal aberration is considered an _________?
Answer- D - translocation.
Explanation- Here the chr-10 and chr-15 parts broken off, and while reconnecting they switched their places chr-10 gets attached to chr-15, as they are non-homologous chromosomes so the joining of chr-10 with chr-15 is a chromosomal aberration called translocation.
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