Ch. 3 - Cell Division and Chromosome Heredity

Problem 1

Chapter 3, Problem 1

Examine the following diagrams of cells from an organism with diploid number 2n=6, and identify what stage of M phase is represented.

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Identify the diploid number of the organism, which is 2n=6, meaning there are 6 chromosomes in total.

Understand that M phase, or mitosis, consists of several stages: prophase, metaphase, anaphase, and telophase.

Examine the diagrams of the cells to determine the arrangement and appearance of the chromosomes.

Look for key characteristics of each stage: condensed chromosomes and spindle formation in prophase, alignment of chromosomes at the metaphase plate in metaphase, separation of sister chromatids in anaphase, and decondensation of chromosomes in telophase.

Match the observed characteristics in the diagrams to the descriptions of the stages to identify the specific stage of M phase represented.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

M Phase

M Phase, or mitotic phase, is the stage of the cell cycle where cell division occurs. It includes both mitosis, the process of nuclear division, and cytokinesis, the division of the cytoplasm. Understanding M Phase is crucial for identifying the specific stage represented in the diagrams, as it encompasses several distinct phases: prophase, metaphase, anaphase, and telophase.

Diploid Number

The diploid number (2n) refers to the total number of chromosomes in a somatic cell, where chromosomes exist in pairs. In this case, 2n=6 indicates that the organism has six chromosomes, or three pairs. Recognizing the diploid number helps in understanding the genetic makeup of the organism and the implications for chromosome behavior during M Phase.

Chromosome Structure During M Phase

During M Phase, chromosomes undergo significant structural changes, becoming highly condensed and visible under a microscope. Each chromosome consists of two sister chromatids joined at the centromere. Identifying the arrangement and number of chromatids in the diagrams is essential for determining the specific stage of M Phase, as the appearance of chromosomes varies between prophase, metaphase, anaphase, and telophase.

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Related Practice

Textbook Question

Answer the following questions for autosomal conditions such as PKU.

If both parents are heterozygous carriers of a mutant allele, what is the chance that their first child will be homozygous recessive for the mutation?

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Textbook Question

Answer the following questions for autosomal conditions such as PKU.

Parents who are each heterozygous carriers for a recessive mutant allele have a child who does not have the condition. What is the chance this child is a heterozygous carrier of the condition?

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Textbook Question

Answer the following questions for autosomal conditions such as PKU.

If the first child of parents who are both heterozygous carriers of a recessive mutant allele is homozygous recessive, what is the chance the second child of the couple will be homozygous recessive? What is the chance the second child will be a heterozygous carrier of the recessive mutation?

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Textbook Question

Homocystinuria is a rare autosomal recessive condition on the RUSP list of conditions screened by newborn genetic testing. The condition results from a mutation that blocks the degradation of the amino acid methionine. The absence of a critical enzyme causes the buildup of the compound homocysteine, which is one of the intermediate compounds in the methionine breakdown pathway. Homocystinuria causes mental impairment, heart problems, seizures, eye abnormalities, and a number of other symptoms that shorten life if not treated. The condition is treated by a specialized diet that is low in methionine and by the ingestion of several supplements.

Why do you think eating a low-methionine diet is critical to controlling homocystinuria?

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Textbook Question

Homocystinuria is a rare autosomal recessive condition on the RUSP list of conditions screened by newborn genetic testing. The condition results from a mutation that blocks the degradation of the amino acid methionine. The absence of a critical enzyme causes the buildup of the compound homocysteine, which is one of the intermediate compounds in the methionine breakdown pathway. Homocystinuria causes mental impairment, heart problems, seizures, eye abnormalities, and a number of other symptoms that shorten life if not treated. The condition is treated by a specialized diet that is low in methionine and by the ingestion of several supplements.

The low-methionine diet must be maintained throughout life to manage homocystinuria. Why do you think this is the case?

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Textbook Question

Our closest primate relative, the chimpanzee, has a diploid number of 2n =48. For each of the following stages of M phase, identify the number of chromosomes present in each cell.

end of mitotic telophase

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