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Chapter 13: Meiosis, Chromosomes-REVIEW

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Q1. How are homologous chromosomes the same? How do homologous chromosomes differ?

Background

Topic: Chromosome Structure and Homology

This question tests your understanding of homologous chromosomes—how they are similar and how they differ, which is foundational for understanding meiosis and inheritance.

Key Terms:

  • Homologous chromosomes: Chromosome pairs (one from each parent) that are similar in length, gene position, and centromere location.

  • Alleles: Different versions of a gene found at the same locus on homologous chromosomes.

Step-by-Step Guidance

  1. List 2–3 characteristics that homologous chromosomes share (think about their structure, gene content, and origin).

  2. Identify at least one way homologous chromosomes can differ (consider genetic information at specific loci).

  3. Reflect on why these similarities and differences are important for meiosis and genetic variation.

Try solving on your own before revealing the answer!

Q2. If a diploid animal’s somatic cells have 122 chromosomes, how many chromosomes are in each sperm?

Background

Topic: Chromosome Number in Gametes vs. Somatic Cells

This question tests your ability to apply the concepts of diploid (2n) and haploid (n) chromosome numbers to predict chromosome counts in gametes.

Key Terms and Formulas:

  • Diploid (2n): Cells with two sets of chromosomes (somatic cells).

  • Haploid (n): Cells with one set of chromosomes (gametes: sperm or egg).

  • Formula:

Step-by-Step Guidance

  1. Identify the diploid number (2n) given in the question.

  2. Recall that gametes (sperm/egg) are haploid and contain half the number of chromosomes as somatic cells.

  3. Set up the calculation: divide the diploid number by 2 to find the haploid number.

Try solving on your own before revealing the answer!

Q3. If a brain cell in a diploid organism has 56 chromosomes, how many chromosomes do the animal’s eggs have?

Background

Topic: Chromosome Number in Gametes vs. Somatic Cells

This question is similar to Q2 and reinforces the concept of diploid and haploid chromosome numbers.

Key Terms and Formulas:

  • Somatic cell: Any cell of a living organism other than the reproductive cells.

  • Egg (gamete): Haploid reproductive cell.

  • Formula:

Step-by-Step Guidance

  1. Note the chromosome number in the somatic (brain) cell (2n).

  2. Remember that eggs are haploid (n).

  3. Divide the somatic chromosome number by 2 to find the number in the egg.

Try solving on your own before revealing the answer!

Q4. An organism is described as 2n = 36. How many chromosomes does each of its somatic cells have, and how many chromosomes are in each gamete?

Background

Topic: Chromosome Number Notation

This question tests your ability to interpret chromosome notation and apply it to somatic and gamete cells.

Key Terms and Formulas:

  • 2n: Diploid number (total chromosomes in somatic cells).

  • n: Haploid number (chromosomes in gametes).

  • Formula:

Step-by-Step Guidance

  1. Identify the diploid number (2n = 36).

  2. State the number of chromosomes in somatic cells (just 2n).

  3. Calculate the haploid number by dividing 36 by 2.

Try solving on your own before revealing the answer!

Q5. What is an autosome vs. a sex chromosome?

Background

Topic: Types of Chromosomes

This question tests your understanding of the difference between autosomes and sex chromosomes, which is important for understanding inheritance patterns.

Key Terms:

  • Autosome: Any chromosome that is not a sex chromosome.

  • Sex chromosome: Chromosomes involved in determining the sex of an organism (e.g., X and Y in humans).

Step-by-Step Guidance

  1. Define autosomes and give an example.

  2. Define sex chromosomes and give an example.

  3. Explain how they differ in function and inheritance.

Try solving on your own before revealing the answer!

Q6. Put the following events in order of when each occurs in meiosis and/or mitosis:

  • Sister chromatids separate

  • Homologous pairs line up

  • Homologous pairs separate

  • Crossing over occurs

  • DNA duplicates

Background

Topic: Events of Meiosis and Mitosis

This question tests your knowledge of the sequence of key events during cell division.

Key Terms:

  • Crossing over: Exchange of genetic material between homologous chromosomes during prophase I of meiosis.

  • Metaphase: Stage where chromosomes align at the metaphase plate.

  • Anaphase: Stage where chromatids or homologous chromosomes separate.

Step-by-Step Guidance

  1. Recall when DNA replication occurs in the cell cycle.

  2. Determine when crossing over happens during meiosis.

  3. Identify the stage when homologous pairs line up and then separate.

  4. Identify when sister chromatids separate.

  5. Arrange these events in the correct chronological order for meiosis and mitosis.

Try solving on your own before revealing the answer!

Q7. When do homologous pairs separate? When do sister chromatids separate? When do chromosomes line up in pairs on the metaphase plate and when do they line up individually? When are chromosomes replicated? When do cells going through meiosis become haploid? What is the product of meiosis?

Background

Topic: Phases and Outcomes of Meiosis

This set of questions tests your understanding of the timing and outcomes of key events in meiosis.

Key Terms:

  • Homologous pairs: Separate during meiosis I.

  • Sister chromatids: Separate during meiosis II.

  • Metaphase plate: Where chromosomes align during metaphase.

  • Haploid: Cells with one set of chromosomes.

Step-by-Step Guidance

  1. Review the stages of meiosis I and II, focusing on metaphase and anaphase.

  2. Identify when chromosomes are replicated (hint: S phase of interphase).

  3. Determine at which point cells become haploid during meiosis.

  4. Describe the final products of meiosis in terms of chromosome number and genetic diversity.

Try solving on your own before revealing the answer!

Q8. Each cell in anaphase II has _____ the chromosomes and ______ the DNA compared to metaphase I. Each cell in metaphase II has ______ the chromosomes and ____ the DNA compared to Prophase I. Each cell at the end of Meiosis II has _____ the chromosomes and ____ the DNA compared to cells in Prophase I.

Background

Topic: Chromosome and DNA Content During Meiosis

This question tests your ability to compare chromosome and DNA content at different stages of meiosis.

Key Terms:

  • Chromosome number: Number of chromosomes present in a cell.

  • DNA content: Amount of DNA present, which can change due to replication and division.

Step-by-Step Guidance

  1. Recall what happens to chromosome and DNA content during DNA replication and each meiotic division.

  2. Compare the chromosome and DNA content at each specified stage to the reference stage.

  3. Use the terms "twice," "half," "equal," or "one-fourth" to fill in the blanks based on your comparisons.

Try solving on your own before revealing the answer!

Q9. What is independent assortment and when does this occur? What is chiasmata, and when is chiasmata observed between homologs? What is crossing over and when does this occur? What is random fertilization and when does this occur?

Background

Topic: Mechanisms of Genetic Variation

This question tests your understanding of the processes that generate genetic diversity during sexual reproduction.

Key Terms:

  • Independent assortment: Random distribution of homologous chromosomes during meiosis I.

  • Chiasmata: Points where crossing over occurs between homologous chromosomes.

  • Crossing over: Exchange of genetic material between homologous chromosomes during prophase I.

  • Random fertilization: Any sperm can fertilize any egg, increasing genetic variation.

Step-by-Step Guidance

  1. Define each term in your own words.

  2. Identify the stage of meiosis or reproduction when each process occurs.

  3. Explain how each process contributes to genetic variation.

Try solving on your own before revealing the answer!

Q10. What process is used so that spores can form a haploid multicellular organism? What process is used so that a zygote can produce haploid (n) cells? How many chromosomes does a cell have if it can be described as 2n=36? How would you characterize a cell that is n=18? How many sets of chromosomes does a cell have if it can be described as n=16? How many homologous pairs of chromosomes does a cell have if it can be described as 2n=82?

Background

Topic: Sexual Life Cycles and Chromosome Number

This set of questions tests your understanding of the processes and terminology related to sexual life cycles and chromosome numbers.

Key Terms and Formulas:

  • Meiosis: Process that reduces chromosome number by half, producing haploid cells.

  • Mitosis: Process that produces identical cells, used for growth and development.

  • Zygote: Diploid cell formed by fertilization.

  • Formula for homologous pairs:

Step-by-Step Guidance

  1. Identify which process (mitosis or meiosis) is responsible for each developmental step described.

  2. Interpret chromosome number notation (e.g., 2n=36 means 36 chromosomes in diploid cells).

  3. Determine the number of sets of chromosomes or homologous pairs based on the given n or 2n values.

Try solving on your own before revealing the answer!

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