Biology Chapter on Chromosomal Structure

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Questions and Answers

Name the proteins that DNA wraps around to form a chromosome in eukaryotic cells.

Histones

How do the structure and location of a prokaryotic chromosome differ from that of a eukaryotic chromosome?

A prokaryotic chromosome consists of a circular DNA molecule. Eukaryotic chromosomes are rod-shaped, associated with histone and nonhistone proteins, and found within the cell's nucleus.

Does chromosome number indicate whether an organism is a plant or an animal? Explain.

No, chromosome number does not indicate whether an organism is a plant or an animal.

Contrast sex chromosomes with autosomes.

Sex chromosomes determine the sex of an organism and other characteristics. All the other chromosomes in an organism are called autosomes. Signup and view all the answers

Using Table 8-1, list the haploid and diploid number of chromosomes for each organism.

Refer to Table 8-1 for diploid numbers. The haploid number is half of that. Signup and view all the answers

Is there a correlation between the number of chromosomes and the complexity of an organism? Give support for your answer.

No; there is no consistent correlation. Signup and view all the answers

What would be the consequence for future generations of cells if sperm and egg cells were normally diploid?

The number of chromosomes would double each generation. Signup and view all the answers

What is the sex of the person whose chromosomes are shown in Figure 8-3 above? Explain your answer.

Male, as indicated by the X and Y chromosomes. Signup and view all the answers

Name the process by which prokaryotic cells divide.

Binary fission. Signup and view all the answers

What is the name of the process by which the cell's cytoplasm divides?

Cytokinesis. Signup and view all the answers

During which of the phases of interphase does an offspring cell grow to mature size?

G1 phase. Signup and view all the answers

During which phase of mitosis do chromatids separate to become chromosomes?

Anaphase. Signup and view all the answers

Explain the main difference between cytokinesis in animal cells and cytokinesis in plant cells.

In animal cells, cytokinesis begins with a pinching inward of the cell membrane; in plant cells, vesicles form a cell plate. Signup and view all the answers

Which type of molecule controls the cell cycle?

Proteins. Signup and view all the answers

What would happen if cytokinesis took place before mitosis?

Chromosomes would be divided haphazardly, resulting in a defective cell. Signup and view all the answers

What would result if chromosomes did not replicate during interphase?

Each new cell would receive only half the information needed to function properly. Signup and view all the answers

Why are individual chromosomes more difficult to see during interphase than during mitosis?

Chromosomes undergo coiling and condensation. Signup and view all the answers

How do the end products of meiosis differ from the end products of mitosis?

Meiosis produces four haploid cells; mitosis produces two diploid cells. Signup and view all the answers

How does anaphase I in meiosis differ from anaphase in mitosis?

In anaphase I of meiosis, homologous pairs separate; in mitosis, sister chromatids separate. Signup and view all the answers

Explain the role of crossing-over in ensuring genetic variation.

Crossing-over permits the exchange of genetic material. Signup and view all the answers

During which stage of meiosis is the diploid number of chromosomes reduced to the haploid number?

Telophase I. Signup and view all the answers

Describe the differences between spermatogenesis and oogenesis.

Spermatogenesis produces four sperm cells; oogenesis produces one egg and three polar bodies. Signup and view all the answers

Why is meiosis essential to sexual reproduction?

Meiosis ensures that the chromosome number in a zygote does not double at fertilization. Signup and view all the answers

Explain why the chromosomes in the haploid cells produced by meiosis I look different from those produced by meiosis II.

Sister chromatids are still together at the end of meiosis I. Signup and view all the answers

Explain how it might happen that a human offspring with 47 chromosomes could be produced.

If a gamete with 24 chromosomes fertilized one with the normal 23, the zygote would have 47. Signup and view all the answers

In humans, the egg is larger than the sperm. Explain how it is possible that a child inherits equally from its mother and father.

Hereditary is carried primarily in DNA, not cytoplasm. Signup and view all the answers

Study Notes

Chromosomal Structure and Differences

DNA in eukaryotic cells wraps around histones to form chromosomes.
Prokaryotic chromosomes are circular and lack histone association; eukaryotic chromosomes are rod-shaped and located in the nucleus.

Chromosome Number and Organism Complexity

Chromosome count does not determine whether an organism is a plant or animal (e.g., potatoes, plums, and chimpanzees share the same chromosome number).
There is no correlation between chromosome number and organism complexity; simpler organisms can have more chromosomes.

Gamete Structure and Division

Sperm and egg cells must be haploid; if diploid, chromosome numbers would double each generation.
Binary fission is the process by which prokaryotic cells divide.

Mitosis and Cytokinesis

Cytokinesis, the cytoplasmic division, follows mitosis and differs between cell types; animal cells use a cleavage furrow while plant cells form a cell plate.
Anaphase is the phase in mitosis when chromatids separate into individual chromosomes.

Interphase and Cellular Growth

G1 phase of interphase is where most cellular growth occurs; chromosomes are less visible during interphase due to coiling.

Meiosis vs. Mitosis

Meiosis results in four haploid cells, while mitosis produces two diploid cells.
Anaphase I separates homologous chromosome pairs, while mitosis separates sister chromatids.

Genetic Variation and Reproduction

Crossing-over during meiosis introduces genetic variation by exchanging genetic material between homologous chromosomes.
Meiosis is crucial for sexual reproduction, ensuring correct chromosome numbers in gametes and genetic diversity in offspring.

Oogenesis vs. Spermatogenesis

Spermatogenesis results in four equal sperm cells; oogenesis yields one egg and three polar bodies that degenerate.

Chromosome Differences in Meiosis

Chromosomes appear different after meiosis I (sister chromatids paired) compared to meiosis II (individual chromosomes).

Genetic Contributions from Parents

A human with 47 chromosomes could arise if a gamete with an abnormal number (24) fertilizes one with the normal count (23).
Despite the egg's larger size due to cytoplasm, inheritance is primarily determined by DNA content from both parents.

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Description

Explore the fascinating world of chromosomes in this biology quiz. Delve into the differences between eukaryotic and prokaryotic chromosomes, understand gamete structures, and learn about the processes of mitosis and cytokinesis. Test your knowledge on chromosomal numbers and organism complexity as well.