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Questions and Answers
What do homologous chromosomes share regarding genetic information?
What do homologous chromosomes share regarding genetic information?
During which phase of the cell cycle do chromosomes duplicate?
During which phase of the cell cycle do chromosomes duplicate?
What is a primary consequence of cells continuing to divide beyond their programmed limits?
What is a primary consequence of cells continuing to divide beyond their programmed limits?
How are the alleles on homologous chromosomes different?
How are the alleles on homologous chromosomes different?
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Which type of chromosomes do humans have an even number of?
Which type of chromosomes do humans have an even number of?
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Which cell cycle phase allows for cell growth and preparation for mitosis?
Which cell cycle phase allows for cell growth and preparation for mitosis?
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What genetic condition results from an abnormal number of chromosomes?
What genetic condition results from an abnormal number of chromosomes?
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What occurs during the mitotic phase of the cell cycle?
What occurs during the mitotic phase of the cell cycle?
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What is metabolism primarily responsible for in living organisms?
What is metabolism primarily responsible for in living organisms?
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Which principle explains why energy transformations in living cells are similar to those in non-living systems?
Which principle explains why energy transformations in living cells are similar to those in non-living systems?
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What best describes selective barriers in biological systems?
What best describes selective barriers in biological systems?
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What is the primary function of homeostasis in living organisms?
What is the primary function of homeostasis in living organisms?
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Why do living things reproduce?
Why do living things reproduce?
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Which characteristic of life involves the ability to grow towards stimuli like light and gravity?
Which characteristic of life involves the ability to grow towards stimuli like light and gravity?
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Which of the following statements is true regarding living cells?
Which of the following statements is true regarding living cells?
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What type of reproduction involves offspring that resemble the parent but may not be genetically identical?
What type of reproduction involves offspring that resemble the parent but may not be genetically identical?
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How many chromosomes are considered to be present despite the duplication during the process?
How many chromosomes are considered to be present despite the duplication during the process?
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During which phase of mitosis do the chromosomes align along the metaphase plate?
During which phase of mitosis do the chromosomes align along the metaphase plate?
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What is primarily responsible for the movement of sister chromatids during anaphase?
What is primarily responsible for the movement of sister chromatids during anaphase?
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What forms during cytokinesis in animal cells to facilitate cell division?
What forms during cytokinesis in animal cells to facilitate cell division?
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Which event marks the end of the mitotic phase?
Which event marks the end of the mitotic phase?
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What significant change occurs during telophase?
What significant change occurs during telophase?
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What distinguishes cytokinesis in plant cells from that in animal cells?
What distinguishes cytokinesis in plant cells from that in animal cells?
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What does the G2 phase ensure before the mitotic process begins?
What does the G2 phase ensure before the mitotic process begins?
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What is the process called that allows genetic variation during meiosis?
What is the process called that allows genetic variation during meiosis?
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During which phase do homologous chromosomes line up on the metaphase plate?
During which phase do homologous chromosomes line up on the metaphase plate?
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How many times can crossing over typically occur for one homologous pair during meiosis?
How many times can crossing over typically occur for one homologous pair during meiosis?
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What is the ploidy of the cells that result from telophase 1 and cytokinesis?
What is the ploidy of the cells that result from telophase 1 and cytokinesis?
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Which of the following statements is true regarding metaphase 2?
Which of the following statements is true regarding metaphase 2?
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What is the result of sexual fertilization involving two 1n gametes?
What is the result of sexual fertilization involving two 1n gametes?
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During which phase of meiosis does crossing over occur?
During which phase of meiosis does crossing over occur?
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How many daughter cells are formed at the end of meiosis?
How many daughter cells are formed at the end of meiosis?
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What happens during Anaphase 1 of meiosis?
What happens during Anaphase 1 of meiosis?
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What is the effect of DNA proofreading during replication?
What is the effect of DNA proofreading during replication?
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Which of the following best describes the outcome of meiosis II?
Which of the following best describes the outcome of meiosis II?
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After which phase do animal cells stop dividing following meiosis?
After which phase do animal cells stop dividing following meiosis?
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In organisms that may reproduce both sexually and asexually, what action can occur after meiosis?
In organisms that may reproduce both sexually and asexually, what action can occur after meiosis?
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Study Notes
Properties of Life
- Metabolism involves the transformation of matter and energy within organisms, similar to processes in non-living systems.
- Energy transformations abide by the laws of thermodynamics, applicable both inside and outside living organisms.
- Life emerges from complex interactions among non-living parts rather than a mysterious force.
- Living organisms demonstrate self-movement and growth, such as plants growing towards light.
- Selective barriers, like cellular membranes, regulate the exchange of substances between the internal and external environments.
Homeostasis
- Homeostasis is the ability of an organism to maintain stable internal conditions despite external fluctuation.
- An example is the consistent body temperature in humans regardless of the ambient temperature.
- Life can be defined as metabolic processes occurring within selective barriers.
Responsiveness to Stimuli
- Living organisms respond to external stimuli, exemplified by plants adjusting their growth toward water and light sources.
Reproduction
- Reproduction can be asexual or sexual; offspring usually resemble but are not identical to parents.
- Genetic traits are transmitted via DNA, organized into chromosomes.
- Humans possess 46 chromosomes in 23 homologous pairs, with each chromosome carrying alleles for specific traits.
Cell Division: Mitosis and Meiosis
- Mitosis produces two genetically identical daughter cells, crucial for growth and repair.
- The cell cycle consists of interphase (G1, S, G2) and the mitotic phase (prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis).
- In interphase:
- G1: Cell growth and preparation for DNA replication. Some cells enter a resting phase (G0).
- S: DNA synthesis where chromosomes duplicate into sister chromatids.
- G2: Final preparations for mitosis; checks for errors in replication.
Stages of Mitosis
- Prophase: Chromatin condenses into visible chromosomes; spindle fibers form.
- Prometaphase: Nuclear envelope breaks; spindle fibers attach to chromosomes.
- Metaphase: Chromosomes align at the metaphase plate; spindle fibers are fully formed.
- Anaphase: Sister chromatids are pulled apart by spindle fibers.
- Telophase: Chromosomes uncoil, nuclear envelopes reform around them.
- Cytokinesis: Cytoplasm divides, forming two distinct daughter cells.
Meiosis
- Meiosis results in four haploid cells from one diploid cell, creating genetic diversity through crossing over and separation of homologous chromosomes.
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Meiosis I:
- Prophase I: Crossing over occurs; homologous chromosomes pair.
- Metaphase I: Homologous pairs line up at the metaphase plate.
- Anaphase I: Homologous chromosomes are pulled apart; chromatids remain attached.
- Telophase I and Cytokinesis: Two haploid cells are formed.
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Meiosis II: Similar to mitosis, separates sister chromatids without further DNA replication.
- Prophase II: No chromosome duplication occurs.
- Metaphase II: Chromosomes align at the metaphase plate.
- Anaphase II: Sister chromatids are pulled apart.
- Telophase II and Cytokinesis: Four haploid daughter cells are produced.
Genetic Variability
- Genetic diversity is crucial for species evolution; arises from meiotic processes like crossing over and independent assortment.
- DNA replication involves the separation of strands and synthesis of complementary nucleotides, with proofing mechanisms to ensure accuracy.
Summary of Meiosis
- Starts with diploid cells and results in haploid daughter cells through two meiotic divisions.
- Crossing over occurs in Prophase I, enhancing genetic variability.
- Meiosis contributes to the formation of gametes, which fuse to create a diploid zygote upon fertilization.
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