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Questions and Answers
What is the primary difference in chromosome pairing during mitosis compared to meiosis I?
What is the primary difference in chromosome pairing during mitosis compared to meiosis I?
At which stage does crossing over occur during meiosis?
At which stage does crossing over occur during meiosis?
What happens to the duplicated chromosome during the S phase of the cell cycle?
What happens to the duplicated chromosome during the S phase of the cell cycle?
How do chromosomes align during Metaphase I of meiosis compared to metaphase of mitosis?
How do chromosomes align during Metaphase I of meiosis compared to metaphase of mitosis?
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Which statement is true regarding the parent cell before the division process in mitosis and meiosis I?
Which statement is true regarding the parent cell before the division process in mitosis and meiosis I?
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What are sister chromatids primarily composed of?
What are sister chromatids primarily composed of?
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What characteristic defines a haploid cell?
What characteristic defines a haploid cell?
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During cell division, what is the role of the centromere?
During cell division, what is the role of the centromere?
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What is the end result of the separation of sister chromatids during cell division?
What is the end result of the separation of sister chromatids during cell division?
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What does a diploid cell contain?
What does a diploid cell contain?
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Which of these statements best describes the process of chromosome duplication?
Which of these statements best describes the process of chromosome duplication?
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What are chromatids related to during cell division?
What are chromatids related to during cell division?
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Why do eukaryotic cells have more complex chromosome structures than prokaryotic cells?
Why do eukaryotic cells have more complex chromosome structures than prokaryotic cells?
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What is the result of crossing over during meiosis?
What is the result of crossing over during meiosis?
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In which phase does chromosome duplication occur in the cell cycle?
In which phase does chromosome duplication occur in the cell cycle?
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How many times do sister chromatids separate during meiosis?
How many times do sister chromatids separate during meiosis?
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What is the end result of meiosis?
What is the end result of meiosis?
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What distinguishes homologous chromosomes?
What distinguishes homologous chromosomes?
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During which phase do homologous chromosomes line up at the metaphase plate in meiosis?
During which phase do homologous chromosomes line up at the metaphase plate in meiosis?
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What is mitosis primarily used for?
What is mitosis primarily used for?
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What occurs during anaphase I of meiosis?
What occurs during anaphase I of meiosis?
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What best describes the role of gametes in reproduction?
What best describes the role of gametes in reproduction?
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What is the main outcome of meiosis II?
What is the main outcome of meiosis II?
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During which phase of meiosis do sister chromatids separate?
During which phase of meiosis do sister chromatids separate?
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What structural feature is involved in the separation of sister chromatids?
What structural feature is involved in the separation of sister chromatids?
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In what phase do homologous chromosomes remain attached?
In what phase do homologous chromosomes remain attached?
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Which of the following correctly describes the cells produced at the end of meiosis I?
Which of the following correctly describes the cells produced at the end of meiosis I?
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What occurs during telophase II?
What occurs during telophase II?
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What essential event occurs in prophase I of meiosis?
What essential event occurs in prophase I of meiosis?
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How does meiosis II differ from meiosis I?
How does meiosis II differ from meiosis I?
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What happens during meiosis I?
What happens during meiosis I?
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What is the primary outcome of meiosis?
What is the primary outcome of meiosis?
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During which phase do homologous chromosomes exchange segments?
During which phase do homologous chromosomes exchange segments?
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What remains attached during anaphase I of meiosis?
What remains attached during anaphase I of meiosis?
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How many times do cells divide during meiosis?
How many times do cells divide during meiosis?
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What is the result of crossing over?
What is the result of crossing over?
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What do the four haploid cells produced at the end of meiosis contain?
What do the four haploid cells produced at the end of meiosis contain?
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What is the primary role of the receptor protein in the signal transduction pathway?
What is the primary role of the receptor protein in the signal transduction pathway?
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What characteristic differentiates malignant tumors from benign tumors?
What characteristic differentiates malignant tumors from benign tumors?
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What is a potential outcome of excessive cell division in cancer cells?
What is a potential outcome of excessive cell division in cancer cells?
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How many chromosomes are typically found in human somatic cells?
How many chromosomes are typically found in human somatic cells?
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What is a shared characteristic of homologous chromosomes?
What is a shared characteristic of homologous chromosomes?
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Study Notes
Cellular Basis of Reproduction and Inheritance
- Cell replication is a normal process for maintaining a healthy body.
- Mitosis allows for asexual reproduction, while meiosis permits sexual reproduction.
- Asexual reproduction involves a single parent, producing identical offspring.
- Sexual reproduction requires gametes from two parents, creating genetically diverse offspring.
- Errors in cell division can cause cancer, infertility, or genetic disorders in offspring.
Two Types of Cell Division
- Life begins as a single cell (zygote), formed by the union of an egg and sperm.
- Meiosis creates gametes (sperm and eggs) with half the number of chromosomes as the parent cell.
- Mitosis produces identical body cells for growth and repair.
Form of Chromosomes
- Chromosomes are located in the cell nucleus.
- Chromosomes are a tightly coiled combination of DNA and proteins (histones).
- DNA carries genetic information, directing development and maintenance.
- Histones support and control gene activity.
- Specific segments of DNA (genes) direct protein synthesis, impacting structure or function.
- Somatic cells (all cells except gametes in humans have 46 chromosomes, two sets of 23 chromosomes from the parents).
- Homologous chromosomes are chromosome pairs with genes for the same traits, one from each parent.
- A diploid cell has two sets of chromosomes.
- A haploid cell has one set of chromosomes (e.g., gametes).
- Sex chromosomes (X and Y) determine gender (XX = female, XY = male)
- Autosomes are the remaining 22 chromosome pairs involved in determining characteristics.
Principles of Inheritance
- Genetic information is carried in equal numbers in egg and sperm chromosomes.
- Homologous pairs of chromosomes pair up with the corresponding chromosomes from each parent.
- Each member of a homologous pair carries genes for the same traits.
- A trait is a characteristic produced by one or more gene-directed proteins.
- Alleles are different forms of the same gene, producing different versions of traits.
- Example trait: freckles are caused by one allele, while another allele doesn't cause them.
Mitosis and Meiosis
- Mitosis produces two identical diploid daughter cells from one parent cell.
- Meiosis produces four unique haploid daughter cells (gametes) from one parent cell, via two successive cell divisions.
- Meiosis involves pairing of homologous chromosomes and crossing over (exchange of genetic material), resulting in genetically unique daughter cells
Cytokinesis
- Cytokinesis is the cell division process that overlaps the end of mitosis. This phase differs for animal and plant cells.
- Animal cells divide via a cleavage furrow that pinches inward to separate parent cells.
- Plant cells form a membranous cell wall to divide parent cells.
Cell Cycle
- The cell cycle consists of interphase (G1, S, and G2 phases) and the mitotic phase.
- During G1 (first gap phase), the cell grows and carries out metabolic activities.
- During S (synthesis phase), the cell duplicates its DNA.
- During G2 (second gap phase), the cell continues growth and generates proteins necessary for mitosis.
- The M (mitosis) phase involves the segregation of sister chromatids, creating two identical daughter cells.
Environmental Factors Affecting Cell Division
- Most normal cells in lab cultures divide only when attached to a surface.
- Cell division stops when cells touch one another.
- Most animal cells divide when stimulated by growth factors, and some do not divide at all.
Growth Factors and Cell Cycle Control
- A set of inter-related proteins controls the cell cycle, influencing critical checkpoints.
- The binding of growth factors to specific receptors and their signal transduction pathways affect cell division.
Cancer
- Cancer cells divide excessively and form a mass (tumor).
- Malignant tumors can invade other tissues.
- Radiation and chemotherapy are effective cancer treatments as they interfere with cell division.
- Benign tumors are non-cancerous and are contained within the tissue.
- Malignant tumors are cancerous and can spread throughout the body.
Meiosis and Crossing Over
- In meiosis, chromosome duplication occurs prior to two successive cell divisions.
- In crossing over, homologous chromosomes exchange corresponding segments during prophase I.
- Sexual reproduction results in genetically unique offspring due to independent orientation of chromosomes and random fertilization.
Accidents during Meiosis
- Nondisjunction during meiosis results in abnormal chromosome numbers, either missing or extra chromosomes.
- Nondisjunction can affect both autosomes and sex chromosomes.
- Nondisjunction in sex chromosomes is less harmful than nondisjunction in other chromosomes.
Karyotype Preparation
- A karyotype is a photographic inventory of an individual's chromosomes.
- Karyotypes are prepared by isolating and culturing white blood cells, arresting them in metaphase for observation under a microscope, and photographing chromosomes showing their ordered pairs.
Trisomy 21 and Down Syndrome
- Trisomy 21, an extra copy of chromosome 21, can result in the development of Down syndrome.
- Down Syndrome: the most common chromosome abnormality, causing developmental and health effects that vary among individuals.
- Maternal age plays a role in the risk of trisomy 21.
Polyploidy
- Polyploidy involves organisms with extra sets of chromosomes, arising from nondisjunction which may lead to the evolution of new species.
Chromosome Structure Alterations
- Chromosomal rearrangements (deletions, duplications, inversions, and translocations) can cause genetic disorders or, if present in somatic cells, cancer.
- Several conditions result for errors regarding chromosome structure during cell divisions, including deletions, duplications, inversions and reciprocal translocations.
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