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Questions and Answers
What is the primary function of mitosis?
Which phase of mitosis involves the chromatin compacting and the formation of the mitotic spindle?
During which phase do chromosomes align at the center of the cell?
What occurs during anaphase?
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What happens during telophase?
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What is the role of cytokinesis in cell division?
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How does meiosis differ from mitosis?
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Which structures migrate to opposite ends of the cell during prophase?
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What is the primary purpose of cell division in multicellular organisms?
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What is the longest phase of the cell cycle?
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During which phase does the cell replicate its genetic material?
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What type of reproduction results in genetically identical offspring?
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Which of the following correctly describes binary fission?
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What occurs during the G1 and G2 phases of interphase?
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How are daughter cells produced during mitotic division?
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Which of the following statements about chromosomes is correct?
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What is the primary purpose of meiosis in terms of genetic information?
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What happens during meiosis I?
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Which phase of meiosis involves crossing-over?
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What is the genetic state of a gamete?
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When does meiosis begin in females?
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How does male meiosis differ from female meiosis?
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What does independent assortment during meiosis refer to?
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What is the outcome of meiosis II?
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What is the function of differentiation in cell division?
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Which type of cells is specifically reserved to produce gametes later in life?
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How many chromosomes are found in a normal human karyotype?
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What do homologous chromosomes refer to in eukaryotic cells?
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What role does genetic variation play in evolution?
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What are mutations primarily responsible for in organisms?
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What is the outcome of crossing-over during meiosis?
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Which statement about stem cells is true?
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Study Notes
Genetic Material
- Genetic material is organized into chromosomes, each containing a single DNA molecule.
- Each DNA double helix forms long strands of chromatin which compose chromosomes.
Cell Division
- Cell division is the process of generating daughter cells from a parent cell.
- Millions of cell divisions occur in our bodies daily to replace dead cells.
- The energy and matter from old cells are recycled during the division process.
Why Cells Divide
- Cell division is necessary for reproduction in all life forms and for growth and repair in multicellular organisms.
- Asexual reproduction results in offspring genetically identical to the parent.
- Sexual reproduction combines genetic information from two individuals to produce genetically similar but not identical offspring.
Binary Fission
- Binary Fission is a type of cell division used by many prokaryotes, including bacteria, for asexual reproduction .
- The process includes four steps:
- DNA is duplicated.
- The cell elongates and the DNA is separated.
- The cytoplasm is separated down the middle.
- Two daughter cells are created, replacing the original parent cell.
Cell Life Cycles
- The cell cycle refers to the life cycle of a eukaryotic cell from its origin to its division through mitosis or meiosis.
- A cell's life cycle is divided into two phases: interphase and cell division.
- During interphase, the cell prepares for division by increasing in size and producing proteins needed for division.
Interphase
- Interphase is the longest phase of the cell cycle, with cells spending approximately 90% of their lives in this stage.
- During interphase, the cell:
- Takes in nutrients.
- Grows in size.
- Manufactures proteins needed for division (G1 and G2).
- Replicates the genetic material needed for division (S).
Mitotic Division
- Mitotic division is the process in which eukaryotes generate two daughter cells from a single parent (asexual reproduction).
- Mitotic division is conventionally divided into five phases: prophase, metaphase, anaphase, telophase and cytokinesis.
- Prophase, metaphase, anaphase, and telophase are considered part of mitosis.
Mitotic Division: Main Role
- The main role of mitosis is to separate sister chromatids and distribute one of each chromosome into each of the daughter cells.
Early Prophase and Late Prophase
- During prophase, the cell prepares to divide its chromosomes:
- The chromatin (genetic material) becomes highly compacted.
- Parts of the cytoskeleton called centrosomes migrate to opposite ends of the cell.
- A structure called the mitotic spindle is formed in the center of the cell, connected to the two centrosomes on either side.
- The mitotic spindle is made of microtubules.
- The nuclear envelope breaks down.
Metaphase
- In metaphase, chromosomes are positioned at the center of the cell along the mitotic spindle.
- Chromosomes are ordered as evenly as possible for equal distribution to the two daughter cells during mitotic division.
Anaphase
- During anaphase, sister chromatids are separated and pulled to opposite ends of the cell by the progressive shortening of the spindle microtubules.
- Once separated, each chromatid is considered a new chromosome.
Telophase
- During telophase, the mitotic spindle breaks down, and nuclear envelopes begin to form around the two new sets of chromosomes at each end of the cell.
- Within each nucleus, the chromosomes decondense.
Cytokinesis
- Cytokinesis is a separate process that occurs at the end of mitotic division.
- Cytokinesis involves the separation of the cytoplasm from the parent cell into the two daughter cells.
- The two daughter cells each have their own genetically identical nuclei and surrounding cell structures.
Meiosis Division
- Meiosis is a specialized form of cell division necessary for the production of gametes (sex cells).
- Meiosis in female animals results in gametes that will mature into eggs.
- Meiosis in male animals produces gametes called sperm.
- Meiosis reduces the genetic information passed to daughter cells by half (n).
Meiosis One and Meiosis Two
- Meiosis occurs in two stages:
- Meiosis I sorts each member of a homologous pair into two different daughter cells, reducing the chromosome sets from 2n to n.
- Meiosis II separates sister chromatids in each cell produced by meiosis I into two different cells, forming four complete cells from the original parent.
Meiosis One: Prophase One
- During prophase I, DNA segments are swapped between nonsister chromatids in a process called crossing-over.
- Crossing-over is a random process where the number and location of crossovers can vary from one meiosis division to another (known as independent assortment).
Cell Fertilization
- Fertilization is the merging of a male and female gamete to produce a zygote.
- A gamete contains half the genetic information as a somatic cell.
Diploid vs Haploid
- The genetic information in a gamete is called a haploid set (n).
- Meiosis reduces the amount of genetic information transmitted by the parent cell to the daughter cells by half, so that only one set of genetic information is inherited by each daughter cell.
- The genetic information in a somatic cell (which is double the amount in a gamete) is called a diploid set (2n).
When Meiosis Begins: Females
- In females, meiosis begins while she is still a fetus.
- The cells begin to undergo meiosis but are put on hold until puberty.
- Once she reaches puberty, one cell resumes the process of meiosis in the ovaries monthly.
- One of the daughter cells produced differentiates into an egg cell (ova).
- This egg cell is either fertilized or reabsorbed into the uterine lining.
When Meiosis Begins: Males
- In males, meiosis begins during puberty when hormones signal the testes to begin producing haploid cells (sperm cells).
- Male meiosis occurs daily and continues into old age.
- Female meiosis dwindles by age 50.
Cell Division Functions
- Cells are specialized or differentiated to help the organism grow, maintain its structure and health, and reproduce within the human body.
- Differentiation allows daughter cells produced during binary fission, mitosis, and meiosis to perform specific functions (think skin cells vs. blood cells).
Cells’ Roles in the Human Life Cycle
- All genetic material present in a zygote remains present in the somatic cells of adults regardless of function.
- Germ line cells are reserved early in the growth of a zygote to be used later in life to produce gametes.
- Stem cells are found in adults and are unspecialized in order to grow, regenerate, and repair tissues in the human body.
Karyotypes
- Karyotypes display chromosomes in somatic cells.
- The 46 chromosomes in a human karyotype represent the 23 homologous pairs.
- The numbered chromosome pairs are non-sex-related chromosomes, while the XY pair is responsible for determining sex (male or female).
Eukaryotic Chromosomes
- Eukaryotes carry two copies of each type of chromosome, known as homologous chromosomes.
- Humans have 46 chromosomes, divided into 23 homologous pairs.
- Females typically have XX sex chromosomes, while males typically have XY sex chromosomes.
Genetic Variation
- Genetic variation is the natural differences in DNA sequences that exist between individuals of the same species.
- It's a key factor in evolution and the survival of species and can be caused by various factors.
- Meiosis and fertilization contribute to differences in organisms’ genetics.
Mutations and Alleles
- Mutations are the ultimate source of genetic variation in all types of organisms.
- A genetic mutation is a change in an organism's DNA sequence that can occur during cell division.
- Different variations of a particular gene created through mutations are called alleles.
Crossing-Over Causes Mutations
- Crossing-over during meiosis I creates new sets of alleles through the exchange of genetic material.
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Description
Explore the fascinating world of genetic material and cell division in this quiz. Learn about chromosomes, DNA structure, and the importance of cell division for growth, reproduction, and repair in living organisms. Test your knowledge on asexual and sexual reproduction, as well as the process of binary fission.
