Chapters 11, 12: How Cells reproduce and Meiosis and Sexual Reproduction

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G1 phase

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Normal function of cells and growth occurs

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S Phase

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Synthesis phase of the cell cycle where cell duplicates its DNA

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51 Terms

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G1 phase

Normal function of cells and growth occurs

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S Phase

Synthesis phase of the cell cycle where cell duplicates its DNA

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G2 Phase

Second growth phase during the cell cycle where proteins are created for the mitosis process

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Prophase:

DNA condenses into chromosomes and nucleus breaks down; spindle fibers also start to attach and centrioles double in animals

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Metaphase:

Spindle fibers attach to centrosomes; sister chromatids are aligned at the equator

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Anaphase:

Sister chromatids separate and spindle fibers shorten to pull the chromatids apart

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Telophase:

DNA becomes chromatin and nucleus forms back; spindle fibers break down and centrioles become one per cell

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Cell Cycle

Series of events from the time a cell forms until its cytoplasm divides

Steps:

Interphase
Prophase
Metaphase
Anaphase
Telophase and cytokinesis

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Asexual reproduction

Reproductive mode of eukaryotes where offspring comes from a single parent only

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Mitosis

Nuclear division mechanism that maintains the chromosome number

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Cytokinesis

Division of the cytoplasm of the two new cells

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Cleavage furrow

The indentation where cytokinesis occurs in a dividing animal cell

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Cell plate

A disk-shaped structure that forms during cytokinesis in a plant cell; matures as a cross-wall between the two new nuclei

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Centrioles

Barrel-shaped cell organelle that aids in cell division in animal cells only

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Spindle Fibers

Temporary structures that move chromosomes during nuclear division; made of microtubules

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Telomeres and their importance in DNA

Noncoding DNA sequences that occur in the end of eukaryotic chromosomes; protects the coding sequences from degradation.

They protect the DNA from being cut out during DNA replication (due to the way the lagging strands are formed) in mitosis

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Tumor

Neoplasm that forms a lump of cancer cells

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Cancer

Disease that occurs when a malignant neoplasm physically and metabolically disrupts body tissues.

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Proto-oncogene

Genes that promote mitosis that can become oncogenes if mutated

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Oncogene

Genes that helps transform a normal cell into a tumor cell

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Checkpoint genes

Code for proteins that monitor mitosis and the condition of the cell during the cell cycle; they are also known as tumor-suppressors because in their absence, tumors form

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Master genes

Gene encoding a product that affects the expression of many other genes

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Homeotic Gene

Type of master gene; its expression controls formation of specific body parts during development.

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Neoplasm

An accumulation of abnormally dividing cells

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Carcinoma

Cancer that forms in the epithelial tissue that lines most of our bodies' organs

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How do normal cells becomes cancerous cells?

They can become cancerous if carcinogens such as radiation, chemicals, viruses, or mutations infect the cells. Once the oncogenes are activated and the tumor-suppressor cells stop working, the cells uncontrollably divide and become cancerous.

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Sexual reproduction

Reproductive mode by which offspring arise from two parents and inherit genes from both.

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Gametes

Mature, haploid reproductive cell such as an egg or sperm

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Meiosis

Nuclear division process that halves the chromosome number. Basis of sexual reproduction.

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Haploid

having one of each type of chromosome (n)

Ex: gametes

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Diploid

Containing two complete sets of chromosomes, one from each parent.

Ex: fertilized zygote, somatic cells

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Crossing over

Process by which homologous chromosomes exchange corresponding segments of DNA during prophase I of meiosis; helps in genetic variation of gametes

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Oogenesis

the production, growth, and maturation of an egg, or ovum

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Spermatogenesis

the production of sperm cells

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Autosomes

Any chromosome that is not a sex chromosome

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Sex chromosomes

Chromosomes that determine the gender of an individual

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Mitosis vs. Meiosis

Mitosis: one division forming 2 identical somatic cells;
Meiosis: two divisions forming 4 genetically different gametes

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Formation of sperm vs egg

In sperm, the cytoplasm is equally distributed and all four sperm are viable for fertilization

In egg production, the cytoplasm is unequally distributed and only one egg is viable (the rest become reabsorbed polar bodies)

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How does meiosis contribute to genetic variation?

  1. Crossing over of sections of parent's homologous chromosomes in prophase 1 allow for varied and mixed chromosomes in gametes

  2. Chromosome segregation (random stacking) of homologous chromosomes in metaphase 1 allows for gametes to have different combination of the mom and dad's chromosomes

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Homologous Chromosomes

Chromosomes with the same length, shape, and genes

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Zygote

Cell formed by fusion of two gametes at fertilization and is the first cell of the new individual

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Germ cells

Reproductive cell that gives rise to haploid gametes when it divides

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Somatic Cells

Any cells in the body other than reproductive cells

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Prophase I

  • DNA forms into homologous chromosomes stacked randomly (chromosome segregation)
  • Nucleus and nucleolus breaks down
  • Spindle fibers attaching to homologous chromosomes
  • centrioles in animals double
  • crossing over occurs between homologous chromosomes and tetrad forms
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Metaphase I

  • Homologous chromosomes are lined up in the middle and spindle fibers attach to individual homologous chromosomes at their centromeres
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Anaphase I

Homologous chromosomes are pulled to opposite ends of the cell.

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Telophase I

-2 haploid daughter cells form and nucleus and nucleolus reforms

  • Spindle fibers break down
  • Centrioles become 1 per cell in animals
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Prophase II

Haploid chromatin condenses into chromosomes and nucleus breaks down; spindle fibers also start to attach and centrioles double in animals

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Metaphase II

Spindle fibers attach to centrosomes; sister chromatids are aligned at the equator

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Anaphase II

Sister chromatids separate and spindle fibers shorten to pull the chromatids apart

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Telophase II

DNA becomes chromatin and nucleus forms back; spindle fibers break down and centrioles become one per cell; Each of the two daughter cells create two new daughter cells (4 daughter cells total)