Chapter 8: The Cellular Basis of Reproduction and Inheritance Cell Cycle & Mitosis/Meiosis
Prophase (Mitosis)
-In the cytoplasm: microtubules begin to emerge from centrosomes, forming the mitotic spindle -In the nucleus: chromosomes coil and become compact, nucleoli disappear
Fragile X Syndrome
-Individuals exhibit a range of developmental problems including delayed speech and language development, some degree of intellectual disability, and various features from the autism spectrum -Mutations in the FMR1 gene on the X chromosome result from an excessive number of ''CGG'' repeats (duplication)
Cat's Cry Syndrome (Cri-du-chat)
-Infant's cry is high-pitched, like that of a cat, due to incomplete development of larynx -Disorder characterized by intellectual disability, delayed development, smaller head size, low birth weight, weak muscle tone -Results from a deletion of part of chromosome 5
Cancer Treatments
-Localized tumors can be removed surgically and/or treated with concentrated beams of high-energy radiation -Chemotherapy is used for metastatic tumors -Personalizing cancer treatments- depends on characteristics of individual cancers; look for mutations in specific genes
Anaphase (Mitosis)
-Sister chromatids separate at centromeres -Daughter chromosomes are moved to opposite poles of cell as motor proteins move chromosomes along spindle microtubules and kinetochore microtubules shorten -Cell elongates due to lengthening nonkinetochore microtubules
Prometaphase (Mitosis)
-Spindle microtubules reach chromosomes where they attach at kinetochores on the centromeres of sister chromatids and move chromosomes to the center of the cell through associated protein motors -Other microtubules meet those from the opposite poles -Nuclear envelope disappears
Cell Cycle Control System
A cycling set of molecules in the cell that triggers and coordinates key events in the cell cycle -Checkpoints in the cycle can stop an event or signal and event to proceed -G1 checkpoint and G2 checkpoint
Homologous Chromosomes
Matched in: length, centromere position, gene locations -Separation of them during meiosis can lead to genetic differences between gametes -May have different versions of a gene at the same locus -One version was inherited from the maternal parent and the other came from the paternal parent
· If it weren't for _____, chromosome number would double with every generation of sexual reproduction
Meiosis
What must happen before a cell can begin mitosis?
The chromosome must be duplicated
A cell replicates its entire chromosomal DNA only _____
Before it is about to divide
· Which of the following conditions would prevent cell division due to density-dependent factors?
Being completely surrounded by other cells
A ____ is a lump of abnormal cells that, although growing out of control, remain at its original site
Benign Tumor
Plant Cells (Cytokinesis)
1. A cell plate forms in the middle, from vesicles containing cell wall material 2. Cell plate grows outward to reach the edges, dividing the contents into two cells 3. Each cell now possesses a plasma membrane and cell wall
Animal Cells (Cytokinesis)
1. A cleavage furrow forms from a contracting ring of microfilaments, interacting with myosin and 2. Cleavage furrow deepens to separate the contents into two cells
Human Chromosomes
23 pairs -1 pair of sex chromosomes (X, Y) -22 pairs of autosomes -One member of each homologous pair is from each parent
Tumor
Abnormally growing mass of body cells -Benign tumors remain at original site -Malignant tombs spread to other locations, called metastasis
Nondisjunction
Accident during meiosis -Failure of chromosomes or chromatids to separate normally during meiosis -Fertilization after this yields zygotes with altered numbers of chromosomes
G1 Checkpoint
Allows entry into the S phase or causes the cell to leave the cycle, entering a non dividing G0 phase
Karyotype
An ordered display of magnified images of an individuals chromosomes arranged in pairs -Produced from divide cells arrested at metaphase of mitosis and allow for the observation of homologous chromosome pairs, chromosome number and structure
Centromeres divide and sister chromatids become full-fledged chromosomes during ___
Anaphase
· The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?
Anaphase
Homologous chromosomes migrate to opposite poles during
Anaphase I
During ____ sister chromatids separate
Anaphase II
Eukaryotic Chromosomes
Are composed of chromatin consisting of one long DNA molecule and proteins that help maintain the chromosome structure and control the activity of its genes
Asexual and sexual reproduction differ in that sexual reproduction ______
Can produce great variation among offspring
An individual with a malignant tumor is said to have ______
Cancer
· In the laboratory, cancer cells fail to show density-dependent inhibition of growth in cell culture. What is one explanation that could account for this?
Cancer cells continuously secrete growth factors into the cell culture medium
The most common type of cancer is a _____; this type always originates in tissues that line the organs
Carcinoma
Telophase (Mitosis)
Cell continues to elongate, nuclear envelope forms around chromosomes at each pole, establishing daughter nuclei, chromatin uncoils and nucleoli reappear, spindle disappears
Meiosis
Converts diploid nuclei to haploid nuclei GERM CELLS
· At the end of the mitotic (M) phase, the cytoplasm divides in a process called ___
Cytokinesis
Cytokinesis (Mitosis)
Cytoplasm is divided into separate cells -Process differs in animal and plant cells
Interphase (Mitosis)
Cytoplasmic contents double, two centrosomes form, chromosomes duplicate in the nucleus during the S phase, nucleoli (sites of ribosome assembly) are visible
Fertilization joins _____ to produce a ______
Haploid gametes... diploid zygote
Mitotic Phase (Cell Cycle)
Division -Mitosis- division of the nucleus -Cytokinesis- division of cytoplasm
Interphase (Cell Cycle)
Duplication of cell contents -G1- growth, increase in cytoplasm -S- duplication of chromosomes -G2- growth, preparation for division
New Species can Arise From Errors in Cell Division
Errors may produce a polypoid species, with more than two chromosome sets -Formation of polypoid species is widely observed in many plant species but less frequently found in animals
Cell Division Controls
Essential nutrients, growth factors, anchorage dependence, density-dependent inhibition
You can determine this is a plant cell rather than an animal cell because it has ______
Formed a cell plate
Meiosis II typically produces ___ cells, each of which is _____
Four... haploid
· When examining cells in the laboratory, you notice that a particular cell has half as much DNA as the surrounding cells. It appears that this cell's cell cycle halted at checkpoint __
G1
In a healthy body cell division allows for
Growth, the replacement of damaged cells and development from an embryo into an adult
Place the events of meiosis in proper order
Homologous chromosomes pair up -> nonsister chromatids form chiasmata -> crossing over occurs -> homologous chromosomes separate -> sister chromatids separate -> four haploid gametes are produced
During anaphase I ______
Homologous chromosomes separate and migrate toward opposite poles
Nucleoli are present during
Interphase
· A fragment of chromosome 21 reattaches to chromosome 21, but in the reverse direction. What is the name given to this change?
Inversion
Cell Division
Is reproduction at the cellular level, requires duplication of chromosomes, and sorts new sets of chromosomes into the resulting pair of daughter cells -Used for: reproduction of single-celled organisms, growth of multicellular organisms from a fertilized egg into an adult, repair and replacement of cells, and gamete production
· During binary fission, each copy of the duplicating chromosome moves to opposite ends of the cell. What does this achieve?
It ensures that each daughter cell receives one copy of the chromosome
A _____ is an abnormally growing mass of cells that is actively spreading throughout the body
Malignant Tumor
The chromosomes line up in the center of the cell during which phase of mitosis?
Metaphase
· During ____ chromosomes align single file along the equator of a haploid cell
Metaphase II
· Looking through a light microscope at a cell undergoing division, you see that the condensed chromosomes have lined up along the midline of the cell. The homologous pairs are NOT joined in tetrads. Each chromosome takes its own place in line, independent of its homolog. You are witnessing ______
Metaphase of mitosis
· Which of the following is a correct representation of an event that occurs during mitosis
Metaphase- chromosomes line up on the equatorial plane
____ is the spread of cancer cells from their site of origin to other sites in the body
Metastasis
In sexually reproducing organisms eggs and sperm result from
Mitosis and meiosis
Metaphase (Mitosis)
Mitotic spindle fully formed, chromosomes align at cell equator, kinetochores of sister chromatids are facing the opposite poles of the spindle
Eukaryotic Cells
More complex and larger than prokaryotic cells, more genes, and store most of their genes on multiple chromosomes within the nucleus
Chronic Myelogenous Leukemia
Most common type of leukemia -Affects cells that give rise to white blood cells and results from part of chromosome 22 switching places with a small fragment from a tip of chromosome 9
Duplication of the chromosomes to produce sister chromatids _____
Occurs in both mitosis and meiosis
Haploid Cells
One set of chromosomes
Cell Cycle (Eukaryotes)
Ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell until its own division -Two Stages: Interphase and Mitotic Phase
Asexual Reproduction
Produces offspring that are identical to the original cell or organism, involves inheritance of all genes from one parent
Sexual Reproduction
Produces offspring that are similar to the parents, but show variations in traits and involves inheritance of unique sets of genes from two parents
Mitosis
Progresses through a series of stages -Prophase, pro metaphase, metaphase, anaphase, telophase -Cytokinesis often overlaps telophase SOMATIC CELLS
Spindle fibers attach to kinetochores during
Prometaphase
Chromosomes become visible during ___
Prophase
· The centrosomes move away from each other and the nuclear envelope breaks up during which phase of mitosis?
Prophase
Synapsis occurs during _____
Prophase I
During _____ a spindle forms in a haploid cell
Prophase II
Which process lead to most genetic variation in sexually reproducing organisms?
Random fertilization, crossing over, independent orientation of chromosomes in meiosis
One version of a gene may encode ____, whereas a different version of the same gene may encode ____
Red eyes; white eyes
Prokaryotes
Reproduce by binary fission (''dividing in half'') -The chromosome of it is a singular circular DNA molecule, associated with proteins and is much smaller than those of eukaryotes
Genetic Variation
Results from: 1. Genetic recombination during prophase I- produces new combinations of genes due to crossing over 2. Independent orientation at metaphase I 3. Random Fertilization- the combination of each unique sperm with each unique egg increases genetic variability
During anaphase II ______
Sister chromatids separate and migrate towards opposite poles
An example of a cell that is 2n is a _____
Somatic Cell
Mitosis occurs in ______; Meiosis occurs in _______
Somatic or body cells.... germ cells in the testes or ovaries
Cancer Cells
Start out as normal body cells, undergo genetic mutations, lose the ability to control the tempo of their own division, reproduce uncontrollably, eventually causing the disease
Cytokinesis often, but not always, accompanies
Telophase
· The chromosomes arrive at the poles and nuclear envelopes form during which phase of mitosis?
Telophase
· At the end of ____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids
Telophase I
· At the end of ____ and cytokinesis there are four haploid cells
Telophase II
· Within one chromosome, what is the relationship between the sequence of bases in DNA of one sister chromatid compared to the other?
The sequences are identical
During mitosis, the chromosomes move because
They attach to a dynamic, precisely regulated mitotic spindle
Extra Chromosomes
Trisomy 21 (Down syndrome)- produces a characteristic set of symptoms which include mental retardation, characteristic facial features, short stature, heart defects, susceptibility to respiratory infections, leukemia, and Alzheimer's disease, and shortened life span -Incidence increases with the age of the mother
During prophase a homologous pair of chromosomes consists of ___
Two chromosomes and four chromatids
· At the end of telophase I of meiosis, as cytokinesis occurs, there are ____
Two haploid cells
Diploid Cells
Two homologous sets of chromosomes
Meiosis I produces ____ cells, each of which is ____
Two... haploid
Crossing over of chromosomes during meiosis shuffles parental chromosomes, resulting in a genetically unique child. Select three true statements about crossing over.
o During meiosis II sister chromatids separate into four different gametes, a hybrid chromosome that has crossed over will contain pieces of both the maternal and paternal chromosomes, during prophase I of meiosis I homologous parental and maternal chromosomes pair up and undergo crossing over