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