BIO 181 Exam 4

genome

A cell's entire amount of hereditary information is the...

Formation of a cleavage furrow

A cellular toxin that destroys actin will most directly affect which event of the cell cycle?

A zygote

A fertilized egg is also known as...

46 chromosomes or 23 pairs

A human somatic cell will contain how many chromosomes?

1. in the testis, a primary spermatocyte is in 2. DNA is replicated 3. synaptonemal complex forms, followed by crossing over 4. homologous chromosomes are pulled apart, two haploid daughter cells are formed 5. prophase II begins a second round of cell division 6. sister chromatids are separated into two new daughter cells 7. one of these daughter cells is the spermatid that will further differentiate into the mature sperm

A month or two before you were conceived, an individual sperm formed in your father's testis. Put the events in order for the formation of this sperm cell

damaged DNA sequences are not repaired.

A mutated copy of the tumor suppressor protein p53 can contribute to cancerous growth of the cell. Fundamentally, this is because...

True

A phenotypic ratio for the F1 generation that results from a testcross will be 1:1 if the unknown parent is heterozygote. (T/F)

recessive

An allele that is present but is not expressed is

cyclin protein

As part of its role in regulating the cell cycle, the levels of _________ fluctuate throughout the cell cycle.

the process of cell division in eukaryotes

Binary fission describes...

-kinetochore formation -adhesion of sister chromatids

Centromeres function in which cellular activity?

Cell-cycle length can vary greatly among cell types. The rate of cell division also responds to changes in environmental conditions. These variations in cell-cycle length suggest that the cell cycle is regulated and that regulation varies among cells and organisms.

Do all cell types grow (divide) at the same rate?

mutations in cell cycle regulators

Fundamentally, all cancers arise from...

there must be enough food for cells to grow

How are nutrient conditions a factor for the G1 checkpoint?

cells are only allowed to pass if they've receive social signals from other neighboring cells

How are social signals a factor for the G1 checkpoint?

regulatory proteins that can stop the cell cycle need to be turned off appropriately

How are tumor suppressors a factor for the G1 checkpoint?

Cancer cells, however, divide without growth factors. They are no longer subject to social control at the G1 checkpoint.

How do cancer cells defy social control?

Each chromosome is duplicated prior to mitosis. As mitosis starts, the chromosomes condense from long, thin filaments into tightly compacted structures that can be moved around the cell efficiently.

How do chromosomes morph during mitosis?

Kinetochore microtubules remain stationary during anaphase; they shorten because tubulin subunits of the microtubules are lost from their plus ends at the kinetochore. Dyneins and other kinetochore motor proteins are attached to the kinetochore's fibrous crown and "walk" toward the minus end of the spindle fiber. As the microtubule shortens and the detach-move-reattach cycle of the motor proteins repeats, the chromosome is pulled to one end of the mitotic spindle.

How do chromosomes move during mitosis?

Growth factors initiate cell division by triggering cyclin synthesis. Cyclin-Cdk complexes are activated, leading to activation of the S-phase proteins

How do growth factors initiate cell division?

Independent shuffling of maternal and paternal chromosomes and crossing over during meiosis I result in four gametes whose chromosome composition is different from that of the parent cells.

How do offspring produced by sexual reproduction have a chromosome makeup different from that of one another and from that of the parents?

The concentration of MPF cyclin increases during interphase, then peaks in M phase before decreasing again

How do the levels of cyclin protein fluctuate in the cell cycle?

Meiosis I is a continuous process with five distinct phases, each of which occurs twice as the parent cell progresses through meiosis I and then meiosis II.

How does Meiosis work?

Cytokinesis in animals, fungi, and slime molds occurs when a ring of actin filaments and myosin motors contracts inside the cell membrane, causing it to pinch inward in a cleavage furrow.

How does cytokinesis occur in animals?

Cytokinesis in plants occurs as vesicles are transported from the Golgi apparatus to the middle of the dividing cell. These vesicles fuse to form a cell plate.

How does cytokinesis occur in plant cells?

Homologous chromosomes line up in meiosis I and duplicated chromosomes line up in meiosis II.

How does metaphase in meiosis I and meiosis II differ?

In some human cancers a G1 cyclin is overproduced, permanently activating Cdk, which then continuously phosphorylates its target proteins. Either the presence of excessive growth factors or cyclin production in the absence of growth factors can cause cyclin overproduction. These types of defects can immortalize cells to produce cancer.

How does the cyclin protein contribute to cancer?

offspring produced during asexual reproduction are clones that are genetically identical to one another as well as to the parent.

How does the offspring of asexual differ from sexual reproduction?

Pairs of homologous chromosomes line up and separate during meiosis I independently, resulting in a variety of combinations of maternal and paternal chromosomes. Thus, each daughter cell gets a random assortment of maternal and paternal chromosomes and so of genes, which generates a great deal of genetic diversity in the subsequent gametes.

How does the process of randomly assorting chromosomes work?

cells must be large enough to split into two functional daughter cells

How is cell size a factor for the G1 checkpoint?

Thus, when cyclin concentrations are high, more MPF is active and the target proteins are phosphorylated, initiating mitosis.

How is mitosis initiated through the MPF?

Many other protein complexes are involved in regulating the cell cycle, either by holding cells in a particular stage or by stimulating their passage to the next stage.

How is protein involved in regulating the cell cycle?

It takes a cell about 24 hours to complete one cell cycle (G1 = 7-9 hours, S phase = 6-8 hours, and G2 phase = 4-5 hours)

How long is the cell cycle?

Although the F1 plants "selfed", they did not produce a clone of themselves genetically, because of the law of segregation - they fertilized each random haploid ovum with a random, haploid pollen

If Mendel's F1 plants self-fertilized to produce the F2 generation, why didn't each F2 offspring look identical to the F1 parent?

12

If a cell has 24 chromosomes and goes through meiosis, each daughter cell has how many chromosomes?

codominance

In ABO blood type, individuals can have AB blood type which is an example of

1/4

In a cross between pea plants that are heterozygote (Pp) for flower color, what is the probability that the offspring will be homozygous recessive?

The Golgi Apparatus

In plants, the cell plate structure is formed by fusion of vesicles originating from...

G0

Mature cells that rarely, if ever, divide (remain metabolically active but do not proliferate) are said to be in what stage of the cell cycle?

4 haploid daughter cells

Meiosis and cytokinesis result in the production of

flower reproduction and the male and female anatomy of flowers

Mendel's ground-breaking experiments in heredity would not have been possible without his clear understanding of

G1 or G2

Most of cell growth occurs during the ________ phase.

Double helix, nucleosomes, chromatin fiber

Order the levels of DNA compaction from lowest level of compaction to highest level of compaction.

The ability to form a mitotic spindle

Prokaryotic FtsZ and eukaryotic tubulin are evolutionarily related and have similar functions in the cell. One characteristic they do NOT share is...

Chromosomes in a seedless watermelon Somatic Cell: 33 Chromosomes in a Sperm Cell from normal diploid pollen: 11 Chromosomes in Egg Cell from a tetraploid watermelon 22

Seedless watermelons ( n= 11) are triploid . Triploidy results in meiotic failure, and thus, no seeds. Interestingly, they are themselves grown from seeds - the product of a diploid by tetraploid watermelon cross.

multiple copies of chromosomes in a single cell

Sometimes certain tissues in an animal will undergo repeated rounds of S phase without undergoing M phase. What do you predict is the result?

directing the formation of a septum that divides a cell.

The FtsZ protein is primarily involved in...

interphase

The cell spends most of its cell cycle in...

ensure all chromosomes have been replicated.

The most important role of the G2 checkpoint is to...

Growth, wound repair, and cellular reproduction

The production of somatic cells in mitosis are responsible for which three key events in multicellular eukaryotes?

sex-linked

Traits controlled by genes on the X chromosome are

Replication (chromosomes are copied) and partitioning of the copied chromosomes to the two daughter cells during M phase

What are 2 key events in the cell cycle?

Before mitosis, chromosomes replicate. Each of the two DNA helices in a replicated chromosome is called a chromatid. Sister chromatids are attached to each other at the centromere; they represent exact copies of the same genetic information.

What are chromatids?

chromosomes with the same genes at the same loci along their length.

What are homologous chromosomes?

small loops of prokaryotic DNA that are not essential for normal growth.

What are plasmids?

Early prophase, Late prophase, metaphase, anaphase, telophase

What are the five phases of meiosis?

Mitosis (M phase) is a continuous process with several subphases (prophase, prometaphase, metaphase, anaphase, telophase) that are named according to specific events.

What are the subphases of mitosis?

Karyokinesis (separation of chromosome copies) and Cytokinesis (physical splitting of cytoplasm into daughter cells)

What are the two phases of mitosis?

The meiotic and mitotic cell division mechanisms are linked tightly with the diploid and haploid phases of an organism's life cycle

What are these cell division mechanisms linked with?

Meiosis reduces the chromosome number of diploid organisms by half to produce haploid gametes (sperm and egg cells)

What does meiosis do?

the replicated chromosomes to split into two identical sets of unreplicated chromosomes, one for each daughter cell. It is at this point that sister chromatids become chromosomes!

What happens during anaphase in mitosis?

During synapsis in prophase I, the two pairs of sister chromatids are held tightly together by a network of proteins called the synaptonemal complex.

What happens during synapsis?

During the first half of meiosis, the chromosome number of the parental cell is reduced by half.

What happens during the first half of meiosis?

building blocks of DNA and of protein are accumulated. Organelles replicate and additional cytoplasm is made in preparation for cell division.

What happens during the gap phases?

Some cancerous cells possess defects that make the proteins required for cell growth, called oncogenes, active at all times. Other cancerous cells possess defects that prevent the proteins used for arresting cell growth, called tumor suppressors, from shutting down the cell cycle when necessary.

What happens in a defected cancerous cell?

During metaphase, the spindle fibers tug on the kinetochores of each chromatid to line up the replicated chromosomes in the middle of the cell. The imaginary plane formed by this lineup is called the metaphase plate.

What happens in the metaphase stage of mitosis?

Just before meiosis begins, each chromosome in the diploid parent cell is replicated. When replication is complete, each chromosome consists of two identical sister chromatids attached to each other at the centromere.

What happens to chromosomes before meiosis?

During mitosis, the two sister chromatids separate to form independent chromosomes, and one copy of each chromosome goes to each of the two daughter cells.

What happens with sister chromatids?

A cell-cycle checkpoint is a critical point in the cell cycle that is regulated. At each checkpoint, interactions between regulatory molecules determine whether a cell proceeds towards division.

What is a cell-cycle checkpoint?

In animal cells, the micro-tubule-organizing center is called a centrosome; it contains a pair of centrioles.

What is a centrosome?

Mitosis-promoting factor (MPF) is present in the cytoplasm of M-phase cells. MPF induces mitosis in all eukaryotes.

What is a mitosis-promoting factor and where is it found?

MPF is composed of two distinct polypeptide subunits: a cyclin and a protein kinase. The cyclin subunit functions as a regulatory protein, and the protein kinase is an enzyme that catalyzes the transfer of a phosphate group from ATP to a target protein.

What is a mitosis-promoting factor made of?

it occurs quickly, populates areas rapidly, and requires only one parent

What is an advantage of asexual reproduction?

Meiosis occurs only in specialized sex cells in the body; thus it is the basis of sexual reproduction and genetic inheritance

What is meiosis the basis of?

Meiosis is a division of the genetic material in the nucleus to produce daughter cells with one-half the amount of hereditary material found in the parent cell. It results in the production of gametes (eggs and sperm)

What is meiosis?

When cancer cells detach from the original tumor and invade other tissues

What is metastasis?

Mitosis is a division of the genetic material in the nucleus that produces daughter cells genetically identical to the parent cell

What is mitosis?

Cells of multicellular organisms respond to signals from other cells, so that cells divide only when their growth benefits the whole organism.

What is social control?

The MPF protein kinase is a cyclin-dependent kinase (Cdk)that is active only when bound to the cyclin subunit. Binding of the cyclin subunit to the Cdk subunit leads to dephosphorylation (removal of a phosphate group) of the latter to activate its kinase activity.

What is the MPF protein kinase?

The orderly sequence of events that occurs starting from the formation of a eukaryotic cell through the duplication of its chromosomes to the time it undergoes cell division

What is the cell cycle?

The key difference between the two processes is that homologs pair in meiosis, but do not in mitosis. Therefore, meiosis produces four daughter cells with half the genetic material of the parents, while mitosis produces two daughter cells that are genetically identical to the parent cells.

What is the difference between meiosis and mitosis?

5. Anaphase: During anaphase, centromeres split and sister chromatids are pulled by the spindle fibers toward opposite poles of the cell.

What is the fifth phase of mitosis?

1. Interphase: After chromosomereplication, each chromosome iscomposed of two sister chromatids.Centrosomes have replicated.

What is the first phase of mitosis?

4. Metaphase: Chromosomes complete migration to middle of cell.

What is the fourth phase of mitosis?

Proto-oncogenes are normal versions of positive cell cycle regulators.

What is the function of proto-oncogenes?

Eukaryotic chromosomes contain a long double helix of DNA wrapped around proteins (histones). The purpose of mitosis is to distribute this genetic material to the daughter cells during cell division

What is the genetic material of eukaryotic chromosomes and how does it relate to cell division?

Crossing over is a form of genetic recombination that increases the genetic variability of gametes produced by meiosis beyond that produced by random assortment of chromosomes.

What is the purpose of crossing over?

Fertilization restores the diploid number of chromosomes.

What is the purpose of fertilization?

Late in the G1 phase, This quality control checkpoint determines whether the cell will continue through the cycle and divide, or exit the cycle and enter an arrested G0 state.

What is the purpose of the G1 checkpoint?

The three cell cycle checkpoints prevent the division of cells that are damaged or that have other problems, and they prevent the growth of mature cells that should stay in the G0 state!

What is the purpose of the cell cycle checkpoints?

Cells stop growing here if chromosome replication has not proceeded properly or if DNA is damaged

What is the purpose of the checkpoint between the G2 and M phases?

Cell division ceases during metaphase if the chromosomes are not properly attached to the mitotic spindle. This critical mechanism prevents incorrect chromosome separation that could give daughter cells the wrong number of chromosomes.

What is the purpose of the checkpoint during the M phase?

Mitosis results in the division of replicated chromosomes and the formation of two daughter nuclei with identical chromosomes and genes

What is the result of mitosis?

2. Prophase: Chromosomes condense, and mitotic spindle begins to form.

What is the second phase of mitosis?

6. Telophase: The nuclear envelopes re-form, and the spindle apparatus disintegrates.

What is the sixth phase of mitosis?

3. Prometaphase: Nuclear envelope breaks down. Spindle fibers connect to chromosomes at centromeres/kinetochores.

What is the third phase of mitosis?

S phase

What phase does DNA replication occur?

Interphase

What phase is the only phase chromosome replication occurs in?

Normally, mammalian cell cultures will not grow unless growth factors are present. Cells release these polypeptides or small proteins to signal other cells to grow.

What role do growth factors play in social control?

Crossing over produces new combinations of alleles on the same chromosome, combinations that did not exist in each parent.

What role does crossing over play?

The recessive traits, such as white flowers, reappeared from parents that both had the dominant phenotype (purple).

What was the surprising thing that Mendel observed in the F2 generation of his hybridization experiments?

The G1 phase occurs before the S phase and the G2 phase occurs after the S phase and before mitosis

When do the gap phases in which no DNA synthesis occurs happen?

Cytokinesis typically occurs immediately after mitosis. During this process, the cytoplasm divides to form two daughter cells, each with its own nucleus and a complete set of organelles.

When does cytokinesis occur?

When two independent nuclei have formed

When is mitosis complete?

Most cancers are thought to arise from cells with defects in the G1 checkpoint!

Where are most cancers though to arise from?

G1, G2, and Metaphase

Where do cell-cycle checkpoints occur?

Crossing over can occur at many locations along the length of such synapsed homologs. Both sets of non-sister chromatids may undergo crossing over, resulting in the swapping of segments between maternal and paternal chromosomes

Where does crossing over occur?

A high density of cells

Which event is likely to inhibit cell division?

Mutuation, sexual reproduction, homologous crossover during prophase I, and independent assortment during metaphase I

Which events contribute to genetic diversity?

nucleotide, gene, chromosome, genome

Which is the correct order of structure from smallest to largest?

Sister chromatids

Which set of chromosomes is the most similar genetically? - Homologous chromosomes - The X and Y chromosome - Sister chromatids - A grandparent's chromosome 16 and the one which was passed down to his grandson

Tumor suppressor proteins prevent uncontrolled division.

Which statement correctly describes the function of tumor suppressor proteins?

Proto-oncogenes increase cell division and tumor suppressor genes decrease cell division.

Which statement describes the relationship of cancer control genes?

Compaction allows genomic DNA to fit inside the nucleus.

Why is genomic DNA in eukaryotic cells compacted?

Since the maternal and paternal gametes fuse, they must be produced as haploid cells by meiosis, or the ploidy number will double each generation

Why is meiosis a necessary component to eukaryote sex?

Genes A and B are likely to stay together, but they are more likely to become separated from gene C since a crossover is more likely to occur in the longer space between them.

You are engaged in a project to breed new color variants in snakes. A certain chromosome carries three genes that all affect pigmentation. Two of the genes, A and B are near each other on the chromosome, but gene C is further away. You are hoping to maintain the versions of the three genes from the maternal chromosome in some of the grandchildren. What would you predict for the behavior of these genes during crossover in meiosis?

"The schedule isn't strict, because there are several checkpoints that allow the cycle to pause until errors are corrected."

You are tutoring your kid sister on the cell cycle for her biology class. "So it's like a clock," she asks, "with each phase starting on schedule?"

"Cigarette smoke and ultraviolet rays damage DNA, sometimes mutating cell cycle regulatory genes. Then unregulated checkpoints lead to further mutations and faster growth."

You learned in class that cell cycle dysfunction is the basis of cancer. Your study buddy is confused. "I thought that smoking caused my grandfather's lung cancer, and too much sunshine caused my aunt's skin cancer. What do those have to do with the cell cycle?" How do you respond?

"We would have trouble separating sister chromatids in anaphase II."

Your discussion section is planning a performance art piece illustrating meiosis. Your friend suggests that each person should stand with their arms and legs in an "X" shape to represent a pair of sister chromatids .What is your response to this idea

"It doesn't undergo mitosis. Terminally differentiated cells like neurons do not further divide, and they are said to be in the G0 quiescent phase of the cell cycle."

Your lab partner is staring intently through the microscope at a zebrafish embryo, which has a long thin motor neuron lit up with Green Fluorescent Protein. "I don't get it," she says. "How could this possibly undergo mitosis? What stage of the cell cycle is this neuron in?" How do you respond?

a recipe book

Your study partner is trying to explain genetics to your four-year old brother. "A gene is like a recipe, and a trait is like the food made from the recipe." What would a chromosome be like?

prophase I

synapsis and crossing over occur in...

The mitotic spindle forms from a microtubule-organizing center. The spindle is made up of groups of microtubules called spindle fibers that attach to the chromosomes. This spindle is the structure that pulls the chromosomes to opposite ends of the parent cell later in mitosis.

what is a mitotic spindle?