Genetics and Cell Biology Quiz

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Questions and Answers

What is the primary benefit of genetic recombination in populations?

It increases the number of mutations in a population.

It ensures that all offspring will have the same traits as their parents.

It enhances genetic diversity, aiding adaptation to environments. (correct)

It reduces competition among individuals for resources.

In Thomas Hunt Morgan's experiments with fruit flies, what was observed in the majority of the offspring when F1 flies were test crossed?

An even distribution of all phenotypes.

A mix of mutated and non-mutated traits.

A majority exhibiting the parental phenotype. (correct)

A predominance of non-parental phenotypes.

What defines genetic linkage?

Genes that have no effect on phenotypic traits.

Genes that are located on different chromosomes.

Genes that are located on the same chromosome and inherited as a unit. (correct)

Genes that are inherited independently of each other.

Which of the following describes the process of general recombination?

A method of genetic mixing that enhances genetic diversity of gametes. Signup and view all the answers

How does genetic diversity relate to natural selection?

Genetic diversity provides various traits for natural selection to act upon. Signup and view all the answers

What is one way in which oncogenes can be activated?

Control by an inappropriate promoter Signup and view all the answers

Which role does the tumor suppressor gene p53 play in the cell cycle?

Inhibits cell cycle progression in response to DNA damage Signup and view all the answers

What often initiates the transformation of a cell into a cancerous cell?

A combination of mutations and loss of tumor suppressor gene expression Signup and view all the answers

What is angiogenesis in the context of tumors?

The development of a tumor's vascular supply Signup and view all the answers

What must occur before a cell can successfully divide?

Full copies of the genome must be made Signup and view all the answers

How does the loss of tumor suppressor gene expression affect a cell?

It increases the likelihood of inappropriate cell division Signup and view all the answers

What emphasizes the significance of fidelity during genome duplication?

To maintain accurate genetic information Signup and view all the answers

What occurs during prophase?

Chromatin condenses into mitotic chromosomes. Signup and view all the answers

What is the function of kinetochores?

They bind microtubules from the spindle apparatus. Signup and view all the answers

Which of the following statements about the metaphase plate is true?

It lies halfway between the two centrosomes. Signup and view all the answers

What remains intact during prophase?

The nuclear membrane. Signup and view all the answers

What is the role of astral microtubules?

Radiate out from the spindle poles. Signup and view all the answers

What happens during prometaphase?

The nuclear membrane disintegrates. Signup and view all the answers

What is produced after the completion of meiosis II upon fertilization?

A second polar body Signup and view all the answers

What is a key event in metaphase?

The lining up of chromosomes at the metaphase plate. Signup and view all the answers

What triggers the acrosomal reaction in sperm during fertilization?

Binding to the zona pellucida Signup and view all the answers

What is the primary function of cortical granules in fertilization?

To prevent polyspermy Signup and view all the answers

What checkpoint is located within M phase?

Spindle attachment checkpoint. Signup and view all the answers

What is a major change seen in prophase compared to earlier stages of the cell cycle?

Condensation of chromatin. Signup and view all the answers

Why is polyspermy a problem in fertilization?

It results in too many chromosomes Signup and view all the answers

What happens to the pronuclei after sperm enters the egg?

They remain separate until the first mitotic division Signup and view all the answers

What provides a centriole during fertilization?

The sperm Signup and view all the answers

What occurs as soon as the first sperm penetrates the egg?

A wave of calcium crosses the cell Signup and view all the answers

Which process is responsible for the degeneration of the zona pellucida once the first sperm enters the egg?

Cortical reaction Signup and view all the answers

What is formed after the nuclear envelope breaks down following the entry of the sperm's haploid nucleus?

A zygote Signup and view all the answers

What major event signifies that fertilization is complete?

First mitotic division Signup and view all the answers

What is formed when mitosis occurs without cytokinesis?

Syncytium Signup and view all the answers

During fertilization in Drosophila, how many nuclear divisions occur without cytokinesis?

13 Signup and view all the answers

What structure do plant cells use to separate into daughter cells during cytokinesis?

Cell plate Signup and view all the answers

What is the process called by which individuals with beneficial traits become more fit for survival?

Natural selection Signup and view all the answers

Mutations in genetic code can result in which of the following outcomes?

Beneficial, detrimental, inconsequential, or lethal Signup and view all the answers

How does E.coli maintain a relatively low mutation rate?

Through DNA polymerases that accurately replicate the genetic code Signup and view all the answers

What is the mutation rate in E.coli approximately equal to?

1 in 1 billion nucleotides Signup and view all the answers

What effect do mutations have on the lineage of a cell?

They are inherited by the cell’s lineage Signup and view all the answers

What can be a source of mutations in DNA?

Replication mistakes, DNA damage, and repair Signup and view all the answers

What happens to the cell plate during plant cytokinesis?

It is enveloped by a plasma membrane and grows to separate cells Signup and view all the answers

Study Notes

Module 4 Summary

Cells commit to division after reaching the S phase checkpoint (G1-S transition).
Mitosis creates a second nucleus, and cytokinesis produces the second cell.
Interphase and M-phase are crucial parts of the cell cycle.
The G2 checkpoint (G2-M transition) ensures quality control.
Early insight into cell cycle regulation came from cell fusion experiments, demonstrating that cells in S-phase trigger replication in cells in G1 phase, and cells in M-phase trigger mitosis in cells in G1 phase, despite the latter not having fully copied its genome.
Cytoplasmic factors (cyclins) peak at specific cell cycle phases and activate cyclin-dependent kinases (Cdks).
The active cyclin-Cdk complex orchestrates events through phosphorylation of targeted proteins within the cell cycle.
G1/S cyclins commit cells to S-phase, while S cyclins initiate DNA replication and M cyclins manage mitosis.
A fourth cyclin, G1 cyclin, facilitates G1 checkpoint progression but isn't always present in all cells.
Cyclin concentration control is primarily achieved by selective proteolytic destruction, which is assisted by ubiquitinoylation and proteosomal degradation.
M-cyclins accumulate during S and G2 phases, forming MPF.
MPF's activity peaks in metaphase, driving mitosis.
The G2 checkpoint is essential as M-cyclin degradation ceases MPF activity, passing the cell into G1 phase. The degradation of cyclin continues and the Cdk component of MPF is recycled.
Cells commit to cell division via external signals—growth factors (like PDGF for fibroblasts).
Cells are anchorage-dependent, needing a substrate for growth and division.
Cells exhibit density-dependent inhibition, stopping division when a monolayer is reached.
Cancer cells often lack anchorage and density-dependent inhibition, enabling uncontrolled proliferation.
Oncogenes are the genes mutated that cause inappropriate cell growth. Ras relays growth factor signals to the nucleus. Proto-oncogenes are the normal genes involved in positive growth signals.
Tumor suppressor genes help with negative growth signals. p53 halts cell replication during DNA damage.
A single mutation rarely causes cancer; several mutations likely occur for cancerous transformation.
Cells that replicate DNA require two copies (one for the parent, and one for the daughter cell).
Semi-conservative replication involves separating parental strands and synthesizing a complementary daughter strand for each.
In 1958, Meselson and Stahl's experiment validated semi-conservative replication.
Prokaryotic DNA replication initiates at an origin of replication, forming a replication bubble or fork, and proceeding in both directions.
Bacterial replication is theta replication because of its shape.
Residents of the replication fork include helicase, which separates parental strands, topoisomerase, which relieves tension, and single-strand binding proteins.
The G2 checkpoint ensures all prerequisites are completed before the cell cycle moves into the next phase.
The G2 checkpoint assures the cell is ready to enter M-phase.
M-Cdk functions to break down the nuclear lamina (phosphorylating lamin), condense chromatin, and form the mitotic spindle.
The nuclear lamina contains lamin (structural protein).
M-Cdk activity results in the nuclear membrane fragmentation.
Chromatin condensation is the preparation of chromatin into chromosomes.
The main event in prophase is the condensation of interphase chromatin.
Prometaphase is the phase during which the nuclear membrane disintegrates and microtubules from the centrosomes attach to the chromosomes.
The kinetochore is a protein plaque forming on the chromosomes' centromeres, where microtubules stably attach.
Kinetochore microtubules help move chromosomes towards the poles. During metaphase, chromosomes align on the metaphase plate.
Spindle attachment checkpoint checks if all the kinetochores are attached to microtubules before proceeding to anaphase to prevent genetic chaos.
The anaphase promoting complex (APC) is a proteolytic complex that drives the metaphase-anaphase transition.
Anaphase A moves chromosomes toward the poles and anaphase B separates the poles.
During telophase, the chromosomes decondense, the nuclear envelope reforms, and cytokinesis begins.
Cytokinesis in animals involves a contractile ring made of actin and myosin to create a cleavage furrow. In plants, a cell plate forms, separating the two daughter cells.
Once a cell divides, it enters G1. The activity of M-Cdk is reduced by M-cyclin degradation via APC, which prevents continued cell cycle activity in mitosis without cytokinesis.
When mitosis is not followed by cytokinesis, a multi-nucleated cell (syncytium) is formed. This process is seen in Drosophila fruit flies following fertilization.
Plant cytokinesis forms a cell plate that grows by adding cellulose microfibrils.
Mutations in DNA can alter the genetic code, leading to various outcomes ranging from neutral effects to deleterious consequences, including lethality. DNA Polymerase proofreads DNA during replication.
Mutation rates are relatively fixed across organisms; however, DNA repair mechanisms greatly reduce these rates.
Spontaneous DNA damage types include depurination (loss of a purine base) and deamination (changing a base).
Pyrimidine dimers are created by UV light and hinder DNA replication.
Repair mechanisms, such as base excision repair and nucleotide excision repair, correct these lesions.
Various chromosomal alterations (deletion, duplication, inversion, reciprocal translocation) can affect chromosome structure or lead to disease.
Translocation in cancer cells can lead to unregulated growth, exemplified by the Philadelphia chromosome.
Cells display immortality in the laboratory, like HeLa cells, due to telomerase expression.

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Description

Test your knowledge on genetic recombination, linkage, and cell cycle regulation. This quiz covers key concepts related to Thomas Hunt Morgan's experiments, oncogenes, and tumor suppressor genes. Challenge yourself to understand how these elements contribute to genetic diversity and cancer development.