Bio-Cells +Genetics Remainder

What are kinetochores and where do they attach?

Kinetochores are protein complexes that form a plaque on the surface of the centromere. They attach sister chromatids to the spindle during mitosis.

How do kinetochores interact with spindle microtubules in animal cells?

In animal cells, each kinetochore binds 10-40 spindle microtubules. Kinetochore proteins bind to the sides of microtubules near their plus end, allowing for polymerization and depolymerization while maintaining attachment.

What is the significance of the dynamic nature of kinetochore-microtubule attachment?

The dynamic attachment (with low-affinity and labile bonds) allows the microtubules to polymerize and depolymerize while staying attached to the kinetochore, which helps in moving chromosomes during mitosis.

How do microtubules move chromosomes during mitosis?

Microtubules move chromosomes during mitosis by attaching to the kinetochores and undergoing polymerization and depolymerization, enabling the movement of chromosomes towards opposite poles of the cell.

What is the result of mitotic cell division?

The result of mitotic cell division is the formation of two genetically identical cells, each containing a full complement of chromosomes and half the cytoplasm and organelles of the parental cell.

What is the role of mitotic cell division in eukaryotes?

In eukaryotes, mitotic cell division proceeds through regulated stages to produce progeny cells with identical copies of nuclear DNA and half of the cytoplasmic content of the parental cell.

What is the function of kinetochores in mitosis?

Kinetochores attach sister chromatids to the spindle and help move chromosomes during mitosis by interacting with microtubules.

How do the bonds between kinetochore proteins and microtubules work?

The bonds between kinetochore proteins and microtubules are low-affinity and labile, meaning they break and reform, allowing the microtubules to polymerize and depolymerize during chromosome movement.

What does the term "sister chromatids" refer to in mitosis?

Sister chromatids are identical copies of a chromosome, connected by the centromere, which are separated during mitosis to ensure each daughter cell gets a full set of chromosomes.

What is the primary outcome of mitotic cell division for the daughter cells?

The primary outcome of mitotic cell division is the production of two genetically identical daughter cells with the same number of chromosomes as the parent cell.

What are the key steps in the regulation of cell replication in eukaryotes?

Cell replication in eukaryotes involves highly regulated stages to ensure that each progeny cell receives an identical copy of the nuclear DNA and appropriate division of cytoplasmic content.

How does the cytoplasm and organelles get distributed between daughter cells during mitosis?

During mitosis, half of the cytoplasm and organelles from the parental cell are distributed between the two daughter cells to maintain cellular function and structure.

What happens during the movement of chromosomes in mitosis?

Chromosomes are moved by microtubules attached to kinetochores, which polymerize and depolymerize to pull the chromosomes toward opposite poles of the cell.

What is the role of the spindle in mitosis?

The spindle is responsible for the physical separation of chromosomes during mitosis, connecting to the kinetochores on each sister chromatid and pulling them apart.

How does the kinetochore ensure accurate chromosome separation?

The kinetochore ensures accurate separation by attaching microtubules and regulating their polymerization and depolymerization, which moves chromosomes to the correct location in the daughter cells.

What is the structure of kinetochores?

Kinetochores are protein complexes that form a plaque on the centromere, which binds to microtubules for chromosome movement during mitosis.

How many microtubules do kinetochores typically bind in animal cells?

Kinetochores in animal cells typically bind 10-40 microtubules to help move chromosomes during mitosis.

What is the role of mitosis in cell replication?

Mitosis is the process that divides the nucleus of a cell, ensuring that genetic material is accurately copied and distributed into two identical daughter cells.

What is the end result of mitotic division in terms of genetic material?

The result of mitotic division is that the daughter cells receive identical copies of the genetic material (DNA) from the parent cell.

What is the significance of the centromere during mitosis?

The centromere is the region where the sister chromatids are joined, and it is the point where the kinetochores form to attach to microtubules during mitosis.

hat was Richard Peto's hypothesis in 1977 regarding large-bodied, long-lived animals and cancer risk?

Peto hypothesized that large-bodied, long-lived animals undergo more cell divisions, and with every division carrying a small risk of mutation, they should have a greater risk of cancer compared to small, short-lived animals.

What is the conclusion of Peto's hypothesis regarding cancer risk in large vs. small animals?

All else being equal, one would expect that large-bodied, long-lived animals would have a greater risk of cancer than small, short-lived animals.

What did Peto find when he investigated cancer incidence in large vs. small animals?

Peto found a lack of correlation between body size and cancer risk, contradicting his original hypothesis. This was referred to as Peto's Paradox.

What does Peto's Paradox suggest?

Peto's Paradox suggests that animals with 1,000 times more cells than humans do not exhibit an increased cancer risk, implying there are mechanisms that suppress cancer more effectively than in humans.

What is the take-home message from Peto's Paradox?

The take-home message is that strict control of the cell cycle is essential for cancer prevention, and large animals like elephants have evolved mechanisms to suppress cancer more effectively.

How do elephants avoid cancer despite their large size and long lifespan?

Elephants have 20 extra copies of the p53 tumor suppressor gene, which helps them suppress cancer more effectively than humans, who only have 1 copy of the gene.

What is the significance of the p53 gene in cancer prevention?

The p53 gene is a crucial tumor suppressor that plays a role in preventing cancer by controlling the cell cycle and inducing cell death in damaged cells. Having more copies of this gene enhances cancer protection.

How can humans protect their p53 gene?

Humans can protect their p53 gene through responsible lifestyle choices, as maintaining the integrity of this gene is crucial for lifelong cancer protection.

What is Peto’s Paradox and why is it important for understanding cancer risk?

Peto’s Paradox refers to the lack of correlation between body size and cancer risk, suggesting that larger animals have evolved mechanisms to suppress cancer more effectively, which challenges the assumption that more cell divisions lead to higher cancer risk.

What is the relationship between cell divisions and cancer risk according to Peto's Paradox?

According to Peto's Paradox, while more cell divisions theoretically increase the risk of mutations that can lead to cancer, larger animals with more cells don’t necessarily have a higher cancer risk due to mechanisms that suppress cancer more effectively.

How many copies of the p53 gene do elephants have?

Elephants have 20 extra copies of the p53 tumor suppressor gene.

How many copies of the p53 gene do humans have?

Humans have 1 copy of the p53 tumor suppressor gene

Why is the p53 tumor suppressor gene important in preventing cancer?

The p53 gene helps regulate the cell cycle and induces cell death in damaged cells, preventing the accumulation of mutations that could lead to cancer.

What did Peto’s Paradox reveal about cancer suppression in large animals?

Peto’s Paradox revealed that larger animals like elephants have evolved more effective cancer suppression mechanisms, such as additional copies of the p53 gene, which help them avoid cancer despite having many more cells.

What is the main conclusion of Peto’s Paradox?

The main conclusion is that larger animals do not necessarily have a higher cancer risk despite having more cells. Instead, they have evolved effective cancer-suppressing mechanisms, such as more copies of the p53 gene.

What could be the reason for the lack of correlation between body size and cancer risk?

The lack of correlation could be due to evolutionary mechanisms that protect large animals from cancer, such as additional copies of the p53 gene, which enhance their ability to suppress tumors.

Why is Peto’s Paradox important for cancer research?

Peto’s Paradox is important because it challenges assumptions about cancer risk based on body size and lifespan, highlighting the need for understanding the evolutionary mechanisms that protect certain species from cancer.

How does Peto’s Paradox inform our understanding of cancer in humans?

Peto’s Paradox suggests that humans could potentially protect their p53 gene and enhance their ability to prevent cancer through lifestyle choices that promote healthy cellular function.

How do mutations in the p53 gene affect cancer risk?

Mutations in the p53 gene can impair its function, reducing the cell’s ability to control the cell cycle and inducing cell death in damaged cells, which can increase the risk of cancer.

How does the presence of extra copies of the p53 gene in elephants contribute to cancer prevention?

The extra copies of the p53 gene in elephants provide enhanced tumor suppression capabilities, allowing them to detect and eliminate damaged cells more effectively than humans, reducing their cancer risk.