human cell bio test 2 part 2

why can different cell types perform different functions even though they contain the same DNA

Different genes are expressed in different cell types

The first step in signal transduction is

binding a signaling molecule to a receptor

Which process allows unspecialized stem cells to become specialized cell types such as neurons or muscle tissue

cellular differentiation

intracellular receptors typically bind

small molecules that can cross the membrane

what processes directly regulates gene expression at the transcriptional level in eukaryotes

Activation of transcription factors that bind DNA

A target cell will respond to a signal only if it

Has the appropriate receptor

paracrine signaling

signaling to nearby cells

endocrine signaling

long distance signaling through bloodstream

ligand

signaling molecule that binds a specific protein

receptor

protein that detects a signal

which of the following is a defining property of stem cells

ability to self renew and differentiate

Explain why cell signaling is essential in multicellular organisms

• cells must communicate to coordinate activities

• allows tissues and organs to function together

• regulates growth, development, and differentiation

• allows cells to respond to environmental changes

• coordinates processes such as immune response and homeostasis

describe two main types of receptors involved in signal transduction

Cell-surface receptors

• located in the plasma membrane

• bind large or hydrophilic signaling molecules

• activate signal transduction pathways

Intracellular receptors

• located inside the cell (cytoplasm or nucleus)

• bind small nonpolar molecules that cross membranes (steroid hormones)

• often directly regulate gene expression

which phase of the cell cycle involves dna replication

S phase

Cyclins and cyclin-dependent kinases regulate the cell cycle by

Acting as molecular switches that control cell cycle

Contact inhibition refers to

cells stopping division when they contact neighboring cells

The Hayflick limit refers to

Maximum number of times a cell can divide

Telomeres shorten during cell division because

DNA polymerase cannot fully replicate chromosome ends

necrosis differs from apoptosis because necrosis

causes inflammation

Normal cells stop dividing when they come in contact with neighboring cells. Explain how loss of this regulatory mechanism could contribute to tumor formation

• normal cells stop dividing when touching neighboring cells

• cancer cells ignore growth control signals

• cells continue dividing even when space is limited

• leads to overgrowth and tumor formation

Many cancer cells express telomerase, while most somatic cells do not. Explain how telomerase activity could allow cancer cells to divide indefinitely

• telomerase rebuild telomeres

• prevents telomere shortening

• allows cells to avoid the hayflick limit

• enabled unlimited cell division

apoptosis is often described as death by design. Explain why programmed cell death is importan for maintaining healthy tissues in multicellular organisms

• removes damaged or abnormal cells

• prevents mutation accumulation

• maintains tissue homeostasis

• essential for normal development

• helps prevent cancer formation

Both intrinsic and extrinsic pathways can trigger apoptosis. Explain how signals from inside the cell and signals from other cells can each lead to programmed cell death

intrinsic pathway

• triggered by internal damage (DNA damage, stress)

• often involves mitochondria

Extrinsic pathway

• triggered by external death signals

• activation of death receptors on the cell surface

Both lead to

• activation of caspases

• controlled cell death

Which charcateristic allows stem cells to maintain their population over time

self-renewel through repeated cell division

what best explains why most differentiated cells cannot regenerate tissues indefinitely

they stop expressing genes required for cell division

why are induced pluripotent stem cells (iPSCs) considered promising for medical therapies

They can be generated from a patients own cells

What best explains how signaling molecules influence cell differentiation during development

They activate different patterns of gene expression

Why might stem-cell therapies carry a risk of tumor formation

Stem cells divide rapidly and may proliferate uncontrollably

One major challenge in developing stem cell therapies is that transplanted stem cells must

integrate into tissues and differentiate into the correct cell type

totipotent

Can form an entire organism

Pluripotent

can produce all tissues of organism

Multipotent

limited to certain cell types within tissue

Differentiated

Specialized cell with defined functions

stem cells and differentiated cells contain the same DNA. Explain how stem cells can give rise to many different specialized cell types

• stem cells and specialized cells share the same genome

• differential gene expression

• activation/repression of different genes

• leads to different proteins and cell functions

induced pluripotent stem cells are created by reprogramming differentiated cells. explain one advantage and one potential risk of using iPSCs in medical treatments

advantage

• generated from patient’s own cells

• reduced immune rejection

• avoids ethical concerns of embryos

Risk

• may form tumors

• repramming may cause genetic instability

• may not fully differentiate correctly

Adult stem cells are usually limited to producing cell types from their tissue of origin. Explain why this limitation might affect their usefulness in regenerative medicine

• multipotent, not pluripotent

• limited to specific tissue types

• cannot regenerate all cell types

• restricts usefulness for whole-organ regeneration

Scientists must carefully control the environment when growing stem cells in the lab. Explain why signaling molecules and growth factors are important for directing stem cell differentiation

• provide developmental instructions

• activate specific gene expression pathways

• control cell fate decisions

• guide cells into specific lineages

Dolly the shepp was created using somatic cell nuclear transfer but developed health problems and died at a relatively young age. Explain one biological reason why cloned animals like dolly may experience premature aging or health issues

• donor nucleus came from an adult somatic cell

• cells had already undergone many divisions

• shortened telomeres

• possible incomplete epigenetic reprogramming

• may lead to health problems

Cancer is considered a genetic disease because

it is caused by DNA mutations affecting cell regulation

A tumor that spreads to other tissues to called

Malignant

Proto-oncogenes normally

Promote normal cell division

tumor suppressor genes normally

Inhibit cell division

Metastasis refers to

Spread of cancer cells to distant tissues

DNA repair genes help prevent cancer by

repairing damaged DNA

Proto-oncogenes normally help regulate cell growth. Explain how a mutation in a proto-oncogene can contribute to the development of cancer

• proto-oncogenes normally promote controlled cell growth

• mutation converts them into oncogenes

• causes excessive cell division

• loss of normal growth control —> tumor development

tumor suppressor genes are often compared to the brakes of the cell cycle. Explain how the loss of tumor suppressor gene function can lead to uncontrolled cell division

• tumor suppressors normally stop cell cycle

• detect DNA damage

• loss removes growth inhibition

• cells divide uncontrollably

cancer cells often display genomic instability meaning they accumulate mutations more rapidly then normal cells. Explain how defects in DNA repair genes could acclerate cancer development

• DNA damage not repaired properly

• mutations accumulate more rapidly

• increases the likelihood of oncogene activation or tumor suppressor loss

Metastasis is responsible for most cancer-related deaths. explain why the ability of cancer cells to invade other tissues makes cancer more difficult to treat

• Cancer spreads to multiple organs

• harder to remove surgically

• cancer cells travel via blood or lymph

• multiple tumors sites harder to eliminate

what best explains how carcinogens increase cancer risk

it prevents DNA replication

how can obesity increase the risk of certain cancers such as breast and uterine cancer

it alters hormone levels that can stimulate cell proliferation

HPV contributes to cancer by

inactivating p53 and Rb tumor suppressors

UV radiation damages DNA primarily by forming

pyrimidine dimers

why do individuals with weakened immune systems often have a higher risk of developing cancer

Their immune system is less able to detect and eliminate abnormal cells

Why do screening tests such as mammograms and colonoscopies reduce cancer mortality

They detect cancers earlier when treatment is more effective

BRCA1/BRCA2 gene 1

Inherited mutation increasing breast cancer risk

UV radiation

environmental radiation causing DNA damage

Smoking

Major preventable cause of lung cancer

HPV

Viral infection linked to cervical cancer

The immune system plays an important role in preventing cancer through a process called immunosurveillance. Explain how a weakened immune system could increase cancer risk

• reduced immunosurveillance

• immune cells fail to detect abnormal cells

• cancer cells escape destruction

Two individuals may carry the same inherited mutation associated with cancer risk but not both develop cancer. Explain why having a genetic predisposition does not guarantee that cancer will occur

• Cancer requires multiple mutations

• environmental factors also contribute

• lifestyle influences risk

• mutation may never occur in critical genes

Environmental chemicals such as BPA can act as endocrine disruptors. Explain how BPA exposure could increase cancer risk

• BPA acts as an endocrine disruptor

• mimics estrogen signaling

• can increase cell proliferation

• more cell division —> greater mutation risk

Why is breastfeeding associated with a decreased risk of breast cancer

it reduces lifetime exposure to estrogen and promotes breast cell differentiation

which treatment physically removes a tumor

surgery

radiation therapy kills cancer cells by

damaging DNA

A patient undergoing chemotherapy develops hairloss and gastrointestinal problems. What best explains these side effects

Chemotherapy damages rapidly dividing cells throughout the body

a tumor is found to contain a mutation that causes overexpression of the HER2 receptor. Which treatment strategy would most directly target this molecular abnormality

Antibody therapy designed to block HER2 signaling

A leukemia patient is diagnosed with BCR-ABL fusion gene. Why would a drug such as imatinib be effective

it blocks the abnormal kinase activity from produced by the fusion gene

CAR-T cell therapy involves modifying a patients immune cells before returning them to the body. What is the main goal of this modification

Allow T cells to specifically recognize tumor cells

A tumor initially responds well to chemotherapy but later begins growing again. What best explains this change

Some cancer cells survived treatment and evolved resistance

Traditional cancer treatments such as chemotherapy and radition are often described as non-specifc. Explain why these treatments affect both cancer cells and normal tissues

• target rapidly dividing cells

• cancer cells divide quickly

  • hair follicles

  • bone marrow

  • intestinal lining

• leads to side effects

Some cancers require molecular diagnostic testing before treatment decisions are made. Explain why identifying specific mutations in a tumor can help guide treatment selection

• identifies specific mutations

• allows use of targeted therapies

• ensures treatment matches tumor biology

• improves treatment effectiveness

cancer cells can sometimes evade immune detection. Explain one mechanism by which tumors avoid immune destruction and how immunotherapy attempts to overcome this problem

tumor evasion

• express PD-L1

• suppress immune response

• hide tumor antigens

immunotherapy

• checkpoint inhibitors

• activate T cells

• restore immune recognition of tumors

combination therapies (e.g., surgery + chemotherapy) are commonly used in cancer treatment. Explain why using multiple treatment strategies may improve patient outcomes

• targets cancer through multiple mechanisms

• reduces chance of drug resistance

• treats primary tumor and metastases

• improves overall treatment success