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Questions and Answers
What is the main difference between benign and malignant tumors?
What is the main difference between benign and malignant tumors?
Malignant tumors are classified as stage IV when they have only spread to nearby tissue.
Malignant tumors are classified as stage IV when they have only spread to nearby tissue.
False
What role does telomerase play in cancer cells?
What role does telomerase play in cancer cells?
Telomerase allows cancer cells to synthesize new telomeres, preventing cell aging.
Cancer cells can send signals to surrounding cells to carry out __________ for space propagation.
Cancer cells can send signals to surrounding cells to carry out __________ for space propagation.
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Match the treatment with its description:
Match the treatment with its description:
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What is the primary function of telomeres in eukaryotic chromosomes?
What is the primary function of telomeres in eukaryotic chromosomes?
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Eukaryotic DNA replication occurs at a rate of 200 nucleotides per second.
Eukaryotic DNA replication occurs at a rate of 200 nucleotides per second.
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Name one type of DNA polymerase found in eukaryotic cells.
Name one type of DNA polymerase found in eukaryotic cells.
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Eukaryotic chromosomes are __________ in shape, whereas prokaryotic chromosomes are __________.
Eukaryotic chromosomes are __________ in shape, whereas prokaryotic chromosomes are __________.
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Match the following terms with their definitions:
Match the following terms with their definitions:
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Which of the following is true about yeast regarding DNA replication?
Which of the following is true about yeast regarding DNA replication?
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What type of mutation results in an individual having an error in chromosome number?
What type of mutation results in an individual having an error in chromosome number?
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What does '21p3' represent in chromosome nomenclature?
What does '21p3' represent in chromosome nomenclature?
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A karyotype is used to identify the number and appearance of chromosomes.
A karyotype is used to identify the number and appearance of chromosomes.
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The lagging strand in DNA replication is synthesized continuously.
The lagging strand in DNA replication is synthesized continuously.
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What happens if a mutation occurs in a gamete?
What happens if a mutation occurs in a gamete?
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An individual with one less or one extra chromosome is termed __________.
An individual with one less or one extra chromosome is termed __________.
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Match the following types of chromosomal mutations with their descriptions:
Match the following types of chromosomal mutations with their descriptions:
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What is the role of telomerase in cells?
What is the role of telomerase in cells?
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What is the most common viable birth involving trisomy?
What is the most common viable birth involving trisomy?
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Euploid individuals have an incorrect number of chromosomes.
Euploid individuals have an incorrect number of chromosomes.
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All somatic cells can activate telomerase to maintain their telomeres.
All somatic cells can activate telomerase to maintain their telomeres.
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What is Cytogenetics?
What is Cytogenetics?
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What is a mutation?
What is a mutation?
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During DNA replication, DNA Polymerase can make mistakes, and if these mistakes are not corrected, they become __________.
During DNA replication, DNA Polymerase can make mistakes, and if these mistakes are not corrected, they become __________.
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Which of the following is true regarding cancer cells?
Which of the following is true regarding cancer cells?
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Spontaneous mutations are always harmful to the organism.
Spontaneous mutations are always harmful to the organism.
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What happens during the G2 checkpoint?
What happens during the G2 checkpoint?
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Which condition is characterized by short stature, stunned digits, and a large tongue?
Which condition is characterized by short stature, stunned digits, and a large tongue?
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Polyploidy occurs more frequently in animals than in plants.
Polyploidy occurs more frequently in animals than in plants.
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What is the structure formed when an X chromosome is inactivated in female mammalian embryos?
What is the structure formed when an X chromosome is inactivated in female mammalian embryos?
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Individuals with Turner syndrome typically have ___________ X chromosomes.
Individuals with Turner syndrome typically have ___________ X chromosomes.
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Match the chromosomal inversion types with their descriptions:
Match the chromosomal inversion types with their descriptions:
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What is a potential consequence of non-disjunction of sex chromosomes?
What is a potential consequence of non-disjunction of sex chromosomes?
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Humans have 48 chromosomes, the same as chimpanzees.
Humans have 48 chromosomes, the same as chimpanzees.
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What is one type of chromosomal inversion that changes the relative lengths of chromosome arms?
What is one type of chromosomal inversion that changes the relative lengths of chromosome arms?
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What is an inversion heterozygote?
What is an inversion heterozygote?
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Translocation involves the removal of a chromosome segment and its reattachment to the same chromosome.
Translocation involves the removal of a chromosome segment and its reattachment to the same chromosome.
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What are the potential consequences of a translocation?
What are the potential consequences of a translocation?
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An exchange of chromosome segments between two chromosomes that results in no gain or loss of genetic information is known as a _____.
An exchange of chromosome segments between two chromosomes that results in no gain or loss of genetic information is known as a _____.
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Match the following concepts with their descriptions:
Match the following concepts with their descriptions:
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Study Notes
DNA Replication
- Eukaryotic genomes are larger than prokaryotic genomes, with 6 billion base pairs, while prokaryotes have fewer.
- Eukaryotes have 100,000 origins of replication, whereas prokaryotes have a single origin.
- The rate of replication is 100 nucleotides per second in eukaryotes, but far faster in prokaryotes (1000 nucleotides/second).
- DNA replication involves 14 DNA polymerases in eukaryotes, while prokaryotes have different types.
Eukaryotic Replication
- DNA is bound to histones to form nucleosomes.
- Chromatin, the complex of DNA and proteins, undergoes chemical modifications, allowing DNA to be accessible to replication machinery.
- A pre-replication complex with initiator proteins forms at the origin of replication.
- Additional proteins are recruited to initiate the replication process.
Prokaryote vs Eukaryote Replication
| Property | Prokaryotes | Eukaryotes |
|---|---|---|
| Origin of replication | Single | Multiple |
| Rate of replication | 1000 nucleotides/s | 50 to 100 nucleotides/s |
| DNA polymerase types | 5 | 14 |
| Telomerase | Not present | Present |
| RNA primer removal | DNA pol I | RNase H |
| Strand elongation | DNA pol III | Pol δ, pol ε |
| Sliding clamp | Sliding clamp | PCNA |
Telomeres
- Eukaryotic chromosomes are linear, unlike prokaryotic chromosomes which are circular.
- DNA polymerase can only add nucleotides in a 5' to 3' direction.
- Leading strand synthesis continues to the end of the chromosome.
- Lagging strand synthesis requires short stretches of DNA with primers, which cannot be synthesized at the end of the chromosome.
- The ends of chromosomes, called telomeres, have repetitive sequences that protect genes from deletion during cell division.
Chromosome Anatomy
- Chromosome arms project from the centromere.
- Short arms are designated "p" and long arms are designated "q."
- Chromosome locations are specified with a locus/loci.
- Example: 21p3 is locus 3 on the short arm of chromosome 21.
Telomerase
- Telomerase is an enzyme with a catalytic component and an RNA template.
- It attaches to the end of the chromosome and adds complementary bases to the RNA template on the 3' end of the DNA strand.
- Telomerase can add nucleotides needed to replicate the chromosome ends.
- It is active in germ cells and adult stem cells, but not somatic cells.
Aging
- Somatic cells generally do not have telomerase, and thus telomeres shorten with each cell division.
- This shortening of telomeres may contribute to aging.
- Age-related diseases are associated with decreasing telomerase activity.
- Cancer cells often have active telomerase and thus do not exhibit telomere shortening.
Mutations
- Mutations are permanent changes in DNA.
- Mutations can occur during DNA replication.
- Some mutations are silent (no effect) or beneficial (positive effect on fitness), but others can be detrimental or lead to death.
- Mistakes in the process of replication are often temporary, but if not corrected, they can become permanent.
- Mutations in repair genes can lead to cancer.
Spontaneous Mutations
- Spontaneous mutations occur naturally within the body.
- They result from DNA polymerase adding the wrong nitrogenous base pair during replication.
- Most mistakes are corrected, but if they aren't, the mutation becomes permanent and can be passed to offspring through reproduction.
Spotting the Mistake
- DNA polymerase III proofreads the newly added base.
- If an incorrect base is detected, DNA polymerase II makes a cut, releases the incorrect nucleotide, and repairs the error via nucleotide excision repair.
- The cell also verifies proper chromosome duplication during the G2 checkpoint.
- Mismatch repair corrects errors after replication is completed.
Induced Mutations
- Induced mutations occur when an organism interacts with the environment.
- Mutagens, physical or chemical agents, can cause mutations.
- Examples include radiation (gamma, X-ray, ultraviolet), radio waves, gas (e.g., from smoking), liquids (contaminated water), and solids (pesticides).
Effects of Mutations
- Mutations are not always harmful. Many are neutral.
- Some mutations can be beneficial for an organism, increasing its fitness (e.g., adaptation).
- Detrimental mutations can cause death or lower fitness.
- Mutations increase genetic diversity, driving the process of evolution.
Cancer
- Mutations in repair genes can lead to cancer.
- Mutations in tumor suppressor genes can lead to uncontrolled cell division.
- Tumor suppressor genes like Rb, p53, and p21 are crucial for preventing uncontrollable cell division.
Tumors
- A tumor is a swelling of body tissue due to abnormal growth.
- Benign tumors grow slowly and do not invade surrounding tissue.
- Malignant tumors grow rapidly and invade surrounding tissue via apoptosis.
- Metastasis occurs when tumors migrate to other body parts.
- Cancer stages 0-IV describe the extent and spread of the disease.
Cause of Death
- Rapid cell division leads to shortened telomeres in normal cells.
- Cancer cells have telomerase, which maintains telomere length.
- This allows cancer cells to divide without shortening telomeres, causing disruption of organ function.
- Treatment involves surgery, radiation, chemotherapy, or gene therapy.
Inheritance
- Somatic mutations do not pass to offspring.
- Germline mutations in gamete cells can be inherited.
- Inherited mutations can increase the risk of certain diseases if the environment is similar.
Chromosomal Mutations Overview
- Chromosomes are categorized as autosomes and sex chromosomes.
- Chromosome disorders include abnormalities in chromosome number (aneuploidy, polyploidy) or structural rearrangements (inversion, translocation).
Identification of Chromosomes
- Cytogenetics involves isolating and observing chromosomes for abnormalities.
- A karyotype is a chart that displays chromosomes based on length, banding pattern, and centromere position.
Abnormal Chromosome Numbers
- Non-disjunction is the failure of chromosome pairs to separate during cell division.
- Aneuploidy is the presence of an abnormal number of chromosomes (e.g., monosomy, trisomy).
- Polyploidy involves having extra chromosome sets
Sex Chromosome Non-Disjunction
- Polyploidy can result from abnormal egg or sperm fertilization.
- X-inactivation is the process where one X chromosome is inactivated in females early in development.
Chromosomal Inversions
- Chromosome inversion: a segment of a chromosome is detached, rotated 180 degrees, and inserted back.
- Pericentric inversions include the centromere.
- Paracentric inversions do not include the centromere.
Translocation
- Translocation: a segment of a chromosome is removed and reattaches to another location.
- It can be reciprocal or non-reciprocal.
- If the fragments are the same size, there is no change in genetic material.
- Translocations can be benign or cause devastating effects due to gene positioning effects.
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Description
Test your knowledge on the critical concepts of cancer biology, including differences between benign and malignant tumors, the role of telomerase, and DNA replication in eukaryotic cells. This quiz also covers chromosome structure and the implications of mutations.
