Cell Cycle
What are the main phases of the cell cycle?
G1, S, G2, and M phases
What are the stages of mitosis?
Prophase, Metaphase, Anaphase, Telophase
What is the overall purpose of meiosis?
"To produce haploid gametes with half the chromosome number"
What is the structure of a chromosome?
DNA wrapped around histone proteins forming chromatin.
Why is genetic variation important?
"It increases a population's ability to adapt and survive."
During which phase does DNA replication occur?
During the S (Synthesis) phase
What happens to the nuclear envelope during prophase?
"The nuclear envelope breaks down."
How many divisions are in meiosis?
"Two divisions: Meiosis I and Meiosis II"
What is a centromere?
The region where sister chromatids are joined.
Name one source of genetic variation during meiosis.
Crossing over
What checkpoints ensure proper cell cycle progression?
G1 checkpoint, G2 checkpoint, and M checkpoint
How do spindle fibers attach to chromosomes?
Via kinetochores at the centromere
What occurs during crossing over?
Homologous chromosomes exchange genetic material in prophase I.
What is the difference between homologous chromosomes and sister chromatids?
Homologous chromosomes are pairs from each parent; sister chromatids are identical copies joined at the centromere.
Name a second source of genetic variation during meiosis.
Independent assortment
What role does cyclin-dependent kinase (CDK) play in the cell cycle?
CDKs phosphorylate target proteins to regulate cell cycle transitions.
What ensures equal chromosome separation during mitosis?
The spindle assembly checkpoint prevents progression until all chromosomes are properly attached.
What is independent assortment?
Random alignment of homologous pairs during metaphase I leading to genetic variation.
Explain the role of telomeres.
Protect chromosome ends from degradation and prevent fusion.
How does random fertilization contribute to genetic variation?
"Any sperm can fuse with any egg, creating many possible genetic combinations."
Explain how external signals can influence the cell cycle.
Growth factors can stimulate progression; DNA damage can halt the cycle via p53.
Describe cytokinesis in animal cells.
A contractile ring forms, cleaving the cell into two daughter cells.
A cell with 2n = 8 experiences nondisjunction of one homologous pair during meiosis I. Assuming meiosis II is normal, what chromosome numbers result in the four gametes?
Two gametes have 5 chromosomes (n + 1), and two have 3 chromosomes (n − 1)
How do chromosome abnormalities lead to genetic disorders?
Deletions, duplications, or nondisjunction can cause disorders like Down syndrome.