Mariam: meiosis & apoptosis Flashcards
What is meiosis?
A special type of cell division that occurs only in sex cells, producing four unique daughter cells with a haploid number (1n) of chromosomes.
Meiosis is crucial for sexual reproduction and genetic diversity.
What is the outcome of sexual reproduction?
The merging of genetic information from a father’s sperm cell and a mother’s ovum to produce a single cell called the zygote.
The zygote has a diploid number of chromosomes (2n).
What is the difference between haploid and diploid?
Haploid (1n) contains one set of chromosomes, while diploid (2n) contains two sets of chromosomes.
In humans, diploid cells have 46 chromosomes (23 pairs).
What are homologous chromosomes?
Chromosomes that are identical in size and shape, containing the same genetic content, with one set from each parent.
Exceptions exist for sex chromosomes (X and Y).
What is crossing over?
The phenomenon where chromosome segments are exchanged between non-sister chromatids during Pachytene of Prophase I.
This process increases genetic diversity.
List the five stages of Prophase I.
- Leptotene
- Zygotene
- Pachytene
- Diplotene
- Diakinesis
Each stage has distinct characteristics important for meiosis.
What happens during Metaphase I of meiosis?
Chromosomes line up along the cell equator in the form of tetrads.
In humans, there are 23 tetrads at this stage.
What is Anaphase I responsible for?
Separating tetrads into dyads, with no new chromosomes formed.
This contributes to genetic diversification.
What is produced at Telophase I?
Two haploid nuclei (1n) are formed, each containing half the number of chromosomes of the original cell.
This is different from mitosis, which produces diploid nuclei.
What are the stages of meiosis II?
- Prophase II
- Metaphase II
- Anaphase II
- Telophase II
Meiosis II resembles mitosis but produces haploid cells.
Define apoptosis.
A form of programmed cell death essential for maintaining cellular homeostasis and development in multicellular organisms.
It is regulated and prevents inflammation.
What are the key characteristics of apoptosis?
- Cell shrinkage
- Chromatin condensation
- Membrane blebbing
- Formation of apoptotic bodies
- DNA fragmentation
These features distinguish apoptosis from necrosis.
What are the two main pathways that trigger apoptosis?
- Intrinsic Pathway (Mitochondrial Pathway)
- Extrinsic Pathway (Death Receptor Pathway)
Both pathways lead to activation of caspases.
How does apoptosis contribute to development?
It shapes tissues by eliminating unnecessary cells, such as those between fingers and toes in an embryo.
This process is crucial for proper limb formation.
What disorders are associated with excessive apoptosis?
Degenerative diseases such as neurodegenerative disorders (e.g., Alzheimer’s, Parkinson’s).
Excessive cell death can lead to loss of function.
What can insufficient apoptosis lead to?
Cancer development, as damaged or mutated cells survive and proliferate.
This highlights the importance of apoptosis in tumor suppression.
Fill in the blank: Apoptosis is a _______ process that eliminates unwanted or damaged cells.
programmed
It is a critical aspect of cellular health.
