24 Questions
What is the main purpose of meiosis?
To reduce the number of chromosomes in gametes
What is the chromosome composition of a diploid nucleus?
Two closely similar versions of each chromosome
Which cells result from meiosis?
Haploid gametes
What makes up the set of chromosomes in a sexually-reproducing organism?
Autosomes and sex chromosomes
What is the outcome of meiosis?
Production of four haploid cells
How many genetically different gametes are produced by each cell entering meiosis?
2n
What is the result of anaphase I in meiosis?
Separation of homologous chromosomes
Which phase of meiosis involves the alignment of homologous chromosomes on the metaphase plate?
Metaphase I
What is the key difference between the second meiotic division and mitosis?
The second meiotic division lacks DNA replication, while mitosis involves DNA replication.
What process leads to genetic variation during meiosis?
Random distribution of maternal and paternal chromosomes
What is the role of meiosis in gametogenesis?
Spermatogonia undergo meiosis to form spermatozoa, while oogenesis results in the formation of an ovum.
What can result from errors in meiosis?
A failure of homologous chromosomes or sister chromatids to separate
How many divisions does meiosis consist of?
Two divisions
What is the main outcome of meiosis?
Production of haploid gametes
What is the process called where homologous chromosomes exchange genetic material?
Crossing over
What structure facilitates the pairing of homologous chromosomes during meiosis?
Synaptonemal complex
Which stage of prophase I involves the formation of large recombination nodules?
Pachytene
What is the process by which DNA double helices are broken and exchanged between homologous chromosomes called?
Crossing over
What are chiasmata?
Points where non-sister chromatids are connected by a chiasma.
What happens to the synaptonemal complex during diplotene?
It disappears.
What happens at the end of prophase I?
The nuclear envelope disappears and the spindle forms.
What aligns on the metaphase plate for separation during metaphase I?
Bivalents (paired homologous chromosomes)
During which stage do homologous chromosomes begin to pair and synapsis occurs?
Zygotene
What is visible on the synaptonemal complex during pachytene?
Large recombination nodules
Study Notes
- Meiosis is a type of cell division that results in the production of haploid gametes.
- During prophase I of meiosis, homologous chromosomes pair up and exchange genetic material through a process called crossing over.
- The pairing of homologous chromosomes is facilitated by a structure called the synaptonemal complex, which keeps the chromosomes together.
- The prophase of meiosis I is a long process, lasting up to 40 years in females, and is divided into five stages: leptotene, zygotene, pachytene, diplotene, and dictyotene.
- During zygotene, homologous chromosomes begin to pair and synapsis occurs, with the formation of a synaptonemal complex.
- During pachytene, large recombination nodules are visible on the synaptonemal complex and exchange of chromatid segments occurs between non-sister chromatids.
- Crossing over is the process by which DNA double helices are broken and exchanged between homologous chromosomes to produce genetic diversity.
- Chiasmata are the points where non-sister chromatids are connected by a chiasma, which is the morphological expression of the genetic phenomenon of crossing over.
- During diplotene, the synaptonemal complex disappears and homologous chromosomes begin to separate, except at their chiasmata.
- At the end of prophase I, the nuclear envelope disappears and the spindle forms, and the bivalents (paired homologous chromosomes) align on the metaphase plate for separation during metaphase I.
Learn about the process of meiosis, a type of cell division that reduces the number of chromosomes in gametes in sexually reproducing organisms. Understand how meiosis leads to the formation of haploid cells like egg and sperm.
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