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Questions and Answers
During meiosis, what is the direct consequence of crossing over?
During meiosis, what is the direct consequence of crossing over?
- It increases genetic variation by creating new combinations of alleles on each chromosome. (correct)
- It halves the chromosome number in daughter cells.
- It ensures the equal segregation of homologous chromosomes.
- It prevents independent assortment of chromosomes.
What event during meiosis is best explained by independent assortment?
What event during meiosis is best explained by independent assortment?
- The pairing of homologous chromosomes during prophase I.
- The separation of sister chromatids during anaphase II.
- The exchange of genetic material between homologous chromosomes during prophase I.
- The random alignment of homologous chromosome pairs during metaphase I. (correct)
An organism has a diploid number of 10. How many different combinations of chromosomes are possible in its sex cells due to independent assortment?
An organism has a diploid number of 10. How many different combinations of chromosomes are possible in its sex cells due to independent assortment?
- 1024
- 5
- 10
- 32 (correct)
Why does oogenesis in females result in only one viable egg cell, while spermatogenesis in males results in four?
Why does oogenesis in females result in only one viable egg cell, while spermatogenesis in males results in four?
What is the fate of the polar bodies formed during oogenesis?
What is the fate of the polar bodies formed during oogenesis?
What is the primary purpose of meiosis?
What is the primary purpose of meiosis?
During which phase of meiosis does crossing over occur?
During which phase of meiosis does crossing over occur?
What is the significance of the first meiotic division (Meiosis I)?
What is the significance of the first meiotic division (Meiosis I)?
If a diploid cell has 4 chromosomes, how many chromosomes will each daughter cell have after meiosis?
If a diploid cell has 4 chromosomes, how many chromosomes will each daughter cell have after meiosis?
What are the two processes in meiosis that create genetically varied sex cells?
What are the two processes in meiosis that create genetically varied sex cells?
What is the term for the structure formed when duplicated homologous chromosomes line up side by side during prophase I?
What is the term for the structure formed when duplicated homologous chromosomes line up side by side during prophase I?
During crossing over, what are the points of overlap where genetic information is exchanged between homologous chromosomes called?
During crossing over, what are the points of overlap where genetic information is exchanged between homologous chromosomes called?
How does Meiosis II differ from Meiosis I?
How does Meiosis II differ from Meiosis I?
Flashcards
Crossing Over
Crossing Over
The exchange of genetic material between homologous chromosomes, creating new combinations of genes.
Independent Assortment
Independent Assortment
The random alignment of homologous chromosome pairs during metaphase I of meiosis, leading to varied combinations of chromosomes in daughter cells.
2^n in Meiosis
2^n in Meiosis
Formula to calculate the number of chromosome combinations due to independent assortment. 'n' is the haploid number of chromosomes.
Sperm Production
Sperm Production
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Egg Production
Egg Production
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Goal of Meiosis
Goal of Meiosis
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Meiosis Outcome
Meiosis Outcome
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Meiosis I
Meiosis I
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Meiosis II
Meiosis II
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Genetic Variation in Meiosis
Genetic Variation in Meiosis
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When Crossing Over Occurs
When Crossing Over Occurs
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Synapsis
Synapsis
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Study Notes
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Meiosis' purpose centers around creating sex cells, namely sperm and eggs.
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Sex cells produced via meiosis contain half of the genetic material necessary for somatic cells.
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Meiosis ensures offspring possess genetic diversity.
Halving the Genetic Information
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Each chromosome comprises two sister chromatids at this stage.
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The first meiotic division of the Genetic Information
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Meiosis results in four sex cells, each containing a haploid number of chromosomes.
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During the first meiotic division, homologous chromosomes separate, differing from mitosis, where sister chromatids separate.
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The resulting two cells only contain (n) a haploid number of chromosomes. This is also known as reduction division.
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The resulting cells contain half the genetic information held in the parent cell after the first meiotic division.
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During the second meiotic division, sister chromatids are separated.
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The separation of sister chromatids is similar to mitosis.
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Only one chromatid remains in each sex cell after the second meiotic division.
Creating Genetic Variation
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The process of meiosis creates genetically diverse sex cells through:
- Crossing over
- Independent assortment
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Both crossing over and independent assortment occur in meiosis I.
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Crossing over occurs during prophase I after DNA replication; each homologous chromosome has two sister chromatids.
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Duplicated homologous chromosomes line up side by side in synapsis.
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A duplicated homologous chromosome pair, lined up side by side, is a tetrad.
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Homologous chromosomes that overlap during synapsis will break, exchange genetic information, and reform.
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Maternal information transfers to a paternal chromosome, and vice versa.
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The points of crossing over are called chiasmata.
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After crossing over, sister chromatids are no longer identical.
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Each chromatid carries both maternal and paternal DNA.
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Independent assortment refers to variable alignments of homologous chromosome pairs at the metaphase plate during metaphase I.
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To find the number of combinations from independent assortment, use 2^n.
- N is the haploid number of chromosomes.
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2^(n-1) is the number of metaphase alignments of homologous chromosomes.
Sex Cells
- Meiosis in males produces four viable sperm.
- Meiosis in females produces one viable egg.
- Only one egg is viable, as eggs need cytoplasm and organelles to support future development.
- The remaining three nuclei produced from meiosis in females are non-viable and called polar bodies.
- Polar bodies do not receive cytoplasm during meiosis and consequently degrade.
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