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During the S phase of interphase, chromosomes replicate but remain ______.
During the S phase of interphase, chromosomes replicate but remain ______.
uncondensed
Homologous chromosomes come together during Prophase I in a process called ______.
Homologous chromosomes come together during Prophase I in a process called ______.
synapsis
Each tetrad has one or more ______ that hold homologs together.
Each tetrad has one or more ______ that hold homologs together.
chiasmata
In Anaphase I, homologous chromosomes are pulled toward opposite ______.
In Anaphase I, homologous chromosomes are pulled toward opposite ______.
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During Telophase II, the chromosomes ______ and uncoil.
During Telophase II, the chromosomes ______ and uncoil.
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During metaphase I of meiosis, homologous pairs of chromosomes orient randomly due to ______.
During metaphase I of meiosis, homologous pairs of chromosomes orient randomly due to ______.
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The number of combinations possible during independent assortment is determined by the formula 2n, where n is the ______ number.
The number of combinations possible during independent assortment is determined by the formula 2n, where n is the ______ number.
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Crossing over occurs during Prophase I and results in ______ chromosomes.
Crossing over occurs during Prophase I and results in ______ chromosomes.
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The likelihood of crossing over between two genes increases as the distance between those genes ______.
The likelihood of crossing over between two genes increases as the distance between those genes ______.
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The frequency of crossing over is measured in ______ units, which denote the distance between genes.
The frequency of crossing over is measured in ______ units, which denote the distance between genes.
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Somatic cells are any body cells other than a sperm or an ______.
Somatic cells are any body cells other than a sperm or an ______.
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Human somatic cells contain ______ chromosomes.
Human somatic cells contain ______ chromosomes.
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Gametocytes are reproductive cells, commonly known as ______ and egg.
Gametocytes are reproductive cells, commonly known as ______ and egg.
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Gametocytes are ______ cells, containing a single set of chromosomes.
Gametocytes are ______ cells, containing a single set of chromosomes.
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Human gametes contain ______ chromosomes.
Human gametes contain ______ chromosomes.
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Meiosis is a cell division process resulting in daughter cells with only half the ______ material of the original cell.
Meiosis is a cell division process resulting in daughter cells with only half the ______ material of the original cell.
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In plants, meiosis results in haploid ______.
In plants, meiosis results in haploid ______.
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The fused cell, known as a ______, is formed during fertilization.
The fused cell, known as a ______, is formed during fertilization.
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Each cell has a haploid set of ______ (unreplicated)
Each cell has a haploid set of ______ (unreplicated)
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Spermatogenesis occurs in the ______; begins at puberty.
Spermatogenesis occurs in the ______; begins at puberty.
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Oogenesis is the development of ______ in ovaries.
Oogenesis is the development of ______ in ovaries.
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Mitosis produces somatic cells which are ______.
Mitosis produces somatic cells which are ______.
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Meiosis produces gametes which are ______.
Meiosis produces gametes which are ______.
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In meiosis, independent assortment of ______ contributes to genetic variation.
In meiosis, independent assortment of ______ contributes to genetic variation.
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One mechanism contributing to genetic variation during meiosis is ______ over.
One mechanism contributing to genetic variation during meiosis is ______ over.
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The behavior of chromosomes during meiosis and ______ is responsible for variation.
The behavior of chromosomes during meiosis and ______ is responsible for variation.
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Polyploidy might be a desired trait in crops, ornamental plants because it leads to more robust plants with larger ______, fruits, and seeds.
Polyploidy might be a desired trait in crops, ornamental plants because it leads to more robust plants with larger ______, fruits, and seeds.
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The cultivated banana is believed to have been derived from a cross between a diploid species Musa acuminata and the ______ species M. balbisiana.
The cultivated banana is believed to have been derived from a cross between a diploid species Musa acuminata and the ______ species M. balbisiana.
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Chromosomal mutations contribute to variation, mostly undesirable changes in phenotype, especially if they result in the loss of function of ______ or DNA sequences.
Chromosomal mutations contribute to variation, mostly undesirable changes in phenotype, especially if they result in the loss of function of ______ or DNA sequences.
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The fly Drosophila mangabeirai has a unique reproductive method where one of the polar bodies acts as a sperm and 'fertilizes' the ______.
The fly Drosophila mangabeirai has a unique reproductive method where one of the polar bodies acts as a sperm and 'fertilizes' the ______.
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In bees, wasps, and ants, unfertilized haploid eggs develop into ______.
In bees, wasps, and ants, unfertilized haploid eggs develop into ______.
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Propagation of the cultivated banana occurs by dividing its ______ system.
Propagation of the cultivated banana occurs by dividing its ______ system.
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Grasshopper Pycnoscelus surinamensis forms a diploid egg by two ______ divisions.
Grasshopper Pycnoscelus surinamensis forms a diploid egg by two ______ divisions.
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Deletion, duplication, inversion, and translocation are types of chromosomal ______.
Deletion, duplication, inversion, and translocation are types of chromosomal ______.
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1 map unit = 1% ______ Frequency (crossover)
1 map unit = 1% ______ Frequency (crossover)
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Genes are 'linked' if RF% < ______%
Genes are 'linked' if RF% < ______%
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The fusion of two gametes produces a zygote with about ______ trillion diploid combinations.
The fusion of two gametes produces a zygote with about ______ trillion diploid combinations.
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Nondisjunction can lead to ______, which is an abnormal number of chromosomes.
Nondisjunction can lead to ______, which is an abnormal number of chromosomes.
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Turner’s Syndrome is an example of ______ due to nondisjunction.
Turner’s Syndrome is an example of ______ due to nondisjunction.
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Down Syndrome is also known as ______ 21.
Down Syndrome is also known as ______ 21.
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Most organisms are either diploid (2n) or ______ (n).
Most organisms are either diploid (2n) or ______ (n).
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Triploid organisms have ______ sets of chromosomes.
Triploid organisms have ______ sets of chromosomes.
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Study Notes
Meiosis
- Meiosis is a type of cell division that produces haploid cells (gametes or spores) from a diploid cell
- The process reduces the chromosome number by half, essential for sexual reproduction
- Meiosis involves two rounds of cell division (Meiosis I and Meiosis II)
- Interphase occurs before meiosis, including G1, S, and G2 phases, like mitosis, with DNA replication in S phase
Cell Types
- Somatic cells are any body cells other than sperm or egg, diploid (two sets of chromosomes), Humans have 46 chromosomes
- Gametes (sperm and egg) are reproductive cells, haploid (one set of chromosomes), Humans have 23 chromosomes
Meiosis Stages
-
Meiosis I involves separation of homologous chromosomes
- Prophase I: Chromatin condenses, homologous chromosomes pair up (synapsis), forming tetrads, crossing over occurs
- Metaphase I: Tetrads line up at the metaphase plate
- Anaphase I: Homologous chromosomes separate and move to opposite poles
- Telophase I and Cytokinesis: Chromosomes arrive at poles, cytoplasm divides, forming two haploid daughter cells.
-
Meiosis II involves separation of sister chromatids
- Prophase II: Chromosomes condense, nuclear envelope breaks down
- Metaphase II: Chromosomes line up at the metaphase plate
- Anaphase II: Sister chromatids separate and move to opposite poles
- Telophase II and Cytokinesis: Chromosomes arrive at poles, cytoplasm divides, forming four haploid daughter cells
Spermatogenesis
- Development of sperm in the testes, begins at puberty
- A series of stages leading to mature sperm, involving meiosis I and meiosis II
Oogenesis
- Development of oocytes (eggs) in the ovaries
- Oocytes begin forming before birth, remain in prophase I until female matures
- Only 1 ovum (egg) is formed, other products are polar bodies
- One egg is released per cycle
- Complete meiosis II only if fertilized
Mitosis vs Meiosis
| Feature | Mitosis | Meiosis |
|---|---|---|
| Location | All tissues | Only in testis/ovaries |
| Products | Somatic cells (diploid) | Gametes (haploid) |
| DNA replication | 1 | 1 |
| Cell division | 1 | 2 |
| Chromosome number | Same | Half |
| Genetic variation | No | Yes |
| Timing | Short | Can be months/years (depending on organism) |
Genetic Variation
- Mutations are the primary source of genetic diversity
- Three mechanisms contribute to genetic variation in meiosis:
- Independent assortment of chromosomes: Homologous pairs align randomly at metaphase I
- Crossing over: Non-sister chromatids exchange genetic material in prophase I
- Random fertilization: Any sperm can fuse with any egg, leading to unique combinations
Meiotic Errors
- Nondisjunction: Failure of homologous chromosomes or sister chromatids to separate during anaphase I or II
- Leads to aneuploidy (abnormal chromosome number), such as trisomy (extra chromosome) or monosomy (missing chromosome)
Polyploidy
- Triploid (3n) and tetraploid (4n) are possible, with more sets of chromosomes
- This can occur due to errors in cell division (extra DNA replication or lack of spindle formation)
- Can lead to reproductive isolation or new species formation
Chromosomal Mutations
- Deletion, duplication, inversion, translocation (rearrangement) of chromosome segments
- Usually not advantageous for organism survival due to loss of gene function or DNA sequences.
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Description
Explore the fascinating process of meiosis, a specialized type of cell division that leads to the formation of gametes. This quiz covers the key stages of meiosis, including Meiosis I and II, and presents information about somatic cells and their chromosomal differences. Test your understanding of how this essential process contributes to sexual reproduction.
