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Questions and Answers
During meiosis I, what is the significance of crossing-over?
During meiosis I, what is the significance of crossing-over?
- It ensures that each daughter cell receives the correct number of chromosomes.
- It prevents the formation of tetrads during prophase I.
- It increases genetic variation by exchanging genetic material between homologous chromosomes. (correct)
- It halts the process of meiosis if there are any genetic defects.
Which of the following statements accurately compares mitosis and meiosis?
Which of the following statements accurately compares mitosis and meiosis?
- Mitosis occurs only after sexual maturity, while meiosis takes place throughout an organism's life.
- Mitosis involves one cell division, while meiosis involves two cell divisions, resulting in half the number of chromosomes as the parent cell. (correct)
- Mitosis results in four genetically identical daughter cells, while meiosis results in two genetically different daughter cells.
- Mitosis occurs in germ cells for sexual reproduction, while meiosis occurs in somatic cells for growth and repair.
What is the primary difference between spermatogenesis and oogenesis in terms of gamete production?
What is the primary difference between spermatogenesis and oogenesis in terms of gamete production?
- Spermatogenesis produces one functional sperm cell from each germ cell, whereas oogenesis produces four functional egg cells.
- Spermatogenesis occurs in the ovaries, while oogenesis occurs in the testes.
- Spermatogenesis produces millions of sperm cells throughout a male's life, while oogenesis produces a fixed number of eggs, with typically one mature egg per monthly cycle. (correct)
- Spermatogenesis begins during fetal development, while oogenesis starts at puberty.
During oogenesis, meiosis II is arrested at metaphase until what event occurs?
During oogenesis, meiosis II is arrested at metaphase until what event occurs?
How did Gregor Mendel's choice of pea plants contribute to his success in studying heredity?
How did Gregor Mendel's choice of pea plants contribute to his success in studying heredity?
What is the significance of homologous chromosomes in the context of heredity?
What is the significance of homologous chromosomes in the context of heredity?
According to Mendel's Law of Segregation, what process occurs during gamete formation?
According to Mendel's Law of Segregation, what process occurs during gamete formation?
How does the Law of Independent Assortment contribute to genetic diversity?
How does the Law of Independent Assortment contribute to genetic diversity?
In genetics, what is the purpose of using Punnett squares?
In genetics, what is the purpose of using Punnett squares?
What two occurrences lead to genetic recombination?
What two occurrences lead to genetic recombination?
In the context of gene linkage, how does the proximity of genes on a chromosome affect their inheritance?
In the context of gene linkage, how does the proximity of genes on a chromosome affect their inheritance?
What phenomenon is represented by the term polyploidy, and why is it often lethal in humans?
What phenomenon is represented by the term polyploidy, and why is it often lethal in humans?
Why is chromosome replication essential before cell division?
Why is chromosome replication essential before cell division?
What is the role of the centromere in chromosome replication?
What is the role of the centromere in chromosome replication?
How do dominant alleles mask recessive alleles in heterozygous individuals, according to Mendel's Law of Dominance?
How do dominant alleles mask recessive alleles in heterozygous individuals, according to Mendel's Law of Dominance?
Flashcards
Chromosome Replication
Chromosome Replication
Duplication of chromosomes before cell division, occurring in the S phase of interphase.
Crossing-Over
Crossing-Over
The process where homologous chromosomes pair up and exchange genetic material during meiosis I.
Mitosis
Mitosis
Cell division that produces two identical daughter cells.
Meiosis
Meiosis
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Spermatogenesis
Spermatogenesis
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Oogenesis
Oogenesis
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Particulate Inheritance
Particulate Inheritance
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Allele
Allele
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Dominant Allele
Dominant Allele
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Recessive Allele
Recessive Allele
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Law of Dominance
Law of Dominance
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Law of Segregation
Law of Segregation
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Law of Independent Assortment
Law of Independent Assortment
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Punnett Square
Punnett Square
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Genetic Recombination
Genetic Recombination
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Study Notes
- Study notes regarding heredity and genetics.
Chromosome Replication
- Chromosome replication happens during the S phase of interphase.
- Chromosome duplication occurs before cell division.
- After replication, the copies are called sister chromatids, held together by the centromere.
Meiosis I: Reductional Division
- Tetrads form when homologous chromosomes join together in synapsis
- Each chromosome contains sister chromatids
- Crossing over occurs and homologous chromosomes exchange genetic material
- Crossing over produces genetic recombination, increasing genetic variation.
Meiosis II: Chromosome Reduction
- Meiosis II separates sister chromatids
Mitosis vs. Meiosis
- Mitosis involves one cell division, while meiosis involves two.
- Mitosis results in two identical daughter cells, while meiosis results in four genetically different cells.
- In mitosis, the chromosome number remains the same as the parent cell, while in meiosis, it is halved (n).
- Mitosis occurs in somatic cells, while meiosis occurs in germ cells.
- Mitosis happens throughout life for growth and repair, whereas meiosis occurs at sexual maturity for sexual reproduction.
Spermatogenesis (Male)
- Spermatogenesis takes place in the testes
- Spermatogenesis produces ~250,000,000 sperm daily Steps include:
- Spermatogonium (diploid) undergoes mitosis
- Primary spermatocytes undergo meiosis I
- Secondary spermatocytes undergo meiosis II
- 4 haploid spermatids mature into sperm
Oogenesis (Female)
- Oogenesis occurs in the ovaries
- Oogenesis produces one egg per 28-day cycle
Steps include:
- Oogonium (diploid) undergoes mitosis
- Primary oocyte goes through meiosis I
- Forms secondary oocyte and first polar body
- Meiosis II stops at metaphase
- Fertilization needed to complete egg formation
- Additional polar bodies produced degenerate
Spermatogenesis vs. Oogenesis
- Spermatogenesis occurs in the testis, while oogenesis occurs in the ovary.
- Spermatogenesis produces millions of gametes throughout life, while oogenesis has a fixed amount (~400 mature eggs).
- Spermatogenesis results in four gametes per germ cell, while oogenesis results in one.
- Spermatogenesis begins at puberty and is continuous, while oogenesis starts during fetal development and occurs in a monthly cycle.
- Meiotic divisions are uninterrupted in spermatogenesis but arrested in oogenesis
Gregor Mendel: Father of Genetics
- Gregor Mendel performed experiments with pea plants in the mid-1800s.
- Mendel proposed the Particulate Hypothesis of Inheritance
- Parents pass distinct genetic factors to offspring.
- Mendel chose pea plants because they reproduce quickly and have obvious trait differences.
Chromosomes and Alleles
- Homologous chromosomes contain DNA coding for the same genes and enable genetic crossing-over.
- Dominant alleles are expressed regardless of the second allele and are represented by a capital letter.
- Recessive alleles are expressed only when both alleles match and are represented by a lowercase letter.
Mendel's Laws of Heredity
- Law of Dominance: one trait version disappears in the hybrid generation; the dominant trait masks the recessive trait.
- Law of Segregation: two alleles separate during gamete formation, with each allele going to different gametes.
- Law of Independent Assortment: gene pairs separate randomly into gametes, allowing diverse genetic combinations.
Genetic Probability and Inheritance
- Punnett Squares: This diagram shows genetic cross probabilities
- Punnett squares are used for monohybrid (single trait) and dihybrid (two traits) crosses.
Genetic Recombination
- New gene combinations result from independent assortment and crossing over.
- Potential combinations are calculated by $2^n$, with over 70 trillion possible combinations in humans.
Additional Genetic Concepts
- Gene Linkage: genes are close together on the same chromosome.
- Chromosome Maps: they show gene sequence.
- Polyploidy: it involves extra chromosome sets and is lethal in humans but increases plant vigor.
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