Biology Chapter 7 - Cellular Inheritance
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Questions and Answers

What type of life cycle do most fungi and algae employ?

  • Diploid-dominant
  • Haploid-dominant (correct)
  • Asexual reproduction
  • Alternation of generations

What is the primary outcome of fertilization in plants?

  • Production of spores
  • Division of sporophytes
  • Formation of a diploid zygote (correct)
  • Formation of gametes

During which process do specialized cells of sporophytes undergo meiosis?

  • Gamete formation
  • Spore production (correct)
  • Mitosis
  • Fertilization

What immediately occurs after the formation of a diploid zygote in fungi?

<p>It undergoes meiosis (A)</p> Signup and view all the answers

In plants, what is the role of gametophytes in the life cycle?

<p>To produce gametes (D)</p> Signup and view all the answers

What happens to the haploid spores formed in fungi after meiosis?

<p>They develop into gametophytes (B)</p> Signup and view all the answers

What distinguishes the life cycle of plants from those of fungi and algae?

<p>It alternates between haploid and diploid multicellular organisms (A)</p> Signup and view all the answers

What is generated during meiosis that contributes to genetic variation?

<p>Independent assortment of chromosomes (A)</p> Signup and view all the answers

What is a potential evolutionary advantage of sexual reproduction?

<p>Increased variation among offspring (B)</p> Signup and view all the answers

What is the term used for chromosomes that have a mixture of maternal and paternal sequences?

<p>Recombinant chromosomes (A)</p> Signup and view all the answers

Which of the following describes a disadvantage of sexual reproduction?

<p>Requiring a mate for reproduction (B)</p> Signup and view all the answers

Why might asexual reproduction theoretically allow a population to grow faster than a sexual population?

<p>Only females are needed for reproduction (A)</p> Signup and view all the answers

What occurs during prometaphase I in meiosis?

<p>Microtubules attach to kinetochores (D)</p> Signup and view all the answers

What commonality is shared among the life-cycle strategies of sexual multicellular organisms?

<p>All involve a phase of genetic mixing (A)</p> Signup and view all the answers

Which phase of meiosis exhibits independent assortment of chromosomes?

<p>Metaphase I (C)</p> Signup and view all the answers

Multicellular organisms that reproduce exclusively asexually are:

<p>Exceedingly rare (D)</p> Signup and view all the answers

What is the primary role of crossing over in meiosis?

<p>To enhance genetic variation (D)</p> Signup and view all the answers

During which process do homologous chromosomes end up at opposite poles?

<p>Anaphase I (C)</p> Signup and view all the answers

What aspect of offspring in asexual reproduction appears to be beneficial in stable environments?

<p>Identical traits to successful parents (D)</p> Signup and view all the answers

What is a key reason for the evolutionary success of sexual reproduction despite its disadvantages?

<p>Enhanced environmental adaptability (A)</p> Signup and view all the answers

What holds homologous chromosomes together during prometaphase I?

<p>Chiasmata (B)</p> Signup and view all the answers

Which of the following statements is generally true about asexual populations in comparison to sexual populations?

<p>Asexual populations can double their reproductive capacity (B)</p> Signup and view all the answers

Which of the following statements is correct regarding the alignment of chromosomes in metaphase I?

<p>Chromosomes align at random orientations (D)</p> Signup and view all the answers

How many chromosomes does each parent contribute in a sexually reproducing organism?

<p>23 from each parent (A)</p> Signup and view all the answers

What is the number of possible alignments of tetrads during meiosis, given that humans have 23 chromosome pairs?

<p>$2^{23}$ (A)</p> Signup and view all the answers

Which phase of meiosis is characterized by the breaking of chiasma connections and the separation of homologous chromosomes?

<p>Anaphase I (C)</p> Signup and view all the answers

What is the role of crossover events during meiosis?

<p>They create genetic variation among sister chromatids. (A)</p> Signup and view all the answers

How does the arrangement of tetrads at the metaphase plate affect genetic diversity?

<p>It randomizes the orientation of the tetrads. (C)</p> Signup and view all the answers

What happens to the sister chromatids during anaphase I of meiosis?

<p>They remain tightly bound at the centromere. (D)</p> Signup and view all the answers

After meiosis I, what occurs during telophase I?

<p>Chromosomes may or may not decondense depending on the species. (D)</p> Signup and view all the answers

What determines the genetic composition of haploid cells resulting from meiosis?

<p>Independent assortment and crossover events. (A)</p> Signup and view all the answers

Why is it unlikely for two haploid cells from meiosis to have the same genetic composition?

<p>Each tetrad's orientation is independent. (B)</p> Signup and view all the answers

What separates the cell contents during cytokinesis in plant cells?

<p>Cell plate (A)</p> Signup and view all the answers

During which phase do sister chromatids become maximally condensed and align at the center of the cell in meiosis II?

<p>Metaphase II (A)</p> Signup and view all the answers

What happens to the nuclear envelopes during prophase II if they had formed in telophase I?

<p>They dissolve completely (A)</p> Signup and view all the answers

What is the primary result of meiosis II?

<p>Formation of four haploid cells (B)</p> Signup and view all the answers

What defines the chromosomes in haploid cells after meiosis I?

<p>Each cell has one complete set of chromosomes with duplicate sister chromatids (B)</p> Signup and view all the answers

What is one key difference between meiosis and mitosis?

<p>Meiosis involves homologous chromosome pairing, while mitosis does not (A)</p> Signup and view all the answers

What do centrosomes do during interkinesis before meiosis II?

<p>Duplicated and moved toward opposite poles (D)</p> Signup and view all the answers

What occurs to sister chromatids during anaphase II?

<p>They are pulled apart to opposite poles (A)</p> Signup and view all the answers

What significant finding is suggested by the comparison of human and chimpanzee genes on chromosome 18?

<p>The inversion breakpoint likely occurred between ROCK1 and USP14. (B)</p> Signup and view all the answers

What effect could the inversion on chromosome 18 have on the enzymes ROCK1 and USP14?

<p>It could alter their expression levels and cellular function. (C)</p> Signup and view all the answers

How do translocations differ from inversions?

<p>Translocations involve reassociation with nonhomologous chromosomes. (B)</p> Signup and view all the answers

What type of translocation results from the exchange of segments between two nonhomologous chromosomes without any genetic gain or loss?

<p>Reciprocal translocation (D)</p> Signup and view all the answers

Which of the following is associated with specific translocations?

<p>Certain cancers and schizophrenia (C)</p> Signup and view all the answers

What role does the expression level of USP14 play in human development compared to chimps?

<p>It is expressed at distinct levels in certain cell types. (C)</p> Signup and view all the answers

What is the primary concern regarding translocations in the context of diseases?

<p>They can sometimes have debilitating effects depending on regulatory sequences. (C)</p> Signup and view all the answers

Which of the following statements is true regarding inversions?

<p>They rearrange the chromosome segments within the same chromosome. (B)</p> Signup and view all the answers

Flashcards

Sexual reproduction's benefit

Sexual reproduction generates variation among offspring, which can be advantageous in evolution by adapting to changing environments.

Sexual Reproduction's life cycle strategies

Multicellular sexual organisms have three main life cycle strategies: a) diploid dominant life cycle, b) haploid dominant life cycle, and c) alternation of generations.

Asexual Reproduction Advantages

Asexual reproduction is faster and doesn't require a mate, allowing for more rapid population growth.

Asexual Reproduction Disadvantages

Asexual reproduction offers no genetic variation, making populations less adaptable to changing environments.

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Sexual Reproduction vs. Asexual reproduction

Sexual reproduction leads to genetic variation, which is crucial for adaptation in changing environments. Asexual reproduction is quicker but less adaptive.

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Evolutionary advantage of sexual reproduction

Variation produced by sexual reproduction provides a species with a broader range of traits to react to environmental changes, giving them a higher probability of survival.

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Asexual Reproduction Examples

Asexual reproduction methods include budding, fragmentation, and producing asexual eggs.

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Rarity of asexual multicellular reproduction

Multicellular organisms that only reproduce asexually are uncommon despite its advantages.

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Haploid Dominant

A type of life cycle where the multicellular organism is haploid, and the diploid stage exists only as a short-lived zygote.

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Diploid Dominant

A type of life cycle where the multicellular organism is diploid, and the haploid stage is gametes.

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Alternation of Generations

A life cycle where both haploid and diploid multicellular organisms are present.

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Gametophyte

The haploid multicellular organism in plants that produces gametes.

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Sporophyte

The diploid multicellular organism in plants that produces spores.

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Meiosis

Cell division that reduces the number of chromosomes by half, producing haploid gametes from a diploid cell.

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What is the role of fertilization in sexual reproduction?

Fertilization is the union of two gametes, each carrying one set of chromosomes, forming a diploid zygote with two sets of chromosomes.

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What is the difference between mitosis and meiosis?

Mitosis produces two identical daughter cells with the same number of chromosomes as the parent cell, while meiosis produces four genetically diverse daughter cells with half the number of chromosomes as the parent cell.

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Recombinant Chromatid

A sister chromatid that carries a mix of maternal and paternal genes created through crossing over, resulting in new combinations of alleles not present in either parent.

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Non-Recombinant Chromatid

A sister chromatid that carries only paternal or maternal genes, without any crossover event.

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Crossing Over

The exchange of genetic material between non-sister chromatids of homologous chromosomes during prophase I of meiosis, leading to genetic diversity.

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Kinetochore Proteins

Proteins located at the centromere of a chromosome, where spindle fibers attach during cell division.

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Spindle Fiber Microtubules

Fibers made of microtubules that extend from the centrosomes and attach to kinetochore proteins to pull chromosomes apart during cell division.

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Prometaphase I

The stage of meiosis I where the nuclear envelope breaks down and spindle fibers attach to kinetochore proteins, preparing chromosomes for separation.

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Metaphase I

The stage of meiosis I where homologous chromosomes line up in the center of the cell, facing opposite poles, ready for separation into daughter cells.

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Independent Assortment

The random orientation of homologous chromosomes at the metaphase plate during meiosis I, resulting in a random distribution of maternal and paternal chromosomes in gametes.

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Cytokinesis

The physical process that divides the cytoplasm of a cell into two daughter cells after nuclear division. It occurs through a cleavage furrow in animals or a cell plate in plants.

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Cleavage furrow

A groove formed on the cell surface during cytokinesis in animal cells, constricting the cell membrane and eventually separating the two daughter cells.

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Cell plate

A structure that forms during cytokinesis in plant cells, which divides the cell into two daughter cells by creating new cell walls.

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Haploid cell

A cell that contains only one set of chromosomes. It is formed during meiosis.

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Sister chromatids

Identical copies of a single chromosome, connected at the centromere. They are separated during meiosis II.

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Crossovers

Exchanges of genetic material between homologous chromosomes during meiosis I. They create genetic variation in offspring.

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Interkinesis

A brief resting phase between meiosis I and meiosis II, similar to interphase but without DNA replication (S phase).

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How many possible chromosome alignments?

The number of potential chromosome alignments during metaphase I is calculated by 2^n, where 'n' is the number of chromosome pairs. Humans have 23 pairs, resulting in over 8 million possibilities.

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Genetic Variability from Meiosis I

Meiosis I generates genetic variability through two mechanisms: crossover events during prophase I and independent assortment of tetrads at metaphase I.

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What happens in Anaphase I?

In anaphase I, spindle fibers pull apart homologous chromosomes, while sister chromatids remain attached at the centromere. Chiasmata connections break as the fibers move the chromosomes.

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Meiosis I's Impact

Meiosis I is crucial for generating genetic diversity by recombining maternal and paternal genes and creating unique combinations of chromosomes in gametes.

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Why is genetic variation important?

Genetic variation increases the chances of survival in changing environments. Offspring with diverse traits are better equipped to adapt to challenges.

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Meiosis I: Summary

Meiosis I is a fundamental process that halves the chromosome number and generates genetic diversity through crossover and independent assortment, ensuring unique genetic combinations in gametes.

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Chromosome Inversion

A type of chromosomal rearrangement where a segment of a chromosome breaks, flips its orientation, and reattaches to the original site.

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Reciprocal Translocation

An exchange of chromosome segments between two nonhomologous chromosomes, resulting in no loss or gain of genetic information.

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Chromosomal Rearrangement Effects

Chromosomal rearrangements, like inversions and translocations, can have various effects on gene expression and organism function.

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ROCK1 and USP14

Two genes located on chromosome 18, whose positions are different in humans and chimpanzees due to an inversion.

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Expression Level Differences

The human and chimpanzee versions of the ROCK1 and USP14 genes are expressed at different levels in specific cell types.

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Chromosome 18 Inversion and Evolution

The inversion on chromosome 18 in humans may have contributed to our evolutionary divergence from other primates.

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Translocations and Disease,

Some translocations are linked to specific diseases, including cancer and schizophrenia.

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Benign Translocation,

Translocations can be benign, meaning they don't cause any noticeable negative effects.

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Study Notes

Chapter 7 - The Cellular Basis of Inheritance

  • Sexual Reproduction: This is the production of haploid cells (cells with a single set of chromosomes) and the fusion of these haploid cells from each parent to create a single, unique diploid cell. It introduces genetic variation in offspring.

  • Variation in Offspring: A key evolutionary advantage of sexual reproduction is the variation it produces in offspring. This variation arises from the mixing of genetic material from both parents during meiosis and fertilization, unlike asexual reproduction which creates clones. Mutation is the only source of variation in asexual organisms, which makes them less adaptable to changing environments.

  • Sexual Life Cycles: There are three main categories:

  • Diploid-dominant: Most animals, including humans, have a multicellular diploid life stage as the most prominent phase, with haploid gametes being a smaller part of the cycle.

  • Haploid-dominant: Fungi and some algae primarily exist as haploid multicellular organisms.

  • Alternation of Generations: Plants exhibit both multicellular haploid (gametophyte) and multicellular diploid (sporophyte) stages.

  • Meiosis: This is a type of cell division that results in haploid cells. It consists of two rounds with a process similar to mitosis, but reduces the number of chromosome sets from two to one to create gametes (sperm or egg cells) for sexual reproduction. The genetic variation in meiosis is generated by crossing over and independent assortment of chromosomes.

  • Crossing Over: Chromosomes exchange pieces before separating, creating new combinations of genes on each chromosome.

  • Independent Assortment: During meiosis I, homologous chromosomes line up independently at the metaphase plate, leading to random combinations of paternal and maternal chromosomes in the gametes.

  • Comparing Mitosis and Meiosis: Both are nuclear divisions, but mitosis maintains the same number of chromosome sets, producing genetically identical cells for growth and repair. Meiosis, on the other hand, reduces chromosome number, generating diverse gametes. Key differences include the number of rounds of division and the behavior of homologous chromosomes during the process.

  • Variations in Meiosis: Errors during meiosis can lead to genetic disorders. This is because of:

  • Nondisjunction: Failure of chromosomes to separate properly during meiosis, resulting in gametes with too many or too few chromosomes. This can lead to trisomies (e.g., Down syndrome) or monosomies (Turner syndrome).

  • Chromosome Structural Rearrangements: Such as inversions or translocations, which involve segments of chromosomes being broken and rejoined in unusual ways. These changes can also lead to developmental issues.

  • Karyotypes: Visual representations of chromosomes in a cell, used to detect abnormalities in chromosome number (e.g., extra or missing chromosomes) or structure. Geneticists use them to identify genetic disorders.

  • X-Chromosome Inactivation: In female mammals, one X chromosome in each cell inactivates during early development to prevent an excess of gene products from that chromosome. This inactivation is random, thus leading to the expression of one or the other X-linked trait in different parts of the same body.

  • Polyploidy: A condition where an organism has more than two sets of chromosomes. It's more frequent in plants and often contributes to larger size and more robust organisms. They're often sterile because the odd number of chromosomes makes meiosis difficult.

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Explore the cellular basis of inheritance in this quiz focused on sexual reproduction and its advantages. Understand how genetic variation in offspring occurs, the process of meiosis, and the different sexual life cycles. Test your knowledge on diploid and haploid dominant life stages.

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