Ch. 13 - Meiosis

Freeman - Biological Science 8th Edition

Freeman8th EditionBiological ScienceISBN: 9780138276263당신이 사용하는 게 아니라요?교과서 변경

Freeman 8th Edition

Ch. 13 - Meiosis

문제 8

13장, 문제 8

Triploid (3n) watermelons, which are seedless, are produced by crossing a tetraploid (4n) strain with a diploid (2n) plant. Explain why this mating produces a triploid individual.

검증된 단계별 안내

Step 1: Understand the terms. In this context, 'diploid' refers to a cell or organism that has two sets of chromosomes, 'tetraploid' refers to a cell or organism that has four sets of chromosomes, and 'triploid' refers to a cell or organism that has three sets of chromosomes.

Step 2: Understand the process of fertilization. In normal sexual reproduction, a diploid organism produces haploid gametes (with one set of chromosomes) through a process called meiosis. These haploid gametes then combine during fertilization to form a diploid zygote.

Step 3: Apply this understanding to the given problem. In this case, a tetraploid watermelon plant (with four sets of chromosomes) will produce gametes with two sets of chromosomes. A diploid watermelon plant (with two sets of chromosomes) will produce gametes with one set of chromosomes.

Step 4: Understand the result of the cross. When a gamete from the tetraploid plant (2n) fertilizes a gamete from the diploid plant (1n), the resulting zygote will have three sets of chromosomes, making it a triploid (3n) watermelon plant.

Step 5: Understand the significance. Triploid plants are often sterile because they cannot form normal gametes due to the uneven number of chromosome sets. This is why triploid watermelons are seedless.

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

영상 길이:

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Polyploidy

Polyploidy refers to the condition of having more than two complete sets of chromosomes. In plants, polyploidy can lead to increased size and vigor, as well as the ability to produce seedless varieties. In the case of watermelons, tetraploid (4n) plants have four sets of chromosomes, which can be crossed with diploid (2n) plants to produce triploid (3n) offspring.

Chromosome Segregation

Chromosome segregation is the process during meiosis where homologous chromosomes are separated into different gametes. In the case of a tetraploid and a diploid cross, the tetraploid can produce gametes with either 2 or 1 set of chromosomes, while the diploid produces gametes with 1 set. When these gametes fuse, the resulting triploid individual has three sets of chromosomes, leading to the seedless trait.

Seedlessness in Triploids

Triploid organisms, such as seedless watermelons, are often sterile because they cannot undergo normal meiosis due to the uneven number of chromosome sets. This results in the inability to produce viable gametes, leading to the absence of seeds. The triploid condition is desirable in watermelons as it results in a fruit that is more appealing to consumers, who prefer seedless varieties.

관련 실천

교과서 질문

A species of rotifer, a small freshwater invertebrate, lost the ability to reproduce sexually millions of years ago. A remarkable feature of its life cycle is the ability to withstand dry conditions. When the rotifer's environment dries out, so does the rotifer, and it can be blown to a new area. Rotifers that land in water will rehydrate and resume an active life. A major pathogen of these rotifers is a species of fungus that cannot survive drying. Some scientists hypothesize that drying rids the rotifers of this pathogen. Why might the ability to withstand drying reduce any potential advantage of sexual reproduction in this rotifer species?

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교과서 질문

Norway rats have 42 chromosomes in their diploid cells. If such a cell enters meiosis, how many chromosomes and double-helical molecules of DNA will be present in each daughter cell at the end of meiosis II?

a. 21 chromosomes and 21 double-helical DNA molecules

b. 21 chromosomes and 42 double-helical DNA molecules

c. 42 chromosomes and 42 double-helical DNA molecules

d. 42 chromosomes and 84 double-helical DNA molecules

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교과서 질문

If you followed a woman's cells through meiosis, at what stage of meiosis would the amount of DNA in one of these cells be equal to the amount of DNA in one of her G1 phase (before DNA replication) kidney cells?

987

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교과서 질문

Select True or False for each statement.

Sister chromatids are homologous chromosomes.

Non-sister chromatids are found on two different homologs.

Crossing over occurs between sister chromatids.

A chiasma forms between two of the four molecules of double-stranded DNA on duplicated homologous chromosomes.

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교과서 질문

Meiosis results in independent assortment of egg-derived and sperm-derived chromosomes. If 2𝑛=4 for a given organism, and there is no crossing over, what is the chance that a gamete produced by this diploid organism will receive only sperm-derived chromosomes? In domestic cats, 2𝑛=38. What is the chance that a cat gamete contains only egg-derived chromosomes?

416

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교과서 질문

A species of rotifer, a small freshwater invertebrate, lost the ability to reproduce sexually millions of years ago. A remarkable feature of its life cycle is the ability to withstand dry conditions. When the rotifer's environment dries out, so does the rotifer, and it can be blown to a new area. Rotifers that land in water will rehydrate and resume an active life. A major pathogen of these rotifers is a species of fungus that cannot survive drying. Some scientists hypothesize that drying rids the rotifers of this pathogen. Design an experimental study to test this hypothesis.

909

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