Sexual reproduction involves the union of two specialized reproductive cells called gametes. Each gamete contains one set of chromosomes. A cell with one chromosome set is haploid. When two haploid gametes unite during fertilization, they form a zygote, which contains two sets of chromosomes and is therefore diploid.
If diploid cells made diploid gametes, fertilization would double the number of chromosome sets in every generation. Meiosis prevents this: it reduces the chromosome-set number by half, allowing haploid gametes to form. Fertilization then restores the diploid state.
All flashcards
What is a haploid cell?
A cell with one set of chromosomes. Gametes are haploid, allowing fertilization to restore the diploid chromosome number.
What is a diploid cell?
A cell with two sets of chromosomes, generally containing one homolog of each pair from each genetic contributor.
What are homologous chromosomes?
Matched chromosomes with the same genes in corresponding locations. They may carry different versions of those genes.
What is the role of meiosis in sexual reproduction?
Meiosis reduces chromosome-set number by half to form haploid reproductive cells; fertilization then combines two such cells to restore diploidy.
How does meiosis differ from mitosis in its overall outcome?
Meiosis includes two nuclear divisions and usually yields four genetically distinct haploid nuclei. Mitosis usually yields two genetically identical nuclei while maintaining ploidy.
Quiz questions
During prophase I, what does synapsis refer to?Answer: The pairing of homologous chromosomes.
During crossing over in meiosis, which chromatids exchange DNA segments?Answer: Nonsister chromatids of homologous chromosomes.
What produces independent assortment during meiosis I?Answer: The independent orientation of homologous pairs at metaphase I.
What separates during anaphase I?Answer: Homologous chromosomes, while sister chromatids remain joined.
What distinguishes interkinesis from the interphase before meiosis I?Answer: Interkinesis has no S phase or DNA replication.
Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.