Study Unit 6 Flashcards
Meiosis and Mendelian Inheritance
What is the key result of meiotic cell division?
Meiotic cell division results in four genetically unique daughter cells, each containing half the number of chromosomes as the parent cell.
What is a karyotype?
A karyotype is the particular array of chromosomes in an individual organism, arranged according to size, staining properties, and location of centromere.
What is the difference between diploid and haploid cells?
Diploid cells have two complete sets of chromosomes (2n), while haploid cells have one set of chromosomes (n).
What are homologous chromosomes?
Homologous chromosomes are pairs of chromosomes that have the same structure and gene sequence, each one inherited from a different parent.
Describe the stages of Meiosis I.
Meiosis I includes Prophase I (homologous chromosomes align and crossing over occurs), Prometaphase I (meiotic spindles attach to kinetochores), Metaphase I (bivalents align at the center), Anaphase I (homologous chromosomes separate), and Telophase I (cells become haploid).
Why is a second round of meiosis necessary?
A second round, Meiosis II, is necessary to separate sister chromatids, resulting in four haploid gametes.
How does meiosis contribute to genetic diversity?
Genetic diversity is increased through the alignment of homologs and crossing over during Prophase I.
Compare the events of Meiosis II and Mitosis.
In both Meiosis II and Mitosis, sister chromatids separate. However, Meiosis II results in haploid cells, whereas Mitosis results in diploid cells.
Describe cytoplasmic division in meiosis for males and females.
In females, one oocyte and three polar bodies are produced (unequal division), while in males, cytoplasmic division is equal, producing four sperms.
What is nondisjunction and its consequences?
Nondisjunction is the failure of chromosomes to move to opposite poles during meiosis, leading to gametes with an incorrect number of chromosomes, causing conditions like Down Syndrome.
Describe first- and second-division nondisjunction.
First-division nondisjunction results in all gametes having an incorrect number of chromosomes, while second-division nondisjunction results in two gametes with an incorrect number of chromosomes.
What are Klinefelter and Turner Syndromes?
Klinefelter Syndrome (extra X or Y chromosome) and Turner Syndrome (missing an X or Y chromosome) are caused by nondisjunction of sex chromosomes.
What is Mendel’s first key discovery?
Mendel’s first key discovery is the principle of segregation, where alleles separate during gamete formation, leading to each gamete carrying only one allele for each trait.
Explain the principle of segregation with an example.
In a monohybrid cross between true-breeding yellow-seeded and green-seeded plants, F1 offspring are all yellow-seeded (dominant), and F2 shows a 3:1 ratio of yellow to green seeds, demonstrating segregation.
What does a Punnett square predict?
A Punnett square is used to predict all possible outcomes and probabilities of offspring genotypes from a genetic cross.
