Gene linkage Flashcards
What is gene-linkage? What does indicate it?
genes that are located on the same chromosome being inherited together.
It indicates that the genes are physically close to each other and do not segregate independently during meiosis.
What is a crossing over/chiasma? What are its roles in meiosis?
It is the reciprocal exchange of genetic material between homologous chromosomes during prophase I of meiosis.
It results in the formation of chiasmata, which are the points of contact and attachment between the homologs.
The roles of crossing over are to create genetic diversity by reshuffling the maternal and paternal alleles on one chromosome, and to physically connect the homologs and ensure their correct segregation during anaphase I.
What does determine gene segregation and genetic diversity?
They are determined by three main factors:
1) reduction in chromosome numbers from 2n to 1n during meiosis I,
which reduces the number of possible alleles for each gene;
2) independent assortment,
which is the random alignment of maternal and paternal chromosomes during metaphase I,
resulting in different combinations of chromosomes in the gametes;
3) recombination,
which is the crossing over between homologous chromosomes during prophase I,
creating new combinations of alleles on one chromosome.
Describe the main steps of mitosis and meiosis.
Mitosis produces two diploid (2n) cells that are genetically identical to the parent cell, and occurs in somatic cells for growth and repair.
Meiosis produces four haploid (1n) cells that are genetically different from the parent cell, and occurs in germ cells for sexual reproduction.
The main steps of mitosis are: prophase, metaphase, anaphase, and telophase, followed by cytokinesis.
The main steps of meiosis are: prophase I, metaphase I, anaphase I, and telophase I, followed by cytokinesis I (meiosis I); and prophase II, metaphase II, anaphase II, and telophase II, followed by cytokinesis II (meiosis II).
