Topic content:
In the process of meiosis, the oogonia of Drosophila melanogaster often has chromosomes that are not separated, so Drosophila melanogaster with abnormal sex chromosomes often has different phenotypes, as shown in the following table: (1) If the meiosis process of female Drosophila melanogaster is normal, the meiosis process of male Drosophila melanogaster spermatogonia is abnormal, The reason for abnormal fertilized egg XO is: _____________________________________________________.
(2) Draw the coordinate curve of chromosome number change in a cell cycle during somatic cell mitosis of female fertile Drosophila melanogaster (XXY), and mark the specific change of chromosome number and each stage of mitosis. (3) In order to explore whether the gene controlling eye color of drosophila is located on the sex chromosome, the famous geneticist T.H. Morgan conducted the following hybridization experiments, allowing white eyed male drosophila to mate with red eyed female drosophila, and all offspring are red eyed drosophila; Let the white eyed female drosophila mate with the red eyed male drosophila. The offspring of the male drosophila are all white eyed and the female drosophila are all red eyed. Dikens, his student, used white eyed female flies to mate with red eyed male flies. Most of the male fruit flies in his offspring were white eyed, and all the female fruit flies were red eyed, but there were a few exceptions. About every 2000 offspring, there was one white eyed female fly or red eyed male fly, and the red eyed male fly was sterile.
Please draw a genetic diagram according to the information in the table above to explain why there are exceptions in the Dickens experiment (set the relevant genes as B and b).
Best answer:
(1) In the first meiotic division of male drosophila primary spermatocytes, the homologous chromosome XY did not separate and moved to the same pole, forming sperm without Y sex chromosome (the answer is reasonable)
Answer analysis:
There is no explanation for this question
Test core:
Biological characteristics:
1. Biological characteristics: physiological characteristics, morphological characteristics and behavioral characteristics.
2. Character type:
(1) Relative character: Different performance types of the same character of an organism.
(2) Character separation: dominant and recessive characters appear simultaneously in hybrid offspring. For example, in the DD × dd cross experiment, the dominant characters (DD and Dd) and recessive characters (dd) appeared in the F2 generation formed after self crossing of hybrid F1 generation.
(3) Dominant trait: the trait shown by F1 in DD × dd cross test; For example, the F1 generation pea in the textbook shows a high stem, that is, a high stem is dominant. Dominant genetic factors (genes) determine dominant traits, which are represented by capital letters. For example, high stems are represented by D.
(4) Recessive traits: traits not shown by F1 in DD × dd cross test; For example, F1 generation pea does not show dwarf stem in the textbook, that is, dwarf stem is recessive. It is the recessive gene that determines the recessive character, which is represented by lowercase letters, for example, dwarf stem is represented by d. Allele: A gene that controls a relative trait.
(5) Dominant relativity: when parents with the same traits cross, hybrid seeds do not show recessiveness in the first generation, showing the intermediate traits of both (incomplete dominance) or colleagues showing the traits of two parents (co dominance).