Zea mays (maize, or corn) was originally domesticated in central Mexico at least 7000 years ago from an endemic grass called teosinte. Teosinte is generally unbranched, has male and female flowers on the same branch, and has few kernels per 'cob,' each encased in a hard, leaf-like organ called a glume. In contrast, maize is highly branched, with a male inflorescence (tassel) on its central branch and female inflorescences (cobs) on axillary branches. In addition, maize cobs have many rows of kernels and soft glumes. George Beadle crossed cultivated maize and wild teosinte, which resulted in fully fertile F₁ plants. When the F₁ plants were self-fertilized, about 1 plant in every 1000 of the F₂ progeny resembled either a modern maize plant or a wild teosinte plant. What did Beadle conclude about whether the different architectures of maize and teosinte were caused by changes with a small effect in many genes or changes with a large effect in just a few genes?
Table of contents
- 1. Introduction to Genetics42m
- 2. Mendel's Laws of Inheritance3h 37m
- 3. Extensions to Mendelian Inheritance2h 41m
- 4. Genetic Mapping and Linkage2h 28m
- 5. Genetics of Bacteria and Viruses1h 21m
- 6. Chromosomal Variation1h 48m
- 7. DNA and Chromosome Structure56m
- 8. DNA Replication1h 10m
- 9. Mitosis and Meiosis1h 34m
- 10. Transcription1h 0m
- 11. Translation58m
- 12. Gene Regulation in Prokaryotes1h 19m
- 13. Gene Regulation in Eukaryotes44m
- 14. Genetic Control of Development44m
- 15. Genomes and Genomics1h 50m
- 16. Transposable Elements47m
- 17. Mutation, Repair, and Recombination1h 6m
- 18. Molecular Genetic Tools19m
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
14. Genetic Control of Development
Developmental Patterning Genes
Multiple Choice
In Drosophila embryogenesis, the bicoid gene is transcribed by which class of developmental patterning gene?
A
Segment polarity gene
B
Gap gene
C
Maternal-effect gene
D
Pair-rule gene
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Understand the role of the bicoid gene in Drosophila embryogenesis: it is involved in establishing the anterior-posterior axis early in development.
Recall the classification of developmental patterning genes in Drosophila: maternal-effect genes, gap genes, pair-rule genes, and segment polarity genes, each acting at different stages and levels of embryonic patterning.
Recognize that maternal-effect genes are transcribed in the mother and their mRNA or proteins are deposited into the egg to direct early embryonic development before the zygotic genome is activated.
Identify that the bicoid gene is a classic example of a maternal-effect gene because its mRNA is localized at the anterior end of the egg by the mother and directs head and thorax formation.
Conclude that the bicoid gene is transcribed by the maternal-effect gene class, which sets up the initial positional information in the embryo.
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