Textbook Question
How was Mendel able to derive postulates concerning the behavior of 'unit factors' during gamete formation when he could not directly observe them?
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2. Mendel's Laws of Inheritance
Mendel's Experiments and Laws
2:31 minutesProblem 1d
Textbook Question
Give the information requested.
The gametes produced by an organism with the genotype Rt/rT
Verified step by step guidance1
Step 1: Understand the genotype Rt/rT. This represents a heterozygous organism where the alleles for two genes (R and T) are located on homologous chromosomes. The slash (/) separates the alleles on the two homologous chromosomes. One chromosome has the alleles R and t, while the other has r and T.
Step 2: Draw a diagram of the homologous chromosomes. On one chromosome, place the alleles R and t in the order given. On the homologous chromosome, place the alleles r and T in the same order. This will visually represent the genotype Rt/rT.
Step 3: Recall the concept of independent assortment and crossing over. During gamete formation (meiosis), homologous chromosomes can segregate independently, and crossing over can occur between them, leading to different combinations of alleles in the gametes.
Step 4: Determine the possible gametes. Without crossing over, the organism can produce two types of gametes: Rt and rT. If crossing over occurs between the genes, recombinant gametes (RT and rt) can also be produced. Thus, the possible gametes are Rt, rT, RT, and rt.
Step 5: Summarize the results. The organism with the genotype Rt/rT can produce four types of gametes: Rt, rT, RT, and rt. The proportions of these gametes depend on the frequency of crossing over between the R and T loci, which is influenced by their physical distance on the chromosome.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Homologous Chromosomes
Homologous chromosomes are pairs of chromosomes in a diploid organism that have the same structure and gene sequence but may carry different alleles. Each parent contributes one chromosome to the pair, resulting in genetic variation. Understanding homologous chromosomes is essential for visualizing how alleles are arranged and inherited during gamete formation.
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Alleles
Alleles are different versions of a gene that can exist at a specific locus on a chromosome. In the context of the genotype Rt/rT, 'R' and 'r' represent different alleles for one gene, while 't' and 'T' represent different alleles for another gene. The combination of these alleles determines the organism's traits and is crucial for understanding genetic variation and inheritance patterns.
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Gamete Formation
Gamete formation, or gametogenesis, is the process by which diploid cells undergo meiosis to produce haploid gametes. During this process, alleles segregate so that each gamete receives one allele from each gene pair. For the genotype Rt/rT, the possible gametes produced would reflect the combinations of these alleles, which is key to predicting offspring genotypes in genetic crosses.
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