Table of contents

1. Introduction to Genetics51m
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
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

17. Mutation, Repair, and Recombination

Induced Mutations

Genetics

17. Mutation, Repair, and Recombination

Induced Mutations

Previous problemNext problem

1:50 minutes

Problem 29d

Textbook Question

A wild-type culture of haploid yeast is exposed to ethyl methanesulfonate (EMS). Yeast cells are plated on a complete medium, and 6 colonies (colonies numbered 1 to 6) are transferred to a new complete medium plate for further study. Four replica plates are made from the complete medium plate to plates containing minimal medium or minimal medium plus one amino acid (replica plates numbered 1 to 4) with the following results:

For colonies 1, 3, and 5, write '+' for the wild-type synthesis and '−' for the mutant synthesis of histidine and leucine.

Verified step by step guidance

Step 1: Understand the experimental setup. The yeast cells are haploid, meaning they have a single set of chromosomes. They were exposed to EMS, a chemical mutagen that induces mutations. The colonies were then tested on different media to determine their ability to synthesize amino acids like histidine and leucine.

Step 2: Analyze the results from the replica plates. Colonies that grow on minimal medium are wild-type for amino acid synthesis, as they can synthesize all required amino acids. Colonies that fail to grow on minimal medium but grow on minimal medium supplemented with a specific amino acid are mutants for the synthesis of that amino acid.

Step 3: For colonies 1, 3, and 5, check their growth patterns on the replica plates. If a colony grows on minimal medium, it is wild-type ('+') for both histidine and leucine synthesis. If it grows only on minimal medium supplemented with histidine, it is mutant ('−') for histidine synthesis. Similarly, if it grows only on minimal medium supplemented with leucine, it is mutant ('−') for leucine synthesis.

Step 4: Assign '+' or '−' for histidine and leucine synthesis for colonies 1, 3, and 5 based on their growth patterns. For example, if colony 1 grows on minimal medium but not on minimal medium supplemented with histidine, it is '+' for histidine synthesis and '−' for leucine synthesis.

Step 5: Summarize the results for colonies 1, 3, and 5. Ensure that the '+' and '−' assignments are consistent with the growth data from the replica plates. This will indicate whether each colony is wild-type or mutant for histidine and leucine synthesis.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Haploid Organisms

Haploid organisms, like yeast, have a single set of chromosomes, which means they carry only one allele for each gene. This genetic simplicity allows for easier observation of mutations and their effects, as any change in a gene will directly manifest in the phenotype. In experiments, haploid yeast can be used to study gene function and the impact of mutagens like ethyl methanesulfonate (EMS).

Mutagenesis

Mutagenesis is the process by which the genetic information of an organism is changed, resulting in mutations. Ethyl methanesulfonate (EMS) is a chemical mutagen that induces point mutations, often leading to changes in amino acid sequences of proteins. Understanding mutagenesis is crucial for interpreting the results of experiments that assess the effects of mutagens on yeast, particularly in relation to amino acid synthesis.

Amino Acid Synthesis Pathways

Amino acid synthesis pathways are biochemical routes through which organisms produce amino acids, essential for protein synthesis. In yeast, certain amino acids can be synthesized from simpler compounds, but mutations can disrupt these pathways, leading to auxotrophy, where the organism cannot grow without the addition of specific amino acids. The ability to synthesize histidine and leucine is critical for understanding the nutritional requirements of the yeast colonies in the experiment.

Watch next

Master Induced Mutations with a bite sized video explanation from Kylia

Start learning

Related Videos

Related Practice

Textbook Question

Following the spill of a mixture of chemicals into a small pond, bacteria from the pond are tested and show an unusually high rate of mutation. A number of mutant cultures are grown from mutant colonies and treated with known mutagens to study the rate of reversion. Most of the mutant cultures show a significantly higher reversion rate when exposed to base analogs such as proflavin and 2-aminopurine. What does this suggest about the nature of the chemicals in the spill?

358

views

Textbook Question

In an Ames test using his⁻ Salmonella bacteria a researcher determines that adding a test compound plus the S9 extract produces a large number of his⁺ revertants but mixing the his⁻ strain plus the test compound without adding S9 does not produce an elevated number of his⁺ revertants.

What is the reason for the different experimental results described?

627

views

Textbook Question

Is the test compound still considered to be a potential mutagen? Explain why or why not.

381

views

Textbook Question

A wild-type culture of haploid yeast is exposed to ethyl methanesulfonate (EMS). Yeast cells are plated on a complete medium, and 6 colonies (colonies numbered 1 to 6) are transferred to a new complete medium plate for further study. Four replica plates are made from the complete medium plate to plates containing minimal medium or minimal medium plus one amino acid (replica plates numbered 1 to 4) with the following results:

Are there any colonies for which genotype information cannot be determined? If so, which colony or colonies?

514

views

Textbook Question

Identify any colonies that are his⁻, arg⁻, leu⁻.

373

views

Textbook Question

A fragment of a wild-type polypeptide is sequenced for seven amino acids. The same polypeptide region is sequenced in four mutants.

Identify the mutation that produces each mutant polypeptide.

340

views