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

5. Genetics of Bacteria and Viruses

Working with Microorganisms

Genetics

5. Genetics of Bacteria and Viruses

Working with Microorganisms

Previous problemNext problem

2:06 minutes

Problem 4c

Textbook Question

Fifteen bacterial colonies growing on a complete medium are transferred to a minimal medium. Twelve of the colonies grow on minimal medium.
The serine biosynthetic pathway is a three-step pathway in which each step is catalyzed by the enzyme product of a different gene, identified as enzymes A, B, and C in the diagram below.

Mutant 1 grows only on min + Ser. In addition to growth on min + Ser, mutant 2 also grows on min + 3-PHP and min + 3-PS. Mutant 3 grows on min + 3-PS and min + Ser. Identify the step of the serine biosynthesis pathway at which each mutant is defective.

Verified step by step guidance

Step 1: Understand the serine biosynthetic pathway diagram. The pathway starts with 3-Phosphoglycerate, which is converted to 3-Phospho-hydroxypyruvate (3-PHP) by Enzyme A. Then, 3-PHP is converted to 3-Phosphoserine (3-PS) by Enzyme B. Finally, 3-PS is converted to Serine (Ser) by Enzyme C.

Step 2: Analyze the growth patterns of the mutants. Mutant 1 grows only when provided with 3-PS, indicating it cannot synthesize 3-PS from 3-PHP. This suggests a defect in Enzyme B.

Step 3: Mutant 2 grows when provided with 3-PHP or 3-PS, indicating it cannot synthesize 3-PHP from 3-Phosphoglycerate. This suggests a defect in Enzyme A.

Step 4: Mutant 3 grows when provided with 3-PS or Serine, indicating it cannot synthesize Serine from 3-PS. This suggests a defect in Enzyme C.

Step 5: Assign the defective step for each mutant based on the analysis: Mutant 1 is defective in the step catalyzed by Enzyme B, Mutant 2 is defective in the step catalyzed by Enzyme A, and Mutant 3 is defective in the step catalyzed by Enzyme C.

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.

Serine Biosynthetic Pathway

The serine biosynthetic pathway is a metabolic route that converts 3-phosphoglycerate into serine through a series of enzymatic reactions. This pathway involves three key enzymes, A, B, and C, each catalyzing a specific step. Understanding this pathway is crucial for identifying where mutations may disrupt serine production in bacterial mutants.

Mutant Analysis

In genetics, mutant analysis involves studying organisms with specific genetic alterations to determine the effects on metabolic pathways. By observing which media the mutants can grow on, researchers can infer which enzymes are functional or defective, thus pinpointing the specific step in the biosynthetic pathway that is affected by each mutation.

Minimal vs. Complete Medium

Minimal medium contains only the essential nutrients required for growth, while complete medium provides additional nutrients, including amino acids like serine. The ability of bacterial colonies to grow on minimal medium indicates their capacity to synthesize necessary compounds, such as serine, which is vital for understanding the implications of mutations in the serine biosynthetic pathway.

Watch next

Master Bacteria in the Laboratory with a bite sized video explanation from Kylia

Start learning

Related Videos

Related Practice

Multiple Choice

True or False:All bacterial cells within a bacteria colony grown on a plate in a laboratory are genetically identical.

Which of the following is NOT a way scientists can phenotypically identify a bacterial mutation?

How do we know that bacteria undergo genetic recombination, allowing the transfer of genes from one organism to another?

320

views

Textbook Question

How do we know that genes exist in bacteria and bacteriophages?

286

views

Textbook Question

Fifteen bacterial colonies growing on a complete medium are transferred to a minimal medium. Twelve of the colonies grow on minimal medium.

The three colonies that do not grow on minimal medium are transferred to minimal medium supplemented with the amino acid serine (min + Ser), and all three colonies grow. Characterize these three colonies.

385

views

Textbook Question

Fifteen bacterial colonies growing on a complete medium are transferred to a minimal medium. Twelve of the colonies grow on minimal medium.

Using terminology, characterize the 12 colonies that grow on minimal medium and the 3 colonies that do not.

579

views

Textbook Question

In general, when recombination experiments are conducted with bacteria, participating bacteria are mixed in complete medium, then transferred to a minimal growth medium. Why isn't the protocol reversed: minimal medium first, complete medium second?

486

views

Textbook Question