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

4. Genetic Mapping and Linkage

Chi Square and Linkage

Genetics

4. Genetic Mapping and Linkage

Chi Square and Linkage

Previous problemNext problem

2:42 minutes

Problem 15d

Textbook Question

Three dominant traits of corn seedlings, tunicate seed (T-), glossy appearance (G-), and liguled stem (L-), are studied along with their recessive counterparts, nontunicate (tt), nonglossy (gg), and liguleless (ll). A trihybrid plant with the three dominant traits is crossed to a nontunicate, nonglossy, liguleless plant. Kernels on ears of progeny plants are scored for the traits, with the following results:

If evidence of linkage is present, calculate the recombination frequency or frequencies from the data presented.

Verified step by step guidance

Step 1: Understand the problem. This is a trihybrid cross involving three traits: tunicate seed (T), glossy appearance (G), and liguled stem (L), each with dominant and recessive alleles. The trihybrid plant (TtGgLl) is crossed with a homozygous recessive plant (ttggll). The goal is to determine if there is evidence of linkage between any of the genes and, if so, calculate the recombination frequency.

Step 2: Identify parental and recombinant phenotypes. Parental phenotypes are those that match the original combinations of alleles in the parents (T-G-L- and ttggll). Recombinant phenotypes are those that result from crossing over, leading to new combinations of alleles. From the data, identify which phenotypes are parental and which are recombinant.

Step 3: Calculate the total number of parental and recombinant offspring. Add the counts of the parental phenotypes together and the counts of the recombinant phenotypes together. This will help determine the proportion of recombinants in the total population.

Step 4: Calculate the recombination frequency. The recombination frequency is calculated as the number of recombinant offspring divided by the total number of offspring, multiplied by 100 to express it as a percentage. Use the formula:

\frac{Number of recombinants}{Total} \times 100

Step 5: Interpret the recombination frequency. If the recombination frequency is less than 50%, it suggests that the genes are linked and located on the same chromosome. If it is close to 50%, the genes are likely unlinked and assort independently. Use the calculated recombination frequency to determine the degree of linkage between the genes.

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.

Mendelian Genetics

Mendelian genetics is the study of how traits are inherited through generations based on the principles established by Gregor Mendel. It involves understanding dominant and recessive alleles, where dominant traits mask the expression of recessive ones. This framework is essential for analyzing inheritance patterns in the corn seedlings, as it helps predict the phenotypic ratios expected from specific crosses.

Linkage and Recombination

Linkage refers to the tendency of genes located close to each other on a chromosome to be inherited together. Recombination occurs during meiosis when homologous chromosomes exchange genetic material, leading to new allele combinations. The recombination frequency quantifies this exchange, providing insight into the genetic distance between linked genes, which is crucial for interpreting the results of the corn seedling cross.

Phenotypic Ratios

Phenotypic ratios represent the relative frequencies of different phenotypes in the offspring resulting from a genetic cross. In this case, the observed phenotypes of the progeny plants can be analyzed to determine if they align with expected Mendelian ratios or indicate linkage. Understanding these ratios is vital for calculating recombination frequencies and assessing the genetic relationships among the traits studied.

Watch next

Master Chi Square and Linkage with a bite sized video explanation from Kylia

Start learning

Related Videos

Related Practice

Multiple Choice

Using the appropriate chi-square value and degrees of freedom, do the coat color and hair length genes assort independently?

Define linkage disequilibrium. What is the physical basis of linkage, and what causes linkage equilibrium? Explain how crossing over eliminates linkage disequilibrium.

628

views

Textbook Question

Researchers cross a corn plant that is pure-breeding for the dominant traits colored aleurone (C1), full kernel (Sh), and waxy endosperm (Wx) to a pure-breeding plant with the recessive traits colorless aleurone (c1), shrunken kernel (sh), and starchy (wx). The resulting F₁ plants were crossed to pure-breeding colorless, shrunken, starchy plants. Counting the kernels from about 30 ears of corn yields the following data.

Why are these data consistent with genetic linkage among the three genes?

323

views

Textbook Question

Three dominant traits of corn seedlings, tunicate seed (T-), glossy appearance (G-), and liguled stem (L-), are studied along with their recessive counterparts, nontunicate (tt), nonglossy (gg), and liguleless (ll). A trihybrid plant with the three dominant traits is crossed to a nontunicate, nonglossy, liguleless plant. Kernels on ears of progeny plants are scored for the traits, with the following results:

Could all three genes be carried on the same chromosome? Discuss why or why not.

764

views

Textbook Question

Using the gene symbols given above, write the genotypes of F₁ and F₂ plants.

458

views

Textbook Question

Is there evidence of independent assortment among any of these gene pairs? If so, identify the evidence.

378

views

Textbook Question

Is there evidence of genetic linkage among any of these gene pairs? If so, identify the evidence.

339

views

Textbook Question

T. H. Morgan's data on eye color and wing form genetic linkage between the two genes. Test the genetic linkage (shown in the figure below) data with chi-square analysis, and show that the results are significantly different from the expectation under the assumption of independent assortment.

671

views

Show more practices

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap