In cucumbers, dull fruit (D) is dominant to glossy fruit (d), and orange fruit (R) is dominant to cream (r) fruit. The gene that codes for dull versus glossy assorts independently from the gene that codes for orange versus cream. A plant that has dull and orange fruits is crossed to a plant that has dull and cream fruits. The cross produces 3⁄8 plants with dull and orange fruits, 3⁄8 plants with dull and cream fruits, 1⁄8 plants with glossy and orange fruits, and 1⁄8 plants with glossy and cream fruits. Give the genotypes of the parents and offspring of the cross.
Note: Your answers need to be placed into the chart below in the order that the parents and progeny are presented in the Problem Statement.
| Generation | Genotypes | ||
|---|---|---|---|
| P | SavNY7tOUuOPnOMx6pg1kA== | × | Oa4ups59IAZ7doWomtZHnw== |
| ↓ | |||
| F1 | SA3ZlRfQMIpF3Hps0RyE1Kj58k/2sn4OPCK/QaRkvVPDLIAy38X4ww== | JBRaEHbPaFyWvqsthBhQACH59mM= | |
| SA3ZlRfQMIpF3Hps0RyE1Kj58k/2sn4OPCK/QaRkvVPDLIAy38X4ww== | uL3O/PKXrenOnHVC6BPyxIgkG5w= | ||
| 105MvCnUuqY/GMDSazpGJCkhiw9uKHbzVsMImvKNLJwv6Mde+GeMyA== | KMYhPy3GAcxldqGH8dNsRQ== | ||
| 105MvCnUuqY/GMDSazpGJCkhiw9uKHbzVsMImvKNLJwv6Mde+GeMyA== | 5yWODAvnKOdbQESht9ud6A== | ||
Read the question carefully. After providing some information about the traits and genes that code for them, the problem asks you to provide some specific information.
This question focuses on a genetic cross, which requires an understanding of the principles of heredity. Review Section 3.2 in Chapter 3 of your textbook if you do not understand the concepts in this problem.
1. Outline the phenotypes of the parents and offspring by choosing from the dropdown menus below.
Note: Your answers need to be placed into the chart below in the order that the parents and progeny are presented in the Problem Statement.
| Generation | Phenotypes | ||
|---|---|---|---|
| P | G8ptcFpX+mGBt6UXRfgOkJHc6/h7oA2kWnPjesg21DnCo/eQgN4YF7Nh8qiScpcAiln9AuxifHHlGK3qsfAThmpSSI1Xf1h+HfRqxCRPVI3X3hQVgfhVlKp87nStz2r7zN+tZ4tT+wd0INDp | × | KZtaelMiS0x6f6mO0YrDxK7LpcGaGr0jkM2hK3jB5lIkI4UVIm+o7e2l9Ffq7p3RpIGF/LzG1HLJgJnB3ABLRsafCUFp448H4alRcR8rzg3pYo6hoWsuOOCzrS0v21LGwMBfolsQgYMY2cfl |
| ↓ | |||
| F1 | 3⁄8 | G8ptcFpX+mGBt6UXRfgOkJHc6/h7oA2kWnPjesg21DnCo/eQgN4YF7Nh8qiScpcAiln9AuxifHHlGK3qsfAThmpSSI1Xf1h+HfRqxCRPVI3X3hQVgfhVlKp87nStz2r7zN+tZ4tT+wd0INDp | |
| 3⁄8 | KZtaelMiS0x6f6mO0YrDxK7LpcGaGr0jkM2hK3jB5lIkI4UVIm+o7e2l9Ffq7p3RpIGF/LzG1HLJgJnB3ABLRsafCUFp448H4alRcR8rzg3pYo6hoWsuOOCzrS0v21LGwMBfolsQgYMY2cfl | ||
| 1⁄8 | rpsrbvVUToVPMhvg8UcKqpH4xuwDqdMGoYeyluqKciPjQoynac6sELg1OxQSm2vaDaLAjB1vX7uNICBOwPhjMxWn7tK5L18pGLmI/EVCzq/ZcLPbCfkXdy4tXxxIH4bUGZ46/Gf8jlAtSSO2 | ||
| 1⁄8 | 5ZIWpbY97uEpTMg/OCn64SzkIj3iWm5VsSkMidMN5JCLrgPJel8TRotBc4upJ83hj4MCl5G816P8vZDPdhkazqu7RVJsNpjtYCTF7r82+6rAzpLYhuboSwinoxIojVvW/zDyXzdHPCesQpOI | ||
Reread the problem statement. The information needed to select the phenotypes of parents and offspring of the cross is provided for you. Remember that your answers need to be placed into the chart in the order that the parents and progeny are presented in the question.
1. Give the single letter that should be used as an allelic symbol for each trait:
| Texture | |
|---|---|
| dull | DD7UQIIkhDI= |
| glossy | ujZVRF1sK00= |
| Color | |
|---|---|
| orange | k2tcaXUqHdo= |
| cream | oUDghrXV/HA= |
2. In cucumbers:
Information about the dominance relationships of the genes coding for color of orange and cream fruits is provided in the problem statement.
3. Genes for texture (D and d) and color (R and r) cvFm9wS9vThdZDgER9W3WHBTzAv93X3QsMHORtF0FJvGALKp.
Linked genes are associated with non-Mendelian ratios of progeny phenotypes.
Now determine what you know about the allelic symbols for the genotypes of the parents, using only what you know from the phenotypes given in the question (not the progeny) to guide you. Use an underscore (_) to indicate any alleles you feel you can not ascertain from the phenotypes.
Some parts of the genotype can be determined from the phenotype alone. Dull fruit (D) is dominant to glossy fruit (d) and orange fruit (R) is dominant to cream fruit (r).
Some parts of the genotype can be determined from the phenotype alone. Dull fruit (D) is dominant to glossy fruit (d) and orange fruit (R) is dominant to cream fruit (r).
3. Now fill in the parental genotypes in the table below.
| Generation | Genotypes | ||
|---|---|---|---|
| P | nS3LyAj5zws/L/xIpK/bhUTnCeg= | (dull, orange) × (dull, cream) | uL3O/PKXrenOnHVC6BPyxIgkG5w= |
| ↓ | |||
| F1 | 3⁄8 dull, orange | ?? | |
| 3⁄8 dull, cream | ?? | ||
| 1⁄8 glossy, orange | ?? | ||
| 1⁄8 glossy, cream | ?? | ||
Refer to the two questions you answered in this step.
Now determine what you know about the allelic symbols for the genotypes of the progeny. Use an underscore (_) to indicate any genes you can not ascertain from the phenotypes.
Dull fruit (D) is dominant to glossy fruit (d) and orange fruit (R) is dominant to cream fruit (r). Individuals that possess a recessive trait must carry two alleles for the recessive trait.
2. Now fill in the genotypes of all the progeny. Remember, where phenotype could correspond to more than one possible genotype, enter genotype as X_, where the underscore indicates either X or x as possible alleles. Based only on the phenotypes, what are the possible genotypes of the parents?
| Generation | Genotypes | ||
|---|---|---|---|
| P | D_ R_ | (dull, orange) × (dull, cream) | D_ rr |
| ↓ | |||
| F1 | 3⁄8 dull, orange | nS3LyAj5zws/L/xIpK/bhUTnCeg= | |
| 3⁄8 dull, cream | uL3O/PKXrenOnHVC6BPyxIgkG5w= | ||
| 1⁄8 glossy, orange | 664BKQy65u8n4IhuveFnh6qLC0I= | ||
| 1⁄8 glossy, cream | 5yWODAvnKOdbQESht9ud6A== | ||
Remember that dull fruit (D) is dominant to glossy fruit (d) and orange fruit (R) is dominant to cream fruit (r). Individuals that possess a recessive trait must carry two alleles for the recessive trait. Use an underscore (_) for alleles you don't know.
1. The next step in solving the problem is to separate the cross into two single-locus crosses, looking at the inheritance of each trait by itself. Let's start with the texture characteristic.
| Generation | Genotypes | ||
|---|---|---|---|
| P | siZyXjF3/IwfAWZEKVDQPD79Qqk= | (dull) × (dull) | siZyXjF3/IwfAWZEKVDQPD79Qqk= |
| ↓ | |||
| F1 | 3⁄8 dull | siZyXjF3/IwfAWZEKVDQPD79Qqk= | |
| 3⁄8 dull | siZyXjF3/IwfAWZEKVDQPD79Qqk= | ||
| 1⁄8 glossy | 3TpmxSEeJfC4j8f6yqO+Ji/aDm8= | ||
| 1⁄8 glossy | 3TpmxSEeJfC4j8f6yqO+Ji/aDm8= | ||
You've already shown that you know this information. Review your work on past steps if necessary.
2. What ratio of dull to glossy fruit is observed in the progeny?
| k7cilDdhoOvWsbxbpmtDqyJwHFNbU2OH4ao5rXPcTVssGVo14rRA1A== | dull (D_) |
| cQTh6dRw7F+gk3hA2vA33ocV7Rujv/2DQN1/QIvybX6wdmUPbPeYUQ== | glossy (dd) |
Add up all the proportions that include dull fruits (3⁄8 + 3⁄8) and add up all the proportions that include glossy fruits.
When progeny with a recessive trait are produced, both parents must carry a recessive allele.
If you can’t remember which genotypes and proportions are produced by a cross between two heterozygotes, draw a Punnett square.
5. In conclusion, then, we can conclude that the texture alleles for the two parents are eA9I1uaDoEhTML7qS5K/SQFWI8w= and eA9I1uaDoEhTML7qS5K/SQFWI8w=.
Now let's consider the color characteristic. First assemble the relevant information.
1. In the table below fill in again what we know about the color alleles for parents and progeny based solely on the information given directly in the question.
| Generation | Genotypes | ||
|---|---|---|---|
| P | dPOKVwJqZomUvueilue47njt4hg= | (orange) × (cream) | yHzo4/FwVQSds8+X7hP2s5TIwlE= |
| ↓ | |||
| F1 | 3⁄8 orange | dPOKVwJqZomUvueilue47njt4hg= | |
| 3⁄8 cream | yHzo4/FwVQSds8+X7hP2s5TIwlE= | ||
| 1⁄8 orange | dPOKVwJqZomUvueilue47njt4hg= | ||
| 1⁄8 cream | yHzo4/FwVQSds8+X7hP2s5TIwlE= | ||
You've already shown that you know this information. Review your work on past steps if necessary.
2. What ratio of orange to cream fruit is observed in the progeny?
| n3mV+x2Yz01eG/8kFcF6VaOj4Cz2WUA9KhSSko1Gk+3RgWDcvUYPPQ== | orange (R_) |
| n3mV+x2Yz01eG/8kFcF6VaOj4Cz2WUA9KhSSko1Gk+3RgWDcvUYPPQ== | cream (rr) |
Add up all the proportions that include orange fruits (3⁄8 + 1⁄8) and add up all the proportions that include cream fruits.
A 1:1 ratio is produced by a cross between a heterozygote and a homozygote.
If you can’t remember which genotypes and proportions are produced by a cross between a heterozygote and a homozygote, draw a Punnett square.
5. In conclusion, then, we can conclude that the texture alleles for the two parents are 6ALDYAJg1pTYHlwLWLM2SZ7N1es= and yHzo4/FwVQSds8+X7hP2s5TIwlE=.
1. Now put it all together and try filling in the whole table again:
Note: Your answers need to be placed into the chart below in the order that the parents and progeny are presented in the Problem Statement.
| Generation | Genotypes | ||
|---|---|---|---|
| P | SavNY7tOUuOPnOMx6pg1kA== | (dull, orange) × (dull, cream) | Oa4ups59IAZ7doWomtZHnw== |
| ↓ | |||
| F1 | dull, orange | SA3ZlRfQMIpF3Hps0RyE1Kj58k/2sn4OPCK/QaRkvVPDLIAy38X4ww== | JBRaEHbPaFyWvqsthBhQACH59mM= |
| dull, cream | SA3ZlRfQMIpF3Hps0RyE1Kj58k/2sn4OPCK/QaRkvVPDLIAy38X4ww== | uL3O/PKXrenOnHVC6BPyxIgkG5w= | |
| glossy, orange | 105MvCnUuqY/GMDSazpGJCkhiw9uKHbzVsMImvKNLJwv6Mde+GeMyA== | KMYhPy3GAcxldqGH8dNsRQ== | |
| glossy, cream | 105MvCnUuqY/GMDSazpGJCkhiw9uKHbzVsMImvKNLJwv6Mde+GeMyA== | 5yWODAvnKOdbQESht9ud6A== | |