Chapter 18, Problem 1P

Match each of the terms in the left column to the best-fitting phrase from the right column.

a. epistatic interaction	1. divide the body into identical units (segments)
b.regulative determination	2. initiated by binding of ligand to determination receptor
c. modifier screen	3. individuals with cells of more than one genotype
d. RNAi	4. the fate of early embryonic cells can be altered by the environment
e. ectopic expression	5. assign identity to body segments
f. homeodomain	6. substance whose concentration determines cell fates
g. green fluorescent protein	7. suppression of gene expression by double-stranded RNA
h. genetic mosaics	8. method for identifying pleiotropic genes
i. segmentation genes	9. a DNA-binding motif found in certain transcription factors
j. homeotic genes	10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development
k. morphogen	11. double mutant has phenotype of one of the two mutants
l. maternal effect genes	12. a gene is turned on in an inappropriate genes tissue or at the wrong time
m. signal transduction	13. a tag used to follow proteins in pathways living cells

Summary Introduction

a.

To determine:

The phrase that describes “epistatic interaction” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

When different types of genes show interaction, this process is called epistatic interaction.

Answer to Problem 1P

Correct answer:

Epistatic interaction: double mutant has phenotype of one of the two mutants

Explanation of Solution

Epistatic is the interaction between different genes. When one allele or a pair of alleles of one gene can mask the expression of an allele of different gene, an allele or a pair of allele of one gene is epistatic to the different gene. Epistatic mutation can give double mutant, which has phenotype of one of the two mutants.

Summary Introduction

b.

To determine:

The phrase that describes “regulative determination” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

When fate of embryonic cells is determined by the environment, the process is called regulative determination.

Answer to Problem 1P

Correct answer:

Regulative determination: the fate of early embryonic cells can be altered by the environment

Explanation of Solution

The cells of an early embryo can alter or regulate their fates according to the environment; this is known as regulative determination.

Summary Introduction

c.

To determine:

The phrase that describes “modifier screen” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

Several types of methods are used for the identification of genes. Modifier screen is one of the method for the identification.

Answer to Problem 1P

Correct answer:

Modifier screen: method for identifying pleiotropic genes

Explanation of Solution

The modifier screen is used to identify pleiotropic genes that are involved in a developmental pathway.

Summary Introduction

d.

To determine:

The phrase that describes “RNAi” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

The process in which a particular gene is suppressed due to the double stranded DNA is called RNA interference.

Answer to Problem 1P

Correct answer:

RNAi: suppression of gene expression by double-stranded RNA

Explanation of Solution

In RNA interference (RNAi), the entry of a double-stranded RNA molecule into cells causes degradation of an mRNA of complementary sequence.

Summary Introduction

e.

To determine:

The phrase that describes “ectopic expression” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

When normal protein is produced as a result of mutation at the wrong time, it is called ectopic expression.

Answer to Problem 1P

Correct answer:

Ectopic expression: a gene is turned on in an inappropriate genes tissue or at the wrong time

Explanation of Solution

Mutation can cause genes to produce the normal protein, but at an inappropriate time or place. This phenomenon is termed as ectopic expression.

Summary Introduction

f.

To determine:

The phrase that describes “homeodomain” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

Homeodomain can be defined as a specific motif for the attachment of DNA.

Answer to Problem 1P

Correct answer:

Homeodomain: a DNA-binding motif found in certain transcription factors

Explanation of Solution

Homeodomain is a region of each protein that can bind to DNA and it is encoded by the homeobox. Homeodomains are transcription factors that are responsible for the sequence-specific binding of the proteins to their target genes.

Summary Introduction

g.

To determine:

The phrase that describes “green fluorescent protein” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

GFPs are used in the form of tags.

Answer to Problem 1P

Correct answer:

Green fluorescent protein: a tag used to follow proteins in pathways living cells

Explanation of Solution

Green fluorescent protein is made up of 238 amino acid residues. It is used as a tag to track proteins in living cells.

Summary Introduction

h.

To determine:

The phrase that describes “genetic mosaics” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

When organisms possess cells with more than one type of genotypes, it is referred to as genetic mosaic.

Answer to Problem 1P

Correct answer:

Genetic mosaics: individuals with cells of more than one genotype

Explanation of Solution

The individuals containing cells of more than one genotype are genetic mosaics. In fruit flies, mosaics are generally created by site-specific recombination between nonsister chromatids during mitosis.

Summary Introduction

i.

To determine:

The phrase that describes “segmentation genes” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

Some genes are responsible for the division of the body into the identical units. These genes are referred to as segmentation genes.

Answer to Problem 1P

Correct answer:

Segmentation genes: divide the body into identical units (segments):

Explanation of Solution

Segmentation genes are the genes which divide the body into identical genes. In Drosophila, these genes are expressed in the hierarchy and subdivide the embryo into 14 identical segments.

Summary Introduction

j.

To determine:

The phrase that describes “homeotic genes” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

Some specialized genes that assign specific identity to the body segments are called homeotic genes.

Answer to Problem 1P

Correct answer:

Homeotic genes: assign an identity to body segments

Explanation of Solution

In Drosophila, homeotic genes code for homeobox transcription factors that are expressed in different segments. These genes provide each segment of its individual identity.

Summary Introduction

k.

To determine:

The phrase that describes “morphogen” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

A particular type of substance whose concentration decide the cell fate is referred to as morphogen.

Answer to Problem 1P

Correct answer:

Morphogen: a substance whose concentration determines cell fates

Explanation of Solution

Morphogens are the substances that defines different cell fates in a concentration-dependent manner.

Summary Introduction

l.

To determine:

The phrase that describes “maternal effect genes” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

Genes that are responsible for the production of protein that will accumulate only in unfertilized eggs are referred to as maternal effect genes.

Answer to Problem 1P

Correct answer:

Maternal effect genes: encode proteins that accumulate in unfertilized eggs and are needed for embryo development.

Explanation of Solution

Maternal effect genes code for a protein that cumulate in unfertilized eggs. These genes are required for the development of the embryo.

Summary Introduction

m.

To determine:

The phrase that describes “signal transduction” among the options given below.

1. divide the body into identical units (segments)

2. initiated by binding of ligand to determination receptor

3. individuals with cells of more than one genotype

4. the fate of early embryonic cells can be altered by the environment

5. assign identity to body segments

6. substance whose concentration determines cell fates

7. suppression of gene expression by double-stranded RNA

8. method for identifying pleiotropic genes

9. a DNA-binding motif found in certain transcription factors

10. encode proteins that accumulate in unfertilized eggs and are needed for embryo development

11. double mutant has phenotype of one of the two mutants

12. a gene is turned on in an inappropriate genes tissue or at the wrong time

13. a tag used to follow proteins in pathways living cells

Introduction:

A pathway that is initiated as a result of binding of ligand is called signal transduction.

Answer to Problem 1P

Correct answer:

Signal transduction: initiated by binding of ligand to determination receptor

Explanation of Solution

The signal transduction pathway is initiated by the binding of ligand to receptors on cell surface. This pathway enables a signal received from a receptor on the cell’s surface to be converted to a final intracellular regulatory response.