Question 1

The genes that determine the fate of cells in the _______ of a flowering plant's shoot apex are called "_______." These genes code for _______.
A) meristem; organ identity genes; transcription factors
B) whorl; homeotic genes; transcription factors
C) meristem; homeotic genes; MADS box proteins
D) whorl; organ identity genes; MADS box proteins
E) meristem; organ identity genes; LEAFY protein

Accepted Answer

The genes that determine the fate of cells in the meristem of a flowering plant's shoot apex are called "organ identity genes." These genes code for transcription factors, which are proteins that bind to DNA and regulate the expression of other genes.

Question 2

A homeobox
A) is a protein sequence.
B) is another name for a homeodomain.
C) binds to DNA.
D) is a DNA sequence present in many transcription factors.
E) is not present in plants.

Accepted Answer

A homeobox is a specific DNA sequence that encodes a domain called a homeodomain. This domain is found in many transcription factors and is responsible for binding to DNA and regulating gene expression. Therefore, while a homeodomain is a protein sequence, a homeobox itself is a DNA sequence. Additionally, homeoboxes are present in both plants and animals.

Question 3

Location of a cell may be critical in the determination of its ultimate fate during development, as in the development of vertebrate limbs. This fact arises from
A) the unequal distribution of transcription factors.
B) expression of organ identity genes.
C) a gradient in the concentration of the morphogen, sonic hedgehog.
D) a gradient in the concentration of ZPA.
E) expression of homeotic genes.

Accepted Answer

The concentration gradient of the morphogen sonic hedgehog is crucial in determining the fate of cells in vertebrate limb development, influencing their positional identity.

Question 4

What is the correct order of expression of the genes listed below in the determination of segmentation in Drosophila?
 (1) Segment polarity genes
(2) Hox genes
(3) Gap genes
(4) Pair rule genes
A) 4, 3, 1, 2
B) 3, 4, 1, 2
C) 1, 2, 3, 4
D) 2, 3, 1, 4
E) 3, 1, 4, 2

Accepted Answer

The correct order of gene expression during the determination of segmentation in Drosophila is gap genes, pair rule genes, segment polarity genes, and finally Hox genes. Gap genes establish the basic body plan by determining the boundaries of broad regions along the anterior-posterior axis. Pair rule genes refine the pattern by dividing the broad regions into smaller segments. Segment polarity genes establish the anterior-posterior polarity within each segment. Finally, Hox genes determine the identity of each segment. Therefore, option B correctly reflects the correct order of gene expression during the segmentation process in Drosophila.

Question 5

The functions of the _______ and _______ genes in the determination of the anterior and posterior ends of a Drosophila embryo were elucidated by mutant analysis and direct _______ of cytoplasm from wild-type eggs.
A) Hunchback; Bicoid; injection
B) Hunchback; Nanos; deletion
C) Bicoid; Nanos; injection
D) Bicoid; Nanos; deletion
E) None of the above

Accepted Answer

The functions of the Bicoid and Nanos genes in determining the anterior and posterior ends, respectively, of a Drosophila embryo were elucidated by injecting cytoplasm from wild-type eggs into mutant embryos. Hunchback is involved in the segmentation of the embryo, but not in the determination of the anterior and posterior ends. Deletion is not mentioned as a method used in the elucidation of gene function in this question. Therefore, choice C is the best option.

Question 6

Which of the following is the last set of genes to turn on in the Drosophila embryo?
A) Segment polarity genes
B) Homeotic genes
C) Maternal effect genes
D) Gap genes
E) Pair rule genes

Accepted Answer

Homeotic genes are activated later than all other genes, once the basic body plan has been established. They determine the identity and differentiation of individual segments and are responsible for the development of specific body structures.

Question 7

The anterior and posterior ends of a Drosophila embryo are determined by _______ that are active _______ fertilization and result in a gradient of the protein _______.
A) segmentation genes; before and after; Bicoid
B) maternal effect genes; before; Hunchback
C) organ identity genes; before and after; Nanos
D) organ identity genes; after; Hunchback
E) maternal effect genes; before and after; Hunchback

Accepted Answer

Maternal effect genes are active before fertilization and result in a gradient of the protein Bicoid, which determines the anterior and posterior ends of a Drosophila embryo.

Quiz 19: Differential Gene Expression in Development

The genes that determine the fate of cells in the ___ of a flowering plant's shoot apex are called "_." These genes code for _____.

A homeobox

Location of a cell may be critical in the determination of its ultimate fate during development, as in the development of vertebrate limbs. This fact arises from

What is the correct order of expression of the genes listed below in the determination of segmentation in Drosophila? (1) Segment polarity genes (2) Hox genes (3) Gap genes (4) Pair rule genes

The functions of the ___ and _ genes in the determination of the anterior and posterior ends of a Drosophila embryo were elucidated by mutant analysis and direct _____ of cytoplasm from wild-type eggs.

Which of the following is the last set of genes to turn on in the Drosophila embryo?

The anterior and posterior ends of a Drosophila embryo are determined by ___ that are active _ fertilization and result in a gradient of the protein _____.