Introduction:
A zygote is a single-celled eukaryotic cell that is formed as the result of fertilization between two gametes. It undergoes mitosis to form an embryo that further develops into a multi-celled eukaryotic organism. The division of cells in the early embryonic stage is known as cleavage.
Answer to Problem 1TYK
Correct answer:
The major contributors to the cleavage development of zygotes are the egg nucleus and the yolk.
Explanation of Solution
Justification/explanation for the correct answer:
Option (d) states that the egg nucleus and the yolk are the major contributors to the cleavage patterns. The cleavage of the embryo occurs depending upon the amount of egg yolk present in the blastula (embryo after cleavage division is known as blastula). These cleavages can be holoblastic (total cleavage) or meroblastic cleavage (partial cleavage) that depends upon the amount of yolk present in the egg and the positioning of the nucleus in the egg. Hence, option (d) is correct.
The explanation for the incorrect answer:
Option (a) is given as sperm and egg cytoplasm. The cytoplasm is not the major contributing factor to the cleavage as the cleavage is mainly classified on the basis of the amount of yolk that is present in the egg. So, it is an incorrect option.
Option (b) is given as sperm and egg chromosomes. The chromosomes have nothing to do with the cleavage patterns. The chromosomes of the sperm and the egg consist of the genetic makeup of the embryo. So, it is an incorrect option.
Option (c) is given as ribosomes and mitochondria. These have an important role in the translation (expression of genetic material or formation of proteins) process and not in the cleavage divisions. So, it is an incorrect option.
Option (e) is given as pigments. Pigments can only be present after the genetic material expresses itself. The yolk and the egg nucleus contribute to the cleavage patterns of a zygote. So, it is an incorrect option.
Hence, options (a), (b), (c), and (e) are incorrect.
Therefore, it can be concluded that the cleavage patterns help in the organization and the development of different regions of the embryo or the blastula and turn it into a specialized region for the functioning of an organism. This depends on the amount of yolk present and the positioning of the nucleus in an egg and are thus, classified accordingly.
Want to see more full solutions like this?
Chapter 50 Solutions
Biology: The Dynamic Science (MindTap Course List)
- Why is a second polar body expelled after fertilisation? a) To remove excess cytoplasm b) Because the oocyte must reactivate the incomplete meiosis before fusing with the sperm c) Before fusion with the sperm it must complete mitosis d) The fertilised oocyte is not a haploid cell until it expels the sperms mitochondriaarrow_forwardThe main function of the acrosome reaction is to (a) activate the egg (b) improve sperm motility (c) prevent interspecific fertilization (d) facilitate penetration of the egg coverings by the sperm (e) cause fusion of the sperm and egg pronucleiarrow_forwardHow does the production of sperm differ from the production of eggs? a. Sperm production involves meiosis, whereas egg production involves only mitosis. b. Meiosis during sperm production produces four sperm cells, whereas meiosis during egg production produces only one functional egg cell. c. Sperm are haploid, whereas eggs are diploid. d. Sperm production begins during fetal development, whereas the meiotic process that begins egg production doesn’t begin until pubertyarrow_forward
- From which of the following is the embryo developed? a) Trophoblasts b) Blastocoelen c) The yellow sacks d) Inner cell massarrow_forwardThe process forming the neural tube and plate via the intercalation of cells along the medial-lateral axis and extension along the anterior-posterior axis occurs is called? a. neurulation b. embryogenesis c. convergent extension d. morphogenesisarrow_forwardIn animals, a key difference between spermatogenesis andoogenesis is thata. only oogenesis involves meiosis.b. only spermatogenesis involves meiosis.c. spermatogenesis produces four sperm, whereas oogenesisproduces only one egg cell.d. None of the above describes a difference between the twoprocesses.arrow_forward
- During embryonic development, unique cell layers develop into specific groups of tissues or organs during a stage called ________. a. the blastula stage b. the germ layer stage c. the gastrula stage d. the organogenesis stagearrow_forwardWhich cell contributes the necessary nutrition to the growing zygote? a a polar body b the egg cell c a spermatocyte d the sperm cellarrow_forwardWhich of the following statements is incorrect?a. The placenta secretes hormones such as progesterone, hCG, and estrogen.b. Embryonic tissue and maternal tissue forms the placenta.c. The chorion supplies nutrients to the embryo by diffusion.d. The umbilical cord is formed by one artery and two veinsarrow_forward
- Which of the following is false? a. The endoderm, mesoderm, ectoderm are germ layers. b. The trophoblast is a germ layer. c. The inner cell mass is a source of embryonic stem cells. d. The blastula is often a hollow ball of cells.arrow_forwardEndoderm, Mesoderm, and Ectoderm are formed during ________. a. Gametogenesis b. Cleavage c. Gastrulation d. Organogenesisarrow_forwardWhich of the following characterizesparthenogenesis?(A) An individual may change its sex during itslifetime.(B) Specialized groups of cells grow into newindividuals.(C) An organism is first a male and then a female.(D) An egg develops without being fertilized.arrow_forward
- Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning