Term
In what portion of the uterus does implantation usually occur? |
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Definition
The Posterior upper third of the uterus |
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Term
The Cytotrophoblast develops into the __________
after the zygote meets the uteran wall. |
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Definition
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Term
Buccopharyngeal membrane, Primitive streak, cloacal membrane, and primitive node (& pit) are all landmarks of what part of the pre-gastrulation embryo? |
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Definition
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Term
The cloacal membrane is the future _________ |
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Definition
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Term
The axes of the embryo are are established before or after gastrulation? |
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Definition
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Term
What is the name given for the formation of 3 germ layers from the Epiblast? What are the germ layers? |
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Definition
Gastrulation is the formation of ectoderm, mesoderm, and endoderm |
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Term
What embryological 'major determining event' is the last stage at which twinning can occur? |
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Definition
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Term
Which of the following is NOT correct?
A. Mesoderm, Endoderm & Ectoderm refer to germ layers and developmental lineage
B. Mesenchyme (M) and epithelium (E) are histological terms that refer to the form of the tissue
C. Mesenchyme is embryonic epithelial tissue
D. Epithelia are derived from all three germ layers & both neural tube and neural crest |
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Definition
C. Mesenchyme is embryonic connective tissue |
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Term
Most mesenchyme is mesodermal in origin, but it can also arise from what? |
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Definition
Neural crest (sometimes called ectomesenchyme) |
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Term
What phase of embryogenesis changes the fate of the epiblast cells so that they become determined? |
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Definition
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Term
Primordial germ cells can be found where and at what week after fertilization? |
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Definition
Gametes are derived from primordial germ cells (PGCs) that are formed in the epiblast during the second week and that move to the wall of the yolk sac |
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Term
| During the fourth week after fertilization, primordial germ cells begin to migrate from the yolk sac toward the developing gonads, where they arrive by the end of the fifth week. Mitotic divisions increase their number during their migration and also when they arrive in the gonad. In preparation for fertilization, what process do these cells undergo, which includes meiosis, to reduce the number of chromosomes and cytodifferentiation to complete their maturation? |
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Definition
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| Some evidence suggests that primordial germ cells that have strayed from their normal migratory paths could be responsible for some of the tumors found in a patient. Another source is epiblast cells migrating through the primitive streak during gastrulation. What type of tumors does this patient have? |
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Definition
Teratomas; these are tumors of disputed origin that often contain a variety of tissues, such as bone, hair, muscle, gut epithelia, and others. |
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Term
A tumor is found in a patient. It is thought that this tumor could arise from a pluripotent stem cell that can differentiate into any of the three germ layers or their derivatives. What type of tumor is this? |
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Definition
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Term
During this phase, the chromosomes are extremely long, they are spread diffusely through the nucleus, and they cannot be recognized with the light microscope. What phase of the cell cycle is described? |
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Definition
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Term
At what phase of mitosis do the chromatids become distinguishable? |
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Definition
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Term
What marks the beginning of anaphase? |
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Definition
Centromere division of chromosomes |
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Term
At the end of the third week, where could one find the primordial germ cells in an embryo? Where will they migrate towards? |
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Definition
In the wall of the yolk sac; they will migrate towards the developing gonad |
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Term
What terms are given to male and female germ cells, respectively? |
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Definition
spermatocytes and primary oocytes |
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Term
What name is given to the process where homologous chromosomes align themselves in pairs in meiosis?
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Definition
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Term
What does Meiosis II separate? |
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Definition
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Term
The approximately 30 to 40 crossovers (one or two per chromosome) with each meiotic I division are most frequent between genes that are closer or farther apart on a chromosome? |
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Definition
crossovers with each meiotic I division are most frequent between genes that are far apart on a chromosome. |
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Term
Segments of chromatids break and are exchanged as homologous chromosomes separate. As separation occurs, points of interchange are temporarily united and form what X-like structure? |
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Definition
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Term
Which of the following is NOT one of the most common chromosomal abnormalities in abortuses (spontaneous abortions)?
A. 45,X (Turner syndrome)
B. Cri-du-chat syndrome
C. Trisomy 16
D. Triploidy |
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Definition
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Term
True or False: Abnormalities in chromosome number may originate during meiotic or mitotic divisions. |
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Definition
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Term
In meiosis, two members of a pair of homologous chromosomes normally separate during the first meiotic division, so that each daughter cell receives one member of each pair. Sometimes, however, separation does not occur, and both members of a pair move into one cel. This is known as what? |
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Definition
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Term
| Occasionally, nondisjunction occurs during mitosis (mitotic non-disjunction) in an embryonic cell during the earliest cell divisions. Affected individuals may exhibit few or many of the characteristics of a particular syndrome, depending on the number of cells involved and their distribution. What is this result of mitotic non-disjunction called? |
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Definition
Mitotic non-disjunctions produce mosaicism, with some cells having an abnormal chromosome number and others being normal. |
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Term
Which of the following is not a common chromosome for translocations involving down syndrome? Why?
A. 13
B. 14
C. 15
D. 16
E. 21
F. 22
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Definition
D;
Chromosomes 13,14,15,21, and 22 cluster during meiosis |
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Term
In 75% of trisomy 21 instances, when does non-disjunction occur (in reference to phases of gametogenesis)? |
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Definition
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Term
What is the clinical features of Klinefelter syndrome, which is only found in males and usually detected by puberty?
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Definition
Sterility, testicular atrophy, hyalinization of the seminiferous tubules, and usually gynecomastia (abnormally large mammary glands in males) |
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Term
47 XXY in addition to the presence of a Barr body (in 80% of cases) describes a male or female with what disorder? |
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Definition
A male with Klinfelter's syndrome |
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Term
Nondisjunction of the XX homologues is the most common causative event in what disorder? |
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Definition
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Term
Which of the following is NOT true?
A. Turner syndrome, with a 45,X karyotype, is the only monosomy compatible with life
B. 98% of all fetuses with Turner syndrome are spontaneously aborted
C. Turner syndrome is characterized by the absence of ovaries (gonadal dysgenesis) and short stature
D. In ~40% of affected men, nondisjunction in the female gamete is the cause |
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Definition
D. In ~40% of affected women, nondisjunction in the male gamete is the cause |
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Term
Patients with ______ syndrome are infantile, with scanty menses and some degree of mental retardation. They have two Barr (sex chromatin) bodies in their cells |
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Definition
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Term
| A well-known syndrome, caused by partial deletion of the short arm of chromosome 5, is the cri-du-chat syndrome. Such children have what unique syndrome? |
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Definition
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Term
| Microdeletions, spanning only a few contiguous genes, may result in microdeletion syndrome or contiguous gene syndrome. Sites where these deletions occur, called contiguous gene complexes, can be identified by high-resolution chromosome banding. An example of a microdeletion occurs on the long arm of chromosome 15 (15q11–15q13). Inheriting the deletion on the maternal chromosome results in what disorder? |
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Definition
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Term
| Microdeletions, spanning only a few contiguous genes, may result in microdeletion syndrome or contiguous gene syndrome. Sites where these deletions occur, called contiguous gene complexes, can be identified by high-resolution chromosome banding. An example of a microdeletion occurs on the long arm of chromosome 15 (15q11–15q13). If the defect is inherited on the paternal chromosome, what syndrome is produced? |
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Definition
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Term
Characteristics that are differentially expressed depending upon whether the genetic material is inherited from the mother or the father are examples of what concept? |
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Definition
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Term
| Fragile sites are regions of chromosomes that demonstrate a propensity to separate or break under certain cell manipulations. For example, fragile sites can be revealed by culturing lymphocytes in folate-deficient medium. Although numerous fragile sites have been defined and consist of CGG repeats, only the site on which chromosome has been correlated with an altered phenotype, resulting in what disorder? |
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Definition
The long arm of the X chromosome (Xq27) has been correlated with an altered phenotype and is called the fragile X syndrome |
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Term
| Males are affected more often than females (1 per 1,000 vs. 1 per 2,000), which may account for the preponderance of males among the mentally retarded. What syndrome, which is second only to Down syndrome as a cause of mental retardation, is caused because of chromosomal abnormalities and can explain this preponderance? |
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Definition
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Term
What molecular technique uses specific DNA probes to identify ploidy for a few selected chromosomes? |
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Definition
fluorescence in situ hybridization (FISH) |
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Term
When (at what point in embryogenesis) can one expect to see oogonia formation? |
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Definition
Once primordial germ cells have arrived in the gonad of a genetic female, they differentiate into oogonia |
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Term
Oogonia undergo a number of mitotic divisions, and by the end of the third month are arranged in clusters surrounded by a layer of flat epithelial cells. Whereas all of the oogonia in one cluster are probably derived from a single cell, what cells originate from surface epithelium covering the ovary? |
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Definition
The flat epithelial cells, known as follicular cells, originate from surface epithelium covering the ovary. |
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Term
By the what month of prenatal development do the total number of germ cells in the ovary reach their maximum, estimated at 7 million? |
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Definition
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Term
A primary oocyte, together with its surrounding flat epithelial cells, is known as what structure? |
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Definition
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