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Embryology > Chapter 2 > Flashcards

Chapter 2 Flashcards

1
Q

Development begins with fertilization, the process by which the male gamete, the ___, and the female gamete, the ___, unite to give rise
to a zygote

A

sperm - oocyte

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2
Q

There are 22 pairs of matching chromosomes, the ____, and one pair of ____

A

autosomes - sex chromosomes

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2
Q

Gametes are derived from ___ that are formed in the
epiblast during the second week, move through
the primitive streak during gastrulation, and migrate to the wall of the yolk sac

A

primordial germ cells (PGCs)

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3
Q

In preparation for fertilization, germ cells undergo _____, which includes meiosis, to reduce the number of chromosomes and ____ to complete their maturation

A

gametogenesis - cytodiflerentiation

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3
Q

____ are tumors of disputed origin that often contain a variety of tissues, such as bone, hair, muscle, gut epithelia, and others

A

Teratomas

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3
Q

Genes on the same chromosome tend to be inherited together and so are known as_____

A

linked genes

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3
Q

In somatic cells, chromosomes appear as 23 ___ to form the ___ number of 46

A

homologous pairs - diploid

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4
Q

Before a cell enters mitosis, each chromosome replicates its ___

A

DNA

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4
Q

One chromosome of each pair is derived from the maternal gamete, the __, and one from the paternal gamete, the __

A

oocyte - sperm

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5
Q

With the onset of mitosis, the chromosomes begin to coil, contract, and condense; these events mark the beginning
of ___.

A

prophase

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5
Q

___ is the process whereby one cell divides, giving rise to two daughter cells that are genetically identical to the parent cell

A

Mitosis

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5
Q

Each chromosome now consists of two parallel subunits, ___, that are joined at a narrow region common to both called the ___

A

chromatids - centromere

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6
Q

Each is attached by ___ extending from the centromere to the centriole, forming the ____

A

microtubules - mitotic spindle

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7
Q

___ is the cell division that takes place in the ____ to generate male and female gametes, sperm and egg cells, respectively

A

Meiosis - germ cells

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8
Q

Meiosis requires two cell divisions, ___ and ___, to reduce the number of chromosomes to the haploid number of 23

A

meiosis I and meiosis II

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9
Q

As in mitosis, male and female germ cells (___ and ___) at the begining of meiosis I replicate their DNA so that each of the 46 chromosomes is duplicated into sister chromatids.

A

spermatocytes and primary oocytes

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9
Q

____, critical events in meiosis I, are the interchange of chromatid segments between paired homologous chromosomes

A

Crossovers

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10
Q

In contrast to mitosis, however, ____ then align themselves in pairs, a process called synapsis

A

homologous chromosomes -

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10
Q

As separation occurs, points of interchange are temporarily united and form an X-like structure, a ___

A

chiasma

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11
Q

In contrast to mitosis, however, homologous chromosomes then align themselves in ___, a process called __

A

pairs - synapsis

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12
Q

Only one of these develops into a mature gamete, however, the oocyte; the other three, the ___, receive little cytoplasm and degenerate during subsequent development

A

polar bodies

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12
Q

Normal somatic cells are __, or 2n

A

diploid

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13
Q

_____, which may be numerical or structural, are important causes of birth defects and spontaneous abortions

A

Chromosomal abnormalities

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14
Q

Chromosomal abnormalities account for 10% of major birth defects, and ____ account for an additional 8%

A

gene mutations

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15
Q

Normal gametes are ___, or n.

A

haploid

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16
Q

___ refers to any exact multiple of n [e.g., diploid or triploid]. ___ refers t
o any chromosome number that is not euploid. It is usually applied when
an extra chromosome is present [____] or when one is missing [____]

A

Euploid - Aneuploid - trisomy - monosomy

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17
Q

Such ____ may be balanced, in which case breakage and reunion occur between two chromosomes, but no critical genetic material is lost and individuals are normal; or they may be unbalanced, in which case part of one chromosome is lost, and an altered phenotype is produced.

A

translocations

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17
Q

Sometimes, however, separation does not occur [____], and both members of a pair move into one cell

A

nondisjunction

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18
Q

In ____, 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

A

meiosis

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19
Q

In 95% of cases, the syndrome is caused by trisomy 21 resulting from meiotic nondisjunction, and
in 75% of these instances, nondisjunction occurs during ___

A

oocyte formation

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19
Q

Such translocations may be ___, in which case breakage and reunion occur between two chromosomes, but no critical genetic material is lost and individuals are normal; or they may be ___, in which case part of one chromosome is lost, and an altered phenotype is produced.

A

balanced - unbalanced

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20
Q

Down syndrome is caused by an extra copy of _____

A

chromosome 21 [trisomy 21]

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21
Q

These individuals have __, with some cells having a normal chromosome number and some having trisomy.

A

mosaicism

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22
Q

Patients with ___ show the following features: intellectual disability, congenital heart defects, low—set ears, and flexion of fingers and hands

A

trisomy 18

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23
Q

The clinical features of _____, found only in males and usually detected by amniocentesis, are sterility, testicular atrophy, hyalinization of the seminiferous tubules, and usually gynecomastia.

A

Klinefelter syndrome

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24
Q

The cells have 47 chromosomes with a sex chromosomal complement of the XXY type, and a ____ is found in 80% of cases

A

sex chromatin [Barr] body

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25
Q

[____: formed by condensation of an inactivated X chromosome; Is also present in normal females because one of the X chromosomes is normally inactivated].

A

Barr body

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26
Q

_____, with a 45,X karyotype, is the only monosomy compatible with life. Even then, 98% of all fetuses with the syndrome are spontaneously aborted

A

Turner syndrome

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27
Q

(Turner syndrome) The few that survive are unmistakably female in appearance and are characterized by the absence of ovaries [____] and short stature

A

gonadal dysgenesis

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28
Q

(Turner syndrome) In 80% of these females, nondisjunction in the ___ is the cause.

A

male gamete

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29
Q

Patients with ____ often go undiagnosed because of their mild physical features.

A

triple X syndrome [47,XXX]

30
Q

_____, which involve one or more chromosomes, usually result from chromosome breakage.

A

Structural chromosome abnormalities

31
Q

In some cases, the broken piece of a chromosome is lost, and the infant with partial ___ of a chromosome is abnormal.

A

deletion

32
Q

A well-known syndrome, caused by partial deletion of the short arm of chromosome 5, is the ____.

A

cri-du-chat syndrome

33
Q

____, spanning only a few contiguous genes, may result in microdeletion syndrome or contiguous gene syndrome. Sites where these deletions occur, called contiguous gene complexes, are usually identified by fluorescence in situ hybridization

A

Microdeletions

34
Q

When the microdeletion occurs on the maternal chromosome, it results in ____, and the children have intellectual disability, cannot speak, exhibit poor motor development, and are prone to unprovoked and prolonged periods of laughter

A

Angelman syndrome

34
Q

Microdeletions, spanning only a few _____, may result in microdeletion syndrome or _____. Sites where these deletions occur, called _____, are usually identified by ____

A

contiguous genes - contiguous gene syndrome - contiguous gene complexes - fluorescence in situ hybridization

35
Q

If the microdeletion occurs on the paternal chromosome, _____ results. Affected individuals are characterized by hypotonia, obesity, intellectual disability, hypogonadism, and undescended testes

A

Prader-Willi syndrome

36
Q

Characteristics that are differentially expressed depending upon whether the genetic material is inherited from the mother or the father are examples of ____

A

genomic imprinting

37
Q

Other contiguous gene syndromes may be inherited from either parent, including ____ [lissencephaly, developmental delay, seizures, and cardiac and facial abnormalities resulting from a deletion at 17p13] and most cases of ___ [palatal defects, conotruncal heart defects, speech delay, learning disorders, and schizophrenia—like disorder resulting from a deletion in 22q11]

A

Miller-Dieker syndrome - 22q11 syndrome

38
Q

____ are regions of chromosomes that demonstrate a propensity to separate or break under certain cell manipulations.

A

Fragile sites

39
Q

Although numerous fragile sites have been defined and consist of ___, only those in the____ gene on
the long arm of the X chromosome [Xq27] have
been correlated with an altered phenotype
that is called the ____

A

CGG repeats - FMRI - fragile X syndrome

40
Q

Many birth defects are directly attributable to a change in the structure or function of a single gene, hence the name _____

A

single gene mutation

41
Q

If a mutant gene produces an abnormality in a single dose, despite the presence of a normal allele, it is a ___

A

dominant mutation

42
Q

With the exception of the X and Y chromosomes in the male, genes exist as pairs, or ____, so that there are two doses for each genetic determinant

A

alleles

43
Q

If both alleles must be abnormal [double dose] or if the mutation is X-linked [occurs on the X chromosome] in the male, it is a ______. Variations in the effects of mutant genes may be a result of ____

A

recessive mutation - modifying factors

44
Q

If the mutation occurs in a
somatic cell, the individual will have ____ [having more than one genetically distinct cell line] with some cells having the mutation and some not.

A

mosaicism

45
Q

In addition to causing congenital malformations, mutations can result in ____

A

inborn errors of metabolism

46
Q

_____ is used to assess chromosome number and integrity

A

Cytogenetic analysis

47
Q

These diseases, among which ____, ____, and ___ are the best known, may be accompanied by or cause various degrees of intellectual disability if proper diets and medical care are not instituted

A

phenylketonuria, homocystinuria, and galactosemia

48
Q

Chromosomes are ____ to reveal light and dark banding patterns unique for each chromosome.

A

Giemsa-stained

48
Q

Recently, _____ have been developed that demonstrate greater numbers of bands representing even smaller pieces of DNA, thereby facilitating diagnosis of small deletions.

A

high-resolution metaphase banding techniques

49
Q

_____, such as fluorescent in situ hybridization [FISH], use specific DNA probes to identify ploidy for a few selected chromosomes and for detecting microdeletions

A

Molecular techniques

49
Q

____ use spots of specific DNA sequences [probes] attached to a solid surface, usually glass or silicon [Affymetrix chips].

A

Microarrays

50
Q

_____ represents a new approach to finding mutations and polymorphisms [single nucleotide changes [SNPs] in a DNA sequence] responsible for birth defects and diseases

A

Exome sequencing

51
Q

Exome sequencing represents a new approach to finding ____ and ___ [single nucleotide changes [SNPs] in a DNA sequence] responsible for birth defects and diseases

A

mutations - polymorphisms

52
Q

Together, these coding regions make up the ___ and represent only 1% of the entire human genome,
thereby making sequencing them more practical than trying to sequence all of the genome

A

exome

53
Q

This arrested state is produced by ____, a small peptide secreted by follicullar cells

A

oocyte maturation inhibitor (OMI)

54
Q

Once ____ have arrived in the gonad of a genetic female, they differentiate into oogonia

A

PGCs

54
Q

Once PGCs have arrived in the gonad of a genetic female, they differentiate into___

A

oogonia

54
Q

Whereas all of the oogonia in one cluster are probably derived from a single cell, the flat epithelial cells, known as ____, originate from surface epithelium covering the ovary

A

follicular cells

55
Q

The majority ofoogonia continue to divide by mitosis, but some of them arrest their cell division in prophase of meiosis I and form ____

A

primary oocytes

56
Q

Cell death begins, and many oogonia as well as primary oocytes degenerate and become ____

A

atretic

57
Q

A primary oocyte, together with its surrounding flat epithelial cells, is known as a ____

A

primordial follicle

58
Q

Near the time of birth, all primary oocytes have started prophase of meiosis I, but instead of proceeding into metaphase, they enter the ___, a resting stage during prophase that is characterized by a lacy network of chromatin

A

diplotene stage

59
Q

Some of these die, whereas others begin to accumulate fluid in a space called the ___, thereby entering the antral or vesicular stage

A

antrum

60
Q

Some of these die, whereas others begin to accumulate fluid in a space called the antrum, thereby entering the ____

A

antral or vesicular stage

61
Q

Fluid continues to accumulate such that, immediately prior to ovulation, follicles are quite swollen and are called ___ or ___

A

mature vesicular follicles or graafian follicles

62
Q

As primordial follicles begin to grow, surrounding follicular cells change from flat to cuboidal and proliferate to produce a stratified epithelium of ___, and the unit is called a primary follicle

A

granulosa cells

63
Q

Granulosa cells surrounding the oocyte remain intact and form the ____. At maturity, the _____ may be 25 mm or more in diameter

A

cumulus oophorus - mature vesicular (graafian) follicle

64
Q

As primordial follicles begin to grow, surrounding follicular cells change from flat to cuboidal and proliferate to produce a stratified epithelium of granulosa cells, and the unit is called a ___

A

primary follicle

65
Q

Granulosa cells rest on a basement membrane separating them from surrounding ovarian connective tissue (stromal cells) that form the ____

A

theca folliculi

66
Q

Also, granulosa cells and the oocyte secrete a layer of glycoproteins on the surface of the oocyte, forming the ____

A

zona pellucida

67
Q

Coalescence of these spaces forms the___, and the follicle is termed a ____

A

antrum - vesicular or an antral follicle

67
Q

As follicles continue to grow, cells of the theca folliculi organize into an inner layer of secretory cells, the ____, and an outer fibrous capsule, the ____

A

theca interna - theca externa

67
Q

When the secondary follicle is mature, a surge in _____ induces the preovulatory growth phase

A

luteinizing hormone (LH)

68
Q

Spermatogenesis, which begins at puberty, includes all of the events by which spermatogonia are transformed into ____

A

spermatozoa

68
Q

One cell, the ____, receives most of the cytoplasm; the other, the ___ body, receives practically none

A

secondary oocyte - first polar

68
Q

____, which begins at puberty, includes all of the events by which spermatogonia are transformed into spermatozoa

A

Spermatogenesis

69
Q

Shortly before puberty, the sex cords acquire a lumen and become the ___

A

seminiferous tubules

69
Q

Spermatogenesis, which begins at puberty, includes all of the events by which ___ are transformed into spermatozoa

A

spermatogonia

70
Q

The last cell division produces ___, which
then divide to form primary spermatocytes

A

type B spermatogonia

70
Q

Supporting cells, which are derived from the surface epithelium of the testis in the same manner as follicular cells, become ___

A

sustentacular cells or Sertoli cells

71
Q

At regular intervals, cells emerge from this stem cell population to form ____, and their production marks the initiation of spermatogenesis

A

type A spermatogonia

72
Q

The last cell division produces type B spermatogonia, which
then divide to form ___

A

primary spermatocytes

73
Q

Primary spermatocytes
then enter a prolonged prophase (22 days) followed by rapid completion of meiosis I and formation of ____

A

secondary spermatocytes

74
Q

During the second meiotic division, these cells immediately begin to form haploid ____

A

spermatids

75
Q

____ is also essential because its binding to Sertoli cells stimulates testicular fluid production and synthesis of intracellular androgen receptor proteins

A

Follicle-stimulating hormone (FSH)

76
Q

The series of changes resulting in the transformation of spermatids into spermatozoa is ____

A

spermiogenesis

77
Q

Every month, 15 to 20 follicles begin to grow, and as they mature, they pass through three stages:

A

(1) primary or preantral
(2) vesicular or antral
(3) mature vesicular or graafian follicle

78
Q

Spermatids go through a series of changes (spermiogenesis), including;

A

(1) formation of the acrosome
(2) condensation of the nucleus
(3) formation of neck, middle piece, and tail
(4) shedding of most of the cytoplasm

Embryology (21 decks)

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