Gametogenesis Flashcards
The process by which the male gamete, the sperm, and the female gamete, the oocyte, unite to give rise to a 💡zygote.
Fertilization
These are the cells were 💡gametes are derived.
They 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
Primordial Germ Cells (PGCs)
During the(1)__, these cells begin to migrate from the yolk sac toward the developing gonads, where they arrive by the end of the (2)__.
(1) fourth week
(2) fifth week
It is a process of of 💡producing gametes
Gametogenesis
Gametogenesis includes:
Meiosis
Cytodifferentiation
Humans have approximately __ genes on 46 chromosomes.
23,000
Genes on the 💡same chromosome tend to be 💡inherited together and so are known as __.
Linked genes
In somatic cells, chromosomes appear as __ to form the diploid number of 46.
23 homologous pairs
22 pairs of matching chromosomes
Autosomes
One pair of matching chromosomes
Sex chromosomes
One chromosome of each pair is derived from the maternal gamete, the (1)__, and one from the paternal gamete, the (2)__.
(1) oocyte
(2) sperm
Each gamete contains a (1)__, and the unión of the gametes at fertilization restores the (2)__.
(1) Haploid number of 23 chromosomes
(2) Diploid number of 46
It is the process whereby one cell divides, giving rise to 💡two daughter cells that are 💡genetically identical to the parent cell
MITOSIS
Before a cell enters mitosis, each chromosome __ its DNA.
replicates
It is a stage in mitosis where the chromosomes begin to 💡coil, 💡contract, and 💡condense.
PROPHASE
Two parallel 💡subunits of chromosome.
Chromatids
It 💡joins the two chromatids into a narrow region forming the chromosome.
Centromere
At what phase of mitosis where the 💡chromatids become distinguishable?
PROMETAPHASE
It is a phase of mitosis where the 💡chromosomes line up in the equatorial plañe, and their 💡doubled structure is clearly visible.
METAPHASE
It is an 💡extension of microtubles that 💡attaches chromosomes from the centromere to the centriole.
Mitotic Spindle
It marks the beginning of anaphase.
Division of centromere of each chromosome
It is a phase of mitosis where the 💡chromatids migrates to opposite poles of the spindle.
Anaphase
What happens during telophase?
Chromosomes uncoil and lengthen
The nuclear envelope reforms
The cytoplasm divides
It is the cell división that takes place in the germ cells to 💡generate male and female gametes, sperm and egg cells, respectively.
MEIOSIS
Why does meiosis requires two cell divisions, meiosis I and meiosis II.
To reduce the number of chromosomes to the haploid number of 23
It is a process seen in meiosis where 💡homologous chromosomes align themselves in pairs
Synapsis
It is the 💡interchange of chromatid segments between paired homologous chromosomes which is a 💡critical events in meiosis I.
These events 💡enhances genetic variability by 💡random distribution of homologous chromosomes to the daughter cells
CROSSOVERS
It is an 💡X-like structure that is formed from the points of interchange that temporarily united as separation occurs.
CHIASMA
Results of meiotic divisions:
- Genetic variability
2. Each germ cell contains a haploid number of chromosomes
The primitive female germ cell (primary oocyte) produces only __, the mature oocyte.
one mature gamete
The primitive male germ cell (primary spermatocyte) produces __, all of which develop into spermatozoa.
four spermatids
What will happen to the 3 daughter cells that did not mature into oocyte?
They degenerate during subsequent development because they receive little cytoplasm.
These are the 💡three daughter cells that 💡did not mature.
Polar Bodies
It is the process whereby 💡oogonia differentiate into mature oocytes.
Oogénesis
Maturation of Oocytes Begins Before __.
Birth
These are cells that formed once PGCs have arrived in the gonad of a genetic female.
Oogonia
It is a layer of single 💡flat epithelial cells where all of the 💡oogonia in one cluster are probably derived.
Follicular Cells
These are formed when the oogonia arrest their cell división in 💡prophase of meiosis I.
Primary Oocytes
By the __ of development, some oogonia give rise to primary oocytes that enter prophase of the first meiotic división.
third month
A 💡primary oocyte, together with its surrounding 💡flat epithelial cells, is known as a __
Primordial Follicles
Oocytes have entered the __ of prophase, in which they remain until just before ovulation
diplotene stage
It is a 💡resting stage during prophase that is characterized by a 💡lacy network of chromatin.
Diplotene Stage
It is a small peptide 💡secreted by follicular cells that causes the 💡primary oocyte to remain arrested in prophase and do not finish their first meiotic división before puberty is reached.
Oocyte Maturation Inhibitor (OMI)
It is a 💡space seen in primary follicles where 💡fluid accumulates as they mature.
Antrum
It is formed when the the small cavities of the primary follicle is 💡💡filled until these cavities fuse together to form a large cavity—the antral cavity/antrum.
Vesicular (Antral) Follicle
It is formed when primordial follicle begin to grow, surrounding follicular cells change from flat to 💡cuboidal and proliferate to produce a 💡stratified epithelium of 💡granulosa cells and presence of a well-defined 💡zona pellucida.
Mature Primary (Preantral) Follicle
By the __, the majority of oogonia have degenerated except for a few near the surface.
seventh month
It is a stage where mature primary (preantral) follicle 💡accumulates fluid in a space called antrum.
💡Longest stage
Antral/ Vesicular Stage
These are 💡stratified cuboidal cells that rest on a basement membrane separating them from surrounding ovarían connective tissue (stromal cells) that form the theca folliculi.
Granulosa Cells
These are 💡ovarian connective tissue (stromal cells)
Theca Folliculi
It is a layer of 💡visible in irregular patches glycoproteins on the surface of the oocyte which is 💡secreted by granulosa cells
Zona Pellucida
It is the 💡cells of the theca folliculi 💡organize into an inner layer of 💡secretory cells.
It is composed of cells having characteristics of 💡steroid secretion, rich in blood vessels
Theca interna
It is the cells of the theca folliculi organize into an 💡outer fibrous capsule and gradually merges with the ovarian connective tissue
Theca externa
It is formed when granulosa cells surrounding the oocyte remain intact.
💡MOUND OF GRANULOSA CELLS
Cumulus Oophorus
The expelled secondary oocyte is surrounded by zona pellucida and one or more layers of follicular cells, which are radially arranged as __.
CORONA RADIATA
With each ovarian cycle, a number of follicles begin to develop, but usually, only __ reaches full maturity.
one
It is a 💡space where the 💡cell membrane of the secondary oocyte lies.
perivitlline space
The secondary oocyte enters meiosis II but arrests in __ approximately 💡3 hours before ovulation.
metaphase
Meiosis II is completed only if the oocyte is __.
Fertilized
It is a process which begins at puberty, where spermatogonia are transformed into spermatozoa.
Spermatogenesis
These are 💡supporting cells, which are derived from the surface epithelium of the testis.
They protect the germ cells, particípate in their 💡nutrition, and assist in the release of mature spermatozoa.
Sustentacular cells, or Sertoli cells
It is where 💡spermatogenesis takes place.
seminiferous tubules
These are formed when PGCs give rise to spermatogonial stem cells.
Their production marks the 💡initiation of spermatogenesis.
Type A spermatogonia
They are formed from the 💡last cell division of type A spermatogonia.
Type B Spermatogonia
These are formed when type B spermatogonia undergoes 💡mitotic division.
Primary Spermatocytes
These are formed when primary spermatocytes then enter a 💡prolonged prophase (22 days) followed by 💡rapid completion of meiosis I
Secondary Spermatocytes
These are haploid cells formed when secondary spermatocytes enter 💡second meiotic division.
Spermatids
A hormone secreted by the 💡anterior pituitary gland which binds to receptors on 💡Leydig cells and 💡stimulates testosterone production, which in turn binds to Sertoli cells to 💡promote spermatogenesis.
Luteinizing Hormone
A hormone secreted by the 💡anterior pituitary gland which stimulates 💡testicular fluid production and 💡synthesis of intracellular androgen receptor proteins upon binding to sertoli cells.
Follicle-stimulating hormone (FSH)
It is the series of changes resulting in the 💡transformation of spermatids into spermatozoa.
Spermiogenesis
These are the changes during spermiogenesis:
(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 as residual bodies that are phagocytized by Sertoli cells.
It covers half of the 💡nuclear surface of the spermatocytes and 💡contains enzymes to 💡assist in penetration of the egg and its surrounding layers during fertilization
Acrosome
These are tumors of disputed origin that often 💡contain a variety of tissues, such as bone, hair, muscle, gut epithelia, and others.
Teratomas
It is a cell that give rise to all 💡three germ layers during 💡gastrulation
Epiblast cells
Numerical chromosomal abnormalities:
Down Syndrome Trisomy 18 Trisomy 13 Klinefelter Syndrome Turner Syndrome Triple X Syndrome
Structural Chromosomal Abnormalities:
Cridu-chat Syndrome Angelman Syndrome Prader-Willi Syndrome Miller-Dieker Syndrome 22q11 Syndrome Fragile X Syndrome
It refers to any exact multuple of n.
Euploid
It refers to any chromosome number that is not euploid; it is usually applied when an extra chromosome is present (trisomy] or when one is missing (monosomy).
Aneuploid
-
Nondisjunction
-
Mosaicism
-
Translocation
It is caused by an extra copy of 💡chromosome 21 (trisomy 21)
Down Syndrome
Clinical features of children with Down Syndrome:
Growth retardation Intellectual disability Craniofadal abnormalities (upward slantíng eyes, epícantlial folds) Flat facies Small ears Cardiac defects Hypotonia Broad hand with a single transverse [simian] crease.
High chances of leukemia, infections, thyroid dysfunction, and premature aging.
Earlier onset of Aizheimer disease
Incidence of Down syndrome among conceptuses for women under age 25
1 in 2,000 newborns
Incidence of Down syndrome among women under 35 years old.
1 in 300 newborns
Incidence of Down syndrome among women under 40 years old.
1 in 100 newborns
It is caused by an extra copy of 💡chromosome 18 (trisomy 18)
Edward’s Syndrome
Clinical features of children with Edward’s Syndrome:
intellectual disability congenital heart defects low-set ears flexión of fingers and hands micrognathia (deficient mandible) renal anomalies syndactyly malformations of the skeletal system
Incidence of Edward’s Syndrome:
1 in 5,000 newborns
It is caused by an extra copy of 💡chromosome 13 (trisomy 13)
Patau’ Syndrome
Clinical features of children with Patau Syndrome:
intellectual dísability holoprosencephaly congenital heart defects deafness cleft lip and palate eye defects (microphthalmia. anophthalmia, and coloboma)
Incidence of Patau Syndrome:
1 in 20,000 live births
It is caused by 💡additional X chromosome that is 💡found only in men.
XXY Chromosome + Barr Body
Klinefelter Syndrome
Clinical features of Klinefelter Syndrome:
sterility testicular atrophy hyalinization of the seminiferous tubules gynecomastia Tall stature
It is formed by 💡condensation of an inactivated X chromosome
Barr Body
Common causative event of Klinefelter syndrome
Nondisjunction of the XX homologues
Incidence of Klinefelter Syndrome
1 in 500 males
It is the only 💡monosomy compatible with life.
Karyotype: 45, X
98% of all fetuses with the syndrome are spontaneously aborted
Turner Syndrome
Clinical features of Turner syndrome:
absence of ovaries (gonadal dysgenesis) short stature webbed neck lymphedema of the extremities skeletal deformities Loose skin at the back of the neck caused by the remains of a cystic hygroma (fluid-filled cyst)
Seen at 6 years of age:
broad chest with widely spaced nipples.
Karyotype is 47, XXX
💡Seen among girls often undiagnosed however, these girls frequently have problems with 💡speech and self- esteem.
They have two sex chromatin bodies in their cells.
Triple X Syndrome
What is the usual cause of structural chromosomal abnormalities?
chromosome breakage
It is caused by 💡partial deletion of the short arm of chromosome 5.
Cri-du-chat syndrome
Clinical features of cri-du-chat- syndrome:
cat-like cry
microcephaly (small head]
intellectual disability
congenital heart disease
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Microdeletions
Contiguous genes may result?
microdeletion syndrome or contiguous gene syndrome
It is the sites where microdeletions occur,
Contiguous gene complexes
Microdeletion occurs on the 💡maternal long arm of chromosome 15
Angelman syndrome
Clinical features of Angelman syndrome:
intellectual disability
cannot speak
exhibit poor motor development
prone to unprovoked and prolonged periods of laughter
Microdeletion occurs on the 💡paternal long arm of chromosome 15
Prader-Willi syndrome
Clinical features of Prader-Willi syndrome:
hypotonia 💡obesity intellectual disability hypogonadism undescended testes
It is caused by a deletion at 💡17p13 and most cases of 💡22q11 syndrome
Miller-Dielker syndrome
Clinical features of Miller-Dielter syndrome:
lissencephaly
developmental delay
seizures
cardiac and facial abnormalities
These are regions of chromosomes that demónstrate a propensity to 💡separate or break under certain cell manipulations.
Fragile Sites
It is caused by altered phenotype in the 💡FMRI gene on the long arm of the X chromosome (Xq27) and exclusively males are affected.
Fragile X Syndrome
Clinical features of fragile X syndrome:
intellectual disability
large ears
prominent jaw
large testes
Incidence of Fragile X syndrome:
1 in 5,000 individuals
Fragile X syndrome is second only to __ as a cause of intellectual disability due to genetic abnormalities.
Down syndrome
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Mutation
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Single gene mutation
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Alleles
If a 💡mutant gene 💡produces an abnormality in a single dose, despite the presence of a normal allele, it is a?
Dominant mutation
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?
Recessive mutation
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Inborn Errors of Metabolism
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Penylketonuria
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Homocystinuria
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Galactosemia
It is used to assess chromosome number and integrity.
Cytogenetic analysis
It uses 💡specific DNA probes to identify p💡loidy for a few selected chromosomes and for detecting microdeletions.
Fluorescent in situ hybridization (FISH)
They use spots of specific DNA sequences (probes) attached to a solid surface, usually glass or Silicon (Affymetrix chips).
Microarrays
This technique represents a new approach to finding mutations and polymorphism where only the coding regions (exons) in the genome are sequenced.
It can find a causative mutation in a single affected individual if the exomes from both parents can also be sequenced.
It can only identify variants in the coding regions of genes that alter proteins
Exome Sequencing
Spermatozoa will obtain full motility in the __.
Epididymis
It is the large, 💡swollen follicle.
Mature Vesicular (Graafian) Follicles
