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123 Cards in this Set
- Front
- Back
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? production of reproductive cells (gametes) from primordial "germ" cells (PGC).
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Gametogenesis
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Gametogenesis production of gametes from ?
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Primordial "germ" cells (PGC)
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reproductive cells are called ?
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gametes
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Combination of a male (sperm) and a female (oocyte) gamete produces a ?
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Zygote
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In the production of gametes, chromosome number is reduced from ? to ? in humans.
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46 (diploid)
23 (haploid) |
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Gametogenesis utilizes a specialized form of cell division called ?
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Meiosis
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Mitosis has how many cell divisions?
Meiosis has how many cell divisions? |
1 cell division
2 cell divisions |
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Mitosis has how many daughter cells?
Are they identical or different? |
2 identical daughter cells
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Meiosis has how many daughter cells?
Are they identical or different? |
4 different daughter cells
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1st cell division of Meiosis I ---gametes are called?
2nd cell division of Meiosis II ---gametes called? |
Primary
Secondary |
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Describe the structure of a Chromosome.
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consists of 2 arms of DNA connected by a Centromere
(p-region + q-region + centromere) |
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Which arm of the chromosome is the short arm?
Long arm? |
short arm = P
long arm = Q |
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? refers to the "n" number of chromosome SETS
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Ploidy
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1 set of chromosomes is called a?
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haploid
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A haploid in humans is?
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1 set = 23 chromosomes
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True or False
Most cells have two sets one from mom and one from dad. |
True
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How many chromosomes do human cells have?
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46 chromosomes
(diploid --2 sets of chromosomes) |
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Males have how many different types of chromosomes?
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24 different types of chromosomes
22 autosomes 2 sex chromosomes |
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Females have how many different types of chromosomes?
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23 types of chromosomes
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"C" refers to the ?
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DNA content
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What occurs in the S-phase?
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DNA synthesis phase
the ARMS of the chromosome are duplicated (Chromatids) |
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True or False
During S-phase, the centromere is duplicated along with the rest of the DNA. |
FALSE
centromeres are NOT duplicated during S-Phase |
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DNA that is replicated during S-Phase is called?
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Chromatids
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During S-Phase, the cell is in a state of PARTIAL chromosomal duplication. The cells therefore have how many chromosomes and how much DNA content?
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Diploid (2n) = 46 chromosomes
4C (4x DNA content) |
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What phase do the arms (chromatids) condense?
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Prophase
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When do chromatids appear?
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S-phase
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When does the nuclear envelope disappear?
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Metaphase
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When do the chromosomes line up on the equatorial plane?
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metaphase
(they line up randomly) |
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When do the centromeres duplicate?
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Late Metaphase
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When the centromeres duplicate, they chromosomes are known as?
What is DNA content at this time? |
Tetraploid
4C |
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When do chromosome sets separate to opposite poles?
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Anaphase
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When does the nuclear envelope reform and chromosomes relax?
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Telophase
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Outer cell membrane subdivides.
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Cytokinesis
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A typical human cell will have how much DNA content?
ex: 1C 2C 3C 4C... |
2C
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What are the three steps of Prophase I during Meiosis I?
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Zygotene Stage
Pachytene Stage Diplotene Stage |
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Prolonged Diplotene stage in oogenesis is called?
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Dictyotene Stage
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When does synapsis of homologous chromosomes pair up and align gene by gene?
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Zygotene Stage (prophase I)
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Crossover / gene swapping between maternal and paternal chromatids --- causing creation of "unique" chromosomes.
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Pachytene Stage (prophase I)
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Loss of this stage during meiosis I will cause a loss of genetic variability.
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Pachytene Stage
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What stage has homologous chromsomes begin to separate, however, at regions of corssover the chromatids "cling" together.
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Diplotene Stage
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When are Chiasma seen?
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Diplotene Stage (prophase I)
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Regions of crossover where chromatids "cling" together.
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Chiasma
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True or False
Orientation of homologous pairs at meridian are random. |
True
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Term used for when homologous pairs separate.
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Disjunction
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Does Centromere duplication occur during metaphase of Meiosis I?
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NO it does NOT occur
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True or False
Chromatids are still present during Metaphase of Meiosis I |
True
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True or False
After Meiosis II, the daughter cells are different and each contain 23 SINGLE chromosomes. |
True
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True or False
After Meiosis I, daughter cells are HAPLOID and still have CHROMATIDS present. (1n, 2C) |
True
they only have 1 SET of chromosomes and 2C of DNA content) |
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Gametes have how many sets of DNA and how much DNA content?
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1n , 1C
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Complete duplication of the chromosome requires duplication of the ? and ?
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Arms (chromatids)
Centromere |
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When are centromeres duplicated in Meiosis?
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Metaphase II (Meiosis II)
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After meiosis I, chromosome # ? and DNA content is ?
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reduced
2C |
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After meiosis Ii chromosome # ? and DNA content ?
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both are reduced to half
1n 1C |
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What are the ways Genetic Variability occurs?
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Crossover (creation of new intermixed chromosomes)
Random distribution of homologous chromosomes to daughter cells |
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Meiotic nondisjunction will lead to?
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gametes with chromosomal abnormalities
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During anaphase of Meiosis I, if a homologous pairs have nondisjunction then one daughter cell will have ?chromosomes and the other ? chromosomes total.
This will ultimately lead to ? abnormal gametes |
24 chromosomes
22 chromosomes 4 abnormal gametes |
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A delay in ? duplication during Second cell division will produce gametes with 24 and 22 chromosomes giving rise to 2 abnormal gametes.
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Centromeric duplication
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When cells with abnormal chromosomal numbers survive, the condition is called?
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mosaicism
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Mitotic nondisjunction can occur when?
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early mitosis of zygote
delay in centromeric duplication |
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When a chromosomally abnormal gamete combines with a normal gamete during fertilization the zygote instead of having homologous pairs of the 23 chromosomes will contain either ? or ?
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one additional chromosome (trisomy)
one less (monosomy) |
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Which chromosome is most commonly seen in trisomies?
what are the other 4 in descending order? |
21
18 13 8 9 |
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Trisomy of chromosome 21 is--
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Down syndrome
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Most common monosomy?
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Turner Syndrome
45 , X0 Lack of Sex chromosome |
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Term used for gene swapping with other than homologous chromosome partner.
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Translocation
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What is the difference between balanced translocation vs unbalanced translocations
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balanced - No loss of genetic info
Unbalance - Genetic info is lost or disrupted |
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Translocations are most common in chromosomes ?
(basically -- homologous pairs cluster together during meiosis) |
13
14 15 21 22 |
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Most common chromosomal abnormalities in abortuses are?
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trisomy 16
triploidy (2 sperms-1 ovum) 45XO |
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Cells migrate from the yolk sac in the 3-week-old embryo
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Primordial germ cells (PGC)
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When do Primordial Germ Cells (PGC) migrate to the embryo?
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3rd week
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PGC migrate to genital ridge to form primitive gonads during what week?
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5th week
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5th week -- PGC migrate to ? to form the primitive gonads
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genital ridge
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True or False
Primordial germ cells are MITOTICALY ACTIVE. |
True
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What determines differentiation into either male or female germ cells?
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hormonal milieu to which the cells are exposed
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REMEMBER
oogenesis = female gametogenesis |
REMEMBER
oogenesis = female gametogenesis |
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Female germ cells are called?
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Oogonia
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Surface epithelium from the gonad that migrates into gonad and surrounds Germ cells
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Follicular Cells
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True or False
Oogonia initial in clusters - separate into individual cells |
True
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True or False
Central oogonia will degenerate |
True
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Thin cortical rim of oogonia survive --enter meiosis
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primary oocyte
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Oogonia have what type of active proliferation?
To what month? |
Mitotic proliferation
5th fetal month |
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True or False
Many postnatal oocytes will form. |
FALSE
Few / none will form POSTNATAL |
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Term used for the primary oocyte and its layer of follicular cells
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primordial follicle
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What regulates entry into meiosis?
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Follicular Cells
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Follicular cells secrete ? that is responsible for the ARREST of the oocytes shortly after their induction
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Oocyte Maturation Inhibitor (OMI)
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What secretes Oocyte Maturation inhibitor (OMI)?
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Follicular cells
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When are oocytes arrested?
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Dictyotene stage of Prophase
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Primary oocytes remain in ? of prophase until after puberty.
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Dictyotene stage
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? increase in size and the surrounding follicular cells are transfromed into steroid-producing cuboidal epithelium known as granulosa cells.
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Preantral (primary) follicles
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What do cuboidal epithelium known as granulosa cells secrete?
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Steroid
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steroid-producing cuboidal epithelium known as ?
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granulosa cells
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Each day primary oocytes become ?
When will they grow? |
Preantral follicles
if their activation coincides with elevated hormones of menstrual cycle => growth |
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What two layers make up the Theca Folliculi?
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Theca Interna
Theca Externa |
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What is found in the Theca Interna?
What is found in the Theca externa? |
Interna = surround stromal cells condense around developing follicles to form an inner layer of steroid secreting cells
Externa - outer layer of fibroblast-like cells |
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In what area do the oocyte and granulosa cells secrete a protective glycoprotein coat around the oocyte.
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Zona Pellucida
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A follicle which has a recognizable cavity is known as ?
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Antral (secondary) follicle
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The fluid secreted by granulosa cells that fill the antrum.
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Liqueur Folliculi
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Granulosa cells that encircle the oocyte as the antrum grows
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cumulus oophorus
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Term for a mature follicle
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Graafian (preovulatory) follicle
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When does the primary oocyte complete Meiosis I forming 2 unequal daughter cells?
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Maturation
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What is the nucleus plus all of the cytoplasm?
(regards to daughter cells of primary oocyte) |
Secondary oocyte
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What daughter cell is composed primarily of the nucleus only?
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first Polar body
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When does ovulation occu in secondary oocyte and first polar body?
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Chromosomes align in Metaphase II (meiosis II)
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When is Meiosis II division completed for the secondary oocyte and first polar body?
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ONLY OCCURS IF the oocyte is FERTILIZED
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When does male gametogenesis begin?
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At puberty (pubertal meiosis)
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Male germ cells are called?
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spermatogonia
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What are composed of Germ cells and sertoli cells?
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seminiferous tubules
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What are supporting cells of the seminiferous tubules called?
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sertoli cells
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What spermatogonia - reserve or stem cells - mitotically active?
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Type A
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What spermatogonia - immediate precursors of primary spermatocytes
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Type B
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True or False
MEIOSIS of the type B spermatogonia produces primary spermatocytes |
FALSE
MITOSIS of type B will produce primary spermatocytes |
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Primary spermatocytes have a prolonge prophase because they are arrested in what phase?
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Diplotene
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Once primary spermatocytes have rapidly completed MEIOSIS I ---leads to formation of ?
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secondary spermatocytes
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Meiosis II of secondary spermatocytes will form ?
How many sets of DNA and DNA content? |
spermatids
1n, 1c 23 chromosomes |
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True or False
Cytokinesis is incomplete during spermatogenesis thus forming protoplasmic bridges. |
True
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Sertoli cells provide ? to the spermatogonia and spermatids.
They also assist in the release of ? |
provide support, protection, nutrition
spermatozoa |
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Describe the production of spermatozoa starting with Type A cells.
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Type A dark Spermatogonia
Type A pale Spermatogonia Type B Spermatogonia Primary spermatocytes Secondary spermatocytes Spermatids => spermatozoa + residual bodies |
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The term used for the transformation of spermatids into spermatozoa
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spermiogenesis
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Describe the transformation of spermatozoa into spermatids
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formation of ACROSOME
nucleus condensation formation of neck, middle, and tail Reduction of cytoplasm |
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Development from spermatagonia to sperm takes how many days?
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74 days
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Spermatozoa are release from ? into the lumen of the ?
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Sertoli cells
Seminiferous tubules |
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Spermatozoans travel through the seminiferous tubules and then through the ?
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epididymis
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When do spermatozoa gain full motility?
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in the EPIDIDYMIS
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More than one primary oocyte within a follicle can give rise to?
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twins/triplets etc.
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