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Human Diploid cells have _____chromosomes in _____pairs
- -46 in 23 pairs
- (22 are nonsex chromosomes)
- (1 pair of sex chromosomes)
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X CHROMOSOME:
- -Large
- Many essential genes not related to sex determination
- -Early embryonic development
- -Barr Body (sex chromatin) represents inactivated X Chromosome
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Y CHROMOSOME:
- -Small
- -Genes in Y chromosome haessential roles in spermatogenesis
- -Short arm of Y Chromosome contains a sex-determining region of the Y (SYR) gene that encodes a testes determining factor
- -If SRY is present an embryo develops testes and becomes a male
- -If SRY is absent the embryo becomes a female.
- -Contains mores than 20 genes or gene families that affect spermatogenesis and other aspects of male growth
- -20 genes as well as the SRY gene are on the part of the Y chromosome that does NOT trade genes with parts of X Chromosome
- -Infertile men could have delted 1 of the 10 genes on the Y chromosome that control various stages of spermatogenesis
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Sex Influenced Trait:
ex: baldness
- -on human x chromosomes there are genes that are sex-linked that produce phenotypic effects that are called sex-linked traits
- -Males require only one allele for baldness becuse they have more circulating levels of testostorone
- -Females must be Homozygous for bald alleles because there is less circulating testostorone in females.
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SEXUAL DIFFERENTIATION IS DETERMINED BY:
- -chromosome and os established when an egg fertilized by a sperm
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Sexually Indifferent Stage:
- *Period when gonads , sex accesory ducts, and external genitalia of both sexes are identical
- *Genital ridges in abdominal cavity of embryo develop into indifferent gonads during the 5th week of development
- *During 6th Week the embryo has indifferent sex accesory ducts consisting of 2 pairs of ducts
- *LASTS UNTIL END OF 7TH WEEK
- *Wolffian Ducts derived from the ducts of the primitive embryonic kidney
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GONADAL SEX DIFFERENTIATION:
- *(4th or 5th week) Germ cells begint o arrive at and penetrate the different gonads
- *Primordial germ cells arise in the region of the developing allantois and migrate by amoeboid movement along the embryonic gut to the indifferent gonads
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OOVARIAN DEVELOPMENT:
If Y chromosome is not present
- *Gonads develop into ovaries
- *PRIMORDIAL GERM CELL DEVELOP INTO OOGONIA WITHIN CORTICAL CORDS OF THE OVARY AND MEDULLA DEGENERATES
- *OOGONIA UNDERGO
MITOTIC PROLIFERATION TO PRODUCE 600,000 by 8 weeks- *From -9 moth gestation the ocaries descend from abdominal position to reside in pelvic cavity
- *At birth all female germ cells are Oocytes in follicles and each ovary has 1/2 to 1 million
- *Number decreases with age cause of atresia
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TESTICULAR DEVELOPMENT:
Presence of y chromosome in the primordial germ cells and gonadal cells
- *results in testes development in 7th week
- *Seminiferous tubules of the testes develop within the medullary cords of the medulla and cortex regresses
- *testostorone producing Leydig cells appear between the medullary cords in week 9
- *Placenta secretes LH-like gonadotroping called hCG whuch may pass into male fetus and stimulate Leydig cells to begin secreting testostorone.
- *From 3-9 Month of fetal life, the testes descend to scrotum
- * testticular descent under control of MIS and TESTOSTORONE TURNED TO DHT
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DAX1
* Gene in X chromosome that is actively involved in ovary formation
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Embryos of each sex contain both _________ducts and _____________duct systems until the 7th week of development.
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Wolffian duct turns to
*epididymus, vas deferens, seminal vesicles, and ejaculatory duct
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Vasa Efferentia:
- Develop from mesonephric tubules whuch lead to wolffian duct
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DHT
-Stimulates part of urethra to develop into the prostrate fland and bulbourethral glands.
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ABNORMALITIES IN PLOIDY NUMBER:
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MATERNAL AGE AND CHROMOSOMAL ABNORMALITIES:
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SEX CHROMOSOME TRISOMY:
XXX,XXY, and XYY
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SEX CHROMOSOME MONOSOMY:
TURNERS SYNDROME:
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PSEUDOINTERSEX:
5ALPHA REDUCTASE DEFICIENCY
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PSEUDOINTERSEX:
5ALPHA REDUCTASE DEFICIENCY IN GUEVEDOCES
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PSEUDOINTERSEX:5ALPHA REDUCTASE DEFICIENCY IN GUEVEDOCES
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MALE SEX DEVELOPMENT ABNORMALITIES:
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FEMALE SEX DEVELOPMENT ABNORMALITIES:
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