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Human cells: how many chromosomes?
a set of 46 chromosomes (23 pairs).- Sex chromosomes ( pair) determine sex in humansFemales: XXMales: XY AutosomesOther 22 pairsof chromosomes TERM 2
Fertilization
DEFINITION 2 Fusion of sperm (X or Y) and egg (only X) .fertilization is the fusion of gametes to initiate the development of a new individual organism. TERM 3
fertilized egg
DEFINITION 3 zygote: XX or XYA zygote, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. If the X-bearing sperm joins with the egg, the result is a female If a Y-bearing sperm joins with the egg, the result is a male TERM 4
Why a Male is a Male?
DEFINITION 4 Anyone who carries a Y chromosome is almost alwaysmale, no matter how many X chromosomes he may have.Female chromosome is (46, XX), and male (46, XY).~ Does the number of X chromosome determine the sex? No~A person with only one X chromosome (45, X)? female~Two X chromosome and one Y chromosome (47, XXY)? male TERM 5
Sperm Sorting for Sex
Selection
DEFINITION 5 Sperm sorted by laser based on how brightly they reflect fluorescent light X chromosome bigger than Y chromosome so they reflect more lightIsolated sperm can be used in GIFT or IVFuses Fluorescence-activated cell sorting (FACS)
FACS
Fluorescence-activated cell sorting TERM 7
GIFT
DEFINITION 7 Gamete Intra-Fallopian Transfer Sperm and eggs placed in uterus directly Cost $4,000 to $6, TERM 8
IVF
DEFINITION 8 In vitro fertilization. Fertilized with eggs in a dish and culture More costSuccess rate: ~90% for female births~73% for male births TERM 9
PGD
DEFINITION 9 Preimplantation Genetic DiagnosisWoman given hormone treatments, Multiple eggs surgically removed, Eggs placed in a dish with sperm for in vitro fertilization (IVF), Embryos develop to the 8-cell stage in the incubator, then PGD is performed.Success rate: ~100% cost $12,000 to $15,0001. Single cell (blastomere) removed from each 8-cell embryo2. Chromosomes analyzed to determine the sex3. Embryos of the desired sex placed into the mothers uterus4. Unused embryos: Frozen for later use Donation to other couples or for research TERM 10
where do egg and sperm
fuse?
DEFINITION 10 Fusion of sperm and egg generally occurs in fallopian tubeform a zygote with 46 chromosomes (diploid, 2n)Usually one sperm enters the egg Chemical changes prevent more than one sperm fromentering the egg
Chorion
Chorion produces human chorionic gonadotropin(hCG) Function of hCG Prevent the lining of the uterus from breakdown Prevent the embryo from expelling hCG in urine used for home pregnancy test Declines after 8 weeks TERM 17
1st Trimester
DEFINITION 17 First Trimester (fertilization to 13 weeks): Weeks 5/6: Most of organ systems formed; Limbs develop Week 7: Baby's head develops Week 8: Baby's eyes are visible Week 9: Baby's toes form TERM 18
2nd Trimester
DEFINITION 18 Second Trimester (14 25/26 weeks):Week 15: Baby's skeleton develops bonesWeek 16: Baby can make sucking motionsWeek 18: Baby begins to hearHeartbeat can be detected with a stethoscope Organ maturation 4th month, mother can feel movement End of the 2nd trimester, fetus~ 700 grams (27 oz.) 30-40 cm (~13) TERM 19
Third Trimester
DEFINITION 19 Rapid growth Fetus doubles in size during the last 8 weeks Circulatory system and respiratory system matureChances for survival outside the uterus increaserapidly(25 38 wks) TERM 20
Formation of reproductive organs controlled
by interaction between:
DEFINITION 20 Gene function Maternal environment: Hormones
Sex Determination 3
Stages
Sex can be defined at several levels:1. Chromosomal sex XY or XX2. Gonadal sex internal organs (testes or ovary)3. Phenotypic sex external appearance In rare case, they are not same. TERM 22
First Stage of Sex
Development
DEFINITION 22 Chromosomal sex begins at fertilization Zygote has either an XX or XY Sex organs do not develop until week 7 or 8o Gonads and ducts - nonspecific TERM 23
Second Stage of Sex
Formation
DEFINITION 23 The second stage = gonadal sex Expression of a gene (SRY) on the Y chromosome causes the gonads to become testes Testes cells secrete testosterone Male sex hormone Control the development of the external and internalmale reproductive organs XX chromosome (no Y) No SRY no testes no testosterone The gonad develops as an ovary Female development is default TERM 24
Third Stage of Sex
Formation
DEFINITION 24 The third stage = phenotypic sex Fetus can be identified by external genitalso Males: penis and scrotumo Females: clitoris, labia minora, and labia majora TERM 25
Complete androgen insensitivity Syndrome
(CAIS)
DEFINITION 25 XY individuals with CAIS: SRY gene expressed normally Gonads (testes) produce testosterone normally Mutation of androgen receptor (AR) gene Receptor for testosterone or hormones derived fromtestosterone is defect Cells in the gonads and duct cannot respond tohormones
Seminal
vesicles
male glands provide fructose (a sugar) - energy source provide prostaglandins - chemical messengers stimulatingcontractions of female reproductive system to assist in spermmovement TERM 32
Prostate
DEFINITION 32 male glands secretes a milky, alkaline fluid - neutralizes acidic vaginalsecretions and enhances sperm viability TERM 33
Bulbourethral glands
DEFINITION 33 male glandssecrete a mucus-like substance - provides lubrication TERM 34
sperm production
DEFINITION 34 Produced by spermatogenesis in the seminiferous tubules. Move to epididymis for storage Muscles move sperm to the vas deferens when amale is sexually aroused Move to the urethra Expelled out by muscular contractions duringejaculation (25 to 250 million sperm) TERM 35
Vasectomy
DEFINITION 35 Surgical procedure for malesterilization (birth control) Vas deferens cut and closed off The secretions of three glands makeup the ejaculate Sperm absent from the ejaculate Sperm still produced but absorbed
Spermatogenesis
Process that sperm form Occurs in seminiferous tubules Begins at puberty and continues throughout life Germ cells celled spermatogonia (2n = 46) divideby mitosis to form spermatocytes Spermatocytes (2n = 46) undergo meiosis toproduce intermediate cells, spermatids (n = 23) Spermatids form mature sperm (n) with tails TERM 37
Fallopian tubes (Oviduct)
DEFINITION 37 Finger-like projections surround the ovary Fertilization occurs Open into the uterus TERM 38
Uterus
DEFINITION 38 Hollow pear-shaped muscular organ Implantation of fertilized egg (blastocyst) Outer thick layer: myometrium Inner uterine tissue: endometrium The innermost layers are shed at menstruation,if fertilization has not occurred TERM 39
Cervix
DEFINITION 39 Lower neck of the uterus Opens into the vagina receives the penis during intercourse serves as the birth canal TERM 40
Egg Production
DEFINITION 40 OogenesisControlled by cycle of hormones: GnRH, LH and FSHFollicles consist of a developing oocyte surrounded by an outer layer follicle cells Oogonia (2n = 46) divide by mitosis to form primaryoocytes during embryonic development Primary oocytes (2n) begin meiosis I around birthand then stop (first arrest) At puberty, meiotic division of primary oocytescompletes to form secondary oocytes (n) Secondary oocytes arrested again in meiosis II After ovulation, 2nd meiosis completed by fertilization
Hormone levels
Estrogen: Produced by follicle cells Induced by LH and FSH Level up before ovulation triggers ovulation No, too little, or irregular estrogen level No egg release from ovary TERM 47
Absent or Damaged Ovaries
DEFINITION 47 Surgical removal (ovariectomy) Damage by other surgeries, inflammation, radiation,or infections Ovarian cysts can prevent egg maturation or release Some genetic conditionscause a female baby to beborn without ovaries TERM 48
Premature Menopause
DEFINITION 48 It is rare Some women stop menstruation and entermenopause at an early age This condition more in women: who are extremely athletic who have had low body weight for many years TERM 49
Secondary Amenorrhea
DEFINITION 49 Secondary amenorrhea woman has been having normal cyclesbut stops getting her periods for 6 monthsor longer caused by hormonal disturbances:stress, low body weight, nutrition, andexcessive physical activities reversible condition TERM 50
Fallopian Tube Blockage
DEFINITION 50 15% of female infertility Sperm and egg cannot connect Causes: Infections by sexually transmitted bacteria and virus inflammation and scarring closing fallopian tubes Appendicitis (inflammation of the appendix),colitis (inflammation of the large intestine) blockage of fallopian tubes Adhesions by previous surgery
Endometriosis
A problem with the inner lining of uterine wall - abnormalor too much/too little material along the endometrium Cells from the lining of the uterus grow in other areas ofthe body cause pain, irregular bleeding, and infertility The cause is unknown Not affect fertilization Leading implantation problemor detachment of embryo fromuterine wall miscarriage TERM 52
Causes of Infertility in Males
DEFINITION 52 One in 25 men are infertile Easier to detect, but often harder to treat Problems with sperm formation or spermthemselves: Low sperm count Low sperm motility No sperm Impotence (ED) TERM 53
Low Sperm Count (Oligospermia)
DEFINITION 53 Most common cause (50%) Less than 20 million per ejaculation Causes: genetic, environmental or habit Exposure to chemicals (lead, pesticide), radiation Drugs (marijuana) Diseases: mumps, diabetes Alcohol consumption Injury to the testes and undescended testes TERM 54
Low Sperm Count
DEFINITION 54 Sperm production is temperature sensitive: Laptop Hot tub Tight underwear High fat/red meat dietsAverage count per ejaculation: 280 million Normal concentration: at least 20 million/ml Average volume at ejaculation: 1.5 to 5 ml Hypospermia: less than 1.5 ml semen volume At least 60% of the spermatozoa should be alive andhave a normal shape (with normal motility) The average sperm count declined TERM 55
Sperm Shape and Motility
DEFINITION 55 Low sperm motility (Asthenozoospermia) Causes: defects in structure No tail, short tail, coiled tail
Egg donor
surrogacy
The surrogate contributes eggs which are fertilized byartificial insemination using sperm of infertile couplesmale partner Surrogate mom carries the embryos to term andsurrenders the baby after term. TERM 62
Gestation surrogacy
DEFINITION 62 The surrogate mom carries the embryo to term but theegg and sperm are from two other people, who maybe unrelated to the infertile couple. TERM 63
Chromosomes
DEFINITION 63 Structure: p arm short q arm long Centromere Telomeres shortenwith each cell division Cytogenetic bands TERM 64
Homologous chromosomes
DEFINITION 64 A homologous chromosomes is a set of one maternal chromosome and one paternal chromosome that pair up with each other inside a cell during meiosis. Homologous chromosome pairs separate to produceshaploid cells with one copy of each chromosome (n = 23) TERM 65
Stages of Meiosis I
DEFINITION 65 Interphase IProphase IMetaphase IAnaphase ITelophase ICytokinesis
Prophase I
As meiosis begin, chromosomes coil and shorted by condensation, and become visible under the microscope.Paired homologouschromosomes may exchange parts by crossing over (recombination) TERM 67
Metaphase I
DEFINITION 67 Paired chromosomes line up at the equator of the cell. Spindle fibers attach to the centromeres of each pair TERM 68
Telophase I
DEFINITION 68 Chromosome becomes uncoiled and nuclei reform TERM 69
Anaphase I
DEFINITION 69 Members of each homologous pair separate and move toward opposite poles of the cells TERM 70
Cytokinesis
DEFINITION 70 Cytoplasm divides resulting in formation of two cells. These cells have half the number of chromosomes of the original cells and are called haploid cells (n, 2c).
Nondisjunction
Unequal separation of chromosomes during meiosis I or II Results in gametes with an abnormal chromosome number normal daughter cells 23 chromosomes extra (n+1, 24) chromosome missing (n-1, 22) chromosome Fertilization by abnormal gametes resulting zygotes withabnormal chromosome number TERM 77
Aneuploidy
DEFINITION 77 variations in chromosome number that involve one or more chromosomes.Most aneuploidy from errors in meiosis. TERM 78
Amniocentesis
DEFINITION 78 Draw about 20 ml of amniotic fluid using a needle with assistant of ultrasound to avoid placenta and fetus damage Isolate fetal cells by centrifugation Chromosome analysis (karyotype) detect any abnormality or sex Protein analysis also possible to detect biochemical disorders Usually performed b/w 14 and 16 weeks of pregnancy Processing and analyzing takes about 7-14 days Risks associated with amniocentesis Miscarriage in 0.2-0.3% rate (1 in 300 to 500) TERM 79
Chorionic villus sampling (CVS)
DEFINITION 79 Fetal cells collected from the chorionic villi Inserting a thin flexible tube (catheter) t/r the vagina andcervix or a needle t/r abdomen into the placenta Ultrasound used to guide catheter (or needle) Can be performed earlier (10 to 12 weeks) thanamniocentesis ( to 16 weeks) Results come out fast (within a few days) Possible risks: cramps, infection, and rate of miscarriage(maybe higher than amniocentesis) TERM 80
Fetal Cell Sorting
DEFINITION 80 Fetal cells or free fetal DNA (ffDNA)are found in the maternal blood. These cells can be separated usingfluorescence- activated cell sorters(FACS). The fetal cells are karyotyped.
Euploid
normal two copies of each chromosome (2n, 46) TERM 82
Aneuploidy
DEFINITION 82 abnormal condition of chromosomal number Gain of one chromosome (three copies of a chromosome) trisomy (2n + 1, 47): Down syndrome, Jacobs syndrome Loss of one chromosome (only one copy of a chromosome) monosomy (2n 1, 45): Turner syndrome TERM 83
Polyploidy
DEFINITION 83 multiple full sets of chromosomes Triploidy (3n, 69) Tetraploidy (4n, 92) Fertilization of an egg with two or more sperm (polyspermy) In human, this is rare and lethal TERM 84
Karyotype
DEFINITION 84 Display of chromosomes in pairs during mitotic metaphase After Giemsa staining, chromosomes are arranged by length,position of centromere, and band pattern Classic karyotype and Spectral karyotype TERM 85
Duplication
DEFINITION 85 parts of a chromosome are repeated
Trisomy 13: Patau Syndrome
(47,+13)1/15,000 live births Survival: 12 months Symptoms: facial malformation eye defect polydactyly extra digits heart defects (80%) severe defects in brain andnervous system TERM 92
Trisomy 18: Edwards Syndrome
DEFINITION 92 (47,+18) 1 in 11,000 in live birth 80% females Survival: 24 months Symptoms: retard development mental disabilities finger defects heart malformation Die from heart failure or pneumonia TERM 93
Trisomy 21: Down Syndrome
DEFINITION 93 (47,+21) 1 in 800 live births (depending onmothers age) Survival up to age 50 - only autosomal trisomy in which patients can survive into adulthood Childhood mental retardation and heart defects (40%) Wide, flat skulls; eyelid folds; large tongues; physical, mental, and development retardation May live rich, productive lives TERM 94
Risk Factor for
Trisomy?
DEFINITION 94 Maternal age - only known risk factor for Down syndrome andother autosomal aneuploidyOlder eggs may have higher risk of nondisjunction due to more chances to get damaged by environmental agents TERM 95
Down Syndrome by Robertsonian
Translocation
DEFINITION 95 5% DS caused by a Robertsonian translocation chromosome 21 attached to chromosome 14 or 15. If translocated chromosome inherited DS with normal number of chromosomes (46)
Monosomy in sex chromosomes
More common than in autosomes Not always lethal TERM 97
Monosomy in sex chromosomes
DEFINITION 97 Turner syndrome (45, X): monosomy of X chromosome Monosomy of Y chromosome (45, Y): always fatal,resulting in miscarriage TERM 98
Trisomy involving sex
chromosomes
DEFINITION 98 Klinefelter syndrome (47, XXY): extra X Jacobs syndrome (47, XYY): extra Y Triplo-X Aneuploidy (47, XXX): extra X TERM 99
Turner Syndrome
DEFINITION 99 (45,X) 1 in 10,000 female births Most cases (9599%) lead to miscarriage Survival to adulthood 75% paternal X is missing Symptoms (female): short stature poor breast development undeveloped ovaries: no menstruation normal intelligence TERM 100
Klinefelter Syndrome
DEFINITION 100 (47,XXY) 1 in 500-1,000 males births Survival to adulthood Symptoms (Male): Features do not develop until puberty usually sterile (small testes) female-like features (broad hips, lack of body hair, female-type nipples) may have learning disabilities
