Biology 191 - Lecture 23

Front 1

Hypothesis for role of mitochondria in male sexual orientation

Back 1

Twin and pedigree studies suggest genetic basis for male homosexuality

Front 2

Evidence of genetic basis for male homosexuality
(2)

Back 2

1. concordance for identical twins = .57
2. concordance for fraternal twins = .25
*i.e. if one twin exhibits a trait, there is a 57% chance that the other twin will also exhibit that trait

Front 3

Maternal line of descent suggests either...
(2)

Back 3

1. X-linked nuclear gene or
2. genetic element in cytoplasm

Front 4

Maternal aunts vs. maternal uncles and homosexuality

Back 4

Maternal aunts outnumber maternal uncles in both homosexual and transexual men but not in their paternal relatives
*this is consistent with death of male embryos in utero

Front 5

How might mitochondria kill or feminize males?

Back 5

Pivotal role in
1. apoptosis and
2. conversion of cholesterol into testosterone in testis

Front 6

Apoptosis is due to...

Back 6

metabolic rate differences

Front 7

Conversion of cholesterol into testosterone in testis is controlled by ...

Back 7

mitochondria.

Front 8

Function of Wolbachia bacteria in male embryos

Back 8

Wolbachia bacteria kill male embryos.

Front 9

Incomplete penetrance of Wolbachia bateria produces...

Back 9

pseudoscorpion inter-sexuals. i.e. half male, half-female. In this case, they are laterally bisexual (one claw female, the other male) because the Wolbachia bacteria didn't kill them, it just feminized them.

Front 10

Just as the pseudoscorpions are laterally bisexual, so too...

Back 10

are they bisexual in their genitalia. Genitalia is female on one side, and male on the other

Front 11

How is gender determined in mammals?
(2)

Back 11

1. Y-chromosome
2. then hormones

Front 12

During the first 6 weeks of embryonic development, ...

Back 12

male and female gonads are unisex. i.e. indistinguishable

Front 13

All fetuses start with..

Back 13

two duct systems:
1. Wolffian
2. Mullerian

Front 14

What happens at week 7?

Back 14

At week 7, SRY gene in males is swithed on and activates other genes on several different chromosomes

Front 15

After SRY gene turns on and activates other genes, ...

Back 15

1. testis develop
2. Mullerian duct system is destroyed
*(thus, males end up with a single duct system)

Front 16

DIAGRAM!!

Back 16

See slide 5 (page 3) for diaram of male reproductive anatomy. REALLY LOOK!

Front 17

# of openings in males

Back 17

Males have a single (common) urinary and reproductive opening

Front 18

Locations of where sperm are produced and mature
(2)

Back 18

1. sperm are produced in the testis
2. but they mature and are stored in the epididymus

Front 19

Seminal fluids are derived from the ...
(3)

Back 19

1. seminal vesicles
2. prostate gland
3. bulbourethal gland

Front 20

% of ejaculate that is actually sperm

Back 20

Only 5% of ejaculate is actually sperm

Front 21

Normal development of sperm depends on...

Back 21

temperature. The temp must be 2-3* cooler than body temp

Front 22

# of sperm males create a day

Back 22

Males create 200-300 million sperm per day

Front 23

Where do sperm cells develop?

Back 23

Sperm cells develop over a great length of the seminiferous tubules

Front 24

Seminiferous tubules are therefore the site of ...

Back 24

spermatogenesis

Front 25

What produces testosterone?

Back 25

Leydig cells in tissue between seminiferous tubles produces testosterone

Front 26

Function of Cytoplasmic bridges

Back 26

connect the 4 cells (goes from 1 cells to 4 cells) which will later become individual spermatazoan. Quantity over quality.

Front 27

What controls male reproduction (production of sperm)?

Back 27

Hormones control male reproduction

Front 28

GnRH stands for

Back 28

Gonadotropin-releasing hormone

Front 29

GnRH is produced in the ___ and released into the ____

Back 29

GnRH is
1. produced in the hypothalamus
2. released into the anterior (front) pituitary gland

Front 30

Function of GnRH

Back 30

GnRH stimulates the release of FSH and LH from the anterior pituitary

Front 31

FSH stands for

Back 31

FSH = follicle-stimulating hormone

Front 32

LH stands for

Back 32

LH = luteinizing hormone

Front 33

Function of FSH in males

Back 33

FSH stimulates spermatogenesis via Sertoli cells

Front 34

Function of LH in males

Back 34

LH stimulates secretion of testosterone by Leydig cells

Front 35

Functions of testosterone
(2)

Back 35

Testosterone
1. stimulates development an maintenance of secondary sexual characteristics
2. promtes spermatogenesis

Front 36

Secondary sexual characteristics
(df)

Back 36

Not directly involved in reproduction. Ex.) muscle mass, facial hair

Front 37

Male reproduction system is an example of a ...

Back 37

negative feedback system

Front 38

# of openings in females

Back 38

Females have separate urinary and reproductive openings, so they have 2

Front 39

Vagina connects to...

Back 39

Vagina connects to uterus (womb), where embryo implants and fetus develops

Front 40

Female gonads

Back 40

Ovaries are the female gonads (where oogenesis takes place)

Front 41

What receives the ovulated eggs?

Back 41

Oviducts (fallopian tubes) receive the ovulated eggs (ova)

Front 42

Ovaries
(df)

Back 42

Eggs mature in and are released by the ovaries.

Front 43

Next,...

Back 43

Eggs are taken into the oviducts, where they travel to the uterus.

Front 44

Fertilization occurs in ...

Back 44

the upper regions of the oviduct, where development begins

Front 45

Endometrium

Back 45

The blastocyte implants in the endometrium of the uterus, where embryonic development continues.

Front 46

Days of ovulation

Back 46

Days 1-14
*ovulation occurs on Day 14

Front 47

Days of post-ovulation

Back 47

Days 15-28

Front 48

HCG

Back 48

HCG = Human chorionic gonadotropin

Front 49

Human chorionic gonadotropin
(df)

Back 49

A hormone secreted by the pregnancy. The presence of this hormone in the woman's blood or urine represents a positive pregnancy test

Front 50

# of potential ova at birth

Back 50

At birth, female has 2 million potential ova

Front 51

# of potential ova by puberty

Back 51

By puberty, female has 200,000 potential ova.

Front 52

# of potential ova over entire lifespan

Back 52

Over entire lifespan, female has 450 potential ova

Front 53

The ovarian cycle: STEP 1

Back 53

Primary oocytes (2n) are present in the ovary

Front 54

The ovarian cycle: STEP 2

Back 54

About once a month, 6-12 primary oocytes begin to mature. A primary oocyte and its surrounding cells constitute a follicle

Front 55

The ovarian cycle: STEP 3

Back 55

The developing oocyte is nourished by surrounding follicular cells, which also produce estrogen

Front 56

The ovarian cycle: STEP 4

Back 56

After 1 week, usually only one primary oocyte continues to develop. A meiotic division just before ovulation creates the secondary oocyte (n)

Front 57

The ovarian cycle: STEP 5

Back 57

At ovultion, the follicle ruptures, releasing the egg
*This occurs in response to spike in LH. The egg then passes into the fallopian tube where it can be fertilized by sperm

Front 58

The ovarian cycle: STEP 6

Back 58

The remaining follicle cells form the CORPUS LUTEUM, which produces progesterone and estrogen

Front 59

The ovarian cycle: STEP 7

Back 59

If pregnancy does not occur, the corpus luteum degenerates.

Front 60

If fertilization does occur,

Back 60

corpus luteum also contributes to thickening of the uterus. Also, embryo produces HCG, which maintains the corpus luteum initially.

Front 61

The female reproductive cycle involves two organs:

Back 61

1. uterus
2. ovaries

Front 62

What 2 things orchestrate the female reproductive cycle?

Back 62

1. secretion of GnRH from the hypothalamus
2. FSH and LH from the anterior pituitary

Front 63

Function of FSH in females

Back 63

FSH stimulates growth of ovarian follicle and secretion of estradiol

Front 64

Functions of LH
(3)

Back 64

LH:
1. stimulates ovulation
2. stimulates conversion of follicles into corpus luteum
3. stimulates secretion of estradiol and progesterone by corpus luteum

Front 65

Function of estradiol

Back 65

Estradiol:
1. stimulates female secondary sex characters
2. prompts preparation of uterus for pregnancy

Front 66

Function of Progesterone

Back 66

Progesterone completes preparation of uterus for pregnancy

Front 67

Contraception methods
(3)

Back 67

1. true contraception
2. post-fertilization/pre-implantation
3. pregnancy termination

Front 68

True contraception
(df)

Back 68

True contraception is the prevention of conception (i.e. fertilization is not allowed to occur)

Front 69

Types of true contraception
(5)

Back 69

1. abstinence
2. rhythym method
3. the pill
4. condoms, spermacides, etc
5. vasectomy, tubal ligation

Front 70

Rhythym method

Back 70

Determine when ovulating. Don't have sex 3-4 days before and after.

Front 71

The pill

Back 71

inhibits LH, FSH, and development of follicles

Front 72

Condoms, spermacides, vasectomies, and tubal ligations

Back 72

prevent sperm and eggs from meeting

Front 73

Types of Post-fertilization/Pre-implantation contraceptive methods
(2)

Back 73

1. IUD = intrauterine device
2. morning after pill

Front 74

IUD

Back 74

irritates uterine lining and prevents blastocyst from implanting

Front 75

morning after pill

Back 75

can prevent pregnancy if taken within 78 hrs of intercourse

Front 76

Pregnancy termination

Back 76

surgical abortion

Front 77

Natural abortions

Back 77

Natural abortions are common. 60-70% of all conceptions spontaneously abort

Front 78

Contraceptive failure rates

Back 78

The pill has the lowest. Douche has the highest.

Front 79

2 types of sterilization procedures

Back 79

1. vasectomy
2. tubal ligation

Front 80

Vasectomy
(df)

Back 80

A short piece of vas deferens is cut out, and the ends are tied off

Front 81

Tubal ligation
(df)

Back 81

The oviducts are cut and the ends are folded over and tied off

Front 82

ART stands for

Back 82

Assisted reproductive technology

Front 83

Assisted reproductive technology
(df)

Back 83

ART inculdes fertility treatment in which both egg and sperm are manipulated in the laboratory to achieve fertilization

Front 84

Most common method of ART

Back 84

In vitro fertilization (IVF)

Front 85

In vitro fertilization
(df)

Back 85

In vitro fertilization involves combining an egg with sperm in a laboratory dish

Front 86

If the egg fertilizes,

Back 86

1. it begins cell division
2. it results in an embryo that can be transferred into a woman's uterus
3. may implant in uterine lining and continue to develop

Front 87

Infertility defined as

Back 87

couples who try for 3 years for fertilization without success

Front 88

Subfertility defined as

Back 88

couples who try for 1 year for fertilization without success

Front 89

Name of the first "test-tube" baby

Back 89

Louise Brown

Front 90

First successful application of assisted reproductive technology in humans took place in ....

Back 90

1978 in Britain

Front 91

The aforementioned event resulted from ...

Back 91

retrieval of a single oocyte in a spontaneous menstrual cycle

Front 92

Assisted reproductive technology was originally developed as a...

Back 92

treatment for women with blocked fallopian tubes

Front 93

Superovulation
(df)

Back 93

Superovulation involving gonadotropin drugs to stimulate ovulation of multiple eggs now standard practice in ART

Front 94

Standard IVF
(df)

Back 94

Standard IVF procedure is to incubate egg with large number of sperm to allow fertilization to occur naturally

Front 95

Intracytoplasmic sperm injection (ICSI)
(df)

Back 95

ICSI an in vitro fertilization procedure in which single sperm injected directly into egg

Front 96

Cryopreservation
(df)

Back 96

Cryopreservation of surplus embryos enables future transfer attempts; sperm and spermatids can also be frozen

Front 97

Cytoplasmic transfer
(df)

Back 97

Cytoplasmic transfer of donor female’s egg cytoplasm now very uncommon procedure

Front 98

Cytoplasmic transfer is also associated with ...

Back 98

a high incidence of Turner Syndrome: women end up with XO chromosomes (instead of XX chromosomes)

Front 99

Preimplantation genetic diagnosis (PGD)
(df)

Back 99

Preimplantation genetic diagnosis (PGD) can be carried out on embryos prior to transfer to test for genetic abnormalities

Front 100

Pre-implantation genetic diagnosis
(df)

Back 100

Latest diagnostic procedure to test for genetic abnormalities in human embryos

Front 101

Process of Pre-implantation genetic diagnosis

Back 101

Can remove a sinle cell during the 8-cell stage. Can then carry out tests to look for abnormalities

Front 102

Most common risk associated with ART

Back 102

High likelihood of multiple births

Front 103

In 1998, # of embryos transferred in 80% of ART cycles

Back 103

In 1998, 3 or more embryos were transferred in 80% of ART cycles

Front 104

As a result,

Back 104

32% of ART births were twins
7% were triplets or higher

Front 105

Reason for transferring high number of embryos

Back 105

High number of embryos transferred to increase likelihood of pregnancy

Front 106

Problem with that.

Back 106

However, transferring more than 2 embryos does NOT increse success rate

Front 107

Statistics show that success rate plateaus at

Back 107

implant of 2 embryos

Front 108

Hazards of multiple gestations (3 or more kids)
(2)

Back 108

1. multiple births increase rates of still birth, infant and perinatal mortality
2. multiple births are associated with premature birth and low birth weight infants

Front 109

Statistics on triplets
(2)

Back 109

1. born on average 6 weeks prematurely
2. typically weigh less than 2500g (half as much as a typical singleton)

Front 110

Newborns weight less than 2500g are ___ more likely to ___

Back 110

Newborns weighing less than 2500g are 40X more likely to die in early infancy

Front 111

Dangers of ART regarding birth defects

Back 111

Meta-analysis of published studies show that ART babies have risk of congenital birth defects 30% to 40% higher than naturally conceived infants

Front 112

Incidence of birth defects: natural pregnancies vs. ART pregnancies

Back 112

4-5% in natural pregnancies
6-9% in ART pregnancies

Front 113

Possible reasons for increased risks with ART

Back 113

1. could be consequence of ART-associated factors
2. or could stem from underlying causes of infertility itself