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LEH U19 00 sexual reproduction 2016

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(1)

Sexual Reproduction

(2)

Why Reproduce?

Survival of the species

Species - a group of closely related organisms that can produce fertile offspring.

Needed to transfer genetic

(3)

Sexual Reproduction

Sexual reproduction-

two parents

Offspring have ½ of their

genetic material from each parent.

Offspring NOT identical to either

(4)
(5)

Sexual Reproduction

How do we get HALF

of the genetic

information from each parent?

(6)

Meiosis: “Double Cell Division”

Involves

ONE

replication and

TWO

divisions.

Prior to the TWO cell divisions

the DNA replicates once

(7)

Crossing Over

Crossing Over: When homologous chromosomes exchange some genetic information during meiosis

(8)
(9)

Meiosis I: First Division

Prophase I

Homologous pairs of chromosomes come

together, form tetrads ( four Chromotids)

crossing over occurs !!!!!!!

(10)

Meiosis I: First Division

Metaphase I

(11)

Meiosis I: First Division

Anaphase I

Disjunction- the tetrads are separated and double-stranded chromosomes are

pulled toward the poles.

The Homologous pairs separate

IDEPENDENT ASSORTMENT - Leads to variation

• Telophase I

(12)

Meiosis II: Second

Division

(13)

Metaphase II

(14)

• As the cell enters

(15)

• These four

(16)

The Results….

Meiosis I : 2 haploid (n)

daughter cells, with ½ the

number of chromosomes as the original cell.

Meiosis II : 4 haploid (n)

(17)

Meiosis – Animation ON WEBSITE

(18)

Fig. 13-7-3

Interphase

Homologous pair of chromosomes in diploid parent cell

Chromosomes replicate

Homologous pair of replicated chromosomes

Sister

chromatids Diploid cell with replicated chromosomes

Meiosis I

Homologous chromosomes separate

1

Haploid cells with

replicated chromosomes

Meiosis II

2 Sister chromatids separate

(19)

Comparing Mitosis &

Meiosis

Mitosis Meiosis

Associated with growth and asexual reproduction

Associated with sexual reproduction - making

sperm and eggs (occurs in testes and ovaries ONLY!) Daughter cells are identical

to the parent

Daughter cells have ½ the # of chromosomes of parent cell

One Replication, One Division

One Replication, TWO Divisions

Two daughter cells are produced

(20)

Gametogenesis

Formation of

gametes

(sperm and

egg)

Gametes are made in the

gonads

(testes and ovaries)

Involves

meiosis – cells produced

(21)
(22)
(23)
(24)

Meiosis I: Reduction Division

DIPLOID cell in an ovary or testes is divided into

two HAPLOID cells.

46

(25)

Meiosis II:

Those 2 HAPLOID cells each divide again

resulting in FOUR gametes that are all genetically different.

23 23

(26)
(27)
(28)

Some Sexual Reproduction

Vocabulary

Gametes

: Specialized sex cells

(sperm & eggs)

Fertilization:

Fusion of the nuclei

of sperm and egg

(29)

More Vocabulary

Diploid: Number of chromosomes in “body

cells” of an organism – 2n (human = 46)

Haploid: Number of chromosomes in an

(30)

More Vocabulary

Body cells: Somatic Cells -(skin cells, nerve

cells, liver cells) of an organism contain a diploid number of chromosomes (2n = 46)

Gamete cells (sperm and eggs) contain a

(31)

Disjunction

Disjunction

When fibers pull homologous chromosomes toward poles.

(32)

Nondisjunction

Nondisjunction

When fibers FAIL to pull

homologous chromosomes toward poles.

This can result in chromosome abnormalities

(33)
(34)
(35)
(36)

Functions of the Male Reproductive System

1. Produce Sperm (male sex cell or gamete)

2. Deposits sperm in female for fertilization.

3. Produces the hormone called testosterone.

Testosterone produces the secondary sex

(37)
(38)

The Male Reproductive System

(39)

Structures &

Function

1. Testes- produce the sperm and testosterone

2. Epididymus- sperm fully mature and are stored here.

3. Vas deferens- carries sperm from epididymis to urethra.

4. Urethra- tube leading outside body through penis. 5. Scrotum- External sac that holds testes. Lower

temperature allows sperm to mature.

(40)

Hormones

FSH : Stimulates Spermatogenesis

LH: Stimulates production of testosterone by

the testis ( Leydig Cells )

Testosterone: Secondary Sex Characteristics

(41)

COMPONENT OF SEMEN

1. Seminal fluid - Seminal vesicles and prostate

gland secrete a fluid for sperm to travel through and nourishes the sperm.

2.

FYI: About 200 to 600 million sperm, are released in an average ejaculation. This increases the

chances of fertilization.

(42)

SPERM

1. Produced in the testes

by meiosis.

2. Haploid- sperm cells

contain 23

chromosomes (n #).

3. A sperm cell consists

(43)
(44)

Acrosome

An organelle that develops over the anterior half

of the head the sperm

It is a cap-like structure derived from the Golgi

apparatus.

Contains digestive enzymes that break down the

(45)
(46)
(47)

FUNCTIONS OF THE FEMALE

REPRODUCTIVE SYSTEM

Produces eggs (female sex cell or gamete)

Ovulation- one egg is released per month

Prepares the female’s body to nourish a

developing embryo

Female secondary sex characteristics are

regulated by estrogen & progesterone.

(48)
(49)

Main Structures of the

Female Reproductive System

1. Ovaries- Paired structures

that produce eggs & hormones.

2. Fallopian tubes ( Oviduct) -

Carries egg to uterus. Where egg is fertilized.

3. Uterus- Development takes

place.

4. Cervix- Lower Uterus

5. Vagina- Where sperm is

(50)
(51)
(52)

Ectopic Pregnancy

(53)

Fibroids

(54)
(55)

Sexually Transmitted Diseases

Chlamydia and Gonorrhea can cause Pelvic

Inflammatory Disease

Syphilis: Final stage can reach nervous

system

(56)

Egg Development

Eggs are produced within

the ovaries of females.

Females are born with

over 400,000 eggs.

Only about 400 of these

eggs will mature and be released.

Ovulation- mature egg is

(57)
(58)

The Reproductive Cycles of Females

In females, the secretion of hormones and the

reproductive events they regulate are CYCLIC

Prior to ovulation, the endometrium thickens with

blood vessels in preparation for embryo implantation

If an embryo does not implant in the endometrium,

the endometrium is shed in a process called

(59)

Stages of the Menstrual Cycle

Follicle Stage - egg matures inside follicle,

estrogen is released to start thickening uterine lining.

Ovulation Stage - Release of egg from follicle

Luteal Stage - Corpus luteum forms from leftover

follicle after ovulation; progesterone gets released to further build-up uterine lining

Menstruation - shedding of uterine lining – occurs

(60)
(61)
(62)
(63)
(64)
(65)

Fertilization

Formation of zygote.Occurs in upper

(66)
(67)
(68)

Development of the

Zygote

Zygote divides by MITOSIS  known as CLEAVAGE!

Blastula :hollow ball of single layered cells that develops

(69)
(70)
(71)

Fig. 46-15

Ovary

Uterus

Endometrium (a) From ovulation to implantation

(b) Implantation of blastocyst

Cleavage Fertilization Ovulation Cleavage continues The blastocyst implants Trophoblast Inner cell mass

(72)

Formation of the Gastrula

The infolding of the Blastula is called Gastrulation

(73)

Animation

(74)

Differentiation

The 3 layers of the Gastrula develop into various tissues and organs.

Ectoderm: Nervous system, Skeletal & SkinMesoderm : Organ systems such as

muscular, circulatory, reproductive, and excretory

Endoderm : lining of the digestive tract

and respiratory tract. Liver and pancreas

The unspecialized (stem cells) cells become

(75)

If body cells have the same DNA –Why do

they look different and have different

functions?

BECAUSE ONLY PART OF THE DNA IN EACH CELL IS EXPRESSED or USED.

(76)

Adaptations for Sexual Development

Fertilization – The fusion of the haploid

sperm cell nucleus (n) with a haploid egg cell nucleus (n) to create a diploid zygote (2n).

Two Types of Fertilization:

(77)

Internal vs. External

Fertilization

External Fertilization:

Sperm and egg fuse

outside body of organism

Large numbers of

sperm and eggs are produced to ensure fertilization

Used by aquatic

organisms (fish & frogs)

Internal Fertilization:

Sperm and egg fuse

inside reproductive tract of the female

Occurs in most

(78)
(79)
(80)

Adaptations for Development

-Nourishment -Oxygen -Temperature -Remove Waste -Protection

Two Places Development Occurs:

- External Development - Internal Development

(81)
(82)

External vs. Internal

Development

External Development

:

Water : (fish and frogs) Offspring develop

outside mother’s body in water – little or no care by parent – many eggs are eaten or destroyed

Land : (birds and reptiles) – fertilized egg

(83)
(84)

Internal Development

Embryos develop within uterus

Offspring are well protected & a

high percentage survive

(85)

Fig. 46-15

Ovary

Uterus

Endometrium (a) From ovulation to implantation

(b) Implantation of blastocyst

Cleavage Fertilization Ovulation Cleavage continues The blastocyst implants Trophoblast Inner cell mass

(86)

Internal Development

Placenta

Site of diffusion; materials are exchanged here

between mother and child. Ex. glucose, water, CO2, O2

*****Through the BLOOD

(87)
(88)
(89)
(90)

During its first 2 to 4 weeks, the embryo obtains

nutrients directly from the endometrium

A layer of the blastocyst, called the trophoblast,

mingles with the endometrium and eventually forms the placenta

Blood from the embryo travels to the placenta

through arteries of the umbilical cord and returns via the umbilical vein

Placenta

(91)
(92)
(93)

Things that cross the Placenta

Drugs – Birth Defects, addicted babies, stillbornsAlcohol- Fetal Alcohol Syndrome, stillborns

Cigarette smoke – Slow growth, stillbornsViruses - Blindness, Mental Retardation,

stillborns

Food: Good nutrition is very important while

(94)

Drugs can cross the placenta and cause birth defects and harm the fetus

(95)

Alcohol can cross the placenta and cause birth defects and harm the fetus

(96)

Viruses can cross the placenta and cause birth defects and harm the fetus

Examples:

Chicken Pox

Herpes

(97)

Internal Development

Amniotic Sac

Nourishing and protecting sac containing liquid (Amniotic Fluid)

Grows and begins to fill, mainly with water, around

two weeks after fertilization.

After 10 weeks it contains proteins, carbohydrates,

lipids which aid in the growth of the fetus.

In the late stages of gestation much of the amniotic

(98)
(99)

Fig. 46-17

(100)

The first trimester ( 1- 12 weeks ) is the main

period of organogenesis : development of the body organs

All the major structures are present by 8 weeks,

and the embryo is now called a fetus

(101)

• Changes occur in the mother

Growth of the placenta

Cessation of ovulation and the menstrual cycle

Breast enlargement

(102)

Second Trimester

During the second trimester (12-27)

The fetus grows and is very active

The mother may feel fetal movements

The uterus grows enough for the pregnancy to

(103)

Fig. 46-17c

(104)

Third Trimester

During the third trimester (28-40), the fetus grows

and fills the space within the embryonic membranes

A complex interplay of local regulators and

(105)

Fig. 46-18

Estradiol Oxytocin

from ovaries

Induces oxytocin receptors on uterus

(106)

Fig. 46-19-1

Placenta

Umbilical cord

Uterus

Cervix

(107)

Fig. 46-19-2

Expulsion: delivery of the infant

(108)

Fig. 46-19-3

Delivery of the placenta

Uterus

Placenta

(detaching)

Umbilical

cord

(109)

Detecting Disorders During

Pregnancy

Amniocentesis and chorionic villus sampling are

invasive techniques in which amniotic fluid or fetal cells are obtained for genetic analysis

Noninvasive procedures usually use ultrasound

imaging to detect fetal condition

Genetic testing of the fetus poses ethical questions

(110)
(111)
(112)
(113)
(114)

Artificial Insemination

Used to treat

infertility

Sperm are injected

into female with

probe

(115)

In Vitro Fertilization

Sperm and egg are

joined in lab and

then zygote is

implanted

in

(116)

Surrogate Pregnancy

In vitro fertilization

is performed

Embryo is implanted in woman who has

no genetic attachment

Woman will house embryo and deliver

(117)

Sex Selection

DNA of sperm and egg

are screened for X and Y chromosomes for desired combination.

Sperm carry X or Y Eggs carry only X

Sorting Technique or

genetically test for X or Y

It’s a Girl XX

It’s a Boy XY

(118)
(119)

Monozygotic Twins

(Identical Twins)

One egg is fertilized by one sperm

Embryo splits into two during the early stages of

development

Have identical genes and must be of the same sex

(120)

Dizygotic Twins

(Fraternal Twins)

• Two eggs are ovulated and each is fertilized by a sperm cell

No more genetically similar than any other sibling in the

family (can be same/different sexes)

Maternal age, use of assisted reproductive technologies are

factors

Incidence (6.7/1000 births in Japan to 40/1000 births in

Figure

Fig. 46-12f Ovary Primary oocyte within follicle Rupturedfollicle Growing follicle Mature follicle Ovulated secondary oocyteCorpus luteum Degenerating corpus luteum
Fig. 46-16 Placenta Uterus Umbilical cordChorionic villus,containing fetalcapillariesMaternal bloodpools Maternalarteries Maternalveins Maternalportion of placenta Fetal arteriole Fetal venule Umbilical cord Fetal portion ofplacenta(chorion)Umbilicalarteri
Fig. 46-18 Estradiol Oxytocin from ovaries Induces oxytocin receptors on uterus from fetus and mother’s posterior pituitary Stimulates uterus to contract Stimulates placenta  to make Prostaglandins Stimulate more contractions of uterus Positive feedback++

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