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22 Cards in this Set

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  • Back
how many chromozomes do humans carry
46 chromosomes
including two sex Chromosomes
Males: XY
Female: XX
(The X has more dna then Y which makes X heavier)
The other 22 pairs are called autosomes
Sex determination
begins when a sperm carrying an x or a y chromosome fuses with an egg (which carries an X chromosome.
fertilization
happens in the upper third of the fallopian tube
Fertilization process
1. sperm flows through the cervix, up the uterus, and into the oviduct.

2. The sperm nucleus fuses with the egg nucleus.

3. Produces a zygote with 46 chromosomes (22 pairs autosomes and 1 pair of sex chromosomes
Embryonic development
1.zygote begins a cellular division which creates an embryo that goes to the uterus.

2.embryo develops into a large hollow ball of cells called blastocyst. (day 5)

3. while the embryo is growing the cells linnning the uterus enlarge, preparing for the embryo to attach, this is called implantation. (day 6-7)

4. villi and maternal tissues form the placenta.
what is Chorion
a protective membrane the protects the embryo makes and releases a hormone called Human chorionic gonadotropin (HCG),
What is human chorionic gonadotropin?
prevents the lining of the uterus from breaking down and expelling the embryo. it is eliminated in the urine. Home pregnancy test detect HCG.
What is the placenta
Nourishes the embryo throughout pregnancy
What is Villi?
fingerlike projections
Fetal development
weeks 5 and 6: organ systems and heart are formed. arms, legs, fingers and toes.

Weeks 8: is a fetus in which organs are functional

week 12- 15: the sex organs can bee seen by ultrasound

week 16- skeleton begins to form, heartbeat can be heard, and begins to move.
Sperm Sorting
1. sperm are isolated using a centerfuge

2. treated with fluorescent dye that binds to the Dna in the chromosomes

3.sperm is sorted using a laser beam (Sperm with X have more dna and glow brighter than Y chromosomes.)

4. based on how bright they floursce the sperm are sorted into two test tubes. x chromosomes in one; Y chromosomes in another.

Success rate (90%-girls and 73%-men)
Preimplantation genetic diagnosis (PGD)
1. Eggs are removed from the ovary, fertilized and grown to the eight-cell stage
2. single cells are identified as either male or female.
3. embryos of the desired sex are selected
4. The selected embryos are transfered to the uterus for development.

100% success rate.
Complete androgen insensitivity(CAI); AKA, Androgen insensitivity syndrome
Is caused by a mutation in a gene on the X chromosome. A condition where she was raised a female and looked like a female, her sex chromosomes were XY, not XX.

(they have testies in their abdomens not ovaries)

SRY gene on Y chromosome produces testes, testes make testosterone, but cells in embryo do not respond to develop remaining male traits.
Barr Body
Inactivated X chromosome in a female
XY males do not have barr bodies
requirements for fertility
A healthy sperm and a healthy egg unite to form a zygote

Place for fertilization to occur (a fallopian tube)

Place for the fetus to grow (a uterus)
Assisted Reproductive technologies (ART)
donation of gametes

in vitro fertilization

surrogacy
In Vitro Fertilization (IVF)
infertility treatment in which sperm and eggs are combined in a laboratory dish and embryos result

1. Eggs are retrieved from the ovary

2. eggs and sperm are placed in a dish were fertilization occurs

3. zygotes are placed in an incubator
Infertility For men
1. low sperm count-
Infertility for women
1. hormone levels- if there is no estrogen or too little estrogen the ovary will not release an egg

2. Absent or damaged overies

3. premature menopause
Sperm donation
Widely used for almost 50 years

Known or unknown donors

Sperm stored frozen in liquid nitrogen

Sperm banks offer sperm from qualified donors
egg donation
Egg donation is more difficult

Retrieval is time-dependent and involves surgery

Donor undergoes hormone treatment and laparoscopy (surgery to remove eggs.)

Storage by freezing is difficult so eggs are used for IVF immediately after retrieval
Surrogacy
Egg Donor Surrogacy- donation of an egg , which is fertilized by artificial insemination using the sperm of the infertile couple's male partner and the surrogate carries the embryo to term.

Gestation Surrogacy- carries the embryo to term but the egg and sperm are from two other people.