Implantation and development during weeks 1&2 (genetic/congenital disorders):
1. Explain what aspects of early mammalian cleavage facilitate molecular screening of embryos for genetic defects
2. Describe the major ectopic sites of implantation. What are the symptoms of an ectopic pregnancy?
3. What risk factors predispose to ectopic or tubal pregnancy?
4. Describe the different mechanisms which results in twins. Discuss population differences in the frequency of twins.
5. Discuss the reason and numbers of pregnancies which abort within the first two weeks. What are the difficulties in obtaining such data?
6. Describe the characteristics, diagnosis and prognosis of choriocarcinoma and Hydatiform mole.
7. Classify the contraceptives. Identify the mechanism and sites of contraceptive blocks of gametogenesis, ovulation and fertilization. What ethical issues impact on the choice of birth control type?

Sample Answer

Sample Answer


Implantation and Development during Weeks 1&2: Genetic/Congenital Disorders

Molecular Screening of Embryos for Genetic Defects

Early mammalian cleavage refers to the rapid division of cells that occurs during the first few days after fertilization.
This process creates multiple cells, providing an opportunity for molecular screening to identify genetic defects.
By extracting a few cells from the developing embryo, scientists can analyze the genetic material for any abnormalities.
As these cells are still undifferentiated, any genetic defects detected at this stage can help determine the viability of the embryo and prevent the transmission of certain congenital disorders.

Ectopic Pregnancy and Major Ectopic Implantation Sites

Ectopic pregnancy occurs when a fertilized egg implants outside of the uterus, typically in the fallopian tubes.
Other major ectopic implantation sites include the ovaries, abdominal cavity, and cervix.
Symptoms of an ectopic pregnancy may include pelvic pain, vaginal bleeding, shoulder pain, dizziness, and fainting.
If left untreated, ectopic pregnancies can lead to rupture of the fallopian tube or other complications.

Risk Factors Predisposing to Ectopic or Tubal Pregnancy

Risk factors for ectopic or tubal pregnancy include previous ectopic pregnancy, previous pelvic surgery, history of pelvic inflammatory disease (PID), use of assisted reproductive technologies, smoking, and advanced maternal age.
Conditions that affect the structure or function of the fallopian tubes, such as tubal scarring or blockages, also increase the risk.

Mechanisms Resulting in Twins and Population Differences

Twins can be classified into two types: monozygotic (identical) and dizygotic (fraternal).
Monozygotic twins result from a single fertilized egg splitting into two embryos, sharing identical genetic material.
Dizygotic twins occur when two separate eggs are fertilized by two different sperm cells.
The frequency of twins varies among populations due to factors like maternal age, hereditary factors, and use of assisted reproductive technologies.

Abortions within the First Two Weeks of Pregnancy

Many pregnancies abort within the first two weeks due to various reasons, such as chromosomal abnormalities or implantation issues.
Obtaining accurate data on the number of pregnancies that abort within this time frame is challenging because many early miscarriages go unnoticed or are mistaken for a delayed menstrual period.
Additionally, some women may not be aware that they were pregnant if the miscarriage occurs very early.

Choriocarcinoma and Hydatiform Mole

Choriocarcinoma is a rare form of cancer that develops from abnormal placental tissue.
It can occur following molar pregnancies (hydatiform mole) or normal pregnancies.
Hydatiform mole is an abnormal pregnancy where a non-viable fertilized egg implants in the uterus and forms a mass instead of a fetus.
Diagnosis of both choriocarcinoma and hydatiform mole involves imaging techniques, blood tests (e.g., beta-hCG levels), and histopathological examination.
Prognosis can vary based on factors such as the extent of cancer spread, timely diagnosis, and patient response to treatment.

Classification of Contraceptives and Ethical Issues

Contraceptives can be classified into various categories, including hormonal methods (e.g., birth control pills, patches), barrier methods (e.g., condoms), intrauterine devices (IUDs), emergency contraception (e.g., morning-after pill), and permanent methods (e.g., tubal ligation).
Mechanisms of contraceptive action include blocking gametogenesis (sperm or egg production), preventing ovulation, inhibiting fertilization, or altering the uterine environment to prevent implantation.
Ethical issues surrounding birth control choice may involve religious beliefs, personal autonomy, access to contraception, and cultural norms regarding family planning practices.

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