Index : R : Reproduction and Genetics

Structure Sub-topic of: Health and Human Biology Interesting Questions, Facts and Information There are a total of 10 general entries. Frequently Asked Questions & Answers There are 4 user-asked question matches ( goto ) Special Topics Prenatal Brain Teasers Baby Knowledge Boy, Girl Or Other Genes and Cancer Test-cross your Mendelian knowledge Craniofacial Anomalies Pregnancy Genes and Mutation Pregnancy, Birth and Newborns! A Bun In The Oven Baby And Child Care Twins Angelman Syndrome Pregnancy And Childbirth It's in the Genes... Pregnancy Complications The 40 Weeks of Pregnancy Reproduction Breastfeeding Myths Need New J(G)enes

Interesting Questions, Facts, and Information

Reproduction and Genetics

The length of an average menstrual cycle is 28 days, however, a 'normal' cycle can range anywhere from 23 to 35 days in length, depending on the woman. What part of the cycle is counted as day 1?

Menstruation-The Facts (Ballykissangel)


First day of menstrual bleeding. When keeping track of the days in a cycle, day 1 is counted as the first day of menstrual flow. Some women will have brownish spotting for a day or two prior to actual blood flow. Your gynecologist will tell you to count the first day of 'bright red' flow as day 1.



Not all women have normal, predictable menstrual cycles. Many women encounter heavy bleeding. Some deal with intense pain. Others may stop having or skip periods. What condition does the term dysmenorrhea refer to?

Menstruation-The Facts (Ballykissangel)


Excessively painful periods. In many young women, the hormone prostaglandin is responsible for uterine contractions causing severe menstrual cramping. Sometimes diseases such as endometriosis or uterine fibriods may be the cause of your pain. In any case a doctor should be consulted.



During the first phase of the menstrual cycle, a woman's estrogen levels are high. This results in the lining of the uterus growing and thickening in order to nourish a developing zygote (fertilized egg) should a pregnancy take place. What hormone acts on the eggs in the ovary causing them to mature?

Menstruation-The Facts (Ballykissangel)


follicle-stimulating hormone (FSH). As its name implies, FSH, or follicle-stimulating hormone, acts on the follicles (or eggs) causing them to mature in readiness for a possible pregnancy.



As FSH stimulates the follicles (eggs), a race begins. Usually one egg (although there can be more than one, as is the case in some multiple births,) will develop and mature quicker than the others. Suddenly there is a surge in the levels of luteinizing hormone (LH). This causes the egg to be released from the ovary. This is referred to as ovulation. In a normal 28 day cycle, on average, on what day would this take place?

Menstruation-The Facts (Ballykissangel)


Day 14. As mentioned above not all fertile cycles are 28 days in length. Ovulation typically takes place 14 days before the first day of the next menstrual cycle. Thus in a 30 day cycle, ovulation would take place on day 16, not day 14.



After the egg (ovum) is released during ovulation, it makes its way via the Fallopian tube to the uterus. This is when the hormone progesterone comes into play. Its levels rise and help prepare the uterine lining for a possible pregnancy. If a pregnancy does not take place, levels of estrogen and progesterone drop and the uterine lining is shed as the woman's next menstrual cycle. What happens to the unfertilized ovum?

Menstruation-The Facts (Ballykissangel)


It is dissolved or absorbed into the body. Menstrual blood is partly blood and partly tissue that is shed from the uterus. It escapes the uterus via the cervix and passes out of the body through the vagina.



'Menarche' is the medical term used to refer to a girl's first menstrual cycle. Every young girl's reaction to her first period is as individual as is each girl herself. How each will deal with this normal and natural event will depend largely on how well informed she is about menstruation. A wise mother will explain to her daughter that having a 'period' is a natural step toward becoming a woman and is something to feel good about. In developed countries, what is the 'average' age at which a girl will have her first period?

Menstruation-The Facts (Ballykissangel)


12. Of course not all girls will begin their period at the same age. Some girls menstruate as early as age 8, while others will not start until 16 years of age. Heredity, as well as environmental and health issues, also seem to have an impact on when a girl will begin to menstruate. In any case, menstruation will not begin until all the parts of a girl's reproductive system have developed and have begun to work together.

• Looking up genetics for another question, I found a diagram of the human genes. Why is the "Y" chromosome so much smaller than the "X" chromosome? ( goto )



• What is the form of reproduction in which the ovum develops into a new individual without fertilization? What kind of animals are capable of this and who first discovered this? ( goto )



• Three of the following were credited with the smallest known reproduction of the Bible. Spot the odd one out - Pawan Sinha, G P Reichelt, Pamela R Lpson, or Keith R Kluender? ( goto )



• One of the first instances of their existance was in a work by the Roman poet Virgil, although evidence may suggest earlier recordings by a Roman Statesman. A 19th century writer known for his unique 'character inspired' posthumous recognition also wrote about their modern geographical origin. What are they, how do they relate to royalty, and what are the guide-lines and 'laws' their native country enforces about the reproduction of them? ( goto )