Conception and Heredity

Fertilization..Conception…aka Baby Makin’ Fertilization: union of an ovum and a sperm within the Fallopian tube Sperm is released upon ejaculation from the male during sexual intercourse and propel themselves through the cervix, uterus, and meet the ovum in fallopian tube Typically 100 to 600 Million Sperm are released during sex Only one sperm can fertilize the egg Egg (ovum): egg and sperm each contribute exactly half of the new individual’s total hereditary material 90,000 times as large as the sperm https://www.youtube.com/watch?v=M14uQ44xBvE

Pregnancy Stages – First Trimester 7 to 9 days following fertilization – New life develops a protective hormone to prevent the mother’s body from rejecting it as foreign tissue 18 days – Heart muscle pulsates sporadically 20 days – Foundation of the central nervous system has been laid down 25 days – Heart beats regularly / Length is 1/10 in

Pregnancy Stages – First Trimester 6 Weeks after conception – Brain waves are recordable and embryo’s first body movements visible on ultrasound 8 Weeks – Known as a “Fetus” Body parts present / hiccups, kicks, waves, moves freely in uterus Length 1 ¼ inch 10 Weeks – All organs are functioning / Swallows, sucks, yawns, has coordinated movements. Length 3 inches

Pregnancy Stages – 2nd and 3rd Trimester 16 Weeks – Hearing fully developed and personality is underway. Length 6 ½ inches 20-24 Weeks – Earliest age that survival is possible outside of uterus Can open eyes and hair appears on head. Weight is about one pound. 28 Weeks – Fetus recognizes voices / Length is around 14 inches 32 Weeks – Nothing new except growth and maturation 37 Weeks – Birth prior to this time is considered premature 40 Weeks – Full-term Pregnancy / Average weight is 7 lbs and length is 20 inches

Alcohol and Tobacco on Unborn Fetal Alcohol Syndrome: babies who have varying degrees of mental retardation, small brain size, poor motor coordination, retarded growth, under-developed jaw, narrow upper lip Can lead to first and second trimester miscarriages Daily consumption of as little as 1 or 2 ounces of alcohol Tobacco: Increased risk of miscarriage, stillbirth (born dead), premature birth, and growth retarded (small or undergrown) babies Nicotine causes reduction in blood flow – reduction in food and oxygen to baby

Genetics Each cell in the human body contains 46 identical chromosomes Exception – sperm and egg: each only carry 23 chromosomes Chromosomes: long, thread-like chains of DNA with important instructions written within Each chromosome is made up of functional units called genes Genes: basic units of heredity / Hold traits from both parents that make you who you are Ex. Facial features, personality, preexisting diseases, etc.

Trait Determination Fertilization occurs with 23 chromosomes of the father uniting with 23 chromosomes of the mother Thus, new celled human being has 46 chromosomes. Containing genetic instructions from both parents Everything is programmed for this new person at the instant of fertilization There are about 100,000 genes that make up who you are Genes determine: eye color/eye sight, hair color, skin color, baldness, blood type, height, left handed/right handed, deafness, etc. Errors within the gens can result in sickness – certain cancers, type one diabetes, mental retardation, hemophilia, types of insanity

Determining the Gender of a Baby Females have a XX chromosome / Males have a XY chromosome Gender is determined by the sperm cell that fertilizes the egg Sperm carry one chromosome – either a Y (male) or X (female) Of the 46 chromosomes - half of the man’s sperm have X chromosomes and Y chromosomes Overall.. If an egg is fertilized by an X-bearing sperm – results in a baby girl (XX) If an egg is fertilized by a Y-bearing sperm – results in a baby boy (XY) Man’s sperm hold the key to the baby’s gender Since men have both XY chromosomes and the female egg posses only the XX chromosomes