Make HowStuffWorks your homepage
Search HowStuffWorks and the web:
Please copy/paste the following text to properly cite this How Stuff Works article:
Freudenrich, Ph.D., Craig. "How Sex Works." 16 April 2001. HowStuffWorks.com. <http://health.howstuffworks.com/human-reproduction.htm> 17 May 2008.
Inside This Article
1.
2.
3.
4.
5.
6.
7.
8.
Production of Sex Cells
9.
10.
11.
12.
13.
14.
15.
Production of Sex Cells
From the time of puberty on, men make sex cells (in the form of sperm cells) continuously. In contrast, by the time a female is born, she has made all of the eggs that she will ever have. As she reaches puberty, the eggs begin to develop and get released, and this process continues until menopause. In both males and females, the production of sex cells involves meiosis, a type of cell division whereby our two sets of genetic instructions are reduced to one set for the sex cell.
 Photo courtesy U.S. DOE, Human Genome Project |
Each cell in your body contains a set of chromosomes from your mother (her egg) and your father (his sperm). When you look at human chromosomes, they are X-shaped, except for the male Y chromosome. When your body produces sex cells (sperm or egg, depending on whether you are a male or female), your body must reduce the number of chromosomes by half to go into the sex cells. To do this, it randomly sorts chromosomes from both sets in one cell division and then reduces them by half in another. Therefore, each sperm or egg that your body produces is unique and different -- it contains a different mix of your mother's and father's genes. This is why two brothers in the same family can look and act totally different from one another even though they come from the same parents -- it all depends on which genes (chromosomes) were randomly chosen when producing the sex cells of the mother and father.
For details on meiosis, see The Biology Project: Meiosis Tutorial and this Question of the Day.
PREVIOUS
Inside This Article
1.
2.
3.
4.
5.
6.
7.
8.
Production of Sex Cells
9.
10.
11.
12.
13.
14.
15.
More Options:
Please copy/paste the following text to properly cite this How Stuff Works article:
Freudenrich, Ph.D., Craig. "How Sex Works." 16 April 2001. HowStuffWorks.com. <http://health.howstuffworks.com/human-reproduction.htm> 17 May 2008.
ADVERTISEMENT
EXPLANATIONS
PRICES
VIDEO SELECTIONS
-
TOP SELLING
SEXUAL HEALTH BOOKS
Release Date: August 28, 2007
$13 - $20
Release Date: July 01, 2004
$7 - $23
SYMPTOM CHECKER:
Abdominal Bloating Abdominal Fullness Prematurely Afte... Abdominal Lumps Abdominal Mass Abdominal Pain Abdominal Rigidity Abdominal Sounds Abdominal Swelling Abnormal Posturing Abnormal Tooth Shape Abnormally Dark Or Light Skin Absent Menstruation Absent Thirst Agitation Ambiguous Genitalia Ankle Pain Appetite Decrease Appetite Increase Apraxia Arachnodactyly Armpit Lump Autistic Behavior Babinski's Reflex Bed Wetting Belching Binge Eating Blackheads Bleeding Gums Bleeding Into The Skin Blindness Blockage Of Leg Arteries Blood In The Semen Blood in Urine Bloody Or Tarry Stools Bone Pain Or Tenderness Bounding Pulse Bowel Incontinence Breast Lump Breast Pain Breath Odor Breath Sounds Breathing - Slowed Or Stopped Breathing Difficulty Breathing Difficulty When Lying Dow... Breathing That Sounds Abnormal Broad Nasal Bridge Bulging Fontanelles Bullae Chemosis Chest Pain Chills Clammy Skin Claw Foot Claw Hand Cloudy Cornea Clubbing Of The Fingers Or Toes Cold Intolerance Coloboma Of The Iris Comedones Confusion Constipation Contracture Deformity Coughing Coughing Up Blood Crying Excessively in Infants Cyst Decerebrate Posture Decorticate Posture Decreased Consciousness Decreased Urine Output Delayed Growth Delayed or Absent Tooth Formation Depression Diarrhea Difficulty with Urination Dizziness Drooling Drowsiness Dry Eyes Dry Hair Dry Skin Ear Discharge Earache Earlobe Creases Elbow Pain Epicanthal Folds Erection Problems Erosion Excessive Or Unwanted Hair In Women Excessive Thirst Excessive Urination Excessive Urination at Night Excessively Large Fontanelles Eye Burning, Itching and Discharge Eye Pain Eye Redness Eye Slant Eyelid Drooping Eyes That Bulge Face Pain Facial Paralysis Facial Swelling Fainting Fatigue Female Sexual Dysfunction Fever Finger Pain Fingers That Change Color Flank Pain Floating Stools Focal Neurological Deficits Foot Pain Foot, Leg, And Ankle Swelling Foul Smelling Stools Frequent Or Urgent Urination Frontal Bossing Gas (Flatulence) Gastrointestinal Bleeding Genital Sores (Female) Genital Sores (Male) Groin Lumps Groin Pain Gynecomastia Hair Loss Hallucinations Hand Or Foot Spasms Hand Tremors Headache Hearing Loss Heart Murmurs And Other Sounds Heart Palpitations Heartburn Heat Intolerance Heavy, Prolonged, or Irregular Mens... Heel Pain Hemolytic Crisis Hepatomegaly Heterochromia Hiccups Hip Pain Hoarseness Or Changing Voice Hump Behind The Shoulders Hyperactivity Hyperelastic Skin Hypermobile Joints Hyperventilation Hypotonia Impaired Smell Increased Head Circumference Indigestion Infantile Reflexes Intercostal Retractions Intertrigo Irritability Itching Jaundice (Yellow Skin) Joint Pain Joint Swelling Knee Pain Leg Pain Lichenified Limited Range Of Motion Lordosis Low Nasal Bridge Lower Back Pain Macule Malaise Memory Loss Metopic Ridge Microcephaly Micrognathia Morbid Obesity Morning Sickness Moro Reflex Motormental Retardation Mouth Sores Muscle Aches Muscle Atrophy Muscle Cramps Muscle Function Loss Muscle Twitching Nail Abnormalities Nasal Congestion Nasal Discharge Nasal Flaring Natal Teeth Nausea And Vomiting Neck Lumps Neck Pain Night Blindness Nightmares Nikolsky’s Sign Nipple Discharge Nodules Nosebleed Numbness And Tingling Obesity Opisthotonos Pain During Sexual Intercourse Painful Menstrual Periods Painful Urination Pale or Clay-Colored Stools Paleness Papule Patches Patchy Skin Color Pectus Carinatum Pectus Excavatum Penis Pain Photophobia Pilonidal Dimple Pinna Abnormalities And Low-set Ear... Point Tenderness Polydactyly Polyhydramnios Poor Feeding In Infants Preauricular Tag Or Pit Premenstrual Breast Tenderness and ... Prognathism Pupils That Are Different Sizes Purpura Pustules Rapid Shallow Breathing Rash in a Child Under 2 Years Rashes Rib Cage Pain Ridged Sutures Scales Scrotal Swelling Seizures Sensorineural Deafness Separated Sutures Shin Splints Short Philtrum Short Stature Shoulder Pain Simian Crease Skeletal Limb Abnormalities Skin Blushing/flushing Skin Discoloration Skin Lumps Skin Turgor Sleeping Difficulty Sneezing Snoring Sore Throat Spasticity Speech Impairment (adult) Splenomegaly Splinter Hemorrhages Strange Behavior Stress And Anxiety Striae Subcutaneous Emphysema Sunburn Sunken Fontanelles Supernumerary Nipples Swallowing Difficulty Swallowing Pain Or Burning Sweating Sweating Decrease Swelling Swollen Glands Swollen Gums Taste Impairment Telangiectasia Tenesmus Testicle Lump Testicle Pain Tinnitus Tongue Problems Tooth Discoloration Toothaches Ulcers Uncontrollable Eye Movements Uncontrollable Movement Uncontrolled Or Slow Movement Uncoordinated Movement Unpredictable Or Jerky Movement Urinary Incontinence Urine Discoloration Vaginal Bleeding Between Periods Vaginal Bleeding In Pregnancy Vaginal Discharge Vaginal Itching Vesicles Vision Problems Vomiting Blood Walking Abnormalities Watery Eyes Weak or Absent Pulse Weakness Webbing Of The Fingers Or Toes Weight Gain Weight Loss Wheezing White Spots in the Pupil Whitehead Widely Spaced Teeth Wrinkles Wrist Pain Yawning