What are multiple births?

GENETICS - The study of the way animals & plants pass on to their offspring such as:

eye color, hair color, height, body build, blood types, intelligence, gender, etc.

HEREDITY - Characteristics that a child receives from both parents

? ? ? ? ? ? ? ? How many chromosomes are there in each cell? 46 CHROMOSOMES or 23 PAIRS

How many chromosomes are in Reproductive (egg & sperm) or Germ cells?

23 CHROMOSOMES• (combined = the 46 chromosomes)

CELL DIVISION

MEIOSIS: Creates 1/2 sets of chromosomes

• Women = 23 Men = 23 Combined = 46

Female Sex Cells XX (Ovum or Egg)

Male Sex Cells XY (Sperm)

Baby Girl = XX Baby Boy = XY• Conception is the union of an OVUM and the SPERM

Gender is determined by the father!• Someone should have told King Henry VIII!

DOMINATE Gene: More powerful or strongest gene- trait seen in person

RECESSIVE Gene: Weaker and hides in the background. Trait can only determine when two of them are present - may show up in future generations.

CARRIER: Has a recessive gene that is not visible

SEX-LINKED: Mother passes the recessive X to son• Color-blind male receives the trait from his mother. • The mother is usually not color-blind herself.

B = BROWN eyes (dominate) b = BLUE eyes (recessive) BB = BROWN eyes bb = BLUE eyes Bb = BROWN eyes but carry the recessive BLUE eye gene

MULTIPLE BIRTHS

Identical Twins – when a fertilized egg splits into two• Fertilized ovum splits into 2

identical cells - Always the same gender

Fraternal Twins - when 2 eggs are released and fertilized at the same time• Will look different - May be

different or the same gender

What 4 FACTORS may contribute to Multiple Births?

1) History in the family

2) Increased hormones naturally

– More than 1 egg released

3) Fertility Drugs– More than 1 egg

released

4) Age 32-36

March 20: Agenda

Goal: Understand environmental and hereditary influences on prenatal development and long-term effects on health of children.

Journal 11:In your own words; what

is a birth defect, what are twins and the two types of twins we discussed ( how does this happen) what are the 4 factors that contribute to a birth defect?

Environmental Influences on Birth Defects

Inadequate nutrition of mother Exposure to diseases or infections

during pregnancy Harmful substances consumed during

pregnancy

Environmental Influences on Birth Defects

Inadequate nutrition of motherStunted brain development of babyLeads to mental retardation

Environmental Influences on Birth Defects

Exposure to diseases or infections during pregnancy

Rubella, or German Measles, can cause blindness, deafness, heart disease, and mental retardation

Toxoplasmosis, can cause hearing loss, learning disabilities and death; found in cat litter and some raw meats

Chicken pox, scarring of babies’ skin, limb defects, eye problems, and miscarriage

STDs can be passed to unborn child and lead to serious illness, physical disabilities, or death

Environmental Influences on Birth Defects

Harmful substances consumed during pregnancy Nicotine from smoking tobacco or secondhand

smoke Smaller babies Miscarriages and premature births Respiratory infections or allergies

Environmental Influences on Birth DefectsHarmful substances consumed during

pregnancy Alcohol can cause fetal alcohol syndrome

(FAS) 20% of infants die Facial deformities, delayed physical growth, heart defects, and

hyperactivity Mental retardation or disabilities Poor coordination Difficulty controlling behavior

Environment Influences of Birth Defects

Harmful substances consumed while pregnant Drugs

Over-the-the counter drugsDrug addictionLong-term learning and behavioral problemsRisk of miscarriagesCongenital heart problems

Environmental Influences on Birth DefectsExposure to hazards during pregnancy Chemicals X-rays Toxoplasmosis – extreme high blood

pressure

Environmental Influences on Birth DefectsAccidental injuries Cerebral palsy caused

by damage to brain before, during, or shortly after birth

Falls lead to a variety of complications

Hereditary Influences on Birth Defects

Dominant genes?

Recessive genes?

Can you explain the difference?

Hereditary Influences on Birth Defects

1. Defective recessive genes inherited from both parents

• Cystic fibrosis • Tay-Sachs disease• Sickle cell anemia

2. Defective dominant gene inherited from one parent• Hemophilia• Huntington’s disease• Duchenne muscular dystrophy• Color blindness

3. Errors in chromosomes• Down syndrome

Tay-Sachs

Tay-Sachs disease is an untreatable disorder that is always fatal. Children born with Tay-Sachs appear normal at birth but lack an enzyme needed to break down certain fats. The fats build up and destroy brain and nerve cells, leading to rapid mental and physical deterioration and death in early childhood.

Combined Influence of Heredity and Environment Birth Defects Drugs + virus = heart defect Cleft lip/cleft palate Spina Bifida – reduce risk by taking folic

acid

Individual Activity

In the blanks place an H if the factor is influenced by heredity, an E if the factor is

environment, and B if it is both.

Case Study : Partner Activity

Read case study and list the various influences in the correctly column

Scrapbook Page # 7Family Tree

Create your family tree.

Begin with your grandparents and add on all your family members, include eye color and hair color.

BE NEAT!

Scrapbook Page 8 TWINS

Your twins: Will they boys, girls, both Will they be Identical or Fraternal and why? Tell me what you will have to do to prepare

for them….childcare choice etc… Draw them!!