Genetic Influences on Development

Question 1

What is the “heritability index”?

Answer 1

A statistic used to estimate the degree to which a particular characteristic can be attributed to genetic factors.

Question 2

What have studies on the heritability index of intelligence shown?

Answer 2

Range from .30 to .70 with average being about .50 meaning that about 50% of individual differences in IQ scores can be explained by genetic factors.

Question 3

22 of the 23 pairs of human chromosomes are ___________ meaning that they are exact duplicates of each other. They are known as ___________.

Answer 3

Homologous; autosomes

Question 4

23rd pair of chromosomes are made up of the _____ chromosomes. In females the pair is ___________ and called the ____ chromosome pair; in males, the pair is ___________ and called the ____ chromosome.

Answer 4

Sex chromosomes; homologous; XX; not homologous; XY

Question 5

What are some examples of dominant characteristics and recessive characteristics?

Answer 5

Dominant = dark hair, immunity to poison ivy, normal hearing, and type B blood

Recessive = red hair, susceptibility to poison ivy, congenital deafness, and type O blood

Question 6

What is one example of a sex-linked characteristic?

Answer 6

Red-green color blindness which is carried on the X chromosome and is twice as common in males than in females.

Question 7

Give a few examples of disorders due to presence of 2 recessive gene.

Answer 7

PKU = lacking enzyme to break down amino acid (phenylalanine) which in undigested form is a toxic agent in brain and causes severe MR. MR preventable by diet low in phenylalanine in first 6-9 years of life (avoid foods like milk, eggs, fish, bread). Tay-Sachs, sickle-cell, cystic fibrosis are other recessive gene examples.

Question 8

Give an example of a disorder due to the presence of a single dominant gene.

Answer 8

Huntington’s Chorea is an example of an autosomal dominant gene disorder. Child of affected parent has a 50% chance of inheriting this disorder.

Question 9

How many babies born with chromosomal abnormalities?

Answer 9

Approximately 1 in 200

Question 10

Chromosomal abnormalities can be caused by:

Answer 10

Extra chromosome, missing chromosome, chromosome translocation (when section of chromosome is attached to another chromosome), or chromosomal deletion (which occurs when part of a chromosome is missing like in Prader-Willi characterized by MR and extreme obesity).

Question 11

What is the most common chromosomal abnormality?

Answer 11

Down Syndrome (trisomy 21); occurs in about 1 of every 800 live births with frequency rising dramatically with increasing maternal age; 1 in 1,900 ages 20-24; 1 in 30 for mothers over 45

Question 12

Characteristics of Down Syndrome

Answer 12

Moderate to profound MR, short, stocky build, flattened face, protruding tongue, almond-shaped eyes; often have heart abnormalities, thyroid dysfunction, malformations of intestinal tract, susceptibility to respiratory infections

Question 13

Sex-linked chromosomal abnormalities include

Answer 13

Klinefelter’s Syndrome and Turner’s Syndrome

Question 14

Klinefelter’s Syndrome

Answer 14

Affects males and caused by extra X chromosome, i.e., XXY; have typical masculine interests and develop normal male identity but show incomplete development of secondary sex characteristics and are often sterile

Question 15

Turner’s Syndrome

Answer 15

Occurs in females when all or part of second X chromosome is missing; they don’t develop secondary sex characteristics, are sterile, and tend to have short stature, stubby fingers, and webbed neck.

Question 16

Fragile X Syndrome

Answer 16

Due to weak site on X chromosome and can occur in both males and females though more evident effects are seen in males who lack influence of normal/2nd X chromosome; constellation of physical, intellectual, and behavioral deficits including mod to severe MR, facial deformities, and rapid, staccato speech rhythm

Question 17

The effects of exposure to teratogens depend on what kinds of factors (name 3)

Answer 17

1. Amount of exposure
2. Length of exposure
3. Period of development when exposure occurs

Question 18

Over what period of time does the germinal period last? What can effects of teratogens over this time be?

Answer 18

Lasts from conception to implantation, occurring 8-10 days later; may only damage a few cells having little to no effect on development OR may affect many cells and cause organism’s death

Question 19

Over what period of time does the embryonic period last? What can effects of teratogens over this time be?

Answer 19

From end of 2nd week after conception to end of 8th week; developing organs are MOST susceptible to major defects, with time of greatest susceptibility depending on particular organ system; i.e., CNS from beginning of 3rd week to beginning of 6th week and heart from middle of 3rd week to middle of 6th week

Question 20

Over what period of time does the fetal period last? What can effects of teratogens over this time be?

Answer 20

Beginning of 9th week to birth; organ systems less affected, but exposure can still cause less severe defects, especially to external genitalia and brain; prolonged exposure tends to cause retarded growth and lowered IQ

Question 21

Most common teratogens include

Answer 21

Alcohol, drugs (illegal, prescription, OTC), smoking, maternal disease

Question 22

Alcohol as a teratogen info

Answer 22

Heavy consumption can lead to severe and largely irreversible abnormalities to child including FAS;

Question 23

FAS

Answer 23

FAS sxs vary depending on amount consumed and can include retarded growth, facial deformities, microcephaly (small, underdeveloped brain), irritability, hyperactivity, variety of neurological abnormalities; most children mentally retarded w/IQs between 65-70; it’s the leading cause of MR in US; can be born w/o full syndrome present and w/1 or more sxs, i.e., lowered IQ, irritability; as many as 1 in every 100 births shows FAS or FAE

Question 24

Heroin or methadone

Answer 24

Increases risk for prematurity, low birth weight, physical malformations, respiratory disease, mortality at birth; born physically addicted to drug and show w/d sxs at birth; may show similar sxs as maternal marijuana use

Question 25

Marijuana

Answer 25

Associated with low birth weight, muscle tremors, increased startle response and visual problems; may show similar sxs as maternal heroin use

Question 26

Cocaine use

Answer 26

Retard fetal growth, can cause preterm birth and malformations of brain, intestinal and genital-urinary tract; Babies may be born w/hemorrhages, lesions and swelling in brain, small head circumference, heart defects, brain seizures, abnormal motor development

Question 27

Cocaine-exposed infants tend to show more…

Answer 27

Irritability, rigidity, muscle tremors, difficulty self-soothing, difficulty being consoled, excessively reactive to environmental stimuli; often impaired sensory fx, decreased visual attention, difficulty regulating own state of arousal (asleep, awake, attentive); in school, concentration/memory problems, learning disabilities, & social problems

Question 28

OTC & Prescription Drugs (benzos)

Answer 28

Benzos associated w/prenatal syndrome including feeding problems, hypothermia, deficiency in baby’s muscle tone

Question 29

Mood stabilizers

Answer 29

Known teratogens; Lithium in 1st trimester increases risk for Ebstein’s Anomaly (heart defect) by 10x & valproic acid increases risk for fetal malformation; lithium around time of birth associated with perinatal syndrome including bluish discoloration of skin and decreased muscle tone

Question 30

Smoking

Answer 30

At risk for spontaneous abortion, prematurity, low birth weight, death during period surrounding birth; less responsive to environment more irritable as compared to infants of nonsmokers; prenatal nicotine exposure linked to increased hyperactivity, short attention span, reduced school achievement in reading, math, spelling

Question 31

Most maternal diseases that cause prenatal defects are viral or bacterial?

Answer 31

Viral

Question 32

Maternal Rubella virus (German measles)

Answer 32

heart defects, eye cataracts, deafness, gastrointestinal anomalies, MR; 20% die shortly after birth; most severe damage during 4th-8th week of pregnancy

Question 33

Maternal Herpes simplex virus (HSV)

Answer 33

3x increased risk of miscarriage if contracted in early pregnancy; babies usually contract it through delivery rather than prenatal development; baby typically delivered via cesarean to prevent exposure; exposed babies have high risk for death, brain damage, or blindness; use of antiviral meds helps about 1/2 infected prevent permanent damage (e.g., serious neurological damage, MR, or even death)

Question 34

Cytomegalovirus (CMV)

Answer 34

Another type of herpes virus that is very dangerous to fetuses; infection during embryonic stage (weeks 2-8) usually results in death of embryo; later infection baby at risk for retarded growth, blindness, deafness, MR, microencephaly (small head circumference associated w/delayed motor, speech, and mental development), and cerebral palsy

Question 35

Syphilis

Answer 35

Baby at risk for birth defects like deafness, facial deformities, malformations of teeth and bones, excess fluid in brain and MR; Tx of mother can protect baby from effects of syphilis

Question 36

HIV virus

Answer 36

Transmission from mother to child during pregnancy, labor, and delivery or breast-feeding called perinatal transmission; in US, w/o antiretroviral therapy approx 25% pregnant women infected will transmit virus to child; however, w/therapy, rate can be decreased to 2% or less; risk reduced w/AZT given to mom during last 2 trimesters of pregnancy and to infant during 1st 6 weeks of life; so far no adverse effects of AZT found

Question 37

HIV Newborns

Answer 37

Higher-than-average rates of prematurity and small for gestational age; during 1st year of life, most develop early sxs of virus including increased susceptibility to other infections, failure to thrive, swollen lymph nodes, and developmental delays

Question 38

Development of HIV

Answer 38

About 25% HIV-infected infants develop AIDS & 15% die during 1st year of life though reports of children living into late adolescence w/current txs of AZT & antibiotics; High risk for infections and immunological abnormalities & CNS dysfunctions including loss of developmental milestones, attention/concentration problems, & declining IQ scores

Question 39

Name 3 other maternal conditions that affect development

Answer 39

Prenatal nutrition, emotional stress, & maternal age

Question 40

Prenatal nutrition

Answer 40

Depends when it occurs and severity; 1st trimester = spontaneous abortion or congenital malformations; 3rd trimester = low birth weight and low brain weight d/t fewer neurons, less dendrite branching, and reduced mylenization; behavioral consequences can include apathy, unresponsive to environmental stimuli, irritability, abnormally high-pitched cry, intellectual deficits, & lags in motor development

Question 41

Emotional stress

Answer 41

Chronic, severe anxiety or stress = more medical complications and infants w/greater number of abnormalities than women who are relatively anxiety-free; stress associated with spontaneous abortion, premature delivery, more difficult labor; high risk for low birth weight, respiratory problems, irritability & hyperactivity, bowel irregularities, sleep & eating problems; high stress during pregnancy doesn’t always lead to negative outcomes and problems associated w/stress greatly reduced w/supportive social relationships

Question 42

Maternal age

Answer 42

Majority of women have healthy births regardless of age; percentage of babies w/low birth weight greatest for moms under 15 y.o. and over 45; over 35, slightly higher risk for complications like miscarriage, placenta previa, high BP, diabetes, & cesarean birth; egg & sperm quality decline w/age; increased risk of congenital defects like Down’s Syndrome in older mothers, especially first time moms in 40s

Question 43

Other complications of pregnancy or delivery =

Answer 43

Premature infants, small-for-gestational age (SGA), and fetal distress

Question 44

Premature infants

Answer 44

Infant born before 37 weeks considered premature; risks linked to lack of prenatal care, malnutrition, maternal age (esp < 15 y.o.), drug use, low SES, multiple gestations; many premature now survive however; w/appropriate medical attention & supportive environment, premature infants w/o significant abnormalities often catch up to peers in terms of cognitive language and social skills by 2-3 y.o.

Question 45

Small-for-gestational age (SGA)

Answer 45

Newborn or birth weight below 10th percentile for expected weight; higher risk for respiratory disease, hypoglycemia, & asphyxia during birth

Question 46

Fetal distress

Answer 46

Condition during birth process that indicates fetus is at risk d/t change in heart rate, respiration, or anoxia; prolonged anoxia may result in delayed cognitive and motor development, MR, & cerebral palsy