Chapter 3 - Hereditary Influences on Development Flashcards
What is the nature vs. nurture debate?
nature = biological predispositions are most important
nurture = environmental influences are most important
actually interaction of biology and environment
What is a chromosome?
threadlike DNA structure made of genes (which hold the DNA)
come in matching pairs (23 x 2)
What is the result of conception?
fathers sperm + mothers ovum = zygote
46 chromosomes total, 23 from each parent
When does mitosis begin? What is it?
after fertilization
cell duplicates its chromosomes and then divides, producing 2 complete, identical daughter cells
continues throughout life, replacing old or damaged cells
What is meiosis?
parent’s original germ cells split into 4 separate gametes with half the chromosomes of parent cell
Which parent determines the sex of the child?
father
females (XX) donating an X chromosome either way
males (XY) could donate an X or a Y, deciding gender
What are genes?
hereditary instructions for development transmitted generation to generation
direct production of AA to form new cells
turning on and off regulate timing of development
What is a genotype?
inherited genetic endowment
What is a phenotype?
the way someone’s genotype is expressed in observable characteristics and behaviours
What are the 2 types of twins?
monozygotic
- zygote divides in 2 and forms 2 genetically identical individuals
- 1 in 250
dizygotic
- 2 ova are released simultaneously, both fertilized by different sperm
- fraternal
- 1 in 125
What is H?
heritability coefficient
how strong the contribution of heredity is to a trait
H = (r identical - r fraternal) x 2
What is the heritability of IQ?
moderate
higher concordance with identical than fraternal
What are concordance rates?
percentage of cases in which a particular attribute is present for both members of a twin/parent-child pair
What is twin design looking at?
are identical twins or fraternal twins more similar when both reared together?
What is adoption design looking at?
are adopted children more similar to biological or adopted parents?
What are the 2 types of environmental influences involved in determining heritability?
non-shared environmental influences
- unique to each individual, not shared by other members of the family in the same environment
shared environmental influences
- experiences common to all family members in the same environment
What is the heritability of personality?
genes moderate at best
shared environment decreases over time, non-shared environment must be important
What does the heritability of mental illness demonstrate about inheritance?
genetics have some role, but inheriting genes does not guarantee expression of these genes
- environment influences expression
What is the canalization principle?
genes restrict development to a small range of outcomes
ex. babbling is a highly canalized attribute
What is the range of reaction principle?
genes set boundaries for range of phenotypes, environment decides where in the range they will fall
not as rigid as canalization
Describe simple dominant recessive inheritance?
dominant alleles are stronger, will be expressed if they are present
recessive alleles will only be expressed if both copies are excessive
ex. dark hair is dominant, blonde hair is recessive
What are congenital problems?
present at birth
- but may not always be apparent
could be due to environmental or hereditary causes
What causes chromosomal abnormalities?
uneven distribution of chromosomes during meiosis
could also occur through mutation
most abnormalities are lethal
What are 2 abnormalities of sex chromosomes in females?
Turner syndrome
- XO
- small, underdeveloped, sterile
Poly-X syndrome
- XXX
- fertile, developmental delays
