Chapter 3: Biology and Behavior

What is heredity

• the passing on of traits from parents to their offspring

What are genes

• sections of chromosomes that code for traits, each containing instructions for making proteins giving rise to specific traits

  • physical traits (eye color, height)

  • psychological traits (aggression, anxiety)

• basic unit of heredity of all living things

What are allele’s

• two or more different versions of a gene (e.g. brown vs blue iris)

What are genome’s

• the complete set of genes of any organism

What are chromosomes

• molecules of DNA that transmit genetic information, divided into 23 pairs (46 total)

What is DNA

• molecules that carry all the biochemical instructions involved in the formation and functioning of an organism

• long string of molecules containing the “instructions” for building and maintaining an organism

What is a genotype

• the genetic material an individual inherits

What is a phenotype

• the observable expression of the genotype, including both body characteristics and behavior

What is environment regarding genetics

• every experience to which an individual is exposed in their surrounding; everything other than genes

  • parents parenting styles; features of the prenatal environment

What effects do the Parents Genotype have on the Childs Genotype

• children inherit their genotype from their parents (one chromosome in each pair from each parent

• Random assortment: explains all the variability in humans, sperm/ovum each has 23 chromosomes, when united it forms 23 pairs

• Crossing over: also explains the variability in humans, when chromosomes split to form gametes, they sometimes exchange pieces of DNA. This creates new combinations of genes, making the offspring’s chromosomes different from their parent

• Mutation: also explains the variability in humans, it is a change in a section of DNA.

What effects do the Child’s Genotype have on the Child’s Phenotype

• Just because you have certain genetic material does not mean it will be expressed

• Genes often have two or more different forms known as alleles

• Some genes are active (turned on), while others are not

• Dominant Allele: if present, it always gets expressed over other alleles

• Recessive Allele: only get expressed in the absence of a dominant allele

• Regulator Genes: the activation or inactivation of one gene is always part of a chain or genetic events. When one genes is switched on, it causes another gene to turn off or on, which has an impact on the status of yet other genes, meaning if a gene never gets switched on it wont be expressed.

• Thalidomide on limb development: prenatal exposure throws off regulator genes during sensitive period of limb development. The genes were there, just did not get turned on

• Polygenic: governed by more than one gene

What effects do the Child’s Environment have on the Child’s Phenotype

• MAO-A Gene: Codes for MAOA, an enzyme (protein) regulating mood, aggression, other things. Has several alleles, varying in the levels of MAOA produced

• What happens when low MAOA allele is combined with a history of maltreatment?

  • Together, likelihood of antisocial behavior skyrocket

  • Without maltreatment, people with low MAO-A are no different from anyone else

• The attention-grabbing name given to this allele is called “the warrior gene”, but as we can see, it is much more than just genetics that determines someone’s eventual behavior

What effects do the Child’s Phenotype have on the Child’s Environment

• Children are not just passive recipients of environmental influences; they directly impact the world around them

• Their behavior will impact how others behave towards them

• Later in childhood, decide which environments to engage with

  • A child who loves reading will read more, become better reader, and learn more

• Engaging personality, he created an environment filled with people - family and strangers alike - smiling and talking to him

• A shy infant who actively avoided contact with strangers; her temperament limited the types of interactions she had with unfamiliar adults

  • These 2 kids, despite living in the same home with the same parents, experienced very different early environments by virtue of their own behaviors

What effects do the Child’s Environment have on the Child’s Genotype

• Epigenetics: stable changes in gene expression that are mediated by the environment

  • Genetic code is fixed but the expression of code is altered

  • Changes of the expression (phenotype)

  • Methylation: silences gene expression

  • child maltreatment silences the expression gene related to coping with stress, with long lasting effects

• changes in expression can be passed to offspring without altering offspings’s DNA

What are behavior genetics

• differences in behavior and development come from a mix of genes and the environment

  • assume behavioral traits, to some extent, heritable

why do we care whether twins share a placenta/amniotic sac?

• gives us insight into the influence of the prenatal environment

• greater similarity between twins sharing a placenta = bigger influence of the prenatal environment on outcomes

What is Neurogenesis

• Proliferation of neurons through cell division; begins weeks after conception

  • after creation, migrate to their ultimate location

  • grow and differentiate according to their role

What is synaptogenesis

• formation of synapses with other neurons, making trillions of connections

  • too many connections are formed

What is synaptic pruning

• process by which synapses that are rarely activated are eliminated

  • only useful pathways are preserved

  • timeline of pruning varies by region

What is plasticity

• capability for the brain to be changed by experience

what is experience-expectant plasticity

• wiring of the brain from experiences it has evolved to expect and learn from such as language and vision

• the brain learns from specific experiences to ensure the organism is perfectly adapted to thrive

• in the absence of these experiences during sensitive periods, brain development can be interrupted

What is sensitive period

• window of development in which a brain must recieve certain kinds of stimulation to develop as it normally would

• if this does not occur, systems involved may never go on to develop as they typically do

What is experience-dependent plasticity

• the ongoing rewiring of neural connections following ones unique life experiences

  • all the other ways your brain changes as you move through life