Bio psych 2 chapter 4

Mendelian genetics

19th century monk Gregor Mendel demonstrated that inheritance occurs through discrete units of heredity called genes

Prior to Mendel

Commonly believed that inheritance was a blending process of the properties of the egg and the sperm

Chromosomes

Strands of DNA that comes in pairs

DNA

Serves as a model for the synthesis of RNA

What is DNA made of?

Adenosine, guanine, cytosine, and thymine

RNA

Single strand chemical that can serve as a template/model for the synthesis of proteins

Proteins

Determine the development of the body by forming part of the structure of the body and serving enzymes

Enzymes

Biological catalysts that regulate chemical reactions in the body

Phenotype

Expression of a gene pair

Genotype

Capital letters refer to dominant genes, small letters refer to recessive genes

The genetic make up

Homozygous

Having an identical pair of genes on two chromosomes (BB or bb)

Heterozygous

Having an unmatched pair of genes of two chromosomes (Bb)

Dominant gene

Expressed in either the homozygous or heterozygous condition (Bb or BB)

Recessive gene

Only expressed in the homozygous condition (bb)

Intermediate gene

Occurs in a phenotype where there is incomplete dominance in the heterozygous condition

How many pairs of chromosomes?

23

female chromosomes

XX

Males chromosomes

XY

Sex genes are

The 23rd pair

Sex linked genes

Genes located on the sex chromosomes

Autosomal genes

All other genes except for sex linked genes

Sex limited genes

Present in both sexes but effect is limited or almost limited to one sex (breast size, chest hair)

Mutation

Heritable change in a DNA molecule

Micro duplication/micro deletion

Part of a chromosome that might appear once might appear twice or not at all

Epigenetics

Field that is concefned with changes in gene expression without the modification of the DNA sequence

Some genes only active at a certain point or certain time of day

Changes in gene expression

Are central to learning and memory

Heritability

Estimate of how much variance in population characteristic is due to heredity

if it is 0

heredity accounts for none of the observed variations.

If 1

Heredity accounts for all of the variations

What is heritability measured by?

Comparing monozygotic and dizygotic twins

Comparing adopted children to biological and adopted parents

Monozygotic twins

Share identical genetic information

Dizygotic twins

Share some genetic information

Stronger resemblance equals

More heritability

Evolution

Refers to a change in the frequency of various genes in a population over generations, regardless whether change is helpful or harmful

What does evolution attempt to answer?

How did some species evolve?

how do species evolve?

How do species evolve?

Offspring generally resemble their parents for genetic reasons

Mutations, recombination, and micro duplications of genes introduce new heritable variations

Certain individuals successfully reproduce more than others

Artificial selection

Refers to choosing individuals desired traits and making them parents of the next generation.

According to Darwin

Nature also selects and successful individuals genes will be prevalent in later generations

Lamarckism evolution

The use or disuse of some structure or behavior causes an increase or decrease in that behavior

Misconceptions about evolution

Humans have stopped evolving

Evolution means improvement

Evolution acts to benefits the individual or species

Brain evolution

our ancestors managed to get enough nutrition to provide a big brain with all the fuel it needs

Cooking food made it easier to digest

Group hunting was more efficient

Humans have a better capacity for glucose transport

Evolutionary psychology

Focuses upon functional and evolutionary explanations of how behaviors evolved

Evolutionary psychology assumes

That behaviors, characteristics of a species, have arisen through natural selection and provide a survival advantage

Behavior and natural selection

Some behaviors are more debatable with a regard to the influence of natural selection

Examples of behavior and natural selection

Life span length

Gender differences in sexual promiscuity

Altruistic behavior

Altruistic behavior

A behavior that benefits someone other than the actor

Altruism is hard to find outside of humans

Group selection

Controversial hypothesis that states that altruistic groups survive better than less cooperative ones

Kin selection

More plausible; selection for a gene benefits the individuals relatives

A gene spreads

If individuals with it reproduce more than individuals without it

Reciprocal altruism

Idea that individuals help those that will return the favor

Building a reputation for helpfulness only works if others are willing to cooperate with you

Plasticity

Ability of the Brian to change

CNS forms when

Embryo is two weeks old

By 7 weeks

The hindbrain, midbrain, and forebrain and are relatively well differentiated

The Brain weighs at birth

350g

The most undeveloped part of the infant brain is

The forebrain

The brain weighs at the end of the first year

1000 grams

Adult brain weighs

1200-1400 grams

Proliferation

Cells in ventricle divide

Some stay as stem cells

Some become primitive neurons and glia that go to new destinations

Migration

Cells follow chemical path toward final destination

What do genetic changes or positions that interfere with proliferation and migration produce?

Mental retardation

Differentiation

Axons and dendrites are formed while migration (arborization)

Myelination

Addition of insulating sheath that speeds transmission (still forming in adulthood)

Synaptogensis

Formation of synapses continues throughout life

Stem cells

Undifferenced cells found in the interior of the brain that generate “daughter cells” that can transform into glia or neurons but not the cerebral cortex

Stem cells differentiate into

New neurons in adult hippocampus of mammals and facilitate learning

Weiss 1924

Axons from normal leg branched to corresponding muscles of grafted leg

Sperry 1943

Cut axons from optic nerve to text I’m and rotated eye of newt, but axons returned to their original sight (newt saw world upside down and backwards)

Levi Montalcini

Proved that muscles determine which neurons survive not how many are formed

We produce

Many more neurons than we need

Neurotrophins

Chemicals that reorganize neural circuitry and promote survival of neuron

When does a cell receive nurotrophin?

When it forms a synapse with other cells

Nerve growth factor

A neurotrophic is present in peripheral NS and acts to stimulate growth of axons and dendrites

Brain derived neurotrophic factor

A neurtrophin in the CNS

Apoptosis

Programmed cell death occurs when synapses receive little nerve growth factor

Neural Darwinism

Competition among neurons for survival and among synapses is a selection process

Fetal alcohol syndrome

Severe health and mental health problems (heart defect, facial abnormalities, hyperactivity and depression)

Neurons received fewer neurtrophins resulting in increased apoptosis

Alcohol is a

GABA agonist inhibitory

Immature neurons

transplanted to a developing part of the cortex develop the properties of the new location

Neurons transplanted at a later stage

Develop some new properties but retain some old properties

Example: ferret experiment

Fine tuning by experience

Exporence changes our brains within limits

Donald Hebb ( kitchen rats vs lab rats)

Kitchen rats made fewer errors on Hebb-Williams maze

Enriched environment stimulates learning

Experience alters dendritic branching

Enriched environments increases branching, develops thicker cortex

Education correlated with branching not sure of the direction here

Physical exercise __ increase neuronal growth

May

Blind at birth

Use occipital love for touch and verbal functions and auditory stimuli also tend to use the visual areas of the brain (occipital and lower temporal)

What part of the cortex is enlarged for professional musicians?

Temporal cortex of right hemisphere

Focal hand dystonia

Neuronal recognization can cause musicians cramp

Stringed instruments enlarges and recognizes

Postcentral gurus devoted to left fingers

Adolescence is marked by

Impulsivity

Antisaccade task

Near impossible for 5-7 years old

Improves sharply by 7-11 years

More difficult for ADHD

Impulsivity is correlated with

Less prefrontal activation

Beginning at 30

The frontal cortex begins to thin

After 60

Lose about .5% of temporal cortex per year on average (memory)

Closed head injury

Sudden trauma that does not puncture the brain

Sources of damage in CHI

Axonal shearing from rotational forces

Bruising from brain hitting skull

Blood clots

Cerebrovascular accident

Stroke, loss of normal blood flow to brain area

Ischemia

Blood obstruction

hemorrhage

Blood vessel rupture

Thrombus

Blood clot formation

Embolus

Thrombus that breaks away and moves

Stenosis

Chronic narrowing of arteries due to atherosclerosis