Overview of Biopsychology and Genetics

• Building blocks of life 

Amino acids - poly peptides - proteins 

• Maintain shape of cells 
• Tissues 
• Enzymes 
• Neurotransmitters

Gene code for proteins 

• Influence the formation of structures in the body and the structure of the nervous system
• Influence events within the nervous system

• Gregor Mendel (1822-1884)
• Related organisms 
• 8 years he planted 30,000 plants, set out to examine & quanitify the physical traits in pea plants 
• Certain particles or "factors" transmitted from parent to offspring 
• Mendel suggested that these factors were directly responsible for physical traits 
• Each individual had not one but two "factors" for each trait 
• Characteristics do not always mix

Crossed plants with one trait with plants with another trait e.g.

• Tall stemmed plants with short stemmed plants 
• All of the offspring would be tall stemmed 
• If these offspring were then bread with one another their offspring would show a pattern of 1 short stemmed plant to a 3 long stemmed plants.

Certain characteristics are inherited on an "all or nothing basis". No blending.

Inheritence occurs in a predictable way.

• A single pair of genes, one from each parent, determines a particular inherited characteristic.
• Genes control a particular trait can have alternative forms called alleles; e.g. the gene that controls blood type has three alleles A, B, and O.
• When the corresponding genes inherited from the parents are the same, then the individual is homozygous for the trait. They will express that characteristic.
• When the alleles are different, the individual is said to be hetrozygous. For dichotomous traits they will display the charctertistic described by the dominant allele, a charactersitc from a recessive allele will not be expressed.

P1 cross                                                                            F1 Cross 

Phenotypes:      tall              dwarf                            Dd           x         Dd 

Genotypes:       DD      x        dd                             D   d                   D    d

Gamete formation                                                          F1 gametes 

DD                     dd

D    Gametes      d                                                         F2 generation 

F1 generation                                                F1 gametes            D               d         x         D               d

D                         d                                         Random fertilization 

     Fetilization                                                 F2 genotypes        DD             Dd                 Dd             dd

   Dd - all tall                                                   F2 phenotypes      tall             tall                 tall           dwarf 

                                                                       Designation    Homozygous - Heterozygous - Heterozygous - Homozygous

rr rr  = rr 100% red hair 

rr RR = Rr 100% no red hair 

rr Rr = rr Rr 50% chance of red hair 

Rr Rr = RR Rr Rr rr 25% chance of red hair 

• Free ear lobes (dominant) vs. attached ear lobes (recessive)
• Dimples (dominant) vs. no dimples (recessive)
• Straight thumb (dominant) vs. curved thumb (recessive)
• Bent fifth digit (dominant) vs. straight fifth digit (recessive)
• Tongue rolling (dominant) vs. non tongue rolling (recessive)

• Individual can display a characterstic that is intermediate e.g. skin colour 
• Expression can depend on the precise compliment of different genes
• Effect of gene may only be seen following some kind of trigger 
• Individual can display a characteristic that is contributed to by both alleles, but rather than being intermediate, it is distinctly different from that specified by either allele, this is called co-dominance 

E.g. a parent with type A blood and a parent with type B blood will produce an offspring with type AB blood which is different from either A or B types.

• 46 chromosomes (23 pairs)
• Contained in nucleas of every cell except sex cells (gametes) which contain only 23 chromosomes
• 44 autosomal chromosomes, & 2 sex-linked chromosomes: X and Y
• Female 2 X chromosomes, males an X and Y chromosome 
• The X chromosome carries many genes, the Y only carries a few genes whcih ensure the developing male foetus becomes 'male'

1. Colour Blindness: Red/green colour blindness is rare in females as they would need both their father and mother to carry the gene. It is fairly common in men as they only need a mother to carry the gene.

2. Haemophilia: Blood clotting disorder, common in the European Royal families. Queen Victoria who carried a recessive gene in one of her X chromosomes. She and all her female family did not show the disease because the defective gene was paired with a dominant non-defective gene. Her male descendants who inherited the defective X chromosome suffered from the disease, and passed it on to their daughters, who in turn passed it down to their sons.

• Superfolded molecule 

Sequence of nucleotides:

• Adenine 
• Cytosine
• Guanine
• Thymine

Bases are linked in a particular fashion (A-T and C-G)

Codon - combination of 3 nucleotides that code for one amino acid.

• Genome = total amount of DNA in one single cell
• Working draft of the Genome was mapped and published in 2001 
• 30,000 genes found - these genes provide the recipe for the devlopment of the human body - average gene is compromised of 10,000 nucleotide 
• 1000 Genomes Project (2008)

"I do not know of a single psychological trait that does not show genetic influence" Plomin (2018)

• Heritability - the extent to which differences between individuals can be explained by inherited DNA differences.
• Heritability estimates can differ depending on the particular population studies at a particular time.

• Exploring correlations for physcial psychological, & behavioural traits between adoptive parents and children.
• Comparing correlation with those for biological parents & their adopted children.
• Comparing correlations with non-adoptive children & parents.
• Similar process used with adoptive & non-adoptive siblings.
• Example - Colorado Adoption Project 

• Monozygotic (MZ) twins - identical twins - share 100% of their genes
• Dizygotic (DZ) twins - Fraternal or Non-identical - twins share 50% of their genes 
• Comparing MZ twins reared together & apart e.g. Minnesota Study of Twins Reared Apart
• Comparing MZ and DZ twins e.g. Twins Early Development Study

• Differences in behaviour
• Schizophrenia, mood disorders, anxiety (Plomin et al, 2001)
• Normal variations in personality (Loehlin, 1992) & cognitive abilities (Plomin & DeFries, 1998)
• Television watching (Plomin et al., 1996), lonliness (McGuire & Cliford, 2000), coffee drinking (Cornelis et al., 2011)