TOPIC PAGE NUMBER
BASIC HUMAN GENETICS 1
QUANTITATIVE GENETICS 11
MOLECULAR GENETICS 19
DEPRESSION 28
GENDER/SEX 48
CHILDHOOD TRAUMA 59
GLOBAL MENTAL HEALTH 68
CULTURE 76
CO-MORBIDITY 87
AUTISM 82
The Origin of Individual
Differences Notes – Level 5
KING’S COLLEGE LONDON
PATRYCJA_KUSACZUK@ICLOUD.COM
, BASIC CONCEPTS IN HUMAN GENETICS
1.1 Describe ✓ Heritability of trait/disease (twin/family/adoption studies)
the structure of ✓ Gene localisation (where approximately – linkage)
the human ✓ Gene identification (which gene exactly – association)
genome ✓ Gene structure, product, function
✓ Differences between people can only be due to genetic differences, not genetic similarity → we
study effect genetic variation
✓ E.g. study gene variants influencing individual differences in height, not: why does everyone grow
up to a certain minimum height
The human genome
• 23 pairs of chromosomes
• 22 pairs of autosomes
• 1 pair of sex chromosomes
• XY = male
• XX = female
• Y chromosome includes genes instructing development of testes
Genes on chromosomes
• Genes organised along the chromosome; same order in homologous pairs
• Different variants of genes – alleles
• E.g. same gene variant (AA) on both chromosomes (homozygous), can also have 2 different
alleles (Aa; heterozygous)
Gene variants
• Suppose ‘a’ stands for albinism allele; people with aa genotype have albinism
• AA = normal skin
• Aa = normal skin
• A = dominant allele
• a = recessive allele
Phenotype and genotype
• Genotype = unique combination of all alleles in individual
➢ Exception = identical twins (have the same genotype)
• Phenotype = observed characteristic of individual e.g. blood pressure, weight, extraversion score,
depressive symptoms score
• Phenotype = genotype + environment
• Or in family studies = phenotype = genotype + shared environment + unique environment
Gene transmission from parents to offspring
Parent cells (diploid)
Germline cells (haploid)
Offspring (diploid)
Genetic variation
• Variation between gametes that parent can transmit to offspring
1
, ➢ Segregation (only 1 pair of chromosomes transmitted)
➢ Independent assortment (which chromosome within pair is transmitted is random)
➢ Crossing-over between members of homologous pairs
1.2 Chemical structure of DNA
Demonstrate • 1953: Watson & Crick publish their research describing the 3-dimensioonal structure of DNA: the
knowledge of double helix
the structure of • DNA’s double helix: 2 strands of DNA coiled around each other like a spiral staircase
DNA • Each strand composed of nucleotides, compromising
➢ Sugar
➢ Phosphate
➢ Base
Structure DNA
• 4 types of bases:
➢ Adenine (A)
➢ guanine (G)
➢ Cytosine (C)
➢ Thymine (T)
• Sugar and phosphate of different nucleotides bind together to form one single DNA strand
• Base paring between 2 DNA strands
➢ A pairs with T
➢ C pairs with G
➢ Within DNA molecule, always same amount of A and T and of C and G
➢ 2 strands are complementary
1.3 Understand DNA replication
the processes
of DNA
replication;
transcription
and translation
Gene to protein
• How to genes exert their effects?
2
, • Genes
• Protein
• Bodily functioning (muscles, endocrine system, nervous system)
• Cognition/behaviour (motor movements, emotions, thought processes)
DNA to protein
• RNA – Ribonucleic Acid
• Single strand instead of double strand
• Bases
• Adenine (A)
• Guanine (G)
• Cytosine (C)
• Uracil (U)
Gene Transcription
Gene Translation
• RNA code composed of
consecutive 3-base
sequences: triplets or
codons
• Each codon codes for amino
acid
• RNA bases: letters; triplets;
words
• Words from sentences:
instructions to build protein
• RNA transcribed from DNA is
called messenger RNA
(mRNA). mRNA produced in
nucleus
• Translation into amino acid
sequences to form protein
takes place on ribosomes in
cytosol
• With help of transfer RNA
(tRNA)
3
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