Genetics in psychology

Question 1

Karyotype

Answer 1

Number form and size of chromosomes

Question 2

p

Answer 2

Short arm of a chromosome

Question 3

q

Answer 3

Long arm of a chromosome

Question 4

Genotype

Answer 4

Describes our genetic makeup

Question 5

Phenotype

Answer 5

Describes the observable characteristics that are joined to genetic makeup and environment

Question 6

X-linked disorder

Answer 6

A disorder resulting from a genetic abnormality on the X chromosome. e.g. Fragile X syndrome which is dominant, X-linked disorder

Question 7

Dominant disorder

Answer 7

A single copy of one abnormal gene is sufficient to cause a genetic condition – 50% risk of inheriting the gene for the disorder e.g. Huntington’s Disease

Question 8

Recessive disorder

Answer 8

Two copies of the abnormal gene are needed to produce the disorder (so both parents must be carriers with one copy each) - 25% risk of inheriting the gene for the disorder e.g. Cystic fibrosis

Question 9

Gender effects of X-linked disorders

Answer 9

Generally the heritability of x-linked disorders is greater for boys because, unlike girls, the have no second unaffected X chromosome as a ‘back up’. There is a ‘buffering’ effect in girls

Question 10

Complexities in the effects of inherited genetic disorders

Answer 10

• Gene-gene interactions
• Gene protein levels
• Inherited set of unaffected genes & their impact
• Environmental factors

Question 11

Allele

Answer 11

Variant form of a given gene

Question 12

Heterozygous genotype

Answer 12

Describes a genotype with different alleles

Question 13

Homozygous genotype

Answer 13

Describes a genotype with the same alleles

Question 14

Fragile-X syndrome

Answer 14

World most common caused of inherited mental retardation. Cause of developmental delay, inhibitory control, repetitive speech. Only gene disorder known to cause autism.
Silencing of fMR1 gene causes the loss of the FMRP protein, resulting in Fragile-X phenotype.
X-linked, dominant gene disorder (50% chance of passing on)
Occurs in 2 stages dependent on number of CCG repeats. Large expansion [over 200] = fully affected, OR medium expansion [>55 repeats] = carrier. Carrier males can only pass on the medium expansion

Question 15

Behavioural phenotype

Answer 15

Observable characteristics that occur more often in individuals with a specific genetic syndrome than individuals without that syndrome.

Question 16

Williams syndrome

Answer 16

Rare neurodevelopmental disorder occurring in 1/7,500 to 20,000 births
Occurs from a micro-deletion of approx. 28 genes on long arm of Chromosome (7q11.23)
Missing the gene elastin, which results in disorders of the circulatory system and heart
Distinct facial phenotype (small upturned nose, wide mouth and spaced teeth, full lips)
Characterised by problems with visual-spatial and motor skills and attention skills. Hypersociability early, but heightened levels of generalised anxiety in later years, , unusual attraction to faces and affinity for music.

Question 17

ADHD

Answer 17

Neurodevelopmental disorder that generally becomes apparent in the preschool and early school years and affects boys and girls. Affects about 5% of children (3 males to 1 female) and 4% of adults (1:1 m:f)
Believed to be linked to dopamine deficieny and often treated with Ritalin
Characterised by poor attention to detail, difficulties in maintaining attention over a sustained period of time, moment-to-moment variability throughout task performance
Inattentiveness is consistent across ages, however impulsivity and hyperactivity are considered to reduce with age.
Neuroimaging demonstrates problems in frontal lobe (attention), parietal lobe (visual-spatial information) and cerebellum (timing and coordination)
ADHD is considered 75-90% heritable

Question 18

Candidate gene approach

Answer 18

Approach that selects genes of interest based upon knowledge of the disorder

Question 19

Dopamine

Answer 19

An important neurotransmitter that is produced in many parts of the brain and plays a critical role in reward, cognition and emotion