Anorexia: Biological Explanation - Genetics

Question 1

What is a gene?

Answer 1

A sequence of DNA that codes certain information.

Question 2

What is a genome?

Answer 2

All genes in a cell.

Question 3

How many pairs of chromosomes do we have?

Answer 3

23

Question 4

What is a dominant gene?

Answer 4

A gene that only needs 1 chromosome for an observable characteristic (phenotype) to show.

Question 5

What is a recessive gene?

Answer 5

A gene that needs 2 of the same chromosome for an observable characteristic (phenotype) to show.

Question 6

How are genetics studied in psychology?

Answer 6

Twin/adoption studies.

Question 7

What are the two types of twins?

Answer 7

• Monozygotic

- Dyzygotic

Question 8

What are monozygotic twins and so how much DNA do they share?

Answer 8

Identical - 100%

Question 9

What are dyzygotic twins and so how much DNA do they share?

Answer 9

Non-identical - 50%

Question 10

Briefly explain what measure determines if a behaviour is genetic in twin studies.

Answer 10

Concordance rates, the higher the rate the more likely the behaviour is to be genetic.

Question 11

List 3 strengths of twin studies.

Answer 11

1) High reliability
- Uses scientific methods such as DNA sequencing which provides objective quant data
2) High reliability
- The number of multiple births are increasing so can replicate easily
3) High validity
- MZ and DZ twins are naturally occurring variables so low researcher bias

Question 12

List 3 weaknesses of twin studies.

Answer 12

1) Low generalisability
- MZ twins may not be representative of other twins in a different environment
2) Low reliability
- Environmental differences between MZ and DZ twins may be hard to compare due to differences
3) Low validity
- One twin of an MZ pair may be exposed to different environmental triggers for one gene

Question 13

What would anorexia being a cause of genes imply in regards to twins?

Answer 13

That frequency is higher in MZ than DZ twins.

Question 14

Define ‘heritability estimate’.

Answer 14

The percentage that a characteristic is due to genes.

Question 15

How is a heritability estimate often calculated?

Answer 15

Looking for similarities between families and twins in relation to that characteristic.

Question 16

Identify 3 supporting pieces of evidence for anorexia being a cause of genes.

Answer 16

1) Kipman et al (1999)
2) Holland et al (1988)
3) Scott-Van Zealand et al (2013)

Question 17

What did Kipman et al (1999) find in regards to the cause for anorexia.

Answer 17

P - Kipman et al (1999) supports the genetic cause of anorexia
E - He gave the concordance rate for MZ twins as 44% and 12% for DZ twins
E - This therefore demonstrates that anorexia has genetic components

Question 18

What did Holland et al (1988) find in regards to the cause for anorexia.

Answer 18

P - Holland et al (1988) supports the genetic cause of anorexia
E - He looked at 25 MZ and 20 DZ twins who were all female and found a 56% concordance rate in MZs compared to 5% in DZ
E - This therefore demonstrates that anorexia has genetic components

Question 19

What did Scott-Van Zealand et al (2013) find in regards to the cause for anorexia.

Answer 19

P - Scott-Van Zealand et al (2013) supports the genetic cause of anorexia
E - He took a DNA sample from 261 anorexics and 500 healthy controls to research 152 potential genes and found that EPHX2 genes (associated with cholesterol and depression) linked with AN
E - This therefore demonstrates that anorexia has genetic components

Question 20

Identify 2 rejecting pieces of evidence for anorexia being a cause of genes.

Answer 20

1) Garner and Fairburn (1988)

2) Wade et al (2007)

Question 21

What did Garner and Fairburn (1988) find in regards to the cause for anorexia.

Answer 21

P - Garner and Fairburn (1988) rejects the genetic cause of anorexia
E - They argued that the increase in eating disorders of 15 in 1979 to over 140 in 1986 cannot be genetic due to no major genetic changes in the past 3 decades
E - Therefore there must be other factors involved such as the environment that is experienced

Question 22

What did Wade et al (2007) find in regards to the cause for anorexia.

Answer 22

P - Wade et al (2007) rejects the genetic cause of anorexia
E - Researched Australian female twins showed that families of anorexics made frequent comments about weight during childhood
E - This therefore shows the role of nurture influencing development of anorexia and so it is not just due to genetics

Question 23

Using the acronym ‘GRV’, evaluate a low ‘generalisability’ point for research into anorexia being genetic.

Answer 23

P - Low generalisability
E - Sample sizes are often small and unrepresentative as twins only make up 1.5% of the population
E - This therefore cannot be generalised to people who don’t have a twin

Question 24

Using the acronym ‘GRV’, evaluate a high ‘reliability’ point for research into anorexia being genetic.

Answer 24

P - High reliability
E - Concordance rates for AN being genetic are consistent in supporting the biological basis of this disorder
E - Therefore shows the consistency of findings and how studies can be compared and replicated easily

Question 25

Using the acronym 'GRV', evaluate 2 low 'validity' points for research into anorexia being genetic.

Answer 25

P - Low validity E - There is never a 100% concordance rate for anorexia being genetic in twins E - Therefore there must be other factors such as the environment affecting whether or not someone develops anorexia with different interactions stimulating different genes P - Low validity E - If the first twin is diagnosed with anorexia then the diagnosis of the second twin may be biased as a result E - This is open to researcher bias and so reduces credibility of results

Question 26

Suggest an alternative explanation for the development of anorexia.

Answer 26

P - Social Learning Theory E - Someone may idolise a role model who they pay attention to being praised for being skinny by the media and so they may reproduce this behaviour by starving themselves to be as skinny as them, receiving motivation through external reinforcement of praise for weight loss from friends E - Therefore demonstrating that anorexia may instead be a disorder caused by the environment

Question 27

Describe a conclusion to the argument of anorexia being biological.

Answer 27

Anorexia may not be completely genetic. The interactionist theory of diathesis-stress model states that someone may be predisposed to developing anorexia but environmental stressors trigger the disorder instead of the genes themselves.