Genes

Question 1

Genotype

Answer 1

The genes an organism has inherited

Question 2

How many genes does an organism inherit from each parent?

Answer 2

23

Question 3

23 genes into chromosomes

Answer 3

46 chromosomes

Question 4

Phenotype

Answer 4

The traits that are actually expressed

Question 5

Examples of a physical phenotype:

Answer 5

Eye colour

Question 6

Examples of non physical phenotype:

Answer 6

Temperament
Depression

Question 7

Whether the gene is expressed or not depends on two different things:

Answer 7

• the interaction of the gene with other genes (dominant or recessive)
• the interaction between the genotype and the environment

Question 8

Dominant allele

Answer 8

[Written as a capital letter]
If a dominant allele is inherited from either parent, the particular characteristic will always be expressed in the phenotype.

Question 9

Recessive allele

Answer 9

[Written as a lowercase letter]

Will only be expressed in the phenotype if inherited from both parents.

Question 10

What is the interaction between genes and the environment:

Answer 10

• psychological disorders
• stress diathesis model

Question 11

Development of disorder=

Answer 11

Combination of diathesis factors (genetic vulnerability) and stress factors (environmental triggers)
- one factor alone can’t cause behaviour

Question 12

Method of investigating influence of genes

Answer 12

Twin study

Question 13

What twin studies do:

Answer 13

Investigate many pairs of twins and assess how often they share a particular characteristic

Question 14

Concordance rate

Answer 14

The likelihood that 2 individuals share the same characteristic

Question 15

Monozygotic twins

Answer 15

Identical
Share 100% of their DNA

Question 16

Dizygotic twins

Answer 16

Non identical
Share 50% of their DNA

Question 17

If a characteristic is purely genetic:

Answer 17

Concordance rate for MZ twins 100%

Concordance rate for DZ twins 50%

Question 18

If the concordance rate is significantly higher for MZ twins than DZ:

Answer 18

The behavioural characteristics are mainly genetic
- increases the likelihood of the twins sharing a behaviour

Question 19

If concordance rate for MZ and DZ is similar:

Answer 19

The characteristic is determined by the environment

Question 20

Golden rule of twin studies:

Answer 20

As the proportion of shared genes increases, so does the likelihood of both twins demonstrating the same behaviour

Question 21

The concordance rate is proportionally acceptable only if it is

Answer 21

Double or more