2.14

Question 1

Our phenotype does not always depend only on our genotype - sometimes it is affected by

Answer 1

environment

Question 2

When scientists are trying to find out the relative effects of genetics and the environment on a particular facto - it is very useful to study

Answer 2

twins

Question 3

2 different kinds of twins:

Answer 3

• Monozygotic (MZ)

- Dizygotic (DZ)

Question 4

Monozygotic twins develop from a single zygote that

Answer 4

splits early in development to form 2 genetically identical individuals
Any difference between monozygotic twins are likely to be as a result of the environment

Question 5

Dizygotic twins develop from 2 different zygotes, although they share about 50% of their genes they are no more alike than any other brothers and sisters and differences between them might be as a result of

Answer 5

genetic or environmental factors

Question 6

Twins are said to be concordant for a characteristic

Answer 6

if they are both similar for that characteristic

Question 7

Twins are said to be discordant if they are

Answer 7

different for that characteristic

Question 8

MZ twins have 100% concordance for blood group as it is determined by

Answer 8

genes and the environment has no effect

Question 9

DZ twins have a fairly high concordance, because they are related and share many of their genes, but they do not always have the same

Answer 9

blood group as their twin

Question 10

Both MZ and DZ have low concordance for breast cancer - suggesting it is that

Answer 10

environmental factors are very important in determining whether a person will develop breast cancer

Question 11

Measles = high concordance between MZ twins and DZ twins due to

Answer 11

living in the same environment - if 1 twin develops measles as will the other

Question 12

Studies on MZ twins raised apart, show that genetic factors must be important in IQ, as the concordance for MZ twins reared together is higher and is higher than DZ twins reared

Answer 12

together

Question 13

MZ twins raised apart do not necessarily have a completely different environment, they might experience environments which are essentially similar, such as:

Answer 13

mental stimulation
diet
housing quality

Question 14

The IQ test used might not give reliable measurements, so differences between twins’ scores might be the result of a

Answer 14

poorly constructed test