Session 7-Genotype, Phenotype And Inheritance

Question 1

Define homozygous

Answer 1

Two alleles of a gene are the same (individual is a homozygote)

Question 2

Define heterozygous

Answer 2

Two alleles of a gene are different (individual is heterozygote)

Question 3

Define hemizygous

Answer 3

Only one allele of a gene is present on the X chromosome (ie males only)

Question 4

Define dominant

Answer 4

Dominant allele in heterozygote determines phenotype

Question 5

Define recessive

Answer 5

Non-dominant allele in heterozygote is recessive

Question 6

Give an example of a co-dominant gene and explain its alleles

Answer 6

Human isoglutamin gene which codes for glycoproteins on the surface of RBCs
Alleles A and B are dominant over allele O
Alleles A and B are co-dominant

Question 7

True or false: heterozygotes are affected in an autosomal recessive condition

Answer 7

FALSE

Question 8

True or false: males and females are equally affected in an autosomal recessive condition

Answer 8

TRUE

Question 9

What % chance do two heterozygotes have of producing offspring with an autosomal recessive condition?

Answer 9

25%

Question 10

True or false: in an autosomal recessive condition, two affected (homozygous) individuals will have affected offspring only

Answer 10

TRUE

Question 11

Give an example of an autosomal recessive condition

Answer 11

Cystic fibrosis

Question 12

True or false: autosomal recessive conditions cannot skip generations

Answer 12

FALSE

Question 13

True or false: heterozygotes are affected in autosomal dominant conditions

Answer 13

TRUE

Question 14

True or false: males and females are not equally affected in autosomal dominant conditions

Answer 14

FALSE

Question 15

What % chance does every affected individual have of producing offspring with an autosomal dominant condition?

Answer 15

50%

Question 16

Give an example of an autosomal dominant condition

Answer 16

Huntington’s disease

Question 17

True or false: autosomal dominant conditions cannot skip generations

Answer 17

TRUE

Question 18

Which males and females are affected by X-linked recessive conditions?

Answer 18

Hemizygous males and homozygous females

Question 19

True or false: X-linked recessive conditions are more common in males

Answer 19

TRUE

Question 20

What % chance does a heterozygous female carrier have of having sons with an X-linked recessive condition?

Answer 20

50%

Question 21

True or false: males with an X-linked recessive condition cannot give the trait to their sons

Answer 21

TRUE

Question 22

Give an example of an X-linked recessive condition

Answer 22

Haemophilia A

Question 23

Which males and females are affected by X-linked dominant conditions?

Answer 23

Hemizygous males and heterozygous females

Question 24

True or false: affected males cannot give X-linked dominant traits to their sons but they will give it to all of their daughters

Answer 24

TRUE

Question 25

Give an example of an X-linked dominant condition

Answer 25

Rett syndrome

Question 26

Give an example of a Y-linked condition

Answer 26

Swyer syndrome

Question 27

True or false: all individuals with mitochondrial diseases inherit the trait from their mothers

Answer 27

TRUE

Question 28

True or false: more than one gene can be involved in producing a particular phenotype

Answer 28

TRUE

Question 29

Give an example of a polygenic condition

Answer 29

Albinism