MCBG - Genotype, Phenotype And Inheritance

Question 1

What is the genetic makeup of an individual termed?

Answer 1

Genotype

Question 2

What is the name given to the physical characteristics of an individual?

Answer 2

Phenotype

Question 3

Give some examples of environmental factors that can influence the genotype.

Answer 3

Radiation, life style, mutagens, diet, chemicals

Question 4

Genetics is the study of which two things?

Answer 4

Inheritance and variation

Question 5

How many copies of each gene does an individual have?

Answer 5

Two (one maternal, one paternal). These may be different alleles of the same gene.

Question 6

What does “homozygous” mean?

Answer 6

Two alleles of a gene are the same.

Question 7

What does “heterozygous” mean?

Answer 7

The two alleles of a gene are different.

Question 8

What does hemizygous mean?

Answer 8

Only one allele of a gene on the X chromosome (males only).

Question 9

If an individual has genotype Aa, which allele determines the phenotype (A or a)?

Answer 9

A because it is the dominant allele and therefore determines the phenotype. a is recessive.

Question 10

Which blood group allele (A or B) is dominant over the other?

Answer 10

Neither, as they are co-dominant. They are both dominant to O though.

Question 11

What would you state as the phenotype for someone with genotype A for glycoproteins on their red blood cells?

Answer 11

Blood group A

Question 12

What does a square indicate on a pedigree chart?

Answer 12

Male

Question 13

What does a circle indicate on a pedigree chart?

Answer 13

Female

Question 14

What does a coloured in shape indicate on a pedigree chart?

Answer 14

Affected individual. Partially coloured in indicates carrier.

Question 15

What does a diamond indicate on a pedigree chart?

Answer 15

Unknown sex (usually a baby)

Question 16

What does a diagonal line through a shape indicate on a pedigree chart?

Answer 16

Individual is deceased.

Question 17

Where does the eldest child go in a pedigree chart?

Answer 17

On the left

Question 18

Give some characteristics of autosomal recessive inheritance.

Answer 18

Can be observed to “come out of nowhere” on pedigree charts (skipping generations), affects males and females equally, does not affect heterozygotes.

Question 19

If two individuals with cystic fibrosis had children how many would be affected? What about if two heterozygous carriers had children?

Answer 19

All of them.

1 in four.

Question 20

Give some characteristics of autosomal dominant inheritance?

Answer 20

Heterozygous are affected, male and females equally affected, cannot skip generations, affected individual has 50% chance of passing on to offspring.

Question 21

Why are autosomal dominant disorders not often found in homozygous states?

Answer 21

The individual may not be viable for life.

Question 22

Give an example of an autosomal dominant condition.

Answer 22

Huntington’s Disease

Question 23

A male with Haemophilia A cannot pass the condition on to his son. Which type of inheritance is this?

Answer 23

X-linked recessive

Question 24

Why are X-linked recessive conditions more common in males?

Answer 24

They have only one X chromosome, so it is expressed even if it is recessive. Women must have two recessive alleles to be affected by the condition.

Question 25

Give some characteristics of an X-linked dominant condition.

Answer 25

Hemizygous males and heterozygous females affected, affected males cannot give trait to sons but will give to all daughters.

Question 26

In mitochondrial inheritance, could a male pass on a condition to his daughters?

Answer 26

No, he could not pass it on to anyone. Mitochondria are inherited solely through the female line.

Question 27

Why are genes sometimes referred to as “linked”?

Answer 27

They are on the same chromosome. These do not undergo independent assortment at meiosis.