Ch 25 Basic genetics

Question 1

Why can a person receive only blood of a certain blood groups during blood transfusion?

Answer 1

If the recipient’s blood contains antibodies that will act against the antigens on the red blood cells of the donor’s blood, the donor’s blood is incompatible with the recipient’s blood, causing clumping of blood cells or haemolysis.

Question 2

Deducing dominant character

Answer 2

DC is the dominant character. Offspring has RC. He must have at least one allele for RC that is inherited from his parents, either father or mother. Both father and mother have DC, they must have at least one allele for DC. At least one of father and mother is heterozygous, with the dominant allele being expressed. As both of the father and mother have DC, the allele for DC must be dominant.

Question 3

Why study environmental factors using identical twins?

Answer 3

Identical twins have the same genetic make-up. All the differences in their phenotypes should be due to environmental factors.

Question 4

Process of DNA replication

Answer 4

1. The hydrogen bonds between two DNA strands break. The two strands separate.
2. Each DNA strand acts as a template for the synthesis of a new DNA strand. The bases in free nucleotides form complementary base pairing with the bases in the DNA strands. DNA polymerase catalyses the joining of the adjacent nucleotides to form a new DNA strand.
3. Two identical DNA molecules are formed. Each contains an original strand and a new strand.

Question 5

How did Mendel come up with the hypothesis of Mendel’s Law of Inheritance when chromosomes had not yet been discovered

Answer 5

• Collected large amount of experimental evidence
• Based on his observation on the number of offspring with different phenotypes
• Worked out a possible explanation for the observation by logical deduction