Crowe questions

Question 1

Glucose isomerase is an enzyme used to convert glucose to fructose. Why is it known as an isomerase?

Answer 1

Fructose is an isomer of glucose

Question 2

Give an advantage of immobilizing an enzyme

Answer 2

• Doesn’t contaminate product;
• Can be re-used
• Is more stable

Question 3

What is the role of a vector?

Answer 3

Transfers genes from one organism to another

Question 4

What is the role of DNA ligase in production of recombiant DNA?

Answer 4

Forms phosphodiester bonds between nucleotides.

Question 5

What is the importance of reducing chromosome number when the cell divides by mitosis?

Answer 5

Allows later fertilization when cells fuse, restoring the original diploid number.

Question 6

What are the differences between mitosis and meiosis?

Answer 6

• In meiosis, homologous chromosomes associate in pairs; in mitosis chromosomes are independent and don’t pair
• Crossing-over occurs in meiosis, not in mitosis
• Two divisions resulting in 4 offspring cells in meiosis. In mitosis there is one, producing 2 daughter cells;
• In meiosis the product is genetically different. In mitosis it is genetically identical

Question 7

Other than form, suggest other sources of evidence used by scientists which suggest two animals are of different genera.

Answer 7

Fossil record
Evolutionary history
Biochemical differences

Question 8

Give an advantage of DNA having two strands.

Answer 8

Stability, replication, to protect bases.

Question 9

What does an RNA nucleotide consist of?

Answer 9

Base
Ribose
Phosphate

Question 10

Why is DNA replication semi-conservative?

Answer 10

Daughter DNA contains one new strand and one original strand.

Question 11

What is RNA polymerase’s role during transcription?

Answer 11

Join RNA nucleotides to form a strand a backbone, forms phosphodiester bonds, making pre-mRNA

Question 12

What is a marker gene?

Answer 12

Gene coding for easily identifiable product, e.g antibiotic resistance gene; Allows scientists to see if bacteria contain transferred gene.

Question 13

Why might resistance genes not be appropriate for marker genes?

Answer 13

Gene may be transferred to harmful bacterium; causing resistance to antibiotic, preventing it’s use.

Question 14

What is a primer?

Answer 14

Single strand of DNA; Bases complementary to part of DNA to be copied;
Marks section being copied and allows attachment of polymerase;

Question 15

What is a DNA marker?

Answer 15

Fragment of DNA of known size

Question 16

Why is gel electrophoresis used in DNA fingerprinting?

Answer 16

Separates DNA; By length/mass/charge/size;

Question 17

Why are radioactive probes used in DNA fingerprinting?

Answer 17

Binds to specific and complementary base sequences; Makes DNA visible

Question 18

Following PCR, scientists discovered the analysed DNA was very similar to another organisms DNA, describe how they found this.

Answer 18

Found DNA base sequence and compared them
OR
Using single-stranded DNA and compared amount of base pairing
OR
Carry out genetic fingerprinting; Compare banding pattern;

Question 19

Difference between independent segregation and crossing over.

Answer 19

Independent segregation – gives different combinations of maternal and paternal chromosomes;
Crossing over – gives new combinations of alleles