4.1 DNA, Genes And Chromosomes

Question 1

Compare prokaryotic and eukaryotic DNA

Answer 1

Prokaryotic:
- Short
- Circular
- Located in the cytoplasm
- Not associated with histones
- Condenses via supercoiling

Eukaryotic:
- Long
- Linear
- Associated with histones
- DNA located in nucleus
- In 23 homologous pairs

Question 2

What does DNA in chloroplasts and mitochondria suggest?

Answer 2

Bacterial cells were engulfed by a larger cell during evolution.
The bacteria and host cell formed a beneficial symbiotic relationship.
The bacterial cell became incorporated into the larger cell to become organelles (chloroplasts and mitochondria)

Question 3

What is a gene?

Answer 3

A section of DNA that codes for a protein

Question 4

What is a locus (loci)?

Answer 4

The specific location of a gene in DNA

Question 5

What is a codon?

Answer 5

Three bases in DNA/mRNA that code for an amino acid

Question 6

What is an exon?

Answer 6

Sequence of a gene which codes for a polypeptide

Question 7

What is an intron?

Answer 7

Sequence of a gene which does not code for a polypeptide

Question 8

What is the process of removing introns called?

Answer 8

Splicing

Question 9

What are the three important features of the genetic code?

Answer 9

• Degenerate
• Universal
• Non-overlapping

Question 10

What does it mean that the genetic code is degenerate?

Answer 10

Some amino acids are coded for by more than one codon

Question 11

How many triplet codons are there in the genetic code?

Answer 11

64

Question 12

How many amino acids exist?

Answer 12

20

Question 13

What does it mean that the genetic code is non-overlapping?

Answer 13

There is no overlapping of triplet codons. Each triplet codon is separate from the next.

Question 14

What does it mean that the genetic code is universal?

Answer 14

The same four bases (A, T, G, C) are used in the DNA in every organism.