Biology AS Chapter 3.4.1: DNA Comparison

Questions and Answers

Compare and contrast the DNA in eukaryotic cells with the DNA in prokaryotic cells.

DNA in eukaryotic cells are linear, DNA in prokaryotic cells are circular. 2. DNA is associated with histone proteins in eukaryotic cells, DNA not associated with histone proteins in prokaryotic cells. 3. The DNA nucleotides in both are the same, and have phosphodiester bonds. 4. Eukaryotic DNA contains introns, prokaryotic DNA does not.

Explain how differences in the primary structure of haemoglobin molecules can provide evidence of phylogenetic relationships between species.

Mutations change base/nucleotide sequence; 2. Change in amino acid sequence; 3. Mutations build up over time; 4. More mutations/more differences between distantly related species.

What is meant by the genetic code being described as degenerate? Use an example to illustrate your answer.

More than one codon codes for a single amino acid.

Why did a change from Glu to Lys at amino acid 300 have no effect on the rate of reaction catalyzed by the enzyme, while the same change at amino acid 279 significantly reduced the rate of reaction?

Change at amino acid 300 does not change the shape of the active site. Amino acid 279 may have been involved in a bond that changes the shape of the active site or may be required for binding the substrate. Signup and view all the answers

What are the two types of molecules from which a ribosome is made?

One of RNA and one of protein. Signup and view all the answers

What are two differences between the structure of mRNA and the structure of tRNA?

<ol> <li>mRNA is a straight molecule but tRNA is a folded/clover-leaf shaped molecule. 2. mRNA contains no paired bases, but tRNA has some paired bases/hydrogen bonds.</li> </ol> Signup and view all the answers

How do organic bases help to stabilize the structure of DNA?

<ol> <li>Hydrogen bonds between the base pairs hold two strands together. 2. Many hydrogen bonds provide strength.</li> </ol> Signup and view all the answers

What is the role of the mRNA base triplets UGA, UAG, and UAA?

<ol> <li>Stop translation; 2. Result in detachment of polypeptide chain from ribosome.</li> </ol> Signup and view all the answers

Why did the scientists use units of μg g-1 for the concentration of ammonia in soil?

μg = very small mass of ammonia; g-1 = allows for comparison. Signup and view all the answers

Study Notes

Comparing Eukaryotic and Prokaryotic DNA

Eukaryotic DNA is linear, while prokaryotic DNA is circular.
In eukaryotic cells, DNA is associated with histone proteins; prokaryotic DNA lacks these proteins.
Both types of DNA have the same nucleotides and utilize phosphodiester bonds.
Eukaryotic DNA contains introns, whereas prokaryotic DNA does not.

Haemoglobin Variations and Phylogenetic Relationships

Mutations alter nucleotide sequences, indicating evolutionary changes.
Changes in amino acid sequences arise from these mutations.
Mutations accumulate over time, leading to more pronounced differences among distantly related species.

Degeneracy of the Genetic Code

The genetic code is termed "degenerate" because multiple codons can specify a single amino acid.

Impact of Amino Acid Changes on Enzyme Activity

Substitution at amino acid position 300 (Glu to Lys) does not alter the active site's shape.
Alteration at position 279 affects enzyme activity likely due to involvement in bonds (ionic, disulfide, or hydrogen) that maintain the active site's structure or substrate binding.

Ribosome Composition

Ribosomes are comprised of ribonucleic acid (RNA) and proteins.

Differences Between mRNA and tRNA Structures

mRNA is a linear molecule, while tRNA has a clover-leaf or folded shape.
mRNA has no paired bases or hydrogen bonds, contrasting with tRNA which features paired bases and hydrogen bonds.

Stabilization of DNA Structure by Organic Bases

Hydrogen bonds between base pairs contribute to the stability by holding the two DNA strands together.
The cumulative effect of many hydrogen bonds strengthens the overall structure.

Roles of Stop Codons (UGA, UAG, UAA)

These codons signal the termination of translation.
They result in the release of the polypeptide chain from the ribosome.

Use of μg g-1 Units for Ammonia Concentration

µg indicates a very small mass of ammonia, suitable for measuring low concentrations.
g-1 units facilitate comparisons between different soil samples or conditions.

Description

This quiz focuses on the differences and similarities between DNA in eukaryotic and prokaryotic cells, highlighting structural and functional distinctions. It is designed to enhance understanding of genetic variation and the role of DNA in cellular biology.