Lecture 2 - Organisation of genetic information

Question 1

How is DNA packaged in prokaryotes?

Answer 1

DNA is circular, lacks a nuclear membrane, and is supercoiled to fit inside the nucleoid region.

Question 2

What are the key differences between chromosomes in prokaryotes and eukaryotes?

Answer 2

Prokaryotic chromosomes are circular and lack introns.

Eukaryotic chromosomes are linear, paired, and contain introns.

Question 3

What is DNA supercoiling, and why is it important?

Answer 3

Supercoiling is the overwinding or underwinding of DNA, important for compaction and facilitating processes like replication and transcription.

Question 4

How is DNA packaged in eukaryotic cells?

Answer 4

DNA is wrapped around histone proteins, forming nucleosomes, and further compacted into chromatin within the nucleus.

Question 5

What percentage of the human genome codes for proteins?

Answer 5

Only about 1.5% of the human genome codes for proteins.

Question 6

What are plasmids, and where are they found?

Answer 6

Plasmids are small, circular DNA molecules found in prokaryotes, often carrying genes for antibiotic resistance or survival.

Question 7

What is an operon, and where is it found?

Answer 7

An operon is a cluster of genes under the control of a single promoter, commonly found in prokaryotes.

Question 8

What is synteny in genome organisation?

Answer 8

Synteny refers to the conserved arrangement of genes on chromosomes across different species.

Question 9

What is the basic unit of chromatin?

Answer 9

The nucleosome, consisting of DNA wrapped around histone proteins.

Question 10

What are copy number variations (CNVs), and why are they significant?

Answer 10

CNVs are variations in the number of copies of a gene between individuals or species, contributing to genetic diversity.

Question 11

What is the difference in genome size and function between prokaryotes and eukaryotes?

Answer 11

Prokaryotic genomes are small and mostly encode proteins, while eukaryotic genomes are larger with a significant portion of non-coding DNA.

Question 12

How does the human genome compare to other species?

Answer 12

The human genome has about 21,000 functional genes, and approximately 45% of its DNA comes from transposable elements.

Question 13

What is the role of histones in DNA packaging?

Answer 13

Histones help organize DNA into nucleosomes, facilitating compaction and regulation.

Question 14

Why is the nucleosome critical for eukaryotic chromatin structure?

Answer 14

It organizes DNA into a compact form while allowing regulated access for replication and transcription.

Question 15

What are introns, and how do they differ between prokaryotes and eukaryotes?

Answer 15

Introns are non-coding regions found in eukaryotic genes but are absent in prokaryotic genes.

Question 16

How does the arrangement of genes in prokaryotes differ from eukaryotes?

Answer 16

Prokaryotes often use operons, while eukaryotic genes typically have their own promoters and regulatory regions.

Question 17

What structural features define eukaryotic chromosomes?

Answer 17

Linear, paired, and contain centromeres, telomeres, and introns.

Question 18

How do transposable elements impact the genome?

Answer 18

They contribute to genome evolution and variation, making up nearly 45% of the human genome.

Question 19

What is the nucleoid in prokaryotes?

Answer 19

The nucleoid is the region in a prokaryotic cell where the circular DNA is compacted and organized.

Question 20

What is the importance of supercoiling in prokaryotic DNA?

Answer 20

Supercoiling reduces the space required for DNA storage and aids in processes like replication, transcription, and recombination.

Question 21

What structural feature distinguishes eukaryotic chromosomes from prokaryotic chromosomes?

Answer 21

Eukaryotic chromosomes are linear, have multiple origins of replication, and are enclosed within a nuclear membrane.

Question 22

How are histone proteins modified to regulate gene expression?

Answer 22

Histones can undergo modifications such as acetylation, methylation, and phosphorylation to change chromatin structure and influence transcription.

Question 23

What is the significance of telomeres in eukaryotic chromosomes?

Answer 23

Telomeres protect the ends of chromosomes from degradation and prevent them from being recognized as DNA damage.

Question 24

Why is genome size not always indicative of organism complexity?

Answer 24

Large portions of many genomes consist of non-coding DNA, repetitive sequences, and transposable elements, which do not directly contribute to organism complexity.

Question 25

What is the role of regulatory elements in eukaryotic genomes?

Answer 25

Regulatory elements like promoters, enhancers, and silencers control the timing, location, and level of gene expression.

Question 26

What are transposable elements, and what is their impact on the genome?

Answer 26

Transposable elements are DNA sequences that can move within the genome, causing mutations, altering gene expression, and contributing to genetic diversity.

Question 27

What is the difference between heterochromatin and euchromatin?

Answer 27

Heterochromatin: Densely packed, transcriptionally inactive regions.
Euchromatin: Loosely packed, transcriptionally active regions.

Question 28

What are the different levels of DNA packaging in eukaryotes?

Answer 28

DNA is packaged into nucleosomes, then into a 30-nm fiber, higher-order loops, and finally into condensed chromosomes.

Question 29

How are genes in operons expressed in prokaryotes?

Answer 29

Genes in operons are transcribed together from a single promoter into one mRNA and translated into multiple proteins.

Question 30

What is chromatin remodeling, and why is it necessary?

Answer 30

Chromatin remodeling involves rearranging nucleosomes to expose or hide DNA regions, allowing transcription, replication, or repair.

Question 31

What are copy number variations (CNVs), and how are they identified?

Answer 31

CNVs are differences in the number of copies of particular DNA segments between individuals, detected using genomic analysis techniques.

Question 32

Why is the 16S rRNA gene commonly used in prokaryotic phylogenetic’s?

Answer 32

The 16S rRNA gene is highly conserved and provides insights into evolutionary relationships among prokaryotes.