In which year did Watson and Crick publish their DNA structure paper?
1953
Who published "A Structure for Deoxyribose Nucleic Acid" in 1953?
Watson and Crick
What is the title of Watson and Crick's 1953 Nature paper?
A Structure for Deoxyribose Nucleic Acid
What does Chargaff's rule say about the ratio of A to T in DNA?
A equals T
According to Chargaff's rules, what is the ratio of (A+G) to (T+C)?
1
According to Chargaff's rules, is (C+G)/(A+T) equal to 1?
No, it is not equal to 1
What three components make up a nucleotide?
A pentose sugar, a nitrogenous base, and a phosphate group.
Which sugar does DNA generally contain?
Deoxyribose.
Which base does RNA contain instead of thymine?
Uracil.
How many base pairs per turn does B-DNA have?
Approximately 10 base pairs per turn.
What is the diameter of B-DNA?
About 2.0 nm.
How many base pairs per turn does A-DNA have?
Approximately 11 base pairs per turn.
What is the diameter of A-DNA?
About 2.3 nm.
What is the distance between adjacent nucleotides on the same strand in B-DNA?
0.34 nm.
When was the Human Genome Project launched?
In late 1988.
Which organizations published the first human genome drafts in 2001?
Celera Genomics and the International Human Genome Sequencing Consortium.
What percentage of the human genome did the 2001 drafts cover?
Approximately 92%.
When did the T2T-CHM13 Consortium produce the first complete human genome sequence?
In 2022.
How many base pairs did the T2T-CHM13 complete human genome sequence contain?
3.055 billion base pairs.
How many base pairs of DNA were added by the T2T-CHM13 Consortium's sequence?
Approximately 200 million base pairs.
What is a nucleosome composed of in terms of DNA and histones?
146 base pairs of DNA wrapped around a histone octamer.
How many copies of each histone are in a nucleosome octamer?
Two copies each of H2A, H2B, H3, and H4.
What is the sequence of DNA compaction from nucleosomes to chromosomes?
Primary nucleosomes to secondary solenoid, tertiary looped domains, then quaternary metaphase chromosome.
How is euchromatin different from heterochromatin in packing and activity?
Euchromatin is loosely packed and transcriptionally active; heterochromatin is tightly packed and inactive.
What accessibility difference exists between euchromatin and heterochromatin?
Euchromatin is accessible; heterochromatin is associated with structural or regulatory regions.
What is a telomere in chromosome structure?
A specialized region at each chromosome end that stabilizes the chromosome.
What sequence repeat is found in telomeres?
Approximately 1000 tandem repeats of 5′-TTAGGG.
Where do kinetochores attach on a chromosome?
At the centromere region.
What role does the centromere play during cell division?
It allows chromosome alignment and equal segregation by attaching spindle microtubules.
What is the human genome?
The complete set of genetic material encoded in DNA of an individual or species.
What percentage of the human genome is coding DNA?
Approximately 1–5%.
How many genes does the human genome include?
19,969 genes.
What is a gene?
A DNA sequence encoding a functional RNA or protein product.
How can a gene produce multiple protein isoforms?
Through alternative splicing.
What happens to exons during RNA processing?
They remain in mature RNA.
What happens to introns during RNA processing?
They are removed.
What roles do promoters, enhancers, and silencers play in transcription?
Promoters regulate transcription upstream; enhancers and silencers regulate it from distant sites.
How do single-nucleotide variants differ from short tandem repeat variants?
Single-nucleotide variants change one nucleotide; short tandem repeat variants change repeat number at a locus.
What defines a microsatellite in DNA?
A short tandem repeat of 1–6 base pairs with highly variable repeat number.
What are LINEs and what do they encode?
Autonomous retrotransposons about 6–7 kb encoding reverse transcriptase.
How do SINEs differ from LINEs in the human genome?
SINEs are non-autonomous, shorter than 500 bp, and depend on LINE machinery.
What are the key features of mitochondrial DNA compared to nuclear DNA?
Mitochondrial DNA is circular, lacks histones and repair, mutates faster, and is maternally inherited.
How is nuclear DNA structurally and genetically different from mitochondrial DNA?
Nuclear DNA is linear, chromosomal, and biparentally inherited.
What percentage of total cellular RNA is messenger RNA?
Approximately 5%.
What is the main function of messenger RNA?
It serves as the template for protein synthesis during translation.
What role does transfer RNA play during translation?
It carries amino acids to ribosomes.
What percentage of total cellular RNA is transfer RNA?
Approximately 15%.
What is the function of ribosomal RNA?
It combines with proteins to form ribosomes.
What percentage of total cellular RNA is ribosomal RNA?
Approximately 80%.
How does DNA differ from RNA in strand structure and sugar content?
DNA is usually double-stranded and contains deoxyribose, while RNA is usually single-stranded and contains ribose.
What important DNA image did Rosalind Franklin produce in 1952?
Photograph 51
How are nucleotides linked during DNA polymerization?
Through the sugar, phosphate, and base components.
What handedness does Z-DNA have?
Left-handed helix.
How many base pairs per turn does Z-DNA have?
Approximately 12 base pairs per turn.
What is the diameter of Z-DNA?
About 1.8 nm.
What connects nucleosomes and how long is it?
Linker DNA of approximately 55 base pairs connects nucleosomes.
Which histone stabilizes the linker DNA between nucleosomes?
Histone H1 stabilizes the linker DNA.
What happens after 40–60 replication cycles regarding telomeres?
Telomere shortening can lead to apoptosis.
How many chromosome pairs does a human nucleated cell contain?
23 pairs of chromosomes.
How does chromosome 1 size compare to chromosome 21 in humans?
Chromosome 1 is nearly five times larger than chromosome 21.
What percentage of the human genome is made of highly repeated DNA sequences?
Approximately 3%.
Which types of DNA are included in highly repeated sequences?
Minisatellite, microsatellite, and satellite DNA.
Which RNA type regulates post-transcriptional expression and is about 22 nucleotides long?
miRNAs.
Answer 26 questions on Human Genome Molecular Biology.
1. Which relationship among DNA bases is expressed by Chargaff’s rules?
2. Which publication did Watson and Crick publish in 1953?
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