GenBio- DNA Packaging and Organization

What is the total number of chromosomes in a diploid human cell?

46 chromosomes (23 pairs).

How many pairs of autosomes are present in human chromosomes?

22 pairs of autosomes.

What are the two arms of a chromatid called?

The 'p' arm and the 'q' arm.

Define the term nucleosome.

Microscopic structures of ~200 base pairs of DNA wrapped around eight histone proteins.

What forms a chromatin fiber?

A 30 nm diameter fiber formed by further condensation of nucleosomes.

What are loop domains in the context of chromatin?

Increasingly-packaged forms of chromatin fibers that are approximately 300 nm in length.

What role do histones play in DNA packaging?

Histones are positively charged and interact with negatively charged DNA.

What is the difference between heterochromatin and euchromatin?

Heterochromatin is highly compacted and not usually active in transcription, while euchromatin is loosely packed and accessible for transcription.

How does acetylation affect histone interaction with DNA?

Acetylation weakens the interaction between histones and DNA.

What happens when an acetyl group is removed from histones?

It strengthens the interaction with DNA favoring heterochromatin.

What percentage of the human genome is non-coding DNA?

98.8% of the human genome is non-coding DNA.

What are VNTRs and why are they significant?

Variable Number Tandem Repeats are short sequences of DNA that vary between individuals, useful for DNA fingerprinting.

What do SNPs stand for in genetics?

Single Nucleotide Polymorphisms.

What is the role of transposable elements in the genome?

They are mobile genetic elements that can change position in the genome.

What are the two classes of transposable elements?

Class I (replicates via a copy and paste mechanism) and Class II (utilizes a cut and paste mechanism).

What is the function of centromeres in chromosomes?

They unite sister chromatids and are essential for the association with spindle fibers during mitosis.

What are telomeres and what is their significance?

Telomeres are repetitive DNA sequences that cap the ends of chromosomes, protecting them from degradation during replication.

What is the sequence of repeat found in telomeres?

The repeat sequence is TTAGGG.

Which types of cells use telomerase to extend telomeres?

Germ cells, stem cells, and cancer cells.

How does the structure of a chromosome help package large amounts of DNA?

Through significant condensation and organization via nucleosomes, chromatin fibers, and further loop domains.

Why are chromosomes considered to be 23 pairs?

Because humans inherit one set of 23 chromosomes from each parent, totaling 46 chromosomes.

What charge does DNA carry and why is it significant?

DNA has a negative charge due to phosphate groups, which enables its interaction with positively charged histones.

What is the main function of nucleosomes in relation to DNA?

They help package DNA into a compact structure, allowing it to fit into the cell nucleus.

What happens during the charging of DNA?

Enzymes add or remove groups from histones, affecting their interaction with DNA.

What is the characteristic structure of chromatin?

Chromatin can exist in two forms: heterochromatin (compact) and euchromatin (loose).

What percentage of the human genome consists of repetitive DNA sequences?

Approximately 33% of the genome is known to be repetitive DNA.

What could happen if centromeres form improperly after toxin exposure?

Problems with chromosome alignment and segregation during cell division could occur.

How can the discovery of non-coding DNA impact genetic research?

It may lead to new understanding of gene regulation and the complexity of genetic expression.

What implications do VNTRs have for forensic science?

They are used for individual DNA fingerprinting in criminal investigations.

What does the term 'charging of DNA' refer to?

The addition or removal of chemical groups from histones affecting DNA interaction.

What are the key components of a replicated chromosome?

Two sister chromatids connected at the centromere.

How do microtubule spindle fibers relate to centromeres during mitosis?

Centromeres are essential for the attachment of spindle fibers which pull the chromatids apart.

What is the role of repetitive DNA sequences in the genome?

They may serve various functions including structural roles and gene regulation.

Define the term 'transposon'.

A mobile genetic element that can change its position within the genome.

What is the significance of acetylation of histone proteins?

It regulates gene expression by altering chromatin structure to favor transcription.

What do the arms of a chromosome represent?

The two segments of a chromosome extending from the centromere, known as the 'p' and 'q' arms.

How are repeat sequences in telomeres functionally significant?

They protect chromosomes from degradation and prevent them from sticking together.

How do histones regulate DNA packaging?

Histones becomes charged and interact with DNA to compact it into nucleosomes.

What could be a consequence if telomeres shorten excessively?

Cellular aging and potential loss of genetic information during cell division.

What are some key uses of SNPs in genetics?

They can serve as biological markers for identifying genetic differences.

What structures are responsible for the integrity of chromosomes during cell division?

Telomeres provide structural integrity and stability at chromosome ends.

In general, what is the composition of a human chromosome?

A chromosome is composed of DNA and proteins, primarily histones.

What is the functional role of heterochromatin during cell division?

Heterochromatin helps maintain chromosome structure in a compact form during division.

What is the main function of the centromere in cell division?

To ensure proper segregation of sister chromatids to daughter cells.

How does the process of DNA packaging affect gene expression?

Tightly packed DNA (heterochromatin) is generally not expressed, while loosely packed DNA (euchromatin) can be transcribed.

What problem is likely to occur if telomeres become critically short?

Possible triggering of cell senescence or apoptosis.

What does the term 'mobile element' refer to in genetics?

Genetic elements that can move within or between genomes, such as transposons.

How do variations in VNTRs contribute to individual uniqueness?

Variations in the number of repeat units can produce different patterns, which are specific to individuals.

What structural feature connects sister chromatids?

The centromere.

What types of chromosomes are included in the 23 pairs?

Autosomes and sex chromosomes.

Define euchromatin in terms of its structure and function.

Euchromatin is loosely coiled chromatin that is accessible for transcription and gene expression.

Why are centromeres important during the metaphase of mitosis?

They ensure proper alignment and separation of chromosomes.

What cellular structures interact with centromeres during cell division?

Kinetochore proteins and microtubules.

How can mutations in the centromere affect cellular processes?

They may lead to errors in mitosis, causing chromosomal abnormalities.

What impact does the presence of transposable elements have on genetic diversity?

They can contribute to mutations and variations within a population's genome.

What type of charge do nucleosomes possess and why does it matter?

Nucleosomes have a neutral charge due to their packaging of DNA, allowing for structural stability.

What is the result of weakened interactions between DNA and histone proteins?

It favors the formation of euchromatin, allowing for transcription.

Describe the general characteristics of Class I transposons.

They replicate via a copy and paste mechanism.

What role do acetyl groups play in modifying histones?

Acetyl groups help alter the charge of histones, influencing their interaction with DNA.

What is the significance of the TTAGGG sequence in telomeres?

It is the repeated sequence that protects chromosome ends from degradation.

How do transposons contribute to genome evolution?

They can create genetic variation, which can drive evolution through natural selection.

What happens to chromosomes during interphase compared to mitosis?

During interphase, chromosomes are less compact (euchromatin), while during mitosis they are tightly packed (heterochromatin).

What can be inferred about the majority of the human genome being non-coding DNA?

It suggests complex regulatory functions that are yet to be fully understood.

Describe a factor that could lead to increased mutation rates in repetitive DNA.

Repetitive DNA sequences may be more prone to replication errors.

What is the impact of histone modifications on gene regulation?

They can either activate or repress transcription based on the type of modification.

How might the presence of transposable elements in a genome be beneficial?

They can lead to adaptability by providing new genetic traits.

What region of a chromosome is formed from repetitive DNA sequences and important for cell division?

The centromere.

How can telomeres be artificially extended and why is it important?

Telomerase can extend telomeres, helping prevent cell aging and potential cancer cell proliferation.

Describe the structure of a typical chromatid in a chromosome.

A chromatid consists of a single, continuous molecule of DNA packaged with histone proteins.

What is the potential consequence of a damaged telomere on cell function?

Cells may undergo apoptosis due to inability to replicate properly.

What is Kreinberg or a similar process in relation to genome structure?

(This term seems fictitious; consider revisiting this in your notes to clarify if needed.)