Molecular Biology BSM 3201: DNA Packaging and Chromatin Structure Quiz

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Questions and Answers

What is the significance of the number of chromosomes in a cell?

The number of chromosomes is unrelated to genome size.

What is the primary function of a chromosome in a cell?

To store DNA in the most compact form in the cell, without loss of structural function.

What is a karyotype, and what does it represent?

A karyotype is the full arrangement of chromosomes in a cell.

How does the structure of a chromosome protect genomic DNA?

The chromosome provides protection of genomic DNA. Signup and view all the answers

What is the advantage of compact DNA packaging in a chromosome?

Compact DNA packaging allows for transmission efficiency. Signup and view all the answers

What would be the approximate length of all the DNA in a human cell if laid end to end?

Approximately 2 meters. Signup and view all the answers

How many genes are there in the mitochondrial genome?

37 genes Signup and view all the answers

What types of genes are present in the mitochondrial genome?

Protein-coding genes, tRNA genes, rRNA genes Signup and view all the answers

What is the approximate size of the mitochondrial DNA in humans and other vertebrates?

~16kb Signup and view all the answers

How do nuclear gene products contribute to mitochondrial function?

By importing proteins like ribosomal proteins for assembly Signup and view all the answers

Why does the dual composition of proteins needed for aerobic metabolism suggest coordination between nuclear and mitochondrial genetic systems?

To ensure equivalent amounts of their products are made Signup and view all the answers

What is necessary in terms of mitochondria and cells for a deficiency in mitochondrial function to manifest?

A large number of mitochondria per cell must be affected Signup and view all the answers

What is the inheritance pattern of Myoclonic Epilepsy and Red Fiber Disease (MERRF)?

Maternally inherited Signup and view all the answers

What are the symptoms of Kearns-Sayre Syndrome (KSS)?

Symptoms in eyes, muscles, heart, brain Signup and view all the answers

What is the cause of Leber’s Hereditary Optic Neuropathy (LHON)?

Point mutation in small subunit of NADH dehydrogenase Signup and view all the answers

Where does photosynthesis occur in green plants?

Chloroplast organelles Signup and view all the answers

What is the approximate size range of chloroplast DNA genomes?

120 to 200 kb Signup and view all the answers

What is the common feature between chloroplast DNA and mitochondrial DNA?

Both are circular, double-stranded Signup and view all the answers

What is the significance of the iojap gene in the context of plant inheritance?

The iojap gene controls the small protein required for the assembly of the chloroplast ribosome, which determines the progeny colour. Signup and view all the answers

What is the key difference between the transmission pattern of organelle genomes and nuclear genes?

The transmission pattern of organelle genomes is exclusively maternal, whereas nuclear genes follow Mendelian inheritance. Signup and view all the answers

What is the molecular basis of leaf variegation in plants?

Mutations in chloroplast DNA, specifically in genes encoding proteins active in photosynthesis, cause leaf variegation. Signup and view all the answers

What is the role of the maternal parent in determining the phenotype of offspring in extrachromosomal inheritance?

The phenotype of the maternal parent is solely responsible for the phenotype of the offspring. Signup and view all the answers

What is the significance of Corren's and Baur's experiments in the context of inheritance?

Their experiments demonstrated maternal inheritance, challenging Mendel's assumption of equal contribution from maternal and paternal gametes. Signup and view all the answers

What is the difference between recessive and dominant traits in the context of plant colour?

White is recessive, and green is dominant. Signup and view all the answers

What is the primary function of chromosome in DNA molecule?

To confer overall organization and stability to the DNA molecule Signup and view all the answers

What is the purpose of origin of replication in eukaryotic chromosomes?

To direct the replication of DNA Signup and view all the answers

What is the function of centromere in chromosomes?

To ensure correct segregation of chromosomes during cell division Signup and view all the answers

What are telomeres, and what is their location in a chromosome?

Telomeres are the repeated nucleotide sequences at the ends of chromosomes Signup and view all the answers

What is the significance of chromosomal organization in regulating gene expression?

It regulates gene expression and creates diversity among individuals through gene recombination between parental chromosomes Signup and view all the answers

How does the origin of replication differ between eukaryotic and prokaryotic chromosomes?

Eukaryotic chromosomes have multiple sites of origin of replication, whereas prokaryotic chromosomes have only one site Signup and view all the answers

Study Notes

DNA Packaging and Chromatin Structure

Chromosomes are thread-like structures found in the nucleus, composed of genomic DNA packaged with proteins
Chromosome numbers are unrelated to genome size; e.g., humans have 46, butterflies have over 200, and kangaroos have 12
Chromosomes are formed by a pair of chromatids, with a karyotype representing the full arrangement of chromosomes

Functions of the Chromosome

Stores DNA in a compact form without loss of structural function, with the double helix of 46 human chromosomes measuring approximately 2m if laid end-to-end
Protects genomic DNA
Enables transmission efficiency
Confers overall organization to each DNA molecule
Regulates gene expression and recombination, creating diversity among individuals

Centromeres, Telomeres, and Origin of Replication

Origin of replication directs DNA replication, with multiple sites in eukaryotic chromosomes, 30-40kb apart, and one site in prokaryotes
Centromeres ensure correct segregation of chromosomes, directing the formation of kinetochore and microtubules to pull sister chromosomes apart
Telomeres are repeated nucleotide sequences at the ends of chromosomes

Extrachromosomal Inheritance

Mitochondrial DNA (mtDNA) is circular, with a copy number that is high per cell, and multiple genomes per mitochondrion
mtDNA has approximately 30,000 genes on 23 human chromosomes, with 13 protein-coding genes, 22 tRNA genes, and 2 rRNA genes
Size of mtDNA varies widely, with 16,569 base pairs in humans, 80kb in yeast, and 100kb to 2Mb in plants
Interplay between mitochondrial and nuclear gene products is necessary for function, with many mtDNA gene products functioning solely within the mitochondrion
Mitochondrial DNA and human disease are related, with point mutations causing disorders such as myoclonic epilepsy, deafness, and dementia

Chloroplast DNA

Chloroplast DNA is circular, double-stranded, and lacks structural proteins, with a %GC content that differs
Chloroplast genomes are much larger than mtDNA, ranging from 120 to 200kb in different plant species
Chloroplast DNA occurs in multiple copies, carries non-coding regions, and originated as symbiotic photosynthetic bacteria
Chloroplast DNA molecules range from 120 to 200kb, with an inverted repeat region, and contain genes for photosynthesis, electron transport, and chloroplast protein synthesis

Conclusions from Corren's & Baur's Experiments

Offspring inherit their form of the variegation trait from the mother only, challenging Mendel's assumption of equal maternal and paternal gamete contribution
Maternal inheritance is a type of transmission that differs from nuclear gene transmission
Mutations resulting in leaf variegation occur in chloroplast DNA, in genes that encode proteins active in photosynthesis

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Description

Test your knowledge on DNA packaging, chromatin structure, and extrachromosomal inheritance in eukaryotic and prokaryotic cells. Learn about the functions of chromosomes, centromeres, telomeres, mechanisms of DNA organization, and features of plasmids.