Biology 2581B Lecture Notes - Lecture 6: Concatemer, Borrelia, Dna Replication

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20 Feb 2017

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Genomes are made of one or more chromosomes. Each chromosome is made up of double stranded dna. Monoploid one copy of each chromsome. Diploid two copies of each chromosome. Polyploid multiple copies of each chromosome. The set of genetic instructions is found on 3 different chromosomes. Genome size in each one these cases is the same. A single set of genetic instructions is grey + yellow + green. Circular or linear: made by up double stranded dna, viruses are exceptions & can have single stranded genomes. Intact or fragmented: fragmented set of instructions are distributed across multiple chromosomes. Intact set of instructions are distributed on that single circle: human nuclear genome = linear fragmented, human mitochondrial genome = circular intact. Mixture of circular and linear: see borrelia example below. Concentated (concatemers: single chromosome strung with multiple copies of itself in a repeating pattern. Sequence is in a head to tail orientation: malaria parasite plamosidum mitochondrial genome.

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The bacterium E. coli, which is a major model system for the study of genes and DNA, has a singular circular chromosome of about 4x106 bp. In contrast, human diploid cells have __1__ chromosomes, of __2__ different types (donât forget that the X Â¹ Y!). The total amount of DNA found in a haploid cell such as a sperm or egg is called the organismâs âC-valueâ; the human C-value is __3__.

Also in contrast to the E. coli circular chromosome is the fact that eukaryotic chromosomes are not circular, but instead are __4__. Eukaryotic chromosomes are complexed heavily with protein to form a DNA-protein complex generically called __5__. The proteins found can be considered to fall into two general classes: __6__ and __7__. The first class is made up of 5 major proteins called __8__, __9__, __10__, __11__, and __12__. On a weight to weight basis, these proteins make up about __13__% of the total mass of a chromosome. Since these proteins must associate relatively non-specifically with DNA, they are rich in the basic amino acids __13__ and __14__, which gives the proteins a net __15__ charge.

One goal of packaging the DNA into chromatin is to compact the genome so it will fit into a nucleus. The basic unit of chromatin structure is the __16__, which has __17__ base pairs of DNA wrapped around a âcore particleâ composed of __18__ copies each of the core histones. Each nucleosome is separated by a stretch of âlinkerâ DNA so that the repeating unit is approximately 200 bp. Lets do a little arithmetic: If we consider that the nucleosome is approximately __19__ nm in diameter, that there is about 200 bp in this structure, and that 200 bp of DNA would normally occupy __20__ nm if stretched out straight (recall that each base is spaced about 0.34 nm from the next), we can see that the nucleosome alone allows for a __21__-fold compaction ratio.

The nucleosome structure is further compacted by histone __22__, which is not a part of the core particle. Instead, this histone __23__ (does what?) to cause the nucleosomal 10 nm fiber to condense into a higher-order structure referred to as the __24__ nm fiber. In the nucleus, chromosomes do not just float around freely: they are tethered to a proteinaceous structure called the __25__ at specific DNA regions called âSARsâ, which stands for __26__. SARs are rich in topoisomerases, to allow the winding and unwinding of the DNA that accompanies replication and transcription to occur, despite this constraint.

The 30 nm fiber discussed above is the form in which transcriptionally active DNA is believed to exist in the nucleus; however, further condensation leads to a highly condensed inactive form called __27__; in this terminology, the active form is referred to as __28__. The inactive condensed form can be divided into two types: one type is essentially invariant between cell types, and since it is âon all t timeâ, it is referred to as __29__. The other type comes and goes, depending on the expression of the genes present in that region of the chromosome; it is referred to as __30__.

Eukaryotic chromosomes carry the genes, of course, but also have other functional regions. One such region is the place where the spindle apparatus attaches during mitosis and meiosis; this region of the chromosome is called the __31__. Another important part of the linear eukaryotic chromosome is the ends; these are called __32__. In humans, the end of each chromosome is composed of many repeats of the short sequence __33__. One more type of functional region on each chromosome is the place where DNA replication starts; in humans, each chromosome has several of these __34__. Thus, eukaryotic chromosomes carry several different types of functional sequences, which together allow for their __35__ during S phase, __36__ during mitosis and meiosis, and the __37__ of their genes

1.If scientists could increase telomerase production in specific cells, the primary reason for this would most likely be the stopping of

A. meiosis.

B. aerobic respiration.

C. cancer cell formation.

D. All of the answer choices are correct.

E. aging of cells.

2. When DNA replicates

A. the original DNA unwinds, and multiple copies of a region are transcribed before the DNA closes back up.

B. transcription factors determine where to begin DNA replication.

C. None of the answer choices are correct.

D.one strand of the original DNA ends up in each of the new DNA molecules.

E. the original DNA is not affected and a new double-stranded DNA is made from two new strands of DNA.

3. In the biology lab, you observe three different animal cells under a microscope. In one cell, the nucleus is uniformly filled, with no distinct chromosome structure visible. In another, you see the nucleus with two nucleolus areas of more compact chromatin. A third cell is in mitosis, and distinct chromosome strands are visible. The value in packaging DNA in tighter forms of chromatin is for

A. mobility and protection of the DNA molecule during mitosis.

B. prevention of ligase enzyme action during replication.

C. Both answers regarding DNA mobility, protection and regulation in mitosis and transcription are correct.

D. regulation and protection of the DNA during transcription.

E.insuring that sister chromatids will be attached prior to replication.

Question 1: For each of the following terms, select the best definition:

gene, phenotype, chromosome, genotype, allele, genome

2.DNA that provides the instructions for synthesizing various types of small RNA molecules1.The complete set of genetic material in a cellan observable trait (or traits) of an organism

3.DNA that provides instructions for building a proteina variant of a gene

4.DNA of no known function

5.The genetic composition that underlies a trait (or traits)

6.A single molecule of DNA & its associated "helper" molecules

7.The portion of DNA that controls when and where proteins are synthesized

Question 2: Fill in the blank with these terms: dependent variable, independent variable, y-axis, x-axis

Understanding graphs is an important skill in science, since being able to visually depict data is often useful for identifying patterns, and can sometimes be the only tool for easily evaluating whether or not the data supports your hypothesis. When viewing a graph, the______ is plotted on the______, and the______we are measuring is plotted on the_____. For example, in one of the photosynthesis experiments last week, temperature was the______, while the size of the bubble at the end of the experiment was the_____

Question 3: For each of the following terms, select the best definition:

diploid cell, haploid cell, fertilization, zygote, gamete, somatic cell

1. The merging of two gametes

2. Any cell in an organism, except those used for reproduction

3. A cell with only one copy of each gene

4. The process of cell division

5. The cells used for sexual reproduction (generally eggs & sperm)

6. The initial cell of an organism

7. A cell that is capable of differentiating into multiple types of specialized cells

8. A cell with two copies of each gene

Biology 2581B Lecture Notes - Lecture 6: Concatemer, Borrelia, Dna Replication

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