Chapter 11
How many complete rotations would most likely correspond to a dsDNA molecule that is 150 bp in length? 30 20 15 10 5
15
Which of the following is not true of bacterial DNA? Many bacteria contain additional DNA in the form of small circular molecules called plasmids. All of the options are correct Most bacterial genomes consist of a single circular DNA molecule. Bacterial DNA is confined to a region in the cell called the nucleosome. Bacterial DNA is attached to any proteins that help to compact it.
Bacterial DNA is confined to a region in the cell called the nucleosome.
11 nm fiber
Coiled DNA that has nucleosomes with H1 attached
Transposable Element
DNA sequence that is capable of moving from one site to another within the genome via a mechanism that is different than recombination of homologs.
Barbara McClintock
Discovered transposable elements in corn
Organelles that possess DNA, typically possess more than one type of genomic DNA. This phenomenon is called __________. Heteroplasmy Pseudoplasmy Paraplasmy Homoplasmy Hemiplasmy
Heteroplasmy
Nucleosome
Histone octamers (2 H2A + 2 H2B + 2 H3 + 2 H4)
"Copy and Paste" Transposons
Moderately repetitive, as these will leave the original copy and makes a second copy that then inserts itself into another region of the genome.
Homoplasmy
Presence of only one version of DNA within the cytoplasm of a single cell
Heteroplasmy
Presence of two or more distinct variants of DNA within the cytoplasm of a single cell.
SINEs
Short interspersed elements; short DNA sequence repeated many times and interspersed throughout the genome
Linker DNA
Stretch of DNA separating two nucleosomes
Organelle Uniparental
The fact that your mitochondrial DNA was inherited just from your mother and not your father
LINEs
long interspersed nuclear elements. long DNA sequence repeated many times and interspersed throughout the genome
Explain the process of replicative segregation
· As the cell divides in mitosis, we can have multiple genotypes for the cell within the mitochondria, and as these replicates and go into their separate cells, we are left with homoplasmic and heteroplasmic cells.
Explain how the telomeres are protected from degradation
· Since telomeres are composed of repeating sequences of DNA at the end of the chromosome, they can produce a loop of this sequence at the tips of the chromosomes that protects them from degradation.
Discuss the chromosomal aberrations that can arise due to the presence of transposons
· Since transposons exist on many different locations of the chromosomes and are exact copies of each other, this can cause problems with recombination. o We can have mistakes where recombination does not occur between homologous chromosomes, but rather on the same chromosome § If they have the same orientation, they will line themselves up in a knot, leading to an incorrect crossover event and deletion, which leaves us with a product chromosome that is significantly shorter than the original. § We can have an instance where the transposons are inverted and pointing towards each other, and when they line up, they do so in a different orientation, which leads to an inversion. § If transposons cause the two homologous chromosomes to line up incorrectly, this leads to unbalanced translocations, giving us a chromosome with not enough genetic material and one with too much.
Explain why the mitochondrial genome is so much smaller than the chloroplast genome
· The mitochondrial genome is so much smaller than that of the chloroplast due to the complexity of photosynthesis, compared to the work of mitochondria. o More complex genes= larger genome
List and discuss the various types of DNA sequence
· Unique o Once or a few times · Repetitive o Multiple copies per genome o Transposons (jumping genes) · Highly repetitive o Usually <10 bp o Hundreds of thousands to millions of repeats o May contribute to telomere and centromere function · Moderately Repetitive: Retrotransposons o Short interspersed elements (SINEs) § 150-300 bp with thousands of repeats § 20% of genome § Mostly inactive o Long interspersed elements (LINEs) § A few thousand bp and thousands of repeats § 13% of genome · DNA sequences differ based on how repetitive they are. Above we see the different types of DNA sequences (and how often they repeat), and some of the effects those have on the human genome.
Explain the Ac/Ds system of transposition that was determines by Barbara McClinton in corn
· Variegated corn kernels are the result of the excision of Ds elements from genes controlling the color production in development. This means that a cell in which Ds is transposed out of the C allele will produce pigment, creating colored spots on a colorless kernel (similar to a mosaic).