What is a megabase (Mb) correct answers Mb = 1 million bases and is a unit used for Genome Size
Is there generally a difference in the amounts of DNA when comparing the genome sizes of viruses --> prokaryotes --> eukaryotes.How does this comparison relate to the complexity of these organis...
Evo exam 3 (with Accurate Answers)
What is a megabase (Mb) correct answers Mb = 1 million bases and is a unit used for Genome
Size
Is there generally a difference in the amounts of DNA when comparing the genome sizes of
viruses --> prokaryotes --> eukaryotes.How does this comparison relate to the complexity of
these organisms Be careful correct answers The genome sizes of each vary, but that does not
necessarily mean the amounts of DNA affect the sizes of the genome of each genome.
Eukaryotes can differ dramatically in complexity (#s of cells, behavior, etc.). Are there
predictable differences in the sizes of genomes when comparing, say, a protist, a plant, and an
animal correct answers Yes, between the 3 taxonomic groups genome sizes have a variety of
ranges. This process can be named the C-VALUE PARADOX.
What is the C-value paradox. What is C-value in the 1st place correct answers C-value Paradox:
states that "organism complexity does not predict the size of a genome.It also measures the
genome size by weight, and how much DNA that genome has.
Besides whole genome sizes, we can also compare the relative numbers of working genes. Are
there predictable differences in the numbers of genes when comparing, say, a protist, a plant, and
an animal correct answers Genomes sizes can vary without any real changes in the number of
genes once they are within Eukaryotes.
Now let's talk about non-coding DNA. (= 'nc DNA') What is that correct answers Extra amounts
of DNA that many Eukaryotes have. Important for the regulation of genes. Also they are binding
sites for transcription factors
Give me examples of nc DNA that are still important for the organism (these ARE subjected to
natural selection, b.t.w, so not all mutations in 'non-coding' DNA are neutral). correct answers
Heterochromatic Non-Coding DNA (8%),Another 11.6% of some Non-Coding DNA is essential.
A eukaryotic genome contains a diversity of sequence structures. Among these are the exons and
introns for genes that function as RNA molecules. What are introns,What are exons correct
answers Exons: The sequence of DNA present in mature messenger RNASome encodes the
amino acids of protein. Only 1.5% of DNA is exons. Introns: Non-coding sections of a RNA
transcript or the DNA encoding it, and they are cut out before the RNA molecules are translated
into proteins.
What is a general description of selfish DNA.. Give examples of DNA structures that seem
'selfish'. Selfish DNA can also be called 'Junk DNA'. Not everyone thinks there is such DNA, but
we can consider evidence. In any case, lets go over the various kinds of DNA that seems selfish /
junk correct answers DNA that uses your own body to replicate and propagate itself through
time.
,Two examples of repeated DNA sequences are correct answers Satellite DNA: randomly
repeated sequences. VTNR (Variable Number Tandem Repeats): Long Repeated DNA
sequences
What repeated DNA sequence is used in DNA fingerprinting correct answers VNTR
Describe how different active transposable elements copy themselves, and insert into genomes.
What enzyme do some use that is also found in some viruses..Are most copies of transposable
elements (a.k.a. 'jumping genes') still able to jump correct answers Most are mutated and are no
longer jumping. Mostly Retrotransposon: Made By Reverse Transcriptase (RvT)Reverse
transcriptase: converts RNA into DNA and this process allows for jumping genes to be replaced
into the Eukaryotes genome.
LINES and SINES: Which are longer. Which contains the gene for reverse transcriptase. Which
lacks reverse transcriptase but was copied by it correct answers A> LINES (Long Interspersed
Nuclear Elements)-Jumping Genes that contains reverse transcriptase-When active the make
copies of themselves. B> SINES (Short Interspersed Nuclear Elements). DO NOT have Reverse
Transcriptase. Copies our own genes. Inserts DNA randomly, but runs in lines of family
lineages.
How do insertions of transposons compare between closely related groups of species correct
answers Groups of species share certain insertions from the genes and close relatives also share
many of those similar insertions.
Now we get into a possible explanation for why eukaryotes especially have a lot of non-coding
DNA that has no clear function and could be selfish a.k.a. junk. Lets walk through it. -- Selfish
DNA elements can increase their copy #, which presumably reduces fitness of an organism by a
very small amount. What are the small costs that are incurred when a little bit of selfish DNA
gets added to a genome correct answers One has to do with energy, the other with cell cycle
time.?ASK IN ZOOM MEETING
-- Bacteria tolerate very little selfish DNA --- most of their DNA is needed for something. Why
might natural selection be able to minimize the amount of selfish DNA that they carry in the very
large bacteria populations. Be sure to describe the interplay of energy expense, population size,
& drift in bacteria. These factors seem to combine so that bacteria populations eliminate those
that are a little short on energy, and/or a little slow at dividing correct answers Bacteria is apart
of the Prokaryote family and since it is small Bacteria is very energy limited.The bacteria MUST
be small because enough ATP cannot be made, which they would need if bigger.Though, being
small they do not need many resources, so they have very large populations.If any bacteria has a
little extra DNA the bacteria would be affected because the energy would only be focused on the
DNA, and this would result in Bacteria being selected out and less fit/
-- Eukaryotes tolerate a LOT of selfish DNA -- Although this extra DNA still has a cost to
eukaryotes, their situation is one where they easily tolerate it so it is nearly neutral to natural
selection. Why is this extra DNA neutral to eukaryotes.. Combine that with an interplay of
energy, population sizes & drift to explain why this --> their accumulating extra DNA, little by
, little, in a 'ratcheting' process. Also, understand why this explains why the extra DNA varies a lot
between different eukaryotes. correct answers Eukaryotes are not very energy limiting; this is
due to Mitochondria (has a high internal surface that is great for ATP).Evolve to larger sizes due
to an abundance of energy.Since they are larger, they have smaller populations, and some drift,
but not as often. Extra DNA does not affect fitness, and the amounts of DNA vary with history.
(Ratchet Process)- Advancement in only one direction, DNA does not revert.
This article presents different opinions about the large amount of non-coding DNA in eukaryote
genomes that appear to be useless baggage. The author, Carl Zimmer, is an excellent writer of
popular science books, b.t.w.. If you are looking for engaging reading about evolution, parasites,
medicine, etc. I suggest you look in your local library or on Amazon for his many books. They
are all excellent. The article talks about how Ryan Gregory (and others) view the seemingly non-
functioning DNA in the eukaryotic genome as Junk DNA. Do all geneticists/evolutionary
biologists view such DNA as being, necessarily, 'junk' correct answers No, there is a turn against
the term junk DNA. Most of the DNA that scientists once thought was junk DNA, turns out to be
doing important things.
On the subject of 'non-coding' DNA in general. I emphasized that some n-c DNA is clearly
important and functioning and it includes stuff that we have known about for many decades.
These important regions of chromosomal DNA are described in even introductory biology texts.
I gave examples in class. In this article, however, you read about how some scientists are broadly
claiming that junk DNA is mislabelled. This DNA, they claim, at least frequently does have
function but we do not yet know what it all can be. Even Francis Collins (who is one of the most
important biologists on the planet (!) is in this camp. This debate is a peek into one of the more
colorful and hotly debated topics in biology right now. Students should understand that even the
ivory tower of science has its politics, camps, and arguments even over matters like recent
science history and the meaning of terms. Anyway, moving on...Later, the article d correct
answers If every piece of the genome were essential, then many of those mutations would lead to
significant birth defects, with the defects only multiplying over the course of generations; in less
than a century, the species would become extinct.
There are cases where DNA that was a good candidate as junk is found to have function (and
these include some unusual but no less important functions). Read and enjoy. The examples are
very interesting, and they hint at some new roles of RNA besides being involved in translation of
proteins. correct answers ?
To finish, Ryan Gregory and others will still argue that most of the putative junk DNA is still
likely junk, despite the above findings that a small portion is found to have been recruited to
have function. correct answers ?
To summarize some of the arguments that a lot of DNA is junk: -- Great differences in the
amounts of this n-c DNA across species (a specific example being the "Onion Test") -- The
understood nature of most of this n-c DNA. Inactivated DNA from old virus DNA insertions,
mutated jumping genes, and tandemly repeated DNA that varies in copy number. -- Much of
what is described as junk DNA is actually transcribed --> RNA but the # the transcripts are
incredibly small. The length is variable, and the transcripts are quickly degraded. We would
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