36

Going through the possible answers (A) Rates tend to be very high in most populations. This is a very unclear statement. What does "high" mean? In humans, the average mutation rate per reproduction per nucleotide is of the order of $10^{-8}$ (Rahbari et al., 2016) (hence of the order of 10 - 100 mutations for the whole genome). Whether someone wants to ...


18

Change in genetic variance From what I have been taught, Natural Selection (or even Artificial Selection) is great for panning favorable genes from a species and bringing them to the fore, however, it does not introduce new genetic changes. Yes, you are pretty much right. In a given population, directional selection will ultimately reduce genetic ...


18

The surface structuresa that are responsible for the structural coloration of peacock feathers are actually barbules and rods made of the very same biopolymer that is responsible for pigmentation in many other animal species, namely melanin. Just as in other animals, melanin is produced in the melanocyte cells which reside in the skin's epidermis. The ...


16

My friend Brightblades is right in one thing. It seems your teacher was working off a caricature of what the theory of evolution actually says. First of all, you should read Sklivvz's excellent answer at this question. Now to address the elephant in the room, the accident at Chernobyl only happened in 1986. That was only 26 years ago. In that timeframe, ...


14

The answer is chance or, even better, contingency. About your calculations, it is true that the theoretical sequences are almost unlimited, but the basic scaffolds are not. Very different sequences can fold into the same basic scaffold and have a similar reactivity/function. So, even if not all the sequences have been explored on this planet, most of the ...


12

Short answer All mutagens are potential carcinogens unless the mutagen is highly specific to a site. As noted in the question, carcinogens need not be mutagenic. HPV causes oncogenic transformation of a cell because of certain proteins that it expresses. HPV is considered a carcinogen by the IARC. Some retroviruses are oncogenic: they might carry an ...


12

Short answer Large animals do get cancer. They may contract cancer with an incidence less than that estimated by absolute cell numbers, but there seems to be a lack of data on cancer rates in large animals to support this hypothesis conclusively. Background Whales contract cancer (Martineau et al, 2002). There does, however, seem to be a lack of correlation ...


12

I accidentally wrote a lot! I first discuss the term Darwinian evolution. I then describe the main evolutionary processes insisting on the two elements of interest in your question, that is mutations and natural selection. In the end, I directly address your two statements and bring a few more complications into the subjects. Did you say Darwinian ...


11

You're right that the mutation must be in a germ cell in order to be passed on. Most errors are introduced during DNA replication (at a rate of around 10-10), which occurs a number of times between the zygote stage and mature gametes. This book estimates that there are 24 divisions between zygote and egg and 23n+34 divisions between zygote and sperm, where n ...


10

I think we may be missing a piece from Darwin's original hypothesis. An outline of the first 4 chapters of Origin of Species form the kernel of the Theory of Evolution: 1: Variation under Domestication 2: Variation under Nature 3: Struggle for Existence 4: Natural Selection Really you can't reduce evolution to less than variations; competition (struggle)...


10

The answer depends on what you mean by "observed". Bacteria acquire antibiotic resistance genes all the time, for example. This happens 'in the wild', but you can see in the lab that bacteria can become resistant overnight - I'd call that 'observed'. There are many papers about the emergence of antibiotic resistance (not that I'm suggesting this is the ...


9

Cancer cells and normal cells differ on the genetic basis but they share the same genetic background, so they have not different DNA in the sense of two different people. They have to be different, since cancer cells have to accumulate mutations on a number of genes to become a cancer cell, which can survive and will not be directed into apoptosis. These are ...


9

A single substitution can often be silent, or at least not impact the structure and function of the resulting protein in a significant way. But what you describe is a frameshift, and that is one of the most destructive mutations. It will completely change the sequence of the protein after this mutation and disrupt the function of those parts of the protein. ...


9

Lets state what a Mutation is first. Mutation: A mutation is any change in an organism's genetic sequence which varies from that of the wild-type reference sequence (hg19/GrCH37 from 2009 or hg38/GrCH38 from 2013, which are the most current genome assembly). Single Nucleotide Polymorphisms (SNPs): These are any single nucleotide base mutations which have ...


8

I don't know, whether the organism you are working with is diploid, but suspect it's an animal (or even a mammal), so the most parsimonious explanation would be that you have homozygotes and heterozygotes at this SNP-position.


8

Welcome to Biology.SE! can environmental factors play a role in the amount of mutations that occur? Yes! The environmental factors that increase the mutation rate are called mutagens. You will definitely want to have a look in the wikipedia article. You may also want to read the wikipedia page on mutagenesis Some chemicals increase the mutation rate, ...


8

Good question. There are many organisms that are technically biologically immortal. However, I would like to point out that the definition of biological immortality is this: ...cells that are not limited by the Hayflick limit, where cells no longer divide because of DNA damage or shortened telomeres. (That's from here.) So biological immortality ...


8

Short answer The claim is unclear but is essentially misleading and wrong. However, IMO, for lay people, it is a good approximation to just think that mutations are random! Here, on Understanding evolution is a great source of information on what it means to say that mutations are random Long answer What is a mutation? Mutation is an event causing an ...


7

That would be hard to say because really beneficial mutations become well distributed through the genome. Basically the differences between us and chimpanzees are a catalog of all the beneficial (or completely neutral) mutations since the ~4.7 M years since we diverged from each other. Separating them from changes which have no special effect would be ...


7

Standing genetic variation is when there is more than one allele at locus in the population at the time-point in question. When an allele goes to fixation there is no standing genetic variation at the locus until new mutations occur. Loci where alleles are not fixed are described as having standing genetic variation. "Standing genetic variation: the ...


7

Pink individuals of the katydid species Amblycorypha oblongifolia are a relatively uncommon but natural phenomenon with a long history of research. It looks from popular press accounts (Science Friday, Scientific American) that the pink coloration may be caused by a dominant allele, and is only rare because of a high selection pressure against pink ...


7

It is called conditional mutation. You flox (put lox sites around) gene of interest and express Cre recombinase driven by tissue-of-interest-specific promoter. Illustration from here: Using chemically-activatable variant of Cre recombinase (cre-ER) you can create knock-out in some cells of tissue of interest, not every. Addition: a bit weird but still ...


7

No, not necessarily! The terms might be confusing I agree. The most common allele (the wild type allele) might be a mutant of one other type of allele (one mutant allele) present in the population. The reason we call the least common alleles the mutant alleles is that beneficial mutations are rare compared to neutral or deleterious mutations. If at a given ...


7

You may be interested in this 2005 Nature paper from the Chimpanzee Sequencing and Analysis Consortium: Initial sequence of the chimpanzee genome and comparison with the human genome. It breaks down the most common categories of genetic variation: Single-nucleotide substitutions occur at a mean rate of 1.23% between copies of the human and chimpanzee ...


7

Not less efficient, but introns are under less selective pressure than exons. Exons actually encode the protein. A single bp insertion will ruin a mRNA encoding a protein by causing a frame shift in how the sequence is read. However the same is not true for introns. 1bp insertion even if the intron has function such as transcription or translation factor ...


7

A recessive gene for four leaves has been identified (Tashiro et al., 2010). The clover is a tetraploid species and together with the fact that environmental conditions may also suppress the development of the fourth leaf, it indeed takes a lot of luck to find one. If it will bring you any is another question though. In fact they are aiming at making a four-...


7

The ability of a population to respond to environmental change through evolution occurs over generations, and so the generation time of an organism has to be less than the time scale of the environmental change for such an increase in mutation rate to be beneficial. For bacteria at least, the answer to your question is yes. Bacterial stress responses ...


7

Yes. Mutations can affect STOP codons and they do relatively commonly. These are important because they can lead to significant changes in the resulting peptide and are likely to affect protein functions or phenotype. For a point mutation (a single base substitution), there are several possible effects: silent mutation is a synonymous base substitution ...


6

I can't answer your third, but I can answer your first two. With one word, in fact: Bioluminescence http://brightnepenthe.blogspot.com/2010/08/palate-cleanser-90.html That's the deep ocean at night for ya. Unlike underground environments and caves, it's not pitch black pretty much anywhere in the ocean. There are things to see everywhere, and they play an ...


Only top voted, non community-wiki answers of a minimum length are eligible