Got into a debate on facebook (I know, I know)
The person I was debating insists that cross-breeding make new genes. I am equally certain it does not.
Can y’all weigh in? Preferably with cites?
Could be referring to this:
My understanding ranging from basic highschool Mendelian genetics to graduate classes in speciation, indicates that ‘New’ genes are not created from cross-breeding.
I suspect there is a misunderstanding, possibly even down to the semantics of what “makes new genes” is defined as, or even ‘Cross-breeding’
But my understanding of what is commonly defined…No…Cross-breeding does not “make new genes.”
Cross-breeding (of species, varietals of plants, or ‘breeds’ of animals) does not innately produce new genes, although it can change how many genes are expressed in sometimes really unexpected ways. I’m not really sure how to cite this other than to say go to any basic text on genetics.
However, the chance combination of non-coding genetic material into a new gene, fusion and fission of extant genes, and lateral gene transfer can result in the generation of new or introduction of novel genes. The more genetic variety in a population, either through broad gene lines or radical mutation will result in more opportunities for de novo gene origination. However, spontaneous generation of viable (protein-coding) genes is relatively rare, and most phenotypical differences in a population are due to changes in gene expression or allomorphic variation within existing genes.
Stranger
To translate: for nearly all cases the answer is ‘No’ but there might be very rare cases where some new code is put together that does something new…but…‘No.’
Count me amongst the “No” camp though cross-breeding between between diverse parents produces hybrid vigour or heterosis where the hybrid will outperform both parents. This is a commonly expressed phenotypic (as distinct from genetic) response and geneticists have been debating the cause for the past century with competing theories based on dominance vs overdominance.
I would consider the rate of genetic change/mutation for an individual (to produce new genes) is roughly constant for members of a species within the same environment. For that mutation to become expressed or widespread in a population, inbreeding is a most efficacious strategy. By definition, cross-breeding will involve one parent from outside the population having the new gene (assuming it’s character is additive rather than dominant).
The problem with finding a quote is that the idea is so fundamentally absurd that no geneticist would bother to say it. It is like finding an astronomer to say the moon is not made of green cheese.
I wonder if the person making that claim is a racist arguing against miscegenation.
No, I was arguing that GMO is not the same as breeding.
It would be exceedingly rare for cross-breeding to create new genes. However, I suppose under some conditions it might result in a change of genes expressed, possibly by complex epigenetic mechanisms that might be modified by environment, and that are not completely understood.
IIRC the majority of the chromosomes are “garbage” or filler between active genes. So the spot where a crossover occurs (the “break” that causes pieces to swap) is very likely to be in the stretch of “garbage” DNA and so have no effect.
What the question seems to be aimed at would be both “would a splice between two sections of garbage DNA create a meaningful gene?” and “would a spice in the middle of an active gene create a ‘different’ gene?”
I’m not versed in DNA details, but as I understand, any genetic change is usually a detriment - i.e. a transcription error in copying a gene - which means the organism has difficulty matching performance of normal peers. Once in a blue moon it produces those changes that make an organism better able to survive its environment. The same would apply to random DNA concatenation or shortening producing an active and effective gene - this requires a double Royal Flush coincidence - once to produce a functional gene and again for it to perform as good or better than what it replaces.
There is a suggestion that many miscarriages are the result of the embryo (or blastocyte?) having genetic errors that make it less than viable. The miracle is that life actually manages to carry on…
Cross-breeding allows for a wider variety of genes to mix-and-match with, so a wider range of traits to add up.
And further - there’s nothing special, generally, about one “breed” versus another unless they are extremely different.
A better example is hemophilia, which can happen spontaneously, and regulalry does. It’s a transcription error in the gene(s) to produce clotting. This then becomes an inherited change in the person’s genome. A female has two X chromosome, so if they inherit at least one which has the complete set of genes then the woman is healthy, but can still pass the defective X (or the healthy one, it’s a 50-50). A male who inherits the defective X, however, suffers from hemophilia because they do not have a “backup” that can fill in.
It does not require cross-breeding to cause this defect. However, if the condition becomes widespread among the healthy females, the risk of a male inheriting is much higher. by mating with a person from outside the community, who is not a carrier, the offspring are unlikely to inherit the condition.
(For males. Obviously, a male who lives long enough to reproduce is likely carrying the defective X. But a female from outside the community likely has two good X’s and so guarantees that - barring a recurrence of the mutation - the children are not carriers or sufferers).
A flat-earther can do it. To apply their editing you could take
“The idea that cross-breeding creating new genes is fundamentally so incorrect that one must question if a proponent of such thinking has done any research in the area.”
becomes
“[C]ross-breeding creating new genes is fundamental.”
Is it possible the person was confusing cross-breeding with genetic modification where a mutagen is used to actually change genes?
Or confusing “crossbreeding can introduce a new gene [variant] to a line”?
I can see someone reading something like (entirely made up quote):
The Persian cat breed has a defective gene for regulating hair shedding. Crossing a Persian with another breed can introduce a healthy shedding gene to the offspring.
Where the emphasized “gene” is just lazy shorthand for a new variant of an existing gene. Both breeds of cats have a “shedding gene”, but the Persian one doesn’t work right, so crossbreeding with a breed that has a working gene means that some of the kittens will get a variant of the gene that works, and is new to the Persian breed.
They then misinterpret it to mean that somehow a whole new gene has appeared: “careful crossing Persians and Abyssinians, because you might get cats with wings.”
Which would be a Babylonian
My graduate research was related to gene expression. We had lines of big and small animals. The promoter region of a differentially expressed gene involved in the phenotype was sequenced (this gene affected the phenotype in a mouse knockout model).
Over 70% of the big animals had a “C” Single Nucleotide Polymorphism (SNP) and all the small animals had a “T” SNP. This SNP was predicted to introduce a transcription factor binding site when C but not T was present and this could potentially affect gene expression.
The lines were crossed and the progeny (F1) had an intermediate phenotype. The F1 progeny were bred to each other and their progeny (F2) had a normal distribution of the trait. The F2 animals in the tails of the distribution (biggest and smallest animals) were sequenced for the promoter region and there was an association between SNP variant and body size–big animals had a much higher frequency of the C SNP, just like the grandparents.
There was no difference in the gene sequence itself, but you could then theoretically select for the C SNP promoter to try to get bigger animals.
Of course, genetics are a lot more complicated than the effect of a single SNP in a gene promoter.