mutations (1 Viewer)

[stressedadfff]

why do neutral or nearly neutral mutations occur more frequently in the population?
and
"in 1926 muller experimented with fruit flies by exposing them to x rays. he found that their offspring showed new phenotypes not observed in the population." explain how the results of these experiments can provide support for darwins theory of evolution by natural selection?
and
does gene flow affect small or larger populations more? why?

how would you go about answering those? thanks!

 

[stressedadfff]

bump

 

[Leadmen4y]

1) not sure myself honestly, the question is a little ambiguous or maybe there are gaps in my knowledge. But you could talk about how there are multiple codons coding for the same amino acid, hence substitution mutation may result in the same amino acid (silent mutation), though I highly doubt that's the actual answer.

2) personally don't know exactly how those two links, but I would note that new phenotypes in the offspring meant that X-ray produced germline mutations in the parent fruit flies, new alleles were introduced to the gene pool. And germline mutations are essential for natural selection as they can be inherited in the offspring, I'm really not sure though.

3) gene flow (and genetic drift) both affect smaller populations more. This is because larger populations have a pre-existing gene pool that is significantly bigger than smaller populations, hence the introduction of new alleles is less impactful in affecting genetic variation. While smaller populations have a smaller gene pool with a lot fewer available alleles, hence introduction of new alleles becomes an overall larger impact.

 

[stressedadfff]

thanks!!

 

[Eagle Mum]

1) Deleterious/highly pathogenic mutations, as the first term implies, may be lethal to the affected individual before they reach reproductive age, or may affect their ability to reproduce (for example congenital bilateral absence of the vas deferens in individuals with milder, less lethal forms of cystic fibrosis), whereas neutral, or nearly neutral mutations which don’t affect reproductive fitness, are propagated by the carrier, at the same rate as the wild type allele, to future generations.

2) I agree with @Leadmen4y, x-rays greatly increase the number of germline mutations, which naturally do occur at a much lower event rate as a result of background radiation energy and seemingly random molecular interactions. The increased number of genetic variants/phenotypes within the same generation allowed scientists to observe, by looking at the frequency of each phenotype in subsequent generations, whether natural selection of the “fitter“ genetic variants/phenotype occurred. Otherwise, the much lower rates that variants would naturally occur, would require many, many generations to be observed before any evidence of natural selection could be seen (the evidence being of increased prevalence of ‘fitter’ variants and disappearance of less fit and/or harmful variants from subsequent generations).

(BTW, check your curriculum dot points - by convention, the term ‘mutation’ is now applied to ‘genetic variants‘ only if the variant is potentially pathogenic/harmful, otherwise, the more generic term ‘genetic variant’ is used, but if the curriculum & teachers use ‘mutation‘ as originally applied to all variants, harmful and benign, then ignore this comment - my daughter always followed NESA conventions even those that were outdated.)

 

[stressedadfff]

1) Deleterious/highly pathogenic mutations, as the first term implies, may be lethal to the affected individual before they reach reproductive age, or may affect their ability to reproduce (for example congenital bilateral absence of the vas deferens in individuals with milder, less lethal forms of cystic fibrosis), whereas neutral, or nearly neutral mutations which don’t affect reproductive fitness, are propagated by the carrier, at the same rate as the wild type allele, to future generations.

2) I agree with @Leadmen4y, x-rays greatly increase the number of germline mutations, which naturally do occur at a much lower event rate as a result of background radiation energy and seemingly random molecular interactions. The increased number of genetic variants/phenotypes within the same generation allowed scientists to observe, by looking at the frequency of each phenotype in subsequent generations, whether natural selection of the “fitter“ genetic variants/phenotype occurred. Otherwise, the much lower rates that variants would naturally occur, would require many, many generations to be observed before any evidence of natural selection could be seen (the evidence being of increased prevalence of ‘fitter’ variants and disappearance of less fit and/or harmful variants from subsequent generations).

(BTW, check your curriculum dot points - by convention, the term ‘mutation’ is now applied to ‘genetic variants‘ only if the variant is potentially pathogenic/harmful, otherwise, the more generic term ‘genetic variant’ is used, but if the curriculum & teachers use ‘mutation‘ as originally applied then ignore this comment - my daughter always followed NESA conventions even those that were outdated.)

thank you!!

 

[stressedadfff]

1) Deleterious/highly pathogenic mutations, as the first term implies, may be lethal to the affected individual before they reach reproductive age, or may affect their ability to reproduce (for example congenital bilateral absence of the vas deferens in individuals with milder, less lethal forms of cystic fibrosis), whereas neutral, or nearly neutral mutations which don’t affect reproductive fitness, are propagated by the carrier, at the same rate as the wild type allele, to future generations.

2) I agree with @Leadmen4y, x-rays greatly increase the number of germline mutations, which naturally do occur at a much lower event rate as a result of background radiation energy and seemingly random molecular interactions. The increased number of genetic variants/phenotypes within the same generation allowed scientists to observe, by looking at the frequency of each phenotype in subsequent generations, whether natural selection of the “fitter“ genetic variants/phenotype occurred. Otherwise, the much lower rates that variants would naturally occur, would require many, many generations to be observed before any evidence of natural selection could be seen (the evidence being of increased prevalence of ‘fitter’ variants and disappearance of less fit and/or harmful variants from subsequent generations).

(BTW, check your curriculum dot points - by convention, the term ‘mutation’ is now applied to ‘genetic variants‘ only if the variant is potentially pathogenic/harmful, otherwise, the more generic term ‘genetic variant’ is used, but if the curriculum & teachers use ‘mutation‘ as originally applied then ignore this comment - my daughter always followed NESA conventions even those that were outdated.)

i was wondering whether you would know how sexual selection changes allele frequencies?

 

[Eagle Mum]

i was wondering whether you would know how sexual selection changes allele frequencies?

Sexual selection refers to how members of each gender select their mates. If within a population/community, the majority of the members of a gender conclude that particular phenotype(s) in the other gender are desirable, then by selecting mates with those phenotype(s)/gene variant(s) for reproducing with, these alleles would increase in frequency.

For example, females in prehistoric societies may have selected bigger, stronger males (to protect them and hunt for food). Even if less muscular males were just as (or more) capable of providing food, by intelligent planning and cunning, sexual selection may have increased the frequency of alleles which produced more muscles as a phenotype. If muscle development isn’t linked to brain development & intelligence, then the increased frequency of the selected allele may occur at the expense of the other. Sexual selection in isolated populations may have contributed to the divergence of phenotypic features between ethnic groups (bit wary about how politically correct HSC answers are expected to be) and I suspect this phenomena, along with Darwin’s ’survival of the fittest’, may have contributed to the distinctly different breeds of birds and animals, which are so divergent, they no longer interbreed.

 

[Eagle Mum]

On further consideration of the last question, it may also be appropriate to explicitly state that the desirable traits may be encoded in the autosomal as well as sex chromosomes, so that the frequency of autosomal alleles can also be increased by this process, to show that it is understood that though this process is described as sexual selection, it is not confined to the sex chromosomes.