Search found 9 matches

by SheffJoe
Wed Jun 06, 2012 9:52 pm
Forum: Genetics
Topic: Linkage disequilibrium
Replies: 0
Views: 2343

Linkage disequilibrium

I understand that alleles located on different chromosomes can be in linkage disequilibrium. How does this occur (the genes are not physically linked). For example, I've read that genes for long-tails and genes for preference for long-tails are in linkage disequilibrium. Can you please explain this....
by SheffJoe
Tue May 29, 2012 8:04 pm
Forum: Cell Biology
Topic: Free-flowing cells and those that are stuck together?
Replies: 2
Views: 3998

Free-flowing cells and those that are stuck together?

I've just been thinking about the development of an embryo from the zygote stage. How is it that when cytokinesis takes place, the cells all stick together in a little ball? But then, later in life, some are not bound to others (red blood cells, sperm cells, etc.). How is it that some cells are stuc...
by SheffJoe
Tue May 22, 2012 7:01 pm
Forum: Genetics
Topic: Genetic drift
Replies: 2
Views: 5696

Genetic drift

I keep seeing lots of different information on genetic drift. I understand it to be the random fluctuations in allele frequencies due to random sampling. But how are all these terms connected: genetic drift, bottleneck, small population, neutral variation?
by SheffJoe
Wed May 16, 2012 11:14 am
Forum: Botany Discussion
Topic: Photorespiration
Replies: 3
Views: 6519

Photorespiration

When plants are in hot environments they'll close stomata to prevent water loss. This closing of stomata leads to low levels of CO2 which leads to photorespiration. But where is the oxygen coming from for photorespiration? In my textbook it says that it is coming from photolysis during the light-dep...
by SheffJoe
Tue May 15, 2012 7:49 pm
Forum: Genetics
Topic: Hardy-Weinberg problems
Replies: 1
Views: 1973

Hardy-Weinberg problems

When a population is in Hardy-Weinberg equilibrium, the allele frequencies are not changing. But look at this: What about an example where disruptive selection favours homozygotes instead of heterozygotes, so the phenotypic frequencies change but the allele frequencies are the same. Is the populatio...
by SheffJoe
Tue May 15, 2012 7:24 pm
Forum: Genetics
Topic: Deleterious alleles
Replies: 0
Views: 1339

Deleterious alleles

As deleterious recessive alleles become rare, do changes in frequency due to selection become more or less important?
Thank you
by SheffJoe
Mon May 14, 2012 9:04 pm
Forum: Evolution
Topic: Combination of advantageous mutation
Replies: 5
Views: 4008

Re:

Sure, they can be combined in the meaning that they will be present in one genome. And because they sort independently, the offspring may have only one, both or any of them. But you must understand, that both parents have some probability of having this mutations. And if they are advantageous, thei...
by SheffJoe
Mon May 14, 2012 8:09 pm
Forum: Evolution
Topic: Combination of advantageous mutation
Replies: 5
Views: 4008

Re:

Nowhere So advantageous mutations can only be combined when recombination takes place? I just don't understand how those on different chromosomes can ever be combined and "fixed". For example, if 2 advantageous mutations (A and B) arise in a population, I always just took it for granted t...
by SheffJoe
Mon May 14, 2012 7:44 pm
Forum: Evolution
Topic: Combination of advantageous mutation
Replies: 5
Views: 4008

Combination of advantageous mutation

If 2 advantageous mutations (A and B) arise in a population, I understand that an individual with A could mate with a B mutant. Some of their offspring could have both mutations. In an example where these 2 mutations lie on the same chromosome at different loci, I understand that through recombinati...