Biology help?

Question

1. How do Punnett squares explain the probability that a particular allele will be in a gamete?

2. What is the difference between nitrogen base, gene, and chromosome?

3. Why is there so much biodiversity on this planet?

4. Why are the conditions for Hardy-Weinberg not likely to appear in nature?

Answer 1

Am I helping you with your homework or something.. ok it's been a long time since I graduated, but let me try...

1) Punnett Squares help you work out the probabilities that children of the parents in each worked example will have particular phenotypes and genotypes. Buy building a grid of dominant and recessive alleles you can work out the likelihood of its representation in the gamete. See the examples I included.

2) The Nitrogen bases are adenine, guanine, cytosine and thymine which are represented on each of the strands of DNA. When individual bases combine they can (either individually or as a group) be defined as a gene. The 3 billion bp (base pairs) in the human genome are organized into 24 distinct, physically separate microscopic units called chromosomes.

3) Not an easy question to answer - there's been a lot of different life forms around for a long time, so there's a large amount of biodiversity. You're probably best looking at the definition of biodiversity and drawing your own conclusion! The Wikipedia page I've included may help you...

4) Tough question...Violations of the Hardy–Weinberg assumptions (you should know these) can cause deviations from expectation. How this affects the population depends on the assumptions that are violated:

The HWP states the population will have the given genotypic frequencies (called Hardy-Weinberg proportions) after a single generation of random mating within the population.

When violations of this provision occur, which is what I think you're asking), the population will not have Hardy-Weinberg proportions. Three such violations are:
i) Inbreeding, which causes an increase in homozygosity for all genes.
ii) Assortative mating, which causes an increase in homozygosity only for those genes involved in the trait that is assortatively mated (and genes in linkage disequilibrium with them).
iii) Small population size, which causes a random change in genotypic frequencies, particularly if the population is very small. This is due to a sampling effect, and is called genetic drift.

Hope this helps - can I go back to my 'proper' work now?! ;-)

Answer 2

1. Punnett squares show all the possible combinations of alleles in the offspring. We can use the results of the square to figure out the probability.

2. A nitrogen base is one part of a nucleotide. The sequence of nitrogen bases in a gene gives the code for a protein.

A gene is a section of the DNA of a chromosome. It is made of the nucleotides on that side of the DNA.

A chromosome is a structure made of DNA and protein. The genes are sections of the chromosome.

3. Our planet has many different habitats with very different abiotic characteristics: different temperatures, landforms, precipitation, wind, etc. That provides many different situations for different types of living things. The more differences in the abiotic factors -- the more types of living things.

4. Hardy-Weinberg is based on genetic equilibrium. In nature, conditions are always changing and upsetting the equilibrium in the gene pool. Mutations happen, individuals move into and out of the population, new predators appear, and so on.

Answer 3

Hi frou...(been a rough couple years lol) Dont know that I am back, but am for a time anyway. As a devout christian ( I know, here we go again, yes?) and speaking for myself, I find the study of these subjects interesting. even fascinating. In my healthier days, before the spina bifida caught up with me, I prepared herbal teas for folk's ailments . I learned how primarily from two people. My grandfather, and my greatgrammie's sister, who was native american. Dont think I even knew the word biology for quite a few years after Grampa started teaching me at about the age of six or seven. When I realized the "borrowed time" aspect of my life was catching up with me I brought as many herbs home from the woods and fields and started a garden out back. And yes, there were several that could not adapt and still needed to be foraged. Did not hear the word psychology till even after I heard biology ( was introduced to biology in high school and loved the study of it ) Again , it had no impact on me except I could say, "oh that's what they call it" Interesting but all the therapy or introspect I ever needed or will need , for me, is found in the Bible where the one who is the first and greatest counciler of all, and for all times, is to be found as is the answer to every question or problem I ever, ever had or will have. I feel that for some people psychology can be a tremendous help and as for myself, I confess to calling pastor a time and again even for a shoulder to cry on. Thing is tho, psychology, in my opinion, has become abused and caused more problems then the ones that caused folks to seek help in the first place. Also many people who desperately feel they need that help cannot find it for lack of funds. Thing that intriques me most is that those same folks give up on themselves and life for the lack of psychologists. Sad. I do run on , dont I dear? LOL Hope you have been well and happy during my vaca from comps. Penumbra

Answer 4

The other answerers had tackled the first three, I can only add a bit to the last. The HW principle, if it is to apply in a population, assumes that breeding occurs evenly across the population. Clearly this is not so, with tribal societies, consanguinity etc. The spread of any genetic trait is staggered and discontinuous.