Help with biology question.?

Question

Mendel is the father of modern genetics, but there are some genetic characteristics that cannot be explained by simple Mendelian genetics. Such is the case with the human blood types in which there are 3 alleles for the same gene, A B, and o. A parent can pass allele A, B, or o to the offspring based on the parent’s genotype.

From these 3 alleles, there are 4 blood types (phenotypes): A, B, AB, and O, and there are six genotypes: AA, Ao, BB, Bo, AB, or oo. This is an example of codominance in which both A and B alleles are codominant to each other.

Blood types can be used in forensics to determine if blood is from the victim or criminal. Blood types can be used to determine parental source in situation where the father is unknown; however, blood types can only eliminate certain blood types. DNA fingerprinting is a better method that is used often in criminal and parental determination cases.

Punnett squares such as the one shown above are used to determine the probabilities (percentages) for genotypes of offspring given specific genotypes for the parents.

In the example above, the Punnett Square represents a cross (mating) between a male (on the left side) with blood type AB, and a female, (top of square), with blood type A, genotype Ao.

Fill out and turn in the Punnett square for AB x Ao above. And, answer the following questions for the cross represented above. Make sure you understand the difference between phenotype (blood type) and genotype. The Punnett Square shows the possible genotypes. When answering the questions, percent (probability) calculations and your answers should be in terms of the phenotypes (the blood types) and NOT the genotypes.

What are the possible blood types for the offspring?

What are the ratios or percentages for each possible blood type from this cross?

What blood type is not possible from this cross?

Fill out two Punnett squares for a cross between a male with blood type B and a female with blood type AB. (Note that we do not know if the father is genotype BB or Bo from the information given. Thus there are two solutions to the possible cross.)

Set up two Punnett squares and answer the following questions about them. Turn in these two Punnett Squares and your answers to the questions. Again, make sure you understand the difference between phenotype (blood type) and genotype. The Punnett Squares that you set up show the possible genotypes. When answering the questions, percent (probability) calculations and your answers should be in terms of the phenotypes (the blood types) and NOT the genotypes.

What are the possible blood types for the cross between the type B (BB or Bo?) male and AB female?

What are the percentages (%) or probabilities for each blood type in the offspring?

What blood type(s) would not be possible in a cross between these two parents?

You will be turning in 3 completed Punnett squares and answers to the questions for Parts 1, A and B above.

Part 2: Cell division, mutations, and genetic variability.

Eukaryotic cells can divide by mitosis or meiosis. In humans, mitosis produces new cells for growth and repair. And, meiosis produces s*x cells (gametes), called sperm and eggs. Changes or mutations in genes in s*x cells can be inherited by human offspring. Genetic variation in a population of organisms is good; however, sometimes mutations can be harmful or cause genetic disorders.

Briefly, answer the following two questions. List and cite your references for this:

How do meiosis and sexual reproduction (fertilization) produce offspring that differ genetically from the parents? Be sure to talk about both meiosis and fertilization.

Describe one example of a human disorder that is inherited and also describe the specific inheritance pattern. For this question, pick disorders that result from mutations in DNA or chromosome number rather than examples such as a genetic tendency for a disorder such as cancer.

You will be turning in answers to the two questions above for Part 2.

Answer 1

meiosis the offspring doesn't differ from its parents because meiosis is the same as cloning because it produced by one organisam using 23 chromozones where as in fertalization there are 2 parents to produce an offspring and there are 46 chromozones which cross and mix togather shall we say and create a offspring that is a mixture of the 2 and is not a exsact copy. diseases such as cance can be passed on by parents to offspring in fertalization because you hav a 50-50 chance of inherating the gene that has cancer in it from your parents but in meiosis  it is garanteed that the cancer gene would be passed on.

Answer 2

Ok the first square will have phenotypes A at 50%, B at 25% and AB at 25% and the only one you wont get will be O.For the second 2 squares if the father was genotype BO then 25% AB, 50% B and 25% A. There could be no O phenotype.If the father was genotype BB then 50% AB and 50% B. There could be no O or A phenotype. There are two main ways in which meiosis can produce genetic variation, crossing over and independant assortment.First in Prophase 1 the chromosomes pair up (homologous pairs) and then each split into chromatids. This happens very close together and there can be a crossing over at a point called chiasma. Bits of the DNA break off and swap over between chromosomes and then rebind, causing variation.The second happens in metaphase 1 where all of the pairs line up along the equator in a random order. This means that when telophase happens any combination of chromosomes could be possible.As for fertilization it can be varied by the fact that any of the millions of gametes (egg/sperm) could be fertilized.The human disorder sickle cell anaemia is genetically inherited. This disease causes the abnormal sickle shape of the red blood cell so that it has difficulty moving through the blood vessels so can lead to a blockage.It is caused by a mutation of the beta chain in haemoglobin and is passed on by the recessive allele S. A normal person would have alleles AA, a carrier would have AS and someone with the disease would have SS.