Genetics and Inheritance

My subtle coloring did not come out well in this scan-imagine light tan skin!

Genetics Problems:                         1.       For each of the diploid genotypes presented below, determine the genetic make up for all of the possible gametes that would result through the process of meiosis. Remember, each egg or sperm must have one of each letter. That letter can be upper or lower case. a.       Rr  R or r b.      RrYy   RY, Ry, ry, c.       rrYy   rY, ry d.      RrYY  RY, rY 2.       For each of the following, state whether the genotype of a diploid or haploid cell is represented. a.       D Haploid b.      GG Diploid c.       P Haploid d.      ee Diploid 3.       Yellow guinea pigs crossed with white ones always produce cream colored offspring. Two cream colored guinea pigs when crossed produced yellow, cream and white offspring in the ratio of l yellow: 2 cream: l white. Explain how are these colors inherited?  No calculations needed! Name the type of inheritance this represents.        This represents incomplete dominance, where the heterozygous type is expressed as an intermediate phenotype. Because the cream colored guinea pigs are heterozygous, they contain one allele each of the yellow or white gene, and when mated with each other, can produce either white, yellow, or cream offspring, depending on which alleles each parent gives. 4.       In sheep white is due to a dominant gene (B), black to its recessive allele (b). A white ewe mated to a white ram produces a black lamb. What are the genotypes of the parents? You might need to construct Punnet squares experimenting with different crosses to come up with this answer. Name the type of inheritance this represents.               B                           b                                                      Allele(s) from Mother Allele(s) from Father Genotype Phenotype Sex of child:  X X XX female Face shape r r rr square Chin Shape (I) v V Vv very prominent Chin Shape (II) R r Rr round Cleft chin a a aa present Skin color abCd abcD aabbCcDd very light brown Hair type c C Cc wavy Widow’s Peak w W Ww present Eyebrows (I) b B Bb bushy Eyebrows (II) N N NN not connected Eyebrow color H H HH darker than hair Eyes distance apart E e Ee average distance Eyes size e E Ee medium Eyes shape A a Aa almond Eyes slant H h Hh horizontal Eyelashes l l ll short Eye color ABC aBc AaBBCc light brown Mouth size M M MM wide Lips L L LL thick Protruding lower lip H h Hh slightly protruding Dimples d d dd absent Nose size N n Nn average Nose shape R r Rr rounded Nostril shape R r Rr rounded Earlobe Attachment F F FF free Freckles on checks f f ff absent Hair color ABCD abCd aabbCcDd brown           BB Bb Bb bb                 B                                                                              b                                                The parents would both have to be Bb heterozygous. This is homozygous recessive inheritance.           G                      g g Gg gg g Gg gg 5.       In peas, yellow color (G) is dominant to green color (g). A heterozygous yellow is crossed with a green. What is the expected phenotype ratio of the offspring? Name the type of inheritance this represents.                                                                         There is a 50/50 ratio of green to yellow. This confers both heterozygous and homozygous recessive inheritance. 6.       White color (Y) is dominant to yellow color (y) in squash. A heterozygous white fruit plant is crossed with a yellow fruit plant. What is the expected phenotype ratio of the offspring? What is this type of inheritance called? Y y y Yy yy y Yy yy There is a 50/50 ratio of white to yellow squash. This is heterozygous and homozygous recessive inheritance. 7.       In certain flowers, a cross between homozygous red and a homozygous white will always result in a pink flower. A cross is made between two pink flowers. What is the predicted phenotype ratio of the colors red, pink and white appearing in the offspring? What is this type of inheritance called    R W R RR RW W RW WW There will be a 25% chance for white or red, and 50% chance of pink.  This is an example of incomplete dominance due to heterozygous genotypes. 8.       In humans, the condition for normal blood clotting dominates the condition for non-clotting or hemophilia. Both alleles are linked to the X chromosome. A male hemophiliac marries a woman who is a carrier for this condition. In this respect, a carrier is a woman who has an allele for normal blood clotting and an allele for hemophilia. What are the chances that if they have a male child he will be normal for blood clotting? What is this type of inheritance called? XH Xh Xh XHXh XhXh Y XHY XhY There is a 50% chance that a son will be normal for blood-clotting.  This is sex-linked inheritance. 9.       A person with an allele for type A blood and type O blood marries someone with an allele for type B blood and type O blood. List the types of offspring they could have and the probability for each blood type in the offspring. (A allele = IA, B allele = IB, O allele = i) What is the expected phenotype ratio of the offspring? What is this type of inheritance called? IA i IB IAIB IBi i IAi ii There is a 25% chance that the blood type will be AB, a 25% chance that it will be O, a 25% chance that it will be A, and a 25% chance that it will be B. This is called codominance. 10.   Skin color in humans becomes darker by the number of dominant alleles; AABBCC have the darkest skin and aabbcc have the lightest skin. Place these genotypes in sequence according to the color of skin expected for each. Place the darkest skin first. What is this type of inheritance called? Genotypes: AaBbCc, AAbbcc, aabbCc, AaBBCc, AaBBCC. AaBBCC, AaBBCc,AaBbCc,AAbbcc,aabbCc This is called polygenic inheritance.

                                                                                                                             

DNA Technology

DNA Extraction

A buccal swab collects skin cells (stratified squamous epithelial cells) from the inside of a cheek. Scissors are used to cut off the end of the swab and place it into an eppendorf tube. Micro pipette is used to add lysis solution, which is a combination of detergent, which breaks apart the cell and nuclear membranes, and proteinase k, which cuts away histones. This tube with lysis is added to a warm water bath, facilitating the action of the lysis. We then use a micro pipette to add concentrated salt solution. This solution causes proteins and other cellular debris to clump together. Then, the tube is added to a micro centrifuge, along with a "balancing" water test tube. The fast spinning in the centrifuge causes the clumped debris to fall to the bottom of the tube, and a micro pipette can then be used to remove the top level of liquid and place it in a different tube. Isopropyl alcohol is added to this solution, which separates out clumped DNA into visible form. This tube goes back into the micro centrifuge, and, this time, the DNA falls to the bottom. A pipette is used to remove the top liquid, and the DNA on the bottom is then ready for use or storage.

  
Electrophoresis

A gel is created by heating agarose along with a salt water solution/liquid buffer in a microwave. This is then added to a mold, and a comb in inserted to create small wells for the DNA samples at one end. It is allowed to cool, and the comb is removed. A buffer is added to an electrophoresis box to allow for conduction of current and to prevent drying out of the mold. The mold is placed into this box. Loading buffer, which allows DNA to be seen, is added to a DNA sample, which is then placed into one of the wells. Standard size DNA (a sample in which DNA length is already known) is added to another well for comparison. A current is then run through the box-the negative charge is at the end with the wells, and a positive charge is on the opposite end. DNA is repelled from the negative charge and begins to make its way to the positive charge. The gel itself is filled with small holes that the DNA travels through to get to the positive charge. Smaller strands are able to move more quickly. Eventually, strands of the same size end up together and clump, which makes them ultimately more visible. Once the process is complete, the mold is removed from the electrophoresis box and placed in an ethidium bromide solution, which stains DNA and makes it visible when it is placed under UV light (accomplished with a UV light box). The clumps appear as bands and their location can be compared with the bands of the known lengths of the standard DNA sample. This gives a rough estimate of the number of base pairs present at each band site.

Electrophoresis can be used to determine paternity. Because each person's DNA pattern is very unique, it shows up in electrophoresis as a unique set of bands, unlikely to be repeated by any but a close relative. Thus, parent and child can be identified by a close match of an electrophoresis reading. This is accomplished by taking the DNA of mother, child, and two possible fathers and putting them through gel electrophorisis. Every band of the child MUST MATCH at least one of the parents. Whatever bands don't match the mother must be found in the father's reading. Therefore, by process of elimination, paternity is determined.

 

Cell Reproduction and DNA

Chromosome 10

 1) IL2RA- interleukin 2 receptor, alpha protein encoding

      IL2RA is a protein that appears on the surface of certain immune cells, and is often found along with beta and theta versions of interleukin 2 receptor. Together, they respond to interleukin 2, a chemical that bonds with the various forms of IL2R, creating chemical signals that are then transferred into the interior of the cell.

2) VIM- vimentin

     This gene encodes a protein that helps to maintain the shape and integrity of a cell's cytoplasm, and is an integral part of the cytoskeleton. It also helps transport LDL (low-density lipoprotein) out of the cell.

3) ITBG1- integrin, beta 1

    This gene encodes a protein that is part of a group of proteins (made up of alpha and beta subunits) that form receptors on the cell membrane. These receptors as a whole help with cell adhesion and recognition, as well as tissue repair, hemostasis, and immune responses.

4) RET- proto oncogene

    RET encodes a cell-surface receptor that translates signals for cell-growth and differentiation. It plays an important role in embryonic development during the formation of the neural crest, one of the important stages of tissue differentiation in embryos.

5) MAPK8- mitogen-activated protein kinase 8

    The protein this gene encodes is part of a larger family of proteins that act as integration stations for multiple biochemical signals, and are therefore involved in many cellular activities. This particular one, once activated, leads to programmed cell death, which is important in preventing tumor proliferation or genetic mutation due to UV radiation.

6) CDK1- cyclin-dependent kinase 1

     This gene creates a kinase (an enzyme that helps create energy in a cell) that works during cell reproduction, helping a cell to move from one phase of cell reproduction to another. It also works as a regulator during cell cycles.

7) PLAU- plasminogen activator, urokinase

    This gene encodes an enzyme that breaks down protein bonds in the extracellular matrix. It specifically breaks down plasminogen into another enzyme called plasmin, which circulates in the blood and breaks down various blood proteins, including those that form clots.

8) FAS- fas cell surface death receptor

    This gene creates a protein that is a receptor protein that helps to convert signals in proliferating T cells and fibroblasts. It is pivotal in programmed cell death, and is implicated in the development of various diseases of the immune system. 

9) TCF7L2- transcription factor 7-like 2 (T cell specific, HMG box)

     This is involved in the transcription of DNA within the cell. It is involved in the stabilization and maintenance of healthy glucose levels in the blood.

10) FGFR2- fibroblast growth factor receptor 2

      This gene encodes a protein that interacts with various forms of fibroblast growth factors, helping to set in motion a cascade of events that lead to cell reproduction and differentiation. These processes are involved in wound healing and embryo development, among other things. 

Genetics Blueprint Critique
1) I often found the instructions unclear and lacking in specificity. The questions did not always relate directly to the information that was shared, and there were aspects to some of the interactive exercises that were not explained. I found myself feeling frustrated at points by what the program wanted.

2) I'm not sure I learned a whole lot more than I did from the textbook or from the above lab. There was a little more about history, but it was so brief and not adequately explained, that I don't think I retained much. It was informative to play around with building the molecules, but again, I'm not sure I would've figured it out without the emailed instructions of Ms. Oellers.

3) Visually, it was appealing. It was interesting to see DNA represented in a variety of forms. I would have actually liked a bit more time spent on this aspect.

4) The questions were phrased in an odd way that made it difficult to figure out which answers were being sought. I don't feel like the writing was the best.

5) The idea of the lab is nice- going through a version of historical experiments, and then playing around with molecules and building DNA helps make things more clear. I just think it could be done better.