BIO 111 Final Exam Short Answer Questions

Cells have 3 choices, all beginning with the letter "D". List and briefly explain each choice.

(1) Divide- Cells divide when they receive molecular signals that initiate division. When they divide, they create two daughter cells that are identical. These cells continue to carry on the organism's functions. (2) Differentiate- Differentiation is when cells stop dividing and instead focus on specializing in structure and function. (3) Die- Cells die in a programmed process called "apoptosis." This gets rid of any unnecessary or extra cells and eliminates those that are damaged or unhealthy.

Understand what a genetically modified plant is. And be able to explain at least 2 potential advantages and disadvantages of GM crops.

A genetically modified crop is a plant that has its traits changed to produce desired characteristics. Some advantages of GM crops reducing world hunger and lowering the cost of biofuel production. Some disadvantages of GM crops are they may be harmful to human health and there is the possibility of altered genes escaping from transgenic crop into weeds through crop-to-weed hybridization.

Understand what is meant by polygenic inheritance (look at your skin color homework problem.)

A single inherited trait, that is controlled by two or more different genes. With each of the genes having an equal influence on the trait. Each gene plays a part in the expression of the phenotype

Be able to explain how alternative splicing can allow production of multiple protein products from one gene. Think of the article you read that explained how "one gene = one protein" is not necessarily true.

Alternative splicing is the mixing and matching of different exons from one gene. When these are spliced together, various versions of a single protein are produced, and these proteins usually have very different functions. Overall, alternative splicing's purpose is to diversify the mRNAs that are produced from the genome.

If I give you information about a disease - autosomal, dominant or recessive, be able to explain the inheritance pattern.

Autosomal refers to the gene being located on one of the numbered chromosomes. Dominant means a single copy of mutation is enough to cause the disease. Recessive means two copies of the mutation is needed to cause the disease.

Explain how genetic variability reduces susceptibility to disease.

Because of genetic variability, the offspring produced by two parents will be more equipped to survive in whatever environment there is. This is because it is a unique individual with both parents' genomes, compared to asexual reproduction in which the offspring is identical to its parent. Because the offspring has both parents' DNA, it is more diverse, and it has a much better chance at survival than an offspring that is identical to its parent. It is also less susceptible to disease because its alleles are so varied.

Explain this statement: "Cancer is a problem of too much cell division and too little cell death."

Cancer becomes a problem because they are able to bypass all the checkpoints of the cell cycle and able to divide at faster rates and is able to avoid the programmed death of cells.

Be able to describe the structure of DNA, including base pairing rules. Explain the importance of hydrogen bonding for Double stranded DNA.

Double helix formed by hydrogen bonds between polynucleotides which contain a phosphate group, deoxyribose sugar, and a nitrogen containing base, either adenine, thymine, cytosine, and guanine. The amount of guanine should be equal to the amount of cytosine, and the amount of adenine should be equal to the amount of thymine. Hydrogen bonds provide stability for the DNA double helix structure. It also assists in specific base formation of the DNA, which DNA requires to form.

Explain 'exponential' bacterial growth and list the 4 phases of bacterial growth.

Exponential growth is when something grows more and more rapidly until it reaches its peak point. In the case of bacterial growth, bacteria begin to multiply themselves, doubling in number every few minutes. They double themselves repeatedly until they reach their maximum limit and start to die off. (1) Lag phase- Bacterial growth starts off slow. Since they are in a new environment, it takes a while for them to get accustomed to their surroundings. They are also seeking food and nutrients that will help them grow. (2) Log phase- Once the bacteria are accustomed to their new environment, it is time to grow. They multiply themselves exponentially, doubling in number every few minutes. (3) Stationary phase- Since there are so many bacteria now, there is less food and nutrients for them to feed on. Less bacteria are formed, and exponential growth stops. (4) Death phase: Now that almost all the nutrients in the body are depleted, the bacteria have nothing else to feed on. Toxic waste also has built up over the previous phases. As a result, the bacteria die off in this final stage.

Be able to explain the role of Franklin and of Watson and Crick in determining the structure of DNA

Franklin's photo 51 is the most famous photo of DNA in history which was later shown to Watson and Crick without her knowledge. This eventually led to them creating the structure of DNA, with her information being used to support their claims.

Name 2 cell cycle checkpoints and explain what is required to "pass" the checkpoint.

G1 Checkpoint, which requires sufficient resources and no DNA damage to pass. G2 Checkpoint, which requires DNA with no damage, a complete chromosome set, and enough cell components.

Be able to explain how genetic engineering could be used to address certain biological problems. Thinking about the TED talk on gene editing, what kind of regulation (if any) would you want to see regarding this kind of technology? Be able to explain your position.

Gene editing can be used to delete certain traits from an organism, which can even be used to add traits. From what we learned from the TED talk, scientists could also use this to design mosquitoes not to carry malaria which would save millions of lives. There should be regulations on this type of technology. In the video, they mentioned that pretty much every lab has the equipment to do this, which means people can design practically anything they want. Therefore, the information on how to do this should be limited, and permission should only be given to genetically modify organisms like this if it helps the general population. There should also be a waiting time before any of these technologies are released to the public to make sure they are safe. This should be enforced by the government by having frequent checkups on the projects and thorough testing.

Understand the importance of gene expression. You should be able to explain why your parents and grandparents' "lifestyles" matter.

Gene expression is important because it allows cells to differentiate and adapt to different conditions. Our parents and grandparents lifestyles matter because it affects our choices and habits, which can affect our epigenetics.

Understand genotype and phenotype and how to report these in a cross.

Genotype is the genetic makeup, or set of alleles, of an organism. Phenotype is the observable physical and physiological traits of an organism, which are determined by its genetic makeup.

What does it mean if a characteristic displays: o Incomplete dominance o Co-dominance

Incomplete dominance is when there is a blending of the two alleles that results in a third phenotype that doesn't look like either of the parents. In codominance, both alleles are expressed together in the offspring.

Genetic diversity is increased due to crossing over, independent assortment, and random fertilization. Explain how each of these is important for genetic diversity.

Independent assortment allows for random combinations for the number of chromosomes in the system. Crossing over allows for portions of the homologous pairs to be exchanged resulting in unique sister chromatids. Random fertilization refers to the large number of potential gametes with different combinations of chromosomes.

Be able to describe or draw the cell cycle.

Interphase- 90% of cell's time is spent here G1- growth and repair S phase- DNA synthesis G2- Growth and preparation for mitosis M phase- Mitosis (cell division) which includes Prophase, Metaphase, Anaphase, Telophase/Cytokinesis

Does number of chromosomes correlate to an organism's complexity. Why or why not?

It does not. For example, a chicken has 78 chromosomes in its somatic cells. This means it inherited 39 from each parent. Meanwhile, humans have 46 chromosomes, inheriting 23 from each parent. Humans are obviously more complex than chickens, seeing as we are bigger and more intelligent beings, and yet chickens still have more chromosomes than us. Thus, more chromosomes does NOT mean an organism is more complex.

Label the appropriate structures on this diagram with the following terms: sister chromatids, centromere, non-sister chromatids, gene loci, chromosome (duplicated), homologous pair, chasma, kinetochore, and sister chromatid cohesion.

Look at pic for reference

Contrast mitosis and meiosis, including at least 5 differences. (The table in your homework is a great resource.)

Meiosis has two divisions compared to mitosis which has one. Meiosis ends with 4 cells, compared to mitosis with 2. Independent assortment does not happen in mitosis, but does in meiosis. Crossing over occurs in meiosis but does not in mitosis. Synapsis occurs in meiosis, but not in mitosis.

Be able to explain the advantage of PCR for forensic analysis. How might PCR and DNA fingerprinting be used together?

PCR allow scientists to multiple small bits of DNA with no limitation. DNA fingerprinting can be used with PCR because everyone's DNA is unique and duplicating small fragments of DNA with PCR can lead scientists to solving crimes.

Explain the normal function of tumor suppressor genes and proto-oncogenes. If both copies of a tumor suppressor gene is mutated, what is the effect on the cell? If a copy of a proto-oncogene is mutated, what is the effect on the cell? Remember the analogy of the "gas" and "brakes".

Proto-oncogenes are stimulating proteins that encode cell cycle regulators. Cell cycle regulators control the cell as it goes through the cell cycle and can either inhibit or stimulate cell cycle progression. Thus, without proto-oncogenes, these cell cycle regulators would not be encoded to do their jobs and cells wouldn't be controlled as they moved through the cell cycle. Like proto-oncogenes, tumor-suppressor genes encode cell cycle regulators. Their job is to catch mutations in these regulators which can lead to cancer. Rather than stimulating the cell cycle like proto-oncogenes, they inhibit it, which means their job is to STOP mutated genes from forming rather than make more of them. Tumor-suppressor genes normally function as "brakes" because their job is to inhibit any tumorous genes from growing. Proto-oncogenes function as "the gas" because they are an accelerator of the cell cycle, contributing to cell division. When there is a mutation in proto-oncogenes, there is a gain of function, and a protein is produced that puts the cell cycle into overdrive. When there is a mutation in a tumor-suppressor gene, there is a loss of function, but both alleles of the gene must be mutated to affect the cell cycle

The Lac Operon is a classic example of control of gene expression. Be able to explain how it works and why it is important.

The lactose bumps into the repressor, changing the shape of the repressor and allowing the RNA Polymerase to go down the DNA, making proteins. These proteins break down the lactose and the repressor returns to the original shape. The lac operon is important because it produces the enzyme necessary for the digestion of lactose.

Explain why you are not genetically identical to your siblings.

You are not genetically identical to your siblings because each parent has different versions of genes called alleles. Alleles get shuffled and moved around during sexual production, meaning the product is unique combination of traits that belong to that specific offspring alone. While you and your siblings may be genetically similar, you do not have the same combination of alleles, meaning you are not genetically identical to them. However, you may be more similar to one sibling than another if your combinations of alleles are more alike.