BIO130H1 Study Guide - Midterm Guide: Okazaki Fragments, Dna Replication, Proteome

QUESTION 10

If you can drink milk as an adult, it means that you have inherited a mutation in the promoter of your lactase gene (the gene that encodes the enzyme you need to break down lactose). Predict the effect of this mutation:

1.2 points

QUESTION 11

A competitive inhibitor is decreasing the activity of an enzyme. Predict the effect of adding more substrate to the reaction.

1.2 points

QUESTION 12

What determines where in the genome a transcription regulator will bind?

1.2 points

QUESTION 13

What is the basic premise of cell theory?

1.2 points

QUESTION 14

What is the benefit of using BOTH the lac activator and the lac repressor to control gene expression?

1.2 points

QUESTION 15

What is the histone code used for?

For years we have been able to analyze the fossils of extincthumans like those of Neanderthals. Their bones gave us clues to howthey looked, how they lived, and how they might be related to us.In the last few years, we have been able to get a better view intothese extinct species and their relationship to our species. Thanksto next generation genomic sequencing technologies, we have beenable to obtain genetic data on Neanderthals, Denisovans and othersthat have allowed us to make direct comparisons between our speciesand theirs. In addition, we have been able to observe the presenceof DNA from these extinct species within our own genomes which tellus that we had kids with these now extinct humans.

If we take Neanderthal DNA as an example, we find that we share99.5 percent of our DNA with them. Which means that we andNeanderthals were separated from each other for more than 500,000years. This also means that we were genetically similar enough tobe able to have offspring with each other. We see evidence of thisgenetic introgression between us and Neanderthals when we look atour DNA. Interestingly, if we obtain one thousand DNA samples fromGrossmont College students, we estimate that we would be able toextract at least 20% of the Neanderthal genome from them. Thismeans that 20% of our collective nucleotide sequences are sharedwith Neanderthals but this doesn’t mean that 20% of our genes areNeanderthal specific genes. Of the twenty-one thousand genes thatNeanderthals had, only a few dozen of their genes survive withinour genome. The same holds true for Denisovans. What is moreinteresting is that older versions of ourselves have a tendency tohave higher levels of DNA from extinct humans compared toourselves. In other words, over the course of thousands of years wehave been slowly weeding out the DNA of the other humans from ourgenome in favor of our genes.

One basic question that we might like to ask is why have we beenlosing Neanderthal and Denisovan genes over time? Also, why do westill have a significant amount of DNA segments that don’t seem tobe going anywhere? The answer to this has to do with selection.

The answer to the first part of the question has to do with thefact that we were not fully genetically compatible with the otherhuman species to begin with. Basically, to have had Neanderthal orDenisovan genes in the past meant that an individual's level offitness was reduced. To get rid of their genes in favor of our ownwould mean that the relative fitness of individuals would increaseovertime.

The answer to the second question has to do with the fact thatDNA segments from Neanderthals and Denisovans that did not code forproteins remained because there was little selective pressureagainst them. As far as genes are concerned, the only Neanderthaland Denisovan genes that remain only exist because they had aselective advantage or at least have been neutral to ourspecies.

DNA segments that that were neutral or that had a selectiveadvantage, whether genes or not, simply remained because they wereadvantages or there was little selective pressure against them.

Your task for this week is to look for information about oneNeanderthal or Denisovan gene that survive within our species andto tell me what function that gene has and how that gene mayincrease the fitness of modern human populations.

• In your post, discussONE Neanderthal orDenisovan gene that is currently found within our species.
  • Tell us about the gene and its function. Explain what it doesfor us. (Make sure you give a citation.)
  • Explain in your own words any possible advantages that yourNeanderthal or Denisovan gene might have. Make sure you give ininformed opinion that is grounded in your research.

2. Explain the structural role of the four different categories of biomolecules within a cell.

3. Explain how water, a steroid hormone, and a monosaccharide are transported into a cell down their concentration gradient and explain why the different molecules are transported in different ways.

4. Explain which forms of transport require energy and why, and how ATP facilitates energy-dependent transport.

5. All of the different types of biomolecules can serve as energy sources. Explain which biomolecules are catabolized in which metabolic pathways.

6. Whether or not the cellular machinery is in place for particular catabolic reactions to go forward depends on which genes are being expressed. Explain the different points, in a eukaryotic cell, at which gene expression might be regulated, and how.

7. The primary tasks of any organism are survival and reproduction. Acquiring biomolecules and catabolizing them to generate energy is a major factor in survival. For reproduction to occur, DNA must first be replicated so that it can be passed on. Describe the process of DNA replication.

8. If you wanted to replicate DNA artificially in large quantities, how would you go about it?

9. Once DNA has been replicated, what is the sequence of events in the cell cycle and in cell division that produce the gametes for sexual reproduction? Where does this event fit, along with other cell cycles, in the life cycle of the organism?

10. A number of physical traits in humans are controlled by a simple dominant/recessive relationship between two alleles; here are some examples (dominant/recessive):

Widow’s peak/no widow’s peak

Free earlobes/attached earlobes

Cleft chin/no cleft chin

Dimples/no dimples

Freckles/no freckles

Naturally curly hair (really curly, not wavy)/straight hair

Make a pedigree of your immediate family indicating the possible genotype of each family member (for the six genes listed above) based on their phenotype. If you are adopted, indicate the possible genotypes and phenotypes of your parents. You may make this part up.