BIO 2133 Lecture Notes - Lecture 8: Massachusetts National Guard, Meiosis, Phenylalanine

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ceriseshark335

26 Nov 2015

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Some genes are getting modified after you get them; modifications occur to the dna. Typically, this occurs in the gametes (it may happen in somatic cells as well) If it occurs in the gametes, it can be transmitted to the next generation. If the modifications come from the mother, it is maternal imprinting. If the modifications come from the father, it is paternal imprinting. Depending on where the imprinting occurs, it may have different effects in the next generation. There are reactions in the cells that cause the methylation of nucleotides. Depending on where the methylation occurs, it could shut off a gene or turn on a gene. Most of the time it shuts off the expression of the gene. If there is methylation in your gametes, it will not necessarily affect you, but it will affect your offspring. Epigenetics has variation depending on the environment in which it occurs.

Related Questions

What are the advantages of recombination? What are the disadvantages? Under what kinds of ecological conditions (stable environment, high predation rates, exposure to rapidly evolving parasites, etc.) would you expect to favor one, or the other?

Suppose you found a region of a genome in a vertebrate that was quite large (say, 10 million base pairs) that had an extremely low recombination rate. Suggest a reason why it might be advantageous to not recombine the genes in that genomic region.

How do prokaryotes distinguish the newly synthesized strand from the old template strand? Why donât eukaryotes use the same mechanism?

What is methylation used for in prokaryotes? In eukaryotes?

What happens if mismatch repair occurs shortly after replication? How does it know which mismatched, normal base is incorrect? What happens if mismatch repair occurs long after replication has occurred?

Why does uracil DNA glycosylase have so an easier task to perform than thymine DNA glycosylase?

Describe the steps that occur following uracil DNA glycosylase activity. What needs to happen; what enzymes are involved?

What do x-rays do to DNA? What does UV radiation do? What do microwaves do?

Is there a safe minimum dose of radiation?

Why is telomerase turned off in human somatic cells? Is it turned off in mouse somatic cells? Would you expect it to be turned off in elephants? Would you expect elephants to have high cancer rates compared to mice?

Where is telomerase necessary? Is it on the leading, or lagging strand, or both? Why donât bacteria need telomerase?

Why is microsatellite instability used by physicians to measure problems with mismatch repair?

What is a genome? What is a genome made of? Describe the bacterial genome. How do bacteria reproduce? What is binary fission? Distinguish between a chromosome and chromatin. Where are chromosomes located in eukaryotic cells? What is the chromosome made of? What is a centromere? What is the centromere's role? What are sister chromatids and how do they arise? Distinguish between somatic cells and germ (gametes) cells. Describe the cell cycle. What are the different phases? What occurs during S phase? What is interphase? How is the cell cycle controlled?

Describe mitosis. What are the phases of mitosis? What occurs in each of the phases of mitosis? What is cytokinesis? How does this differ between plant and animal cells? What is a kinetochore? Where does it form? What is its role? What is the role of microtubules in mitosis? What is a centriole and what is it composed of? What is a centrosome and what is its role in mitosis? What is the metaphase plate and why is this important? What is the mitotic spindle, its role and its makeup? What defines a diploid cell? How many copies of each chromosome is in a diploid cell? What about a haploid cell? Why do the daughter cells of mitosis always have the same complement of chromosomes?

Describe meiosis. What are the phases of meiosis? What occurs in each of the phases of meiosis? Distinguish between meiosis I and meiosis II and describe how each of these processes compare to mitosis. Why do animal cells undergo meiosis? What is a gamete? What is a zygote? What are recombination, crossing-over, and chiasma? When and why does this occur? What is meant by 'homologous pair of chromosomes'? Why don't the daughter cells of meiosis have the same genetic makeup? What controls the segregation of chromosomes into the gametes?

What are genetic characters? What are genetic traits? What is an allele? What is a locus? How many alleles at each locus would a human cell have and why? Distinguish between genotype and phenotype. What is meant by a dominant gene? What is meant by a recessive gene? How do these differ? What is the genotype of a homozygous dominant organism? What is its phenotype? What is the genotype of a homozygous recessive organism? What is its phenotype? What is the genotype of a heterozygous organism? What is its phenotype? What is a genetic cross? Distinguish between the P, F1, and F2 generations. What is a true-breeding line? What is the genotype and phenotype of a cross between homozygous dominant and homozygous recessive parents? If the F1 progeny are crossed, what would be the genotype and phenotype of the F2 generation? What would be the phenotypic ratio? What would be the genotypic ratio? Be ready to generate Punnet square tests or probability analyses of crosses involving more than one genetic locus. Describe a dihybrid cross where two alleles are homozygous dominant in one parent and homozygous recessive in the other. What would be the phenotypic ratio of the F2 generation from this dihybrid cross? What is meant by independent assortment? Be prepared to calculate probabilities resulting from different crosses.

Distinguish between complete and incomplete dominance. How would incomplete dominance alter the results of a hybrid cross? What would the resulting F2 generation phenotype and genotype ratios be? What is codominance? How does this affect the results of crosses? Be prepared to determine likely blood types of parents based on the blood types of their offspring. What is a polygenic trait? What is a carrier state for a genetic disease? What is meant by linked genes? How does this affect expected outcomes of genetic crosses? How is gene linkage used for chromosomal mapping? Distinguish between autosomes and sex chromosomes. What sex chromosomes are found in women? What sex chromosomes are found in men? What are sex-linked traits? Be prepared to give the results of crosses that involve sex-linked recessive traits. What is the process of nondisjunction? What are the likely results? Why is this important? What is a Barr body? Recognize the genetic abnormality of Downs Syndrome, Turner's Syndrome, and Klinefelter's Syndrome.

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Part III â Just How âIdenticalâ Are We?

Elise had been home from college for a week, and she was still preoccupied with Shannonâs diagnosis and her own potential risk for mental illness. Elise expressed her anxiety and concerns to her mother one night after dinner. âElise,â her mother said, âyour concerns are perfectly valid, and you have every reason to want to get more information. Why donât we make you an appointment to consult with a psychiatrist?â Elise decided to make the appointment the next day. * * * * * Elise left Dr. OâBrienâs offi ce feeling that some of the weight had been lifted from her shoulders. On the car ride home, she thought about the things that Dr. OâBrien had said to her during their consultation. âIt was good of you to come in to see me, Elise. You are absolutely right to have concerns for yourself when your identical twin has been diagnosed with schizophrenia. Research shows that schizophrenia is almost 50% heritable, and since you share nearly identical DNA with your sister, that puts you at a higher risk for developing this disease as well.â âFifty percent may sound like a scary number, but remember that schizophrenia is a very complex disease, and 50% of what causes schizophrenia is due to things other than your DNA.â âWell, like what? What else could be contributing to Shannonâs schizophrenia that wouldnât necessarily aff ect me?â Elise asked. Dr. OâBrien replied, âTh ere are many, many environmental infl uences that seem to play a role in the development of this disease, such as increased stresses and anxiety, or diffi cult relationships with other people. Interestingly, there is some groundbreaking research that is going on that suggests that the environment itself might even play a role at infl uencing oneâs DNA at the molecular level. Th is concept is called epigenetics. An example of epigenetics in nature is the calico cat. Each calico cat has a unique orange and black fur color pattern because of alterations, called epigenetic changes, which occur within the cells that produce coat color during the catâs development. Research in the fi eld of epigenetics suggests that individuals with schizophrenia appear to have some of these epigenetic changes to their DNA that are due to environmental infl uences, and that these alterations could be contributing to their development of mental illness.â âBut wouldnât I also have these âepigenetic alterationsâ in my DNA?â Elise asked. âNot necessarily, because you and Shannon have not experienced completely identical environments throughout your lives. For example, you and Shannon have had diff erent teachers and jobs throughout high school. And I also understand that you spent many childhood summers with a friend and her family out in the Grand Canyon, while your sister was off at swim camps. If you are interested, I can give you some literature to read about this subject.â Elise was defi nitely interested. She took the articles and headed home.

1. Briefly describe what you know about the structure of DNA and how DNA is packaged in a cell.

2. At the molecular level, speculate on some ways that the environment might have an infl uence on DNA and its packaging

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BIO 2133 Lecture Notes - Lecture 8: Massachusetts National Guard, Meiosis, Phenylalanine

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