Answer:
The delivery of the paternal genome to the egg is a primary goal of fertilization. In preparation for this step, the nucleus of the developing spermatozoon undergoes extensive morphological and biochemical transformations during spermatogenesis to yield a tightly compacted sperm nucleus. These modifications are essentially reversed during fertilization. As a result, the incorporated sperm nucleus undergoes many steps in the egg cytoplasm as it develops into a male pronucleus. The sperm nucleus (1) loses its nuclear envelope, (2) undergoes nucleoprotein remodeling, (3) decondenses and increases in size, (4) becomes more spherical, (5) acquires a new nuclear envelope, and (6) becomes functionally competent to synthesize DNA and RNA. These changes are coordinate with meiotic processing of the maternal chromatin, and often result in behaviors asynchronous with the maternal chromatin. For example, in eggs fertilized during meiosis, the sperm nucleus decondenses while the maternal chromatin remains condensed. A model is presented that suggests some reasons why this puzzling behavior exists. Defects in any of the processes attending male pronuclear development often result in infertility. New assisted reproductive technologies have been developed that ensure delivery of the sperm nucleus to the egg cytoplasm so that a healthy embryo is produced. An emerging challenge is to further characterize the molecular mechanisms that control sperm nuclear transformations and link these to causes of human infertility. Further understanding of this basic process promises to revolutionize our understanding of the mystery of the beginning of new life.
Explanation:
The delivery of the paternal genome to the egg is a primary goal of fertilization. In preparation for this step, the nucleus of the developing spermatozoon undergoes extensive morphological and biochemical transformations during spermatogenesis to yield a tightly compacted sperm nucleus. These modifications are essentially reversed during fertilization. As a result, the incorporated sperm nucleus undergoes many steps in the egg cytoplasm as it develops into a male pronucleus.
Based on the diathesis-stress model schizophrenia is the result of interaction between environmental and biological/genetic factors. According to this model, when the combination of the predisposition (diathesis) and the stress (biological, social, and psychological stressors) exceeds a threshold, the person will develop a disorder.
The correct answers are:
- Methylation of histone tails in chromatin can promote condensation of the chromatin.
- DNA is not transcribed when chromatin is packaged tightly in a condensed form.
- Acetylation of histone tails is a reversible process.
- Some forms of chromatin modification can be passed on to future generations of cells.
- Acetylation of histone tails in chromatin allows access to DNA for transcription.
Histone modifications are post-translational modifications of histone protein that can affect gene expression by altering chromatin structure or recruiting histone modifiers.The most common modifications are methylation, phosphorylation, acetylation and ubiquitylation. All of them affect the binding affinity between histones and DNA and thus loosening (gene activation) or tightening (gene repression) the condensed DNA.
Histone methylation is a transfer of methyl group by histone methyltransferases to lysine or arginine amino acid of protein. Effect of methylation depends on the type of protein that is modified. Demethylation is the reverse process.
Histone acetylation is the process of adding of an acetyl group(by histone acetyltransferases) to histone proteins and it can also activate or inhibit the gene expression. Deacetilation is reverse process.
Name
Date: May 1st
Date completed: May 12th
Hypothesis: I believe the seeds will grow 1-2 feet based on my research
Procedure: I put my seeds in small pots and put on a self I have outside in the sun. They can absorb good sunlight this way
Growth of seeds: all varied but stayed within 3 feet
Type of seeds:
1. Cornflowers
Growth
Day 3: about 2 inches
Day 6: about 5 inches
Day 9: about 12 inches
Day 12: about 22 inches
Day 15: about 34 inches
Interpretations: cornflower- the meaning is wealth, prosperity, fortune and friendship.
I don’t know what was asked in the lab...
Conclusion: my hypothesis was kind of correct. My cornflowers grew to be over 2 feet, but not by much. Some even stayed under, but not by much I say again. This was a fun and educational experience and I learned a lot about this wonderful plant. I hade no idea that it was even a real thing before this project! I learned that different flowers grow at different paces, even if they get the same amount of sunlight and water.
