Rapid Learning Center Chemistry :: Biology :: Physics :: Math Rapid Learning Center Presents Teach Yourself AP Biology in 24 Hours 1/35 *AP is a registered trademark of the College Board, which does not endorse, nor is affiliated in any way with the Rapid Learning courses. Molecular and Human Genetics AP Biology Rapid Learning Series Wayne Huang, PhD Andrew Graham, PhD Elizabeth James, PhD Casandra Rauser, PhD Jessica Habashi, PhD Sara Olson, PhD Jessica Barnes, PhD Rapid Learning Center www.rapidlearningcenter.com/ Rapid Learning Inc. All rights reserved. Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 1
Learning Objectives By completing this tutorial, you will learn about: Structure and Function of DNA Structure of RNA Protein Synthesis Molecular Genetics: Northern Blot, Southern Blot, and DNA Cloning Human Genetics 3/35 Concept Map Karyotype Genetics Human Genetics Sex-linked Traits Molecular Genetics mrna Structure of RNA rrna Structure and Function of DNA trna 4/35 Functional Protein Synthesis Protein Translation Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 2
Structure and Function of DNA Molecular Genetics, DNA 5/35 Molecular Genetics Molecular genetics is a division of biology that is involved in the study of gene structure and function. The study of gene structure has lead to a further understanding of certain disease processes, as well as potential gene therapies. 6/35 Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 3
Cell Nucleus The cell nucleus is usually near the center of the cell; it contains the majority of the genetic material in a cell. Within the nucleus, the DNA is compacted and organized into chromosomes. Also within the nucleus is the nucleolus. The nucleolus has no true membrane surrounding it, and this is where ribosomes are produced. 7/35 The cell nucleus is surrounded by a nuclear envelope, which contains pores to limit flow in and out of the nucleus. The pores allow small water-soluble molecules to diffuse into the nucleus but prevent large molecules, such as proteins, from randomly entering the cell. The outside of the nuclear membrane is continuous with the endoplasmic reticulum and the attached ribosomes. Question: Challenge Define, in general, what the nuclear envelope is. The cell nucleus is usually near the center of the cell; it contains the majority of the genetic material in a cell. The cell nucleus is surrounded by a nuclear envelope, which contains pores to limit itflow in and out of fthe nucleus. The pores allow small water-soluble molecules to diffuse into the nucleus but prevent large molecules, such as proteins, from randomly entering the cell. 8/35 Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 4
Nucleic Acids: DNA Deoxyribonucleic acid (DNA) is the blueprint of life; it is present in almost every cell in the body. A copy from a male donor and a copy from a female donor, through fertilization, can create a human being. Structurally, DNA is made up of 2 polymers of nucleotide in a complementary-based pair double helix. These anti-parallel strands run in opposite direction from one another and are held together through hydrogen bonds. 9/35 The structure of the double helix provides a major groove in which transcription factors can bind and impact gene expression. The four different DNA nucleotides follow a strict base pairing arrangement: Guanine Cytosine (3 hydrogen bonds) and Adenine Thymine (2 hydrogen bonds). Genetic Code The genetic code dictates nucleic acid structure and function. The formation of the end-product amino acids and proteins is controlled by the genetic code set of rules. Within the code are codons, which are a nucleic acid sequence that specifies the formation of an amino acid. 10/35 The genetic code allows for more than one codon to specify an amino acid. However, there is no ambiguity, as each codon specifies only one amino acid, depending on the reading frame or the context each codon is read in. Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 5
Semi-Conservative DNA Replication DNA replication must take place in order for a cell to divide during mitosis. During DNA replication, the parental DNA is separated and each parent strand acts as a template for the formation of a new complementary strand. This is known as semi-conservative DNA replication. Each daughter cell receives one strand from the parental cell DNA, along with its one entirely new strand. 11/35 Question: Challenge Define, in general, what the genetic code is. The genetic code dictates nucleic acid structure and function. The formation of the end-product amino acids and proteins is controlled by the genetic code set of rules. Within the code are codons, which are a nucleic acid sequence that specifies the formation of an amino acid. 12/35 Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 6
RNA and Protein Synthesis Structure of RNA, Protein Synthesis 13/35 Nucleic Acids: RNA Ribonucleic acid (RNA) is usually singlestranded. It is made from a DNA blueprint. RNA translates the message from the DNA to produce the correct protein. The different types of RNA include: (1) Messenger RNA (mrna) binds to ribosomes and provides the template for protein translation, (2) Transfer RNA (trna) transfers a specific amino acid to the growing gpolypeptide p protein at the site of translation, (3) Ribosomal RNA (rrna ) the central component of the ribosome. It decodes messenger RNA and provides the actual binding site for the incoming trna. 14/35 Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 7
RNA Transcription Genes drive protein synthesis in the following manner: DNA is transcribed into RNA, and then RNA is translated into proteins. RNA is produced d by an enzyme known as RNA Polymerase. RNA polymerase transcribes a complementary base-paired RNA strand. During the base pairing, Uracil is substituted in the growing RNA strand for Thymine. The RNA strand produced by this process is known as messenger RNA (mrna). The process involves initiation, elongation of the transcript, and termination; it takes place in 5ʹ to 3ʹ direction. Only 1 DNA strand (template strand) is transcribed and, due to the complementary base pairing, the original instructions of the DNA are carried out. 15/35 Types of RNA There are three types of RNA: (1) Ribosomal RNA (rrna) ribosomal RNA is the central part of the ribosome, along with its associated proteins. rrna decodes messenger RNA into the individual amino acids. 3) Messenger RNA (mrna) messenger RNA is the blueprint necessary for protein production. It binds to the ribosome and provides the codon, which is matched with the anti-codon of trna. This ensures the protein is assembled in strict 16/35 accordance with the DNA template. (2) Transfer RNA (trna) transfer RNA contains an anti-codon region, which interacts with the appropriate codon on messenger RNA to ensure the proper amino acid is added to the growing protein. Transfer RNA has a single amino acid, which transfers to the growing protein. Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 8
Question: Challenge What are the 3 types of RNA? (1) Messenger RNA (mrna) binds to ribosomes and provides the template for protein translation, (2) Transfer RNA (trna) transfers a specific amino acid to the growing gpolypeptide p protein at the site of translation, (3) Ribosomal RNA (rrna ) the central component of the ribosome. It decodes messenger RNA and provides the actual binding site for the incoming trna. 17/35 Protein Translation Protein translation is the process whereby amino acids are assembled into a polypeptide chain or protein, based on the DNA code. The process involves the following steps: (1) Initiation Once the ribosome is assembled, initiator trna, carrying methionine, binds to the start site on the mrna. (3) Termination Translation stops when one of three termination codons moves into the A site on the mrna. Release factors trigger the 18/35 release of the new protein. (2) Elongation After the initiator trna is bound to the P site, the next trna is able to bind to the A site. Amino acids are added to the growing polypeptide chain by forming a peptide bond with the previous amino acid. Next, the mrna is shifted by one codon, freeing up the A site to receive the next amino acid. Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 9
Molecular Genetic Techniques Cell Culture for Nucleic Acid Samples, Northern Blot and Southern Blot 19/35 Tissue Cell Culture Tissue culture is the process of growing cells and established cell lines in a controlled environment. Cells are grown in specific media, containing the necessary nutrient supplements and additives, such as hormones and growth factors. 20/35 Cells are grown in flasks, coated plates with individual wells, or in petri dishes. Most cells can be maintained in log phase growth by replacing the growth media when needed and storing the cells in humidified incubators at 37 C to simulate body temperature. Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 10
Nucleic Acid Extraction After cells are harvested by enzymatic digestion, they are prepared for nucleic acid extraction. First, the cells are broken or lysed, and then detergents and proteases are used to remove membrane lipids and unwanted proteins. For extracting DNA, graded alcohol solutions are used to precipitate the DNA out of solution. To detect DNA, light absorption spectroscopy can be used. Extracting RNA from cells requires the deactivation of ribonuclease enzymes, which would degrade the RNA sample. Usually, this takes place in the lysis buffer when the RNA extraction begins. 21/35 RNA Extraction: Northern Blot The Northern Blot technique allows the experimenter to detect and study the RNA from cells. In general, total RNA is extracted from cells, and then mrna can be isolated to study gene expression. 22/35 Once the RNA sample is extracted from the cells or tissue, it must be separated to probe for the RNA of interest. RNA can be separated using gel electrophoresis. Gel electrophoresis involves applying a current to a gel matrix containing the RNA sample. RNA samples move through the gel and separate into bands based on their charge to mass ratio. After separation, they can be transferred to a blot membrane and probed for the RNA of interest using a specifically labeled probe. Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 11
DNA Extraction: Southern Blot A Southern Blot is a technique to study the presence and levels of DNA sequences in cells under certain conditions. Similar to Northern blots, after the DNA is extracted from the cells, it is usually separated using gel electrophoresis. After using a specific probe to identify the DNA of interest, the results appear as bands. The bands are a result of autoradiography or other detection methods. 23/35 Gene Cloning Gene cloning can be used to create many copies of a defined DNA sequence. The sequence of DNA or gene can then be used to test the effect of over-expression or deletion of that gene from the genetic material of cells. First, the DNA sequence of interest must be isolated. Next, the sequence is typically ligated into a plasmid, which then is used to transform the target cell or bacteria for gene production. 24/35 Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 12
Question: Challenge Define, in general, the method used to extract and investigate the DNA in cells. A Southern Blot is a technique to study the presence and levels of DNA sequences in cells under certain conditions. Similar to Northern blots, after the DNA is extracted from the cells, it is usually separated using gel electrophoresis. After using a specific probe to identify the DNA of interest, the results appear as bands. The bands are a result of autoradiography or other detection methods. 25/35 Human Genetics Karyotype, yp Population Genetics, and Genetic Counseling 26/35 Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 13
Karyotype Cytogenetics involves the study of chromosomal abnormalities and deficiencies. As part of these studies, a karyotype is prepared. A karyotype is a visual pattern of the chromosomes within cells. By using stains and probes, whole chromosomes, short and long arms, and even small regions on chromosomes can be visualized. Normally, there are 22 pairs of autosomes and 1 pair of sex chromosomes, for a total of 46. Karyotypes can reveal the sex of the individual, as well as more finite details of the health. An example would be Down Syndrome, which is evidenced by 3 copies of all or part 27/35of chromosome 21. Sex-Linked Traits: X-Linked For example: A gene (e.g. hemophilia) is recessive and located on the X chromosome; this is the inheritance pattern for that gene. 28/35 X-linked means the gene of a particular trait resides on the X chromosome. Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 14
Y-Linked Traits Y-linked traits appear only in males and are only passed from father to son. Males contribute either an X or Y chromosome during fertilization. If an X chromosome is contributed, the genotype will be XX female; if a Y is contributed, the genotype will be XY, resulting in male offspring. Y-linked genes reside only on the Y chromosome. There are very few Y-linked traits. 29/35 A pedigree of Y- linked traits Population Genetics The study of gene allele frequency distribution across a population is known as population genetics. This type of study addresses changes in populations, such as adaptation and speciation. The frame work of population genetics, involving the mapping of a set of genotypes to a set of phenotypes, is called a genotype-phenotype map. Genotype-phenotype maps can depict changes in phenotype or morphology, even though the genotype is very similar or identical in some cases. 30/35 Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 15
Genetic Counseling Genetic counselors discuss and advise patients about the risk of potential inherited disorders. The likelihood of disease transmission in children and the effects of the inherited disease or disorder are presented. In the USA, genetic counselors are trained in genetic disease outcomes, possible treatments, and heritability. This education is in addition to their previous biology, psychology or medical background. They are certified by the American Board of Genetic Counseling. 31/35 Question: Challenge What is the inheritance pattern of a Y-linked trait? Males contribute either an X or Y chromosome during fertilization. If an X chromosome is contributed, the genotype will be XX female; if a Y is contributed, the genotype will be XY, resulting in male offspring. Y-linked traits appear only in males and are only passed from father to son. 32/35 Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 16
Learning Summary Genetic counselors discuss and advise patients about the risk of potential inherited disorders. The cell nucleus is usually near the center of the cell; within the nucleus, the DNA is compacted and organized into chromosomes. RNA is usually single-stranded. It is made from a DNA blueprint. RNA translates the message from the DNA to produce the correct protein. 33/35 The genetic code dictates nucleic acid structure and function. The formation of the end-product amino acids and proteins is controlled by the genetic code set of rules. Y-linked traits appear only in males and are only passed from father to son. Y-linked genes reside only on the Y chromosome. There are very few Y-linked traits. Congratulations You have successfully completed the tutorial Genetics I: Molecular and Human Genetics Rapid Learning Center Rapid Learning Inc. All rights reserved. :: http://www.rapidlearningcenter.com 17
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