Test 3 review
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This 13 page Study Guide was uploaded by Trung Do on Sunday February 28, 2016. The Study Guide belongs to bio 1134 at Mississippi State University taught by Evan Kaplan in Winter 2016. Since its upload, it has received 29 views.
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Date Created: 02/28/16
Chapter 11 – Nucleic Acid Structure, DNA Replication, and Chromosome Structure 1. What is DNA and what does DNA stand for? Deoxyribonucleic acid. It holds our genetic material. It meets the following criteria: information, replication, transmission, and variation 2. What is the structure of the DNA nucleotide(three parts)? DNA is made of a fivecarbon sugar (deoxyribose), a phosphate group, and a nitrogenous base 3. What are Chargaff’s rules? 1. The amount of adenine equals the amount of thymine 2. The amount of guanine equals the amount of cytosine 3. Human DNA is 30% A/T and 20% G/C 4. What was the role of Watson and Crick in determining the overall structure of the DNA molecule? They used known data to determine that the structure of DNA was made up of two chains of nucleotides intertwined 5. Explain how the structure of the DNA molecule is analogous to a “rope” ladder. The sugar phosphate component of each nucleotide makes up the handrails or sides of the ladder. Pairs of nitrogen bases, one from each strand, oppose each other to form the steps. The ladder twists every ten bases. 6. What does basepairing is complementary mean? What are the basepairings? Bases are paired in specific combinations. Adenine is paired with thymine(two hydrogen bonds) and guanine is paired with cytosine(three hydrogen bonds). Nitrogen bases opposing each other form hydrogen bonds to connect the two strands. Although the strands are not identical, they each specify each other by base pairing. 7. What does antiparallel mean in the context of DNA? How do you determine the 5’ and the 3’ end? Antiparallel means opposite directions. One end of DNA terminates in a hydroxyl group attached to a Carbon #3 and other end terminates in a phosphate group attached to a Carbon #5. 8. How does the leading strand of DNA get replicated? What is the semiconservative model of replication and in what stage of the cell cycle does this occur? When a cell copies a DNA molecule, the two strands separate (parental strands) and each strand serves as a template for ordering nucleotides into a new complementary strand. One at a time, nucleotides lines up along the template strand according to the base pairing rules and are joined by a phosphodiester bond. When the double helix replicates, each daughter molecule has one old strand and one new one. 9. What are the major “players” involved and what are their roles (helicase, DNA single stranded binding proteins, primase, primer, DNA polymerase)? 1. Helicase – helicase is an enzyme that is used in the denaturation of DNA (first step of replication 2. DNA singlestranded binding proteins – these bind to the separated strands to keep them from reforming the double helix 3. Primase – an RNA polymerase, makes the primer 4. Primer – a short segment of RNA which starts a new chain of nucleotides on which DNA polymerase can build. 5. DNA polymerase – this catalyzes the elongation of new DNA. Synthesizes DNA in the leading and lagging strands, removes RNA primers, fills in the gaps 10. What are telomeres? What is their function and the role of telomerase? Telomeres are specialized structures at the end of DNA molecules composed of short repeated sequences of DNA. Telomeres protect genes from being eroded through multiple rounds of DNA replication. 11. What does it mean by DNA having proofreading capability? When DNA polymerase is moving along the DNA strand during replication, unstable bonds form if the wrong base is inserted. When the wrong base is inserted, a separate enzyme moves in to correct the error. Chapter 12 – Gene Expression at the Molecular Level 1. What is the central dogma? Each protein is coded by a specific segment of DNA called a gene. Gene expression is the process by which info from a gene is used in the synthesis of a functional gene product. The expression of genes at the molecular level affects the structure and function of the cells. Two steps are involved in gene expression: transcription and translation. Transcription is DNA is copied into RNA and the RNA moves to the cytoplasm. This occurs in the nucleus. Translation occurs in the cytoplasm and is when RNA is converted to form polypeptide chains. These polypeptide chains fold to form proteins. 2. What is the structure of the RNA nucleotide and molecule (three parts)? Compare and contrast with the DNA nucleotide and molecule. RNA is chemically similar to DNA. It contains ribose as its sugar instead. It substitutes uracil for thymine. It consists of a single strand usually. There are many different types of RNA with different functions. 3. What are the three main classes of RNA and their functions? 1. Messenger – the transcript of the coding strand of DNA involved in “carrying” the proteinbuilding instruction. This acts as a bridge between DNA and protein synthesis. It serves as the template for the synthesis of proteins. 2. Ribosomal – the major component of ribosomes involved in the process of assembling amino acids into proteins 3. Transfer – delivers amino acids to ribosomes for the process of assembling amino acids into proteins 4. What is transcription (three stages) and where does it occur? Compare and contrast transcription with DNA replication. 1. Initiation – Several different transcription factors (proteins) bind to a specific nucleotide sequence before the beginning of the gene, called the promoter. This initiates the binding of RNA polymerase to begin transcription of the gene. 2. Elongation – As RNA polymerase moves along the DNA, it unwinds the double helix about 10 base pairs at a time, adding on RNA nucleotides to the 3’ end of the growing strand. 3. Termination – RNA polymerase transcribes a terminator nucleotide sequence found at the end of the gene in the DNA. 10 to 35 nucleotides after this sequence, the RNA transcript is cut from the enzyme. It is then processed/modified to help protect the RNA and direct it to where it needs to go for translation. This occurs in the nucleus. RNA polymerase doesn’t proofread like DNA polymerase so errors occur. 5. What is the genetic code? The order of nucleotides of the DNA determines the order of amino acids in the protein. The genetic code specifies which amino acids will be used to build a protein. The genetic code is read in increments of three nucleotide bases called codons. The code is read continuously. 6. What is a codon? A codon is an increment of three nucleotide bases that specifies one of the 20 amino acids to be incorporated during translation at a corresponding position along the polypeptide. 7. What is translation and where does it occur in the cell? Translation is the process of making a polypeptide chain from mRNA. 1. Initiation – brings together mRNA, tRNA with the first amino acid, and the ribosome at the start codon 2. Elongation – consists of a series of cycles as each amino acid is added to the proceeding one 3. Termination – when one of the three stop codons is reached, the translation complex is released. tRNA molecules are transcribed in the nucleus. Once is reaches the cytoplasm, each tRNA is used repeatedly. 8. What is the relationship between ribosomes, protein synthesis, and the endomembrane system? Ribosomes make proteins. Proteins made from bound ribosomes enter the endomembrane system where they are modified and shipped out. Chapter 14 and 15.4 – Mutation, DNA Repair, and Cancer 1. What is a mutation? A mutation is a heritable change in the genetic material 2. What are the two categories of mutations? 1. Good – chimp to human 2. Bad – extinction of genetic disorder 3. What is the basepair substitution and what effect will it have on protein function (how does it affect the codons)? a basepair substitution is when one base is wrongly paired with another base during replication. This can little to no impact. Some alterations indicate the same amino acids because of redundancies. Other changes lead to switches to similar amino acids. Some have drastic impacts such as sicklecell anemia. 4. What is a frameshift mutation (how does it affect the codons)? Frameshift mutations involve the addition and deletions of nucleotides in a gene. This can have a disastrous effect on the resulting protein more often than substitutions. Unless formed in groups of three, all nucleotides downstream will be improperly grouped leading to a nonfunctional protein. 5. What are chromosomal mutations and what are the four categories? 1. Deletion – loss of some portion of the chromosome (lethal or cause serious disorder) 2. Duplication – repeated two or more times in a row (can occur in normal and abnormal chromosomes 3. Inversion – chromosomal rearrangement when a segment of a chromosome is reversed and put back 4. Translocation – a piece of one chromosome is broken off and attached to another Chromosomal mutations are alterations in chromosomal structure by external sources or internal processes 6. How do mutations occur? Can be two ways: 1. Spontaneous – result of problems during DNA replication. Also result of metabolic processes within a cell that produces toxic material 2. Induced – Occur as a result of exposure to mutagen 7. What is a mutagen and how does it mutate DNA? A mutagen is a chemical that induces mutations in a cell. It can insert itself into a cell and interfere with DNA replications by inserting itself into DNA and distorting the double helix. 8. How is a carcinogen different than a mutagen? Carcinogens are mutagens that cause cancer. All carcinogens are mutagens but not vice versa. Chapter 15 – An Introduction to Energy, Enzymes, and Metabolism 1. What is meiosis? a reduction division 2 n 2. Which cells does it occur to? Gametes 3. What stages are involved in meiosis (phases and sub phases)? 1. Interphase 2. Meiosis I Prophase I – individual chromosomes become visible while the nuclear membrane begins to dissolve and centrioles move to opposite sides. Spindles begin to form. Homologous chromosomes pair with one another(synapsis). Crossing over may occur Metaphase I – Synapsed pairs of chromosomes move to the equatorial plate. Centromeres of each chromosome attach to the spindle. The difference from mitosis is that the homologous chromosomes are still attached. Chromosomes randomly align along the metaphase plate Anaphase I – the chromosome number is reduced from diploid to haploid. Essentially the pairs split up. Each pair of homologous chromosomes move to opposite poles. Each chromosome is independently attached to a spindle at the centromere. The centromeres do not replicate at this stage. Telophase I – chromosomes uncoil and become long thin threads. The nuclear envelope reforms around each set of chromosomes. Cytokinesis – divides the cell into two daughter cells 3. Meiosis II – two daughter cells formed in Meiosis I undergo division similarly to Mitosis. Previous to this phase, there is no chromosome duplication Prophase II – the nuclear envelope breaks down and spindles are formed Metaphase II – this will be a typical metaphase because the chromosomes are attached by their centromeres to the spindle. The chromosomes move to the equatorial plate. Pairs of chromosomes are not attached therefor each chromosome moves as a separate unit. Chromosomes randomly align. Anaphase II The difference between Anaphase I and II is that in II, the centromere of each chromosome divides. The chromatids (daughter chromosomes) move to opposite poles as in mitosis. There are no paired homologs at this stage. Telophase II – the nuclear envelope reforms. Chromosomes uncoil. Nuclei reform. The spindles disappear. Cytokinesis – same Four haploid cells are formed (egg or sperm). In humans, only 1 functional egg forms. The other 3, known as polar bodies, disintegrate. 4. What is synapsis? Homologous chromosomes pair with one another 5. What is crossing over? Two parts of a chromosome switch places. 6. What is independent assortment? when two or more traits are inherited during meiosis, they sort independently of one another 7. How does meiosis (and other mechanisms) lead to genetic diversity? it allows genes from both the mother and father to cross over to the child 8. What is nondisjunction? Failure of chromosomes to move to opposite poles during anaphase I or II. Usually results in cell death. If the sperm or egg carrying the wrong number fertilizes the gamete, abnormalities can occur 9. Compare and contrast mitosis to meiosis. The chromosome number is reduced by half in meiosis, not mitosis. Mitosis is for somatic cells. Meiosis is for sex cells. Mitosis produces identical daughter cells. Meiosis does not. Meiosis is two consecutive divisions resulting in four cells. Chapter 16 – Simple Patterns of Inheritance 1. What is blending inheritance and how did the findings of Mendel disprove this theory? this theory was that traits inherited were an intermediate between the two parents. Mendel showed that specific traits were passed on, not intermediates, in pea plants. 2. What is the role of Mendel’s “unit factors” in heritability? Mendel hypothesized that sperm and eggs carried info that was passed onto offspring in the form of distinct “unit factors” now genes. 3. What are genes? Organized units of heredity, comprised of DNA, that code for information about specific traits 4. What are alleles? In diploid organisms, each individual carries two genes for a given characteristic, called alleles. 5. What is a genome? The complete genetic composition of a cell species 6. What is a gene’s locus? The physical location of a gene on a chromosome 7. What does homozygous mean? Heterozygous? Homozygous – both alleles of a gene are identical Heterozygous – both alleles of a gene are different 8. What is the genotype? The genetic composition of an organism 9. What is the phenotype? The manner in which each combination of alleles are expressed 10. What is the dominant allele? The allele whose phenotypic trait is expressed 11. What is the recessive allele? The allele which is masked and not expressed 12. What is Mendel’s Law of Segregation? The two alleles of a gene separate during the formation of gametes so that every gamete receives only one allele 13. What is the relationship between this law and meiosis? The law of segregation is a result of what happens during meiosis. Mendel did not known anything about meiosis. 14. What is the purpose of a Punnett Square? A Punnett square is a way to predict the outcome of a simple genetic cross between individuals of known genotype 15. What is Mendel’s Law of Independent Assortment? the alleles of each gene assort independently of each other during gamete formation 16. What is the chromosome theory of inheritance? Chromosomes contain the genetic material (DNA). Chromosomes are replicated and passed from parent to offspring. The nucleus of a diploid cell contains two sets of chromosomes, found in homologous pairs. At meiosis, one member of each chromosome pair segregates into each daughter nucleus. Gametes are haploid cells that combine to form a diploid cell during fertilization, with each gamete transmitting one set of chromosomes to the offspring. 17. What are the sex chromosomes in humans and how do they determine sex? Sex chromosomes determine gender. The genes that determine males are located on the Y chromosome. Human males have XY chromosomes. Females have XX chromosomes. As a result of meiosis, all eggs contain one X chromosome. Half sperm contain one Y chromosome. The other half contain one X chromosome. 18. What is the importance of the SRY gene? The Y chromosome has over 300 genes. The SRY gene is the master gene for male sex determination. If the gene is present, testis form. If the gene is not present, ovaries form. 19. What are the four heritable variations and specific examples of each that are not predicted by Mendelian genetics? 1. Pleiotropy – multiple effects a gene may have on phenotype (ex: phenylketonuria or PKU) 2. Incomplete dominance – one allele of a pair is not completely dominant over its partner so the phenotype is a combination of the two. (ex: Pink fouro’clocks and red snapdragons) 3. Multiple alleles and codominance – there are more than two alleles for a particular gene, and depending upon which of those alleles you inherit, will determine phenotype (ex: ABO blood type) 4. The environment – sometime the environment plays a role in expression of a gene (ex: fur color in Himalayan rabbits and Siamese cats)
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