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BIO 101 Unit 3 Test
Question and Answer
| Question | Answer |
|---|---|
| Describe the expected outcomes of monohybrid crosses involving dominant and recessive alleles. | A monohybrid cross between two heterozygous individuals typically results in a 3:1 phenotypic ratio, where 75% display the dominant trait and 25% display the recessive trait. |
| Explain the relationship between genotypes and phenotypes in dominant and recessive gene systems. | The genotype (genetic makeup) dictates the phenotype (observable trait) based on whether alleles are homozygous or heterozygous. A single dominant allele ensures a dominant allele. A recessive allele only occurs if the genotype is homozygous recessive. |
| What Punnett squares calculate the expected proportions of genotypes and phenotypes in a monohybrid cross? | A 2 x 2 Punnett square is used for a monohybrid cross to calculate expected proportions by mapping one parent’s alleles on top and the other’s on the side. |
| Explain Mendel's law of segregation and independent assortment in terms of genetics and the events of meiosis. | Mendel’s Law of Segregation states that allele pairs separate during gamete formation (Meiosis I), ensuring each gamete carries only one allele for a trait. |
| Explain the purpose and methods of a test cross. | A test cross is a genetic method used to determine if an organism displaying a dominant trait is homozygous dominant or heterozygous. It involves breeding the unknown individual with a homozygous recessive individual. |
| Identify non-Mendelian inheritance patterns such as incomplete dominance, codominance, multiple alleles, and sex lineage from the result of crosses. | Non-Mendelian inheritance patterns are identified when cross results deviate from expected 3:1 or 9:3: 3:1 ratios, often showing blended traits (incomplete dominance), dual expression (codominance), or skewed distributions based on sex. |
| Explain the effect of lineage and recombination on gamete genotypes | Lineage and recombination dictate gamete genotypes by determining whether alleles are inherited together or shuffled. Linked genes, close on the same chromosome, stay together, and produce high-frequency parental types. |
| Explain the phenotypic outcomes of epistatic effects among genes. | Epistatic effects Epistasis when one gene masks or modifies the expression of another. Phenotypic ratios deviate from Mendelian expectations. |
| Describe the structure of DNA | DNA structure is a double helix consisting of two antiparallel strands of nucleotides. Each nucleotide contains a deoxyribose sugar, a phosphate group, and a nitrogenous base (A, T, C, G). Strands are held together by hydrogen bonds. |
| What is the story of Rosalind Franklin? | Rosalind Franklin used X-ray crystallography to produce “Photo 51”, providing critical evidence of the helical structure, diameter, and spacing of DNA, which enabled Watson and Crick to build their model. |
| Explain the process of DNA replication. | DNA replication is semi-conservative. Helicase unwinds the helix; DNA polymerase adds nucleotides in the 5’ to 3’ direction. The leading strand is synthesized continuously, while the lagging strand forms Okazaki fragments joined by ligase. |
| Describe mechanisms of DNA repair. | DNA repair mechanisms Cells use proofreading by DNA polymerase, mismatch repair and excision repair to maintain genomic integrity. |
| Explain the central dogma | The central dogma is the flow of genetic information from the DNA to RNA to the protein. DNA is transcribed into mRNA, which is then translated into a polypeptide chain. |
| Explain the main steps of transcription | Transcription RNA polymerase binds to the promoter, unwinds DNA, and synthesizes a complementary mRNA strand using the template strand. Transcription terminates when a specific sequence is reached. |
| Describe how eukaryotic mRNA is processed. | Eukaryotic mRNA processing undergoes three modification: 5’ capping (stability), 3’ poly-A tail addition (export/stability), and splicing (removal of introns by the spliceosome to join exons). |
| Describe the different steps in protein synthesis | Protein synthesis, ribosomes read mRNA in codons, tRNA molecules carry specific amino acids to the ribosome, matching their anticodons to mRNA codons, the polypeptide chain grows until a stop codon is reached. |
| Describe the genetic code and how the nucleotide sequence determines the amino acid and the protein sequence | Each codon corresponds to a specific amino acid or a stop signal. The sequence of codons in mRNA dictates the primary structure of the protein. |
| Explain the basic techniques used to manipulate genetic material. | Isolating, cutting, pasting, and amplifying DNA to analyze or alter organisms. |
| Explain molecular and reproductive cloning | Molecular cloning involves creating identical copies of specific DNA segments or genes, often using bacteria to amplify the DNA for research or biotechnology. |
| Describe uses of biotechnology in medicine and agriculture | Producing therapeutic drugs and genetic testing in medicine, alongside creating genetically modified crops for improved nutritional value in agriculture. |
| Define genomics and proteomics | Genomics is the study of an organism’s entire set of genes, focusing on DNA structure, function, and inheritance. Proteomics is the large - scale study of the full set of proteins expressed by a cell, tissue or organism. |
| Explain different applications of genomics and proteomics | To identify disease biomarkers, develop targeted drug therapies, and enable personalized medicine. |
| Describe how the present-day theory of evolution was developed. | Combining Darwin’s concept of natural selection with Mendelian genetics to explain how traits are inherited and change within populations over time. |
| Describe how population genetics is used to study the evolution of populations | Tracking changes in allele frequencies within a gene pool over time, providing a mathematical framework to understand microevolution. |
| Describe the four basic causes of evolution: natural selection, mutation, genetic drift, and gene flow | Alter allele frequencies in populations. They introduce, transfer, or randomly eliminate genetic variation, with natural selection specifically favoring adaptive traits. |
| Explain how each evolutionary force can influence the allele frequencies of a population | Evolutionary forces alter allele frequencies through chance, migration, fitness, and new variation. |
| Explain the sources of evidence for evolution | Evidence for evolution includes fossils, anatomy, molecular data, biogeography, and embryology. |
| Describe the definition of species and how species are identified as different | Species are defined by reproductive compatibility, with speciation occurring via geographic or non-geographic isolation. |
| Explain allopatric and sympatric speciation | Allopatric occurs due to geographic isolation - a physical barrier, such as a mountain, or a river splits a population. Sympatric speciation happens without physical barriers, often caused y ecological niches or genetic changes. |
| Identify common misconceptions and criticisms of evolution. | Common misconceptions often stem from confusing scientific theory with conjecture or misunderstanding the population - level nature of evolutionary change. |
Created by:
ajpatton08