Genetics: DNA, RNA, and Inheritance

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Questions and Answers

Describe how semi-conservative replication ensures genetic continuity between parent and daughter cells.

Semi-conservative replication results in two DNA molecules, each containing one original strand and one newly synthesized strand. This preserves the original genetic information in each new molecule.

Explain the roles of mRNA, tRNA, and ribosomes in the process of translation.

mRNA carries the genetic code from DNA to the ribosome. tRNA brings specific amino acids to the ribosome, matching its anticodon to the mRNA codon. Ribosomes facilitate the binding of tRNA and catalyze the formation of peptide bonds between amino acids.

How does the environment (internal or external) influence gene expression and ultimately affect an organism's phenotype?

Environmental factors can activate or repress gene expression. For example, temperature can influence sex determination in some reptiles, or the availability of nutrients can affect plant growth. These changes in gene expression lead to different physical traits, or phenotypes.

A man with Type A blood and a woman with Type B blood have a child with Type O blood. What are the genotypes of the man and the woman? (Blood type is determined by multiple alleles)

The man's genotype is $I^Ai$ and the woman's genotype is $I^Bi$. Signup and view all the answers

Explain how DNA fingerprinting can be used to determine genetic relationships or identify individuals. What aspects of DNA are analyzed, and how do they differ among individuals?

DNA fingerprinting analyzes highly variable regions of DNA, such as short tandem repeats (STRs). The number of repeats at these loci differs among individuals, creating unique DNA profiles that can be used for identification or to establish genetic relationships. Signup and view all the answers

Briefly explain the role of tRNA in the process of translation and how its structure supports this function.

tRNA carries specific amino acids to the ribosome. Its anticodon sequence pairs with the mRNA codon, ensuring the correct amino acid is added to the growing polypeptide chain. Signup and view all the answers

Describe how semi-conservative replication ensures genetic continuity between generations of cells.

Each new DNA molecule consists of one original strand and one newly synthesized strand. This ensures that genetic information is inherited with high fidelity because each daughter cell receives a DNA molecule with one original, accurate strand. Signup and view all the answers

Outline the key differences in the enzymes involved in DNA replication and transcription, and explain why these differences are necessary.

DNA replication uses DNA polymerase, which requires a primer and replicates both strands of DNA. Transcription uses RNA polymerase, which does not require a primer and only transcribes a single strand of DNA. These differences are necessary because replication must accurately copy the entire genome, while transcription only needs to produce specific RNA molecules from particular genes. Signup and view all the answers

Explain how a mutation in a gene could lead to a change in phenotype, and provide an example of a scenario where this change might be beneficial to an orgranism.

A mutation can alter the sequence of a gene, leading to a different protein being produced or a non-functional protein. If the mutation is beneficial, such as antibiotic resistance in bacteria, it can increase the organism's survival and reproductive success in certain environments. Signup and view all the answers

How do internal and external environmental influences affect gene expression, and provide one example of each?

Internal influences such as hormones can activate or repress gene transcription. External influences such as temperature can affect protein folding and stability. An example of an internal influence is the production of estrogen influencing the expression of genes related to female secondary sexual characteristics. An example of an external influence is the change in coat color of arctic foxes due to seasonal temperature changes. Signup and view all the answers

How does the semi-conservative nature of DNA replication contribute to genetic stability across generations?

Each new DNA molecule contains one original strand and one newly synthesized strand, reducing the chance of accumulating errors during replication. Signup and view all the answers

Describe the roles of mRNA, tRNA, and rRNA in protein synthesis, emphasizing how their functions are interconnected.

mRNA carries genetic code from DNA to ribosome; tRNA brings amino acids to ribosome according to mRNA codons; rRNA forms the ribosome, which facilitates the assembly of the polypeptide chain. Signup and view all the answers

Explain how both internal (e.g., hormones) and external (e.g., diet) environmental influences can alter gene expression and ultimately affect an organism's phenotype.

Internal factors such as hormones can activate or repress gene transcription, while external factors like diet provide the necessary building blocks or signals that influence metabolic pathways and gene expression. Signup and view all the answers

How does the concept of multiple alleles increase the potential for genetic variation within a population, using the ABO blood group system as an example?

Multiple alleles (like $I^A$, $I^B$, and i for blood type) allow for more genotypes and phenotypes than simple dominant/recessive systems, increasing diversity. Signup and view all the answers

Differentiate between transcription and translation, noting the location, purpose, and key enzymes involved in each process.

Transcription is copying DNA to RNA in the nucleus using RNA polymerase to produce mRNA; translation is using mRNA to synthesize proteins in the ribosome. Signup and view all the answers

Briefly explain the significance of semi-conservative replication in the context of DNA replication. What would be the immediate consequence if DNA replication were fully conservative instead?

Semi-conservative replication ensures genetic continuity by producing two DNA molecules, each with one original and one new strand. If replication were fully conservative, the original DNA would remain entirely intact alongside a completely new copy, potentially leading to unequal distribution of genetic material during cell division and increased accumulation of mutations. Signup and view all the answers

Compare and contrast the roles of mRNA, tRNA, and rRNA in protein synthesis. What specific function does each type of RNA perform during translation?

mRNA carries the genetic code from DNA to the ribosome, tRNA brings specific amino acids to the ribosome based on codon-anticodon pairing, and rRNA forms a structural and catalytic part of the ribosome itself, facilitating the formation of peptide bonds. mRNA carries genetic information, tRNA carries amino acids, and rRNA catalyzes peptide bond formation. Signup and view all the answers

How does understanding polygenic inheritance help explain continuous variation in traits like height or skin color in a population? Give a brief example.

Polygenic inheritance, where multiple genes contribute to a single trait, explains continuous variation as each gene adds a small, additive effect to the phenotype, resulting in a wide range of possible outcomes. For instance, skin color is influenced by several genes, each with multiple alleles, leading to a spectrum of skin tones in the population, rather than distinct categories. Signup and view all the answers

Explain how a test cross can be used to determine if an organism with a dominant phenotype is homozygous or heterozygous for a particular trait. What phenotypic ratio in the offspring would indicate the organism is heterozygous?

A test cross involves crossing an individual with a dominant phenotype with a homozygous recessive individual. If the dominant individual is heterozygous, the offspring will show a 1:1 phenotypic ratio (dominant:recessive). If the dominant individual is homozygous, all offspring will exhibit the dominant phenotype. Signup and view all the answers

How might internal and external environmental factors influence gene expression and ultimately affect an individual's phenotype? Provide examples of each.

Internal factors, such as hormones, can activate or repress gene expression, leading to changes in phenotype. An example is the influence of testosterone on muscle development. External factors, like diet or exposure to toxins, can also alter gene expression; for example, malnutrition during development can affect growth potential despite genetic predisposition for tall stature. Signup and view all the answers

Explain how the semi-conservative nature of DNA replication ensures genetic continuity between generations. What would be the consequence if replication were fully conservative?

Each new DNA molecule contains one original strand and one newly synthesized strand, preserving genetic information. Fully conservative replication would mix parental and new strands, potentially leading to loss of information. Signup and view all the answers

Compare and contrast the roles of mRNA, tRNA, and rRNA in protein synthesis. How do their structures relate to their functions?

mRNA carries genetic code from DNA to ribosomes, tRNA brings amino acids to the ribosome, and rRNA makes up the ribosome structure. mRNA is a linear sequence, tRNA has a cloverleaf shape for amino acid and codon binding, and rRNA folds into a complex 3D structure to form the ribosome. Signup and view all the answers

Describe how a mutation in a gene could lead to a change in the phenotype of an organism. Give an example when there would be no change in the phenotype.

A mutation alters the DNA sequence, leading to a different mRNA sequence, potentially changing the amino acid sequence and protein structure, thus affecting the phenotype. A silent or synonymous mutation, which does not change the amino acid sequence, would result in no change in the phenotype. Signup and view all the answers

Explain how environmental factors can influence the expression of a polygenic trait, using human height as an example.

Human height is determined by multiple genes (polygenic), but nutrition during development can significantly impact the extent to which these genes are expressed. Poor nutrition can limit growth, resulting in a shorter height than genetically predetermined. Signup and view all the answers

A couple, both with blood type A, have a child with blood type O. Based on this information, what are the most probable genotypes of the parents? Explain how this inheritance pattern is an example of multiple alleles.

Both parents must be heterozygous (AO) for the A allele to have a child with blood type O (OO). This blood type inheritance is an example of multiple alleles because there are three possible alleles (A, B, and O) that determine blood type, not just two. Signup and view all the answers

Flashcards

DNA

Deoxyribonucleic acid, carries genetic information.

RNA

Ribonucleic acid, involved in protein synthesis.

Codon

A sequence of three nucleotides that codes for an amino acid.

Punnett Square

A diagram to predict genotypes of offspring from parental genes.

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Mutation

A change in DNA sequence that can lead to different traits.