MYP5: DNA, RNA & Genetics

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Questions and Answers

During DNA replication, which enzyme is primarily responsible for unwinding the double helix structure?

DNA Polymerase
Helicase (correct)
Ligase
Primase

A certain mRNA sequence is 5'-AUG-GCA-UCG-UAA-3'. How many tRNA molecules are required to translate this sequence into a polypeptide?

3 (correct)
2
4
5

In a test cross, an organism with an unknown genotype is crossed with a homozygous recessive organism. If the resulting offspring show a 1:1 phenotypic ratio of dominant to recessive traits, what is the genotype of the unknown organism?

Homozygous dominant
Homozygous recessive
Hemizygous
Heterozygous (correct)

Which of the following sequences represents the correct order of events during gene expression?

Replication → Transcription → Translation (A) Signup and view all the answers

What is the probability of producing a child with blood type O from parents who are both heterozygous for blood type A (genotype: $I^Ai$)?

25% (A) Signup and view all the answers

In a species of plant, flower color is controlled by a single gene with two alleles: R (red) and r (white). If a heterozygous plant (Rr) is crossed with a homozygous white plant (rr), what percentage of the offspring are expected to have white flowers?

50% (B) Signup and view all the answers

A scientist is analyzing a DNA sample and finds that 20% of the bases are adenine (A). According to Chargaff's rules, what percentage of the bases are guanine (G)?

30% (C) Signup and view all the answers

Which of the following inheritance patterns involves multiple genes contributing to a single trait, resulting in a wide range of phenotypes?

Polygenic Inheritance (D) Signup and view all the answers

Describe the process of semi-conservative replication and explain its significance in maintaining genetic information.

Semi-conservative replication results in two DNA molecules, each with one original and one new strand, ensuring accurate inheritance of genetic information. Signup and view all the answers

Compare and contrast the roles of mRNA, tRNA, and rRNA in protein synthesis.

mRNA carries genetic code from DNA, tRNA transfers amino acids to the ribosome, and rRNA forms the ribosome structure facilitating translation. Signup and view all the answers

Explain how a mutation in a gene can lead to a change in the corresponding protein, and how this change might affect an organism's phenotype.

Mutations alter the DNA sequence, potentially changing the amino acid sequence of a protein, which can affect its structure and function, leading to phenotypic changes. Signup and view all the answers

A plant species shows incomplete dominance for flower color. When a red-flowered plant ($CRCR$) is crossed with a white-flowered plant ($CWCW$), the offspring are pink-flowered ($CRCW$). What phenotypic ratio is expected when two pink-flowered plants are crossed?

1 red : 2 pink : 1 white Signup and view all the answers

What is the purpose of a test cross, and how can it be used to determine the genotype of an individual with a dominant phenotype?

A test cross involves breeding an individual with a dominant phenotype with a homozygous recessive individual to determine the unknown genotype based on the offspring's phenotypes. Signup and view all the answers

How do internal and external environmental factors influence the expression of genes and ultimately affect an organism's phenotype? Provide an example of each.

Internal factors like hormones and external factors like temperature can affect gene expression, leading to phenotypic variations. For example, hormones control the timing of puberty (internal), and temperature affects fur color in arctic foxes (external). Signup and view all the answers

Explain how DNA fingerprinting is performed and its application in forensic science.

DNA fingerprinting analyzes repetitive DNA sequences (e.g., short tandem repeats) to create a unique genetic profile. It can be used to identify criminals or victims by matching DNA samples. Signup and view all the answers

In a species of bird, feather color is determined by a single gene with multiple alleles: $B^1$, $B^2$, and $B^3$. $B^1$ is dominant to both $B^2$ and $B^3$, while $B^2$ is dominant to $B^3$. If a male bird with genotype $B^1B^2$ mates with a female bird with genotype $B^2B^3$, what are the possible genotypes and phenotypes of their offspring?

Possible genotypes: $B^1B^2$, $B^1B^3$, $B^2B^2$, $B^2B^3$. Possible phenotypes: $B^1$ (dominant), $B^2$ (dominant). Signup and view all the answers

Explain the significance of semi-conservative replication in maintaining genetic information.

Semi-conservative replication ensures that each new DNA molecule consists of one original strand and one newly synthesized strand. This reduces the chance of errors and maintains the integrity of the genetic information. Signup and view all the answers

Describe how a mutation in a gene could lead to a change in phenotype. Provide an example.

A mutation can alter the DNA sequence, leading to a different mRNA sequence, potentially changing the amino acid sequence of a protein. This altered protein may function differently, leading to a change in phenotype. For example, a mutation in a gene for melanin production can result in albinism. Signup and view all the answers

Explain the difference between genotype and phenotype, and discuss how environmental factors can influence phenotype.

Genotype is the genetic makeup of an organism, while phenotype is the observable characteristics. Environmental factors can influence phenotype by affecting gene expression. For example, the same plant genotype may exhibit different heights based on the amount of sunlight it receives. Signup and view all the answers

Describe the steps involved in transcription, including the enzymes involved and the final product.

Transcription involves RNA polymerase binding to DNA, unwinding it, and synthesizing an mRNA molecule complementary to the template strand. The final product is a pre-mRNA molecule, which is then processed to form mature mRNA. Signup and view all the answers

How does the process of translation ultimately determine an organism's traits?

Translation converts the information in mRNA into a specific sequence of amino acids, which folds into a protein. The structure and function of proteins determine an organism's traits, by catalyzing reactions, providing structure, or acting as signals. 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.

A test cross involves crossing the organism with the dominant phenotype with a homozygous recessive individual. If any offspring display the recessive phenotype, the parent with the dominant phenotype is heterozygous; if all offspring display the dominant phenotype, the parent is likely homozygous. Signup and view all the answers

Describe the difference between incomplete dominance and codominance. Give a brief example of each.

Incomplete dominance is when the heterozygous phenotype is a blend of the two homozygous phenotypes, like a red flower and a white flower making a pink flower. Codominance is when both alleles are fully expressed in the heterozygous phenotype, like a red cow and a white cow making a roan cow. Signup and view all the answers

Describe the roles of mRNA, tRNA, and rRNA in the process of protein synthesis.

mRNA carries the genetic code from DNA to the ribosome, tRNA brings the correct amino acids to the ribosome based on the mRNA codon, and rRNA is a component of the ribosome, catalyzing peptide bond formation. Signup and view all the answers

Explain how DNA replication is considered semi-conservative. What is the significance of this mechanism?

Semi-conservative replication means each new DNA molecule consists of one original strand and one newly synthesized strand. This ensures genetic information is passed on with high fidelity, minimizing errors during cell division. Signup and view all the answers

Differentiate between transcription and translation, including where each process occurs within a eukaryotic cell and the key enzymes involved.

Transcription occurs in the nucleus and involves RNA polymerase creating an mRNA copy of a DNA sequence, while translation occurs in the cytoplasm at the ribosome, where the mRNA sequence is used to synthesize a protein. Signup and view all the answers

Compare and contrast the terms 'genotype' and 'phenotype'. Provide an example to illustrate the difference.

Genotype refers to the genetic makeup of an organism (e.g., BB or Bb), while phenotype refers to the observable characteristics (e.g., brown eyes). An example is that different genotypes (BB or Bb) can result in the same phenotype (brown eyes) if 'B' is dominant. Signup and view all the answers

Briefly explain how environmental factors can influence gene expression, providing one internal and one external example.

Environmental factors can alter gene expression; an internal example is hormones influencing the development of secondary sexual characteristics, and an external example is UV radiation causing mutations that lead to skin cancer. Signup and view all the answers

Describe the purpose and basic procedure of DNA fingerprinting. What biological concept is it based upon?

DNA fingerprinting creates a unique genetic profile to identify individuals. It uses gel electrophoresis of restriction fragments, based on the concept that individuals have unique patterns of repetitive DNA sequences. Signup and view all the answers

Explain the significance of Chargaff's rules in understanding the structure of DNA. How do these rules contribute to the stability of the DNA double helix?

Chargaff's rules state that in DNA, the amount of adenine (A) equals the amount of thymine (T), and the amount of guanine (G) equals the amount of cytosine (C). These rules ensure consistent base pairing (A-T and G-C), which stabilizes the DNA double helix. Signup and view all the answers

In the context of genetics, what is a 'test cross,' and why is it a useful tool? Provide an example of how it's used.

A test cross involves mating an individual with an unknown genotype to a homozygous recessive individual to determine the unknown genotype. For example, crossing a plant with purple flowers (unknown genotype) with a plant with white flowers (homozygous recessive) to determine if the purple-flowered plant is homozygous dominant or heterozygous. Signup and view all the answers

Describe the roles of mRNA, tRNA, and rRNA in protein synthesis.

mRNA carries the genetic code from DNA to the ribosome, tRNA transfers amino acids to the ribosome according to the mRNA code, and rRNA forms part of the ribosome structure and catalyzes peptide bond formation. Signup and view all the answers

Explain how the process of semi-conservative replication ensures genetic continuity.

Semi-conservative replication results in two DNA molecules, each containing one original strand and one newly synthesized strand. This ensures that genetic information is passed on with high fidelity from one generation to the next. Signup and view all the answers

How does the sequence of codons in mRNA relate to the sequence of amino acids in a protein?

Each codon (a sequence of three nucleotides) in mRNA corresponds to a specific amino acid, according to the genetic code. The sequence of codons in the mRNA determines the order of amino acids in the resulting polypeptide chain during translation. Signup and view all the answers

Differentiate between genotype and phenotype, and explain how they are related.

Genotype refers to the genetic makeup of an organism (the specific alleles it possesses), while phenotype refers to the observable characteristics or traits of an organism. The phenotype is the result of the interaction between the genotype and the environment. Signup and view all the answers

Explain how a mutation in a gene could lead to a change in the phenotype of an organism.

A mutation in a gene can alter the DNA sequence, which may change the mRNA sequence and, consequently, the amino acid sequence of the protein it encodes. If the altered protein has a different structure or function, it can result in a change in the organism's phenotype. Signup and view all the answers

Consider a cross between two heterozygous individuals (Aa). What are the expected genotypic and phenotypic ratios if allele 'A' exhibits complete dominance over 'a'?

The genotypic ratio would be 1 AA : 2 Aa : 1 aa. The phenotypic ratio would be 3 dominant : 1 recessive, as both AA and Aa genotypes express the dominant phenotype. Signup and view all the answers

Describe the differences between simple Mendelian inheritance, incomplete dominance, and codominance.

Simple Mendelian inheritance has one allele completely dominant over the other. Incomplete dominance results in a blended phenotype. Codominance results in both alleles being equally and fully expressed. Signup and view all the answers

How might external environmental factors influence gene expression and ultimately affect an organism's phenotype?

External environmental factors such as temperature, nutrition, or exposure to toxins can influence gene expression by affecting processes like transcription or translation. These changes in gene expression can then alter the organism's phenotype, leading to observable differences in traits. Signup and view all the answers

During translation, what role does tRNA play in ensuring the correct sequence of amino acids in the polypeptide chain?

tRNA molecules recognize specific mRNA codons through their anticodon region and deliver the corresponding amino acid to the ribosome, ensuring the correct amino acid sequence. Signup and view all the answers

Describe how a mutation in the DNA sequence could affect the process of transcription and ultimately alter the structure of the protein.

A mutation in DNA can change the mRNA sequence during transcription. This altered mRNA may then code for a different amino acid sequence during translation, potentially changing the protein's structure and function. Signup and view all the answers

Explain the significance of the start codon (AUG) in the mRNA sequence during the initiation of translation.

The start codon (AUG) signals the ribosome to begin translation at that specific point on the mRNA. It also codes for the amino acid methionine, which is often the first amino acid in a polypeptide chain. Signup and view all the answers

What is the role of chaperones in protein synthesis, and why is their function crucial for the cell?

Chaperones are proteins that assist in the proper folding of other proteins. Their function is crucial because the correct three-dimensional structure is essential for a protein to function correctly. Misfolded proteins can be non-functional or even toxic to the cell. Signup and view all the answers

Outline the steps involved in the termination of translation, including the roles of release factors and stop codons.

Termination occurs when a stop codon (UAA, UAG, or UGA) enters the A site of the ribosome. Release factors bind to the stop codon, causing the release of the polypeptide chain and the dissociation of the ribosome from the mRNA. Signup and view all the answers

Describe two post-translational modifications that a protein might undergo, and briefly explain their significance.

Two post-translational modifications are glycosylation (addition of a sugar) which can affect protein folding and targeting, and phosphorylation (addition of a phosphate group) which can regulate protein activity. Signup and view all the answers

If a mutation occurs in the promoter region of a gene, how might this affect protein synthesis?

A mutation in the promoter region may alter the binding affinity of RNA polymerase, potentially leading to decreased or increased transcription of the gene and thus affecting protein synthesis. Signup and view all the answers

How does the process of splicing contribute to protein diversity?

Splicing allows for different combinations of exons to be included in the final mRNA, resulting in the production of different protein isoforms from a single gene. Signup and view all the answers

What is the role of tRNA in the process of translation, and how does its structure support this function?

tRNA molecules carry specific amino acids to the ribosome and match them to the mRNA codons through their anticodon loop. Its structure includes an amino acid attachment site and an anticodon loop for codon recognition. Signup and view all the answers

Describe the consequences if a cell's ribosomes were non-functional. Focus on the immediate impact.

If ribosomes were non-functional, the cell would be unable to synthesize proteins. This would immediately halt all cellular processes that rely on proteins, leading to cell dysfunction and eventual death. Signup and view all the answers

Explain how the redundancy of the genetic code (multiple codons for one amino acid) can be both beneficial and potentially problematic for an organism.

The redundancy of the genetic code is beneficial because it provides some protection against mutations; a change in the nucleotide sequence might still code for the same amino acid. However, it can be problematic if a mutation results in a different codon for the same amino acid but affects tRNA binding affinity or translation rate, potentially impacting protein folding or function. Signup and view all the answers

Flashcards

What is DNA?

Deoxyribonucleic acid; the molecule that carries genetic information in living organisms.

What is RNA?

Ribonucleic acid; a molecule similar to DNA, but single-stranded, that plays a role in protein synthesis.

What is a Double Helix?

The structure of DNA, resembling a twisted ladder, with two strands connected by base pairs.

What are Nucleotides?

The basic building blocks of DNA and RNA, consisting of a sugar, a phosphate group, and a nitrogenous base.