Biology Chapter: Molecular Genetics

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Questions and Answers

What is the role of RNA polymerase during transcription?

To bond free RNA nucleotides to form the sugar-phosphate backbone. (correct)

To transport mRNA out of the nucleus.

To unwind the DNA double helix.

To splice introns from the mRNA molecule.

What must happen to the primary transcript before it becomes mature mRNA?

Introns must be spliced out. (correct)

Nucleotides must be removed from the ends.

It must be re-transcribed.

It must undergo translation.

Which of the following accurately describes a gene mutation?

It always results in a beneficial trait.

It occurs only during transcription.

It changes the sequence of base pairs in DNA. (correct)

It can only occur due to environmental factors.

What is the function of tRNA in translation?

To attach amino acids and recognize codons on mRNA. Signup and view all the answers

During which step does the mRNA molecule exit the nucleus?

Transcription. Signup and view all the answers

What type of bond links the deoxyribose sugars and phosphate groups in the DNA backbone?

Phosphodiester bonds Signup and view all the answers

What happens when a 'stop' codon is reached during translation?

The amino acid chain is completed. Signup and view all the answers

Which direction does DNA polymerase synthesize a new strand?

5' to 3' Signup and view all the answers

Which characteristic of tRNA allows it to attach to specific amino acids?

The presence of a triplet anticodon. Signup and view all the answers

What is an example of an insertion mutation?

An extra nucleotide is added to the DNA sequence. Signup and view all the answers

What is the significance of the term 'semi-conservative' in DNA replication?

It indicates that each daughter DNA contains one old and one new strand. Signup and view all the answers

What are the components that make up a nucleotide?

A nitrogenous base, a pentose sugar, and a phosphate group Signup and view all the answers

Which nitrogenous bases are classified as purines?

Adenine and Guanine Signup and view all the answers

Which nitrogenous base always pairs with adenine in DNA?

Thymine Signup and view all the answers

What role does DNA helicase play in DNA replication?

It breaks hydrogen bonds between base pairs. Signup and view all the answers

How many hydrogen bonds are formed between adenine and thymine?

2 hydrogen bonds Signup and view all the answers

What distinguishes DNA from RNA?

DNA contains deoxyribose while RNA contains ribose. Signup and view all the answers

What are the two categories of nitrogenous bases in DNA?

Purines and pyrimidines Signup and view all the answers

Which statement accurately describes the antiparallel nature of DNA strands?

One strand runs from 3' to 5', and the other 5' to 3'. Signup and view all the answers

Which of the following statements about DNA structure is true?

DNA strands are antiparallel. Signup and view all the answers

What is the primary function of DNA ligase in the synthesis of the lagging strand?

To join Okazaki fragments together Signup and view all the answers

What is the primary function of adenosine triphosphate (ATP) in cells?

Providing energy for cellular processes Signup and view all the answers

What is the result of the condensation reaction catalyzed by DNA polymerase?

Creation of the sugar-phosphate backbone Signup and view all the answers

What distinguishes RNA from DNA in terms of structure?

RNA contains uracil instead of thymine Signup and view all the answers

Which of the following best describes the components of ATP?

Three phosphate groups, ribose sugar, and the base adenine Signup and view all the answers

What type of sugar is found in RNA nucleotides?

Ribose Signup and view all the answers

Why is the genetic code described as degenerate?

Multiple codons can code for the same amino acid Signup and view all the answers

What role does messenger RNA (mRNA) play in protein synthesis?

It acts as a template for polypeptide synthesis Signup and view all the answers

During the transcription process, where does this stage occur within the cell?

In the nucleus Signup and view all the answers

Which of the following statements about RNA structure is correct?

RNA is made up of ribose sugars and nitrogenous bases linked by phosphodiester bonds Signup and view all the answers

What defines a gene in the context of DNA?

A portion of DNA coding for a specific polypeptide Signup and view all the answers

What does the term 'triplet code' refer to in genetics?

A three-nucleotide sequence that codes for amino acids Signup and view all the answers

What is the primary effect of an insertion mutation in DNA?

It changes the original codon and affects subsequent codons. Signup and view all the answers

What distinguishes a substitution mutation from an insertion or deletion mutation?

It only affects the amino acid in the triplet where it occurs. Signup and view all the answers

Which type of mutation is specifically known to create a premature stop codon?

Nonsense mutation Signup and view all the answers

What is a common outcome of a frameshift mutation caused by insertion or deletion?

A completely different amino acid sequence is produced. Signup and view all the answers

Which of the following best describes a silent mutation?

It does not change the resulting protein's amino acid sequence. Signup and view all the answers

What may be a consequence of a mutation that results in a significantly altered polypeptide?

The protein may lose its ability to function. Signup and view all the answers

Which example represents a missense mutation?

Changing one base that leads to a different amino acid. Signup and view all the answers

Which mutation is least likely to have an effect on the polypeptide's function?

Silent mutation Signup and view all the answers

Study Notes

Nucleic Acids & Protein Synthesis

Nucleic acids, like DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are polynucleotides. Their monomers are nucleotides.
Nucleotides consist of three parts: a nitrogenous base, a pentose sugar, and a phosphate group.
Nitrogenous bases are categorized as purines (double ring structure - adenine and guanine) or pyrimidines (single ring structure - cytosine, thymine, and uracil).
DNA is double-stranded with deoxyribose sugar and bases A, T, C, G. DNA strands are antiparallel (5' to 3' and 3' to 5'). Hydrogen bonds link complementary base pairs (A-T, G-C).
RNA is single-stranded with ribose sugar and bases A, U, C, G.
Adenosine triphosphate (ATP) is a phosphorylated nucleotide, providing energy for cellular processes.
RNA nucleotides can have one, two, or three phosphate groups (AMP, ADP, ATP).

DNA Replication

DNA replication is semi-conservative, meaning each new DNA molecule consists of one original strand and one newly synthesized strand.
DNA helicase unwinds the DNA double helix, breaking hydrogen bonds between complementary base pairs.
DNA polymerase synthesizes new DNA strands using the original strands as templates. It can only build in the 5' to 3' direction. The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments (Okazaki fragments). DNA ligase joins the Okazaki fragments.

Protein Synthesis

Genes are sequences of nucleotides that code for polypeptides (proteins). DNA's nucleotide code is a triplet code (codons).
Transcription occurs in the nucleus. DNA unwinds. mRNA is synthesized using one DNA strand as a template. mRNA carries the genetic code from DNA to the ribosome.
Translation occurs in the cytoplasm. mRNA binds to ribosomes. tRNA molecules carry specific amino acids to the ribosome, matching codons on the mRNA to anticodons. Amino acids are linked to form a polypeptide chain (protein).
Translation proceeds until a stop codon on the mRNA is reached. This polypeptide chain is the final protein.

Gene Mutations

Gene mutations are changes in the DNA sequence, which can cause alterations in the resulting polypeptide and protein function.
Mutations occur when nucleotides are inserted, deleted or substituted.
Different types of mutations include insertion, deletion, and substitution.
Frameshift mutations (insertions or deletions) affect the reading frame and subsequently change the amino acid sequence downstream of the mutation, significantly altering the polypeptide.
Substitutions can be silent (no amino acid change), missense (different amino acid), or nonsense (premature stop codon).
Mutations can profoundly alter gene expression and protein function, sometimes leading to disease.

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Description

Test your knowledge on key concepts in molecular genetics, including transcription, translation, and DNA replication. This quiz covers the roles of RNA polymerase, tRNA function, and various types of mutations. Dive into the intricacies of genetic processes and enhance your understanding of molecular biology!