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Questions and Answers

What is the main function of helicase during DNA replication?

  • Links nucleotide subunits to form a new DNA strand
  • Unwinds the double helix at replication forks (correct)
  • Synthesizes messenger RNA from DNA
  • Binds to single strands of DNA to prevent re-formation

Which of the following correctly represents the pathway of gene expression?

  • DNA → mRNA → Protein (correct)
  • DNA → rRNA → mRNA
  • DNA → tRNA → Protein
  • mRNA → DNA → Protein

What distinguishes genotype from phenotype?

  • Genotype encompasses all genes, whereas phenotype refers to expressed traits (correct)
  • Genotype is the expressed properties while phenotype is the sum of all genes
  • Genotype refers to genetic information while phenotype reflects environmental interactions
  • Genotype is the combination of traits while phenotype is their genetic basis

Which of the following components is NOT part of the basic structure of DNA?

<p>Ribose (A)</p> Signup and view all the answers

Which statement about DNA replication is correct?

<p>Each daughter strand consists of both original and newly synthesized DNA (D)</p> Signup and view all the answers

What role do single-strand binding proteins (SSB) play in DNA replication?

<p>They stabilize unwound DNA strands and prevent re-annealing (B)</p> Signup and view all the answers

Which type of RNA is synthesized during the transcription phase of gene expression?

<p>Messenger RNA (mRNA) (B)</p> Signup and view all the answers

What component links the nucleotide subunits to form a new DNA strand during replication?

<p>DNA polymerase (B)</p> Signup and view all the answers

What is the role of RNA polymerase in transcription?

<p>It catalyzes the formation of mRNA from the DNA template. (C)</p> Signup and view all the answers

In the genetic code, what does the AUG codon signify?

<p>The start codon that encodes the amino acid methionine. (D)</p> Signup and view all the answers

What is the main purpose of transfer RNA (tRNA) during translation?

<p>To link the anticodon with the corresponding amino acid. (D)</p> Signup and view all the answers

Which of the following components is NOT part of ribosomes?

<p>RNA polymerase. (A)</p> Signup and view all the answers

Which process does not occur during transcription?

<p>Reading of codons. (D)</p> Signup and view all the answers

What signifies the end of the translation process?

<p>UAA, UAG, or UGA codons. (C)</p> Signup and view all the answers

During the elongation step of transcription, which direction does RNA polymerase synthesize the mRNA?

<p>5' to 3' (B)</p> Signup and view all the answers

What is the significance of a polyribosome during protein synthesis?

<p>It indicates multiple ribosomes translating a single mRNA simultaneously. (D)</p> Signup and view all the answers

Study Notes

Genetics

  • Study of genes
  • Genome holds all genetic information
  • Genes are DNA fragments
  • DNA is a double helix
  • DNA is composed of nucleotides containing A, T, C, and G bases
  • DNA contains a ribose (deoxyribose) group and phosphate group linked by hydrogen bonds

Chromatin

  • Chromatin is the complex of DNA, RNA, and proteins found in the nucleus of eukaryotic cells
  • It condenses during cell division to form chromosomes

Genotype & Phenotype

  • Genotype: The sum of all genes that encode for the characteristics of an organism
  • Phenotype: Refers to expressed properties and is the manifestation of the genotype

DNA Replication

  • Each daughter double helix has an original strand from the parent and a newly synthesized complimentary strand
  • Replication occurs when the two strands of the double helix unwind
  • Each strand serves as a template for forming a new complementary strand

DNA Replication Enzymes

  • Helicase: Opens the double helix by disrupting hydrogen bonds
  • Single-strand binding protein: Prevents the helix from reforming before replication
  • DNA polymerase: Links nucleotide subunits to form a new DNA strand from a DNA template

Nucleic Acids and Proteins

  • Genes are converted into messenger RNA (mRNA)
  • mRNA is transcribed into proteins
  • Genes can also be converted to ribosomal RNA (rRNA) or transfer RNA (tRNA) which then produce proteins

Gene Expression

  • Gene expression is the process by which DNA is expressed into proteins
  • The two stages of gene expression are transcription and translation

Transcription

  • Only one strand of DNA is translated into mRNA
  • This strand is called the DNA template strand
  • RNA bases include C, G, U, and A (U replaces T in DNA)

Translation

  • The synthesized mRNA is read in a sequence of triplets
  • Every three nucleotides form one amino acid
  • Amino acids are joined together to form a protein

Codons

  • The table includes 64 codons
  • 61 codons encode amino acids
  • Codons are read in the 5’→ 3’ direction
  • The AUG codon codes for methionine, acting as the start codon for translation
  • UAA, UAG, and UGA are stop codons, indicating the end of the translation process

Transcription Components

  • RNA polymerase: The enzyme for transcription
  • Transcription factors: Proteins needed for transcription
  • Promoter and terminator: DNA sequences that control transcription

Transcription steps

  • Initiation: Beginning of transcription
  • Elongation: RNA polymerase moves down the DNA template strand, building mRNA
  • Termination: Stop codons signal the end of transcription

Translation components

  • Messenger RNA: Carries the genetic code
  • Transfer RNA: Carries specific amino acids
  • Ribosomes: Organelle responsible for protein synthesis
  • Amino Acids: Building blocks of proteins

Transfer RNA (tRNA)

  • tRNA pairs a complementary anticodon with a codon
  • tRNA links the codon to a corresponding amino acid
  • The anticodon is read in the 3’→ 5’ direction

Ribosomes

  • Ribosomes consist of two subunits:
    • A large subunit with three binding sites for tRNA
    • A small subunit with a binding site for mRNA

Poly Ribosomes

  • Poly Ribosomes allow multiple ribosomes to translate a single mRNA at a time
  • This creates a functional protein
  • Microscopic observation shows polyribosomes

Eukaryotic Cell

  • In eukaryotic cells, translation and transcription occur at different locations
  • Transcription takes place in the nucleus
  • Translation takes place in the cytoplasm

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