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General Biology: Genetics, DNA Replication, Transcription, and Translation

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이 집합의 용어 (27)

  • What is a karyotype?

    A karyotype is a picture of all condensed chromosomes inside a cell, used to analyze chromosome number and structure.

  • What is a Barr body and its function?

    A Barr body is an inactivated X chromosome in mammals with multiple X chromosomes, condensed to prevent excess gene expression.

  • Define nondisjunction and when it occurs.

    Nondisjunction is the failure of chromosomes to separate properly during metaphase in Meiosis I or II, causing abnormal chromosome numbers.

  • Name two viable autosomal nondisjunction disorders.

    Trisomy 21 (Down Syndrome) and Trisomy 18 (Edwards syndrome) are examples of viable autosomal nondisjunction disorders.

  • What is the genotype and disorder for Triple X syndrome?

    Triple X syndrome has the genotype XXX, caused by nondisjunction of sex chromosomes, typically assigned female at birth.

  • Describe the three main steps of DNA isolation.

    1. Homogenization: breaks cell membranes; 2. Deproteinization: removes histones; 3. Precipitation: uses alcohol to isolate DNA.

  • What are the components of a nucleotide?

    A nucleotide consists of a phosphate group, pentose sugar, and a nitrogenous base.

  • What type of bonds hold nitrogenous bases and sugar-phosphate backbone together in DNA?

    Hydrogen bonds hold nitrogenous bases together; phosphodiester covalent bonds hold the sugar-phosphate backbone.

  • Differentiate purines and pyrimidines.

    Purines (adenine, guanine) have two rings; pyrimidines (thymine, cytosine) have one ring.

  • State Chargaff's rule.

    In DNA, the amount of adenine equals thymine, and guanine equals cytosine: \(A=T\) and \(G=C\).

  • Explain the antiparallel nature of DNA.

    DNA strands run in opposite directions: one 5’ to 3’, the other 3’ to 5’, affecting replication mechanisms.

  • What is the role of helicase in DNA replication?

    Helicase unwinds DNA by breaking hydrogen bonds between nitrogenous bases during replication.

  • Why are single-strand binding proteins important?

    They prevent separated DNA strands from re-pairing during replication.

  • What is the function of primase in DNA replication?

    Primase synthesizes an RNA primer to provide a free 3’ OH group for DNA polymerase to start DNA synthesis.

  • What are the requirements for DNA polymerase activity?

    DNA polymerase needs a template strand, a free 3’ OH group, and free nucleotides to synthesize DNA.

  • In which direction does DNA polymerase synthesize DNA?

    DNA polymerase synthesizes DNA in the 5’ to 3’ direction, reading the template strand 3’ to 5’.

  • Why does the lagging strand form Okazaki fragments?

    Because DNA polymerase can only synthesize 5’ to 3’, the lagging strand is synthesized discontinuously in short fragments called Okazaki fragments.

  • How is the RNA primer replaced during DNA replication?

    DNA polymerase I removes RNA primers and replaces them with DNA nucleotides.

  • What enzyme seals gaps between Okazaki fragments?

    Ligase forms covalent bonds to join Okazaki fragments, completing the lagging strand.

  • Compare DNA and RNA in terms of sugar and bases.

    DNA has deoxyribose sugar and bases A, T, C, G; RNA has ribose sugar and bases A, U, C, G (uracil replaces thymine).

  • What is the Central Dogma of Molecular Biology?

    Information flows from DNA to RNA to Protein.

  • What is transcription?

    Transcription is the process of synthesizing RNA from a DNA template inside the nucleus.

  • Describe the three stages of transcription.

    Initiation: RNA polymerase binds promoter; Elongation: RNA strand synthesized 5’ to 3’; Termination: RNA polymerase stops at terminator sequence.

  • What is translation?

    Translation is the process of synthesizing protein from mRNA at the ribosome.

  • Define a codon and its role.

    A codon is a sequence of three nucleotides in mRNA that codes for one amino acid.

  • What is the start codon and which amino acid does it code for?

    The start codon is AUG, which codes for methionine and signals the start of translation.

  • Name the stop codons and their function.

    Stop codons UGA, UAG, UAA signal termination of translation and do not code for amino acids.