Molecular Biology: DNA and Protein Synthesis

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Questions and Answers

What is the purpose of recombinant DNA technology?

  • To transfer genetic information between organisms (correct)
  • To isolate DNA fragments
  • To sequence DNA
  • To analyze protein structures

All mutations lead to a phenotypic change in an organism.

False (B)

Which nitrogenous base is found in RNA but not in DNA?

  • Adenine
  • Thymine
  • Cytosine
  • Uracil (correct)

What phase of the cell cycle involves DNA replication?

<p>S phase</p> Signup and view all the answers

During metaphase, chromosomes align along the __________.

<p>equatorial plate</p> Signup and view all the answers

During DNA replication, both strands of the original DNA molecule are copied completely.

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

Which process forms two daughter cells?

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

What is the role of mRNA in protein synthesis?

<p>mRNA carries coded information from DNA to ribosomes for protein synthesis.</p> Signup and view all the answers

In the process of ____ synthesis, ribosomes translate the mRNA code into a sequence of amino acids.

<p>protein</p> Signup and view all the answers

Match the phases of mitosis to their descriptions:

<p>Prophase = Chromatin condenses and mitotic spindle forms Metaphase = Chromosomes align along the equatorial plate Anaphase = Sister chromatids separate and move to opposite poles Telophase = Nuclear membrane reforms around decondensed chromosomes</p> Signup and view all the answers

What is the first step in the process of transcription?

<p>Initiation (C)</p> Signup and view all the answers

What is a frameshift mutation?

<p>A mutation that shifts the reading frame of the genetic code</p> Signup and view all the answers

Crossing over occurs during Meiosis II.

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

The central dogma of molecular biology states that information flows from DNA to RNA to proteins.

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

What is the function of the promoter region in DNA?

<p>The promoter region serves as a binding site for RNA polymerase to initiate transcription.</p> Signup and view all the answers

Match the following terms with their correct descriptions:

<p>DNA = Double-stranded molecule storing genetic information RNA = Single-stranded molecule involved in protein synthesis tRNA = Transfers amino acids to ribosomes during translation mRNA = Carries genetic information from DNA to ribosomes</p> Signup and view all the answers

What occurs during anaphase I of meiosis?

<p>Chromatid pairs of each tetrad move to opposite poles (A)</p> Signup and view all the answers

Telophase I results in four daughter cells.

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

What are the final products of meiosis II?

<p>Four haploid cells called monads</p> Signup and view all the answers

During non-disjunction, ____ chromosomes move to the same pole, leading to an extra chromosome in one daughter cell.

<p>homologous</p> Signup and view all the answers

Match the chromosomal conditions to their corresponding syndromes:

<p>Trisomy 21 = Down's syndrome Trisomy 18 = Edward's syndrome Monosomy X = Turner’s syndrome XXY = Klinefelter’s syndrome</p> Signup and view all the answers

Which of the following is true regarding the genotype of an organism?

<p>It is the set of genes that an organism carries for a specific trait (B)</p> Signup and view all the answers

Trisomy X refers to females having an extra X chromosome.

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

What term describes the cycling between diploid (2N) and haploid (N) generations?

<p>Alternation of generations</p> Signup and view all the answers

Flashcards

Semiconservative replication

DNA replication produces two new DNA molecules, each consisting of one original strand and one newly synthesized strand.

Gene

A segment of DNA that codes for a specific protein.

Messenger RNA (mRNA)

A molecule that carries genetic information from DNA to ribosomes for protein synthesis.

Transcription

The process of copying genetic information from DNA to mRNA.

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Translation

The process of using mRNA to synthesize proteins.

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Codon

A sequence of three nucleotides in mRNA that specifies a particular amino acid.

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Anticodon

A sequence of three nucleotides in tRNA that is complementary to a codon in mRNA.

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Transfer RNA (tRNA)

A molecule that carries amino acids to ribosomes for protein synthesis.

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Mutation

A change in the sequence of DNA that can alter gene function, leading to changes in protein production or even disease development.

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Point Mutation

A type of mutation that changes a single base pair in DNA, potentially causing a change in the amino acid sequence of a protein.

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Nonsense Mutation

A mutation that introduces a premature stop codon in a gene, resulting in a shortened and often non-functional protein.

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Frameshift Mutation

A mutation that shifts the reading frame of a gene, leading to a completely different amino acid sequence, often resulting in a non-functional protein.

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Recombinant DNA technology

A process that combines DNA from different sources, often involving inserting a gene from one organism into the genome of another organism.

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Restriction endonuclease

A type of enzyme that cuts DNA at specific sequences, used in recombinant DNA technology for isolating genes.

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DNA ligase

An enzyme that joins DNA fragments together, used in recombinant DNA technology to insert genes into a host genome.

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Cell cycle

A process where a cell grows, replicates its DNA, and divides into two daughter cells.

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Anaphase I

The stage of meiosis where homologous chromosome pairs separate and move to opposite poles of the cell. Sister chromatids remain attached and begin migrating to the poles. Humans have 23 doubled chromosomes at each pole.

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Telophase I

The final stage of Meiosis I, where secondary gametocytes are formed. Each cell contains one homologous pair (not yet separated), and the nuclear membrane forms around the dyads of sister chromatids.

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Interphase

A short resting phase after Meiosis I, where chromosomes don't completely unwind and there's no DNA replication.

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Prophase II

The stage of meiosis II where the nuclear membrane disappears, and spindle fibers form. The chromatid pairs (dyads) align at the equator of the cell, and spindle fibers attach to the centromeres.

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Anaphase II

The stage of Meiosis II where centromeres split, and the sister chromatids move to opposite poles of the cell.

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Telophase II

The final stage of Meiosis II, where cytokinesis and complete decondensation are completed, forming four haploid cells (monads) each with varying structures. Each monad is a single, unreplicated chromosome.

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Nondisjunction

The unequal distribution of chromosomes during meiosis, resulting in one daughter cell with an extra chromosome (trisomy) and the other with one less chromosome (monosomy).

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Alternation of Generations

The cycling between diploid (2N) and haploid (N) stages in a life cycle.

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Study Notes

Molecular Biology (DNA and Protein Synthesis)

  • DNA is composed of two strands of nucleotides.
  • Nucleotides consist of a phosphate, sugar, and a nitrogenous base (Adenine, Thymine, Guanine, Cytosine).
  • RNA is a single strand of nucleotides.
  • Uracil replaces thymine in RNA's nitrogenous bases.

The Central Dogma

  • The central dogma outlines the process of how DNA directs protein synthesis.
  • DNA replicates to create new DNA molecules.
  • DNA is transcribed into mRNA.
  • mRNA migrates to the cytoplasm.
  • mRNA carries the genetic code to ribosomes for translation.
  • Translation results in protein synthesis using the genetic code on mRNA.

DNA Replication

  • DNA replication is a semi-conservative process.
  • Each original strand serves as a template for a new strand.
  • DNA polymerase III synthesizes a new complementary strand.
  • Each new DNA molecule contains one original and one newly synthesized strand.

mRNA Synthesis (Transcription)

  • RNA polymerase uses a DNA strand as a template.
  • Transcription begins at a promoter region on the DNA.
  • mRNA is synthesized in the 5' to 3' direction.
  • Transcription ends at a termination sequence.
  • The resulting mRNA molecule moves to the cytoplasm.

Protein Synthesis (Translation)

  • Ribosomes read the mRNA in codons (three nucleotides).
  • Each codon codes for a specific amino acid.
  • tRNA molecules carry amino acids to the ribosomes.
  • Amino acids are linked together to form a polypeptide chain (protein).
  • The polypeptide chain starts at a start codon and ends at a stop codon, creating a protein.

Recombinant DNA Technology

  • This involves transferring genetic material from one organism to another.
  • The aim is to get the engineered cell to create a specific protein.
  • DNA restriction enzymes cut DNA strands.
  • DNA ligase then glues the strands together.

Cell Division (Mitosis and Meiosis)

  • Mitosis is nuclear division.
  • Cytokinesis is cytoplasm division.
  • Interphase is the growth phase, including G1 (growth), S (synthesis), and G2 (growth).
  • DNA replication occurs during the S phase.
  • Mitosis is divided into prophase, metaphase, anaphase, and telophase.
  • Meiosis produces gametes (sex cells).
  • Meiosis involves two cell divisions to reduce the chromosome number to half.
  • Meiosis is essential for sexual reproduction.

Polygenic Traits

  • Inherited traits affected by more than one gene.
  • Examples include human hair color, skin color, and height.
  • Epistatic genes can mask the expression of other genes.

Sex Linkage

  • Traits linked to sex chromosomes (X or Y).
  • The inheritance patterns differ between males and females due to the presence of one X chromosome in females and an X and a Y chromosome in males.

Gene Linkage

  • Linked genes tend to be inherited together during gamete formation.
  • Crossing over can separate linked genes in meiosis.
  • Recombinant gametes are formed with different combinations of genes from parents.

The Endocrine System

  • Hormones are chemical messengers produced and released by glands.
  • The hypothalamus and pituitary glands control other endocrine glands.
  • Hormones play critical roles in various bodily functions, such as growth, metabolism, reproduction, and response to stress.

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