chapter 15 Flashcards
Who isolated DNA for the first time and in what year?
Friedrich Miescher in 1869
What term did Miescher coin to describe the substance he found in DNA?
Nucleic acid
What are the two natural forms of nucleic acids?
- Deoxyribonucleic acid (DNA)
- Ribonucleic acid (RNA)
What role does DNA play in cells?
Governs the processes of heredity
What is the role of RNA in cells?
Plays a role in gene expression and protein synthesis
What phenomenon did Frederick Griffith discover in his 1928 experiment?
The transforming principle
What did Griffith use to demonstrate the transforming principle?
Heat-killed pathogenic bacteria and live non-pathogenic bacteria
What happened when Griffith treated heat-killed bacteria with a protein-destroying enzyme?
Transformation still occurred
What happened when Griffith treated heat-killed bacteria with a DNA-destroying enzyme?
Transformation did not occur
What did Hershey and Chase demonstrate in 1952?
DNA, not proteins, carries genetic information
What method did Hershey and Chase use to label the components of the virus?
Radioactive labeling
What is a nucleotide?
The basic building block of nucleic acids
What components make up a nucleotide?
- A sugar molecule (ribose in RNA or deoxyribose in DNA)
- A phosphate group
- A nitrogen-containing base
What are the nitrogenous bases found in DNA?
- Adenine (A)
- Cytosine (C)
- Guanine (G)
- Thymine (T)
What base does RNA have instead of thymine?
Uracil (U)
What did Chargaff discover about nucleotide proportions in DNA?
Adenine equals thymine and cytosine equals guanine
Who used X-ray photography to analyze the structure of DNA?
Rosalind Franklin
What is the structure of DNA as described by Watson and Crick?
A double helix
What are complementary base pairs in DNA?
- Adenine (A) pairs with Thymine (T)
- Cytosine (C) pairs with Guanine (G)
What are the two types of nucleic acids discussed?
- DNA
- RNA
What is the defining feature of RNA compared to DNA?
RNA is single-stranded
What is the definition of a gene?
A functional sub-unit of DNA that directs the production of one or more polypeptides
What constitutes the genome of an organism?
The sum of all the DNA, including genes and non-coding DNA
What is DNA replication?
The process of creating an exact copy of a molecule of DNA
What is the error rate of DNA replication in human cells?
About one per billion nucleotide pairs
What are the three main steps of DNA replication?
- Initiation
- Elongation
- Termination
What enzyme is responsible for unzipping the DNA molecule during replication?
Helicase
What is the role of DNA polymerase?
Adds nucleotides during DNA replication
What is the role of RNA primers in DNA replication?
Serve as starting points for DNA synthesis
What is the process of DNA sequencing?
Identifying the precise nucleotide sequence of a DNA fragment
What was the first entire genome to be sequenced?
The genome of the virus θX174 in 1977
What is transcription?
The process by which DNA is copied into mRNA
What enzyme catalyzes the synthesis of RNA during transcription?
RNA polymerase
What is the role of mRNA in protein synthesis?
Carries the information needed for protein synthesis from the nucleus to the cytoplasm
What is the process by which mRNA directs the synthesis of a protein?
Translation
What base in RNA replaces thymine found in DNA?
Uracil
In RNA, thymine is replaced by uracil.
In which direction do RNA polymerases transcribe DNA?
5’ to 3’ direction
RNA polymerases transcribe only one strand of the template DNA.
What signals the RNA polymerases to detach from the DNA during transcription?
A specific nucleotide sequence in the template DNA
This sequence serves as a signal to stop transcription.
Where is mRNA transported after transcription?
Into the cytoplasm, to the ribosome
mRNA is formed during transcription and then transported for translation.
What molecule links each mRNA codon to its specific amino acid?
Transfer RNA (tRNA)
tRNA recognizes and binds to the corresponding codon in the ribosome.
What is a codon?
A three-base stretch of mRNA
One codon contains the information for a specific amino acid.
How does the genetic code exhibit redundancy?
More than one codon can code for the same amino acid
This means that multiple codons can produce the same amino acid.
What does it mean for the genetic code to be continuous?
It reads as a series of three-letter codons without spaces, punctuation, or overlap
Knowing where to start and stop translation is essential.
What is a mutation?
A permanent change in the genetic material of an organism
Mutations can be spontaneous or induced.
What type of mutations affect the genetic information in an organism’s gametes?
Germ line mutations
These mutations can be passed on to offspring.
What are somatic cell mutations?
Mutations that occur in body cells
These mutations are not passed on to offspring.
What is a point mutation?
A chemical change that affects just one or a few nucleotides
It may involve substitution, insertion, or deletion of nucleotides.
What is a silent mutation?
A mutation that has no effect on the cell’s metabolism
It does not alter the polypeptide produced.
What is a mis-sense mutation?
A mutation that results in an altered protein
It can be harmful, such as in sickle cell disease.
What is a nonsense mutation?
A mutation that renders the gene unable to code for a functional polypeptide
This type of mutation can lead to premature termination of protein synthesis.
What is a frameshift mutation?
A mutation caused by insertion or deletion of nucleotides
It alters the entire reading frame of the gene.
What are mutagens?
Substances or events that increase the rate of mutation
Mutagens can be physical (e.g., x-rays) or chemical (e.g., carcinogens).
What is genetic engineering?
The manipulation of genetic material to alter genes
It blends plant, animal, and bacterial DNA.
What is recombinant DNA?
A molecule of DNA that includes genetic material from different sources
It is used in genetic engineering.
What are restriction enzymes?
Proteins produced by bacteria that cleave DNA at specific sites
They are essential tools in recombinant DNA technology.
What is the purpose of the polymerase chain reaction (PCR)?
To amplify DNA sequences
PCR can generate billions of copies of a specific region of DNA.
How does gel electrophoresis work?
Separates mixtures of DNA, RNA, or proteins according to molecular size
Molecules travel through a gel under an electrical field.
Cytosine bonds with what?
Thymine
Adenine bonds with what?
Guanine.
What nitrogen RNA base replaces Thymine?
Uracil
What are Okazaki fragments?
short pieces of DNA created on the lagging strand during DNA replication. These fragments form in small sections and are later connected by an enzyme called DNA ligase.
What occurs when an individual receives 3 copies of chromosomes instead of the normal two?
Down Syndrome
What occurs when an individual inherits only a single X chromosome, and the Y chromosome is missing?
Turner Syndrome
what’s the name for when a man has an extra X chromosome?
Klinefelter syndrome
