Genomes and DNA Flashcards
What are prokaryotes?
Bacteria and archaea
Prokaryotes are the simplest and most basic life forms, characterized by the absence of a nucleolus.
What are eukaryotes?
More complicated organisms that have organelles, including animals, plants, and fungi
Eukaryotes are generally larger than prokaryotes.
What is the structure of prokaryote genomes?
Circular genome, can be one or many, occasionally linear
Includes plasmids and is compact due to supercoiling.
What is supercoiling in DNA?
Twisting of the DNA structure, can be negative or positive
It results from the addition or removal of turns in the double helix.
What are plasmids?
Extra areas of DNA that can confer antibiotic resistance and the ability to use complex compounds as food
Plasmids can transfer between bacteria, spreading genetic information.
What is a gene?
A sequence of DNA or RNA that codes for a molecule (protein) with a function
Genes are fundamental units of heredity.
What are introns?
Non-coding sections of DNA
They are removed during RNA processing.
What are exons?
Coding sections of DNA
Exons are retained in the final mRNA molecule.
What are retrotransposons?
Elements that copy themselves throughout DNA using reverse transcription, including SINEs, LINEs, and LTRs
They contribute to genome evolution and diversity.
What is a transposon?
DNA that can move around the genome
Transposons are often referred to as ‘jumping genes’.
What is a tandem repeat?
Repeated sections of DNA that occur immediately after each other
They can vary in length and number of repeats.
What is mitochondrial DNA (mtDNA)?
Small, circular DNA located in the mitochondria, containing genes for mitochondrial function
It has a high copy number per cell and is inherited maternally.
What is chloroplast DNA (cpDNA)?
DNA located in chloroplasts, coding for about 200 genes related to photosynthesis
cpDNA is larger than mtDNA and also exhibits low variation due to uni-parental inheritance.
What is the primary role of DNA?
To carry and store genetic information
DNA also serves as a means of passing information down generations.
What are the components of DNA?
A pentose sugar, a nitrogenous base, and a phosphate group
These components form nucleotides, the building blocks of DNA.
What differentiates RNA from DNA?
RNA contains ribose, uracil instead of thymine, and is usually single-stranded
This structural difference impacts their functions in protein synthesis.
What are the types of RNA involved in protein synthesis?
Messenger RNA (mRNA), Transfer RNA (tRNA), Ribosomal RNA (rRNA)
Each type of RNA plays a specific role in the process of translating genetic information into proteins.
What is the central dogma of molecular biology?
The flow of genetic information from DNA to RNA to protein
It describes the processes of transcription and translation.
What is RNA polymerase?
An enzyme that catalyzes the synthesis of RNA from a DNA template
It functions by adding ribonucleotides in the 5’ to 3’ direction.
What are the phases of transcription?
Initiation, elongation, and termination
Each phase involves specific interactions and processes to produce RNA.
What is the TATA box?
A DNA sequence that serves as a promoter for transcription in eukaryotic cells
It is typically located about 25 base pairs upstream of the transcription start site.
What is a molecular marker?
A specific piece of DNA that provides unique information
Molecular markers are used in various applications, including forensic science.
What are the three main types of molecular markers?
Gene regions, SNPs, STRs
Each type has unique applications and characteristics in genetic analysis.
What are STRs?
Short Tandem Repeats, co-dominant markers inherited in a Mendelian fashion
STRs can vary in repeat length and can be used in DNA profiling.
What is Polymerase Chain Reaction (PCR)?
A method used to amplify specific DNA sequences
PCR is fundamental for DNA detection and analysis.
What is the purpose of fluorescence detection in DNA analysis?
To measure the presence of DNA through emitted light
Fluorescence allows for the detection of DNA without direct visualization.
What happens during DNA melting?
Separation of double-stranded DNA into single strands
Melting occurs at a specific temperature, known as the melting temperature (Tm).
What is the significance of the melting temperature (Tm)?
It is the temperature at which half of the helical structure of DNA is lost
Tm is influenced by GC content; higher GC content results in a higher Tm.
What is qPCR?
Quantitative PCR that combines amplification and detection of DNA in real-time
It allows for the quantification of DNA during the amplification process.
What is the difference between a heterozygote and a homozygote in STR analysis?
A heterozygote shows two peaks of different sizes, while a homozygote shows a single peak
This difference is used to determine genetic variation in populations.
What is the role of ribosomal RNA (rRNA)?
Major component of ribosomes, essential for protein synthesis
rRNA forms the structural and functional core of ribosomes.
What is messenger RNA (mRNA)?
RNA that encodes the information for protein synthesis
mRNA is transcribed from protein-coding genes and serves as a template for translation.
What is transfer RNA (tRNA)?
RNA that carries amino acids to the ribosome during protein synthesis
tRNA acts as an adaptor between mRNA and the corresponding amino acids.
What is the approximate percentage of cellular RNA that is ribosomal RNA (rRNA)?
Approx 80% of cellular RNA
Several forms of rRNA are present, such as 23S, 16S, and 5S in prokaryotes.
What is the major function of ribosomal RNA (rRNA)?
Major component of ribosomes, structures where proteins are synthesized.
How is the structure of rRNA characterized?
Folded into complex, 3D shapes.
What percentage of cellular RNA is transfer RNA (tRNA)?
Approx 15% of cellular RNA.
What is the primary role of transfer RNA (tRNA) in protein synthesis?
Carries and delivers amino acids in an activated form to ribosomes for peptide bond formation.
What are the two key sites present in tRNA?
- Amino acid attachment site
- Anticodon (template-recognition site)
What is translation in the context of protein synthesis?
Synthesis of proteins where the sequence of bases in mRNA specifies the sequence of amino acids in the protein product.
What are the three binding sites on a ribosome?
- P (peptidyl-tRNA)
- A (aminoacyl-tRNA)
- E (exit)
What is a codon?
A group of 3 bases that codes for an amino acid.
True or False: The genetic code is degenerate.
True.
What does it mean that the genetic code is unambiguous?
A codon only codes for one amino acid.
What is the initiation sequence for translation in eukaryotes?
AUG, coding for methionine.
What is the Shine-Dalgarno sequence?
A purine-rich sequence needed in prokaryotes for translation initiation.
What are the stop codons that designate chain termination?
- UAA
- UAG
- UGA
What role do release factors play in translation termination?
They bind to the ribosome and release the newly synthesized protein.
What is the direction of mRNA translation?
5’ to 3’ direction.
What is the primary function of DNA polymerases?
Promote formation of phosphodiester bonds joining units of the DNA backbone.
What does DNA polymerase I do during DNA replication?
- 5’ - 3’ polymerase activity
- 3’ - 5’ exonuclease activity for proofreading.
What is the role of DNA ligase?
Forms a phosphodiester bond joining two DNA chains.
What are Okazaki fragments?
Short segments synthesized on the lagging strand during DNA replication.
What is the function of topoisomerases in DNA replication?
Solve physical problems in the coiling of DNA during unwinding.
What is the role of DNA primase?
Synthesizes a short stretch of RNA primer.
What is the action of DNA polymerase III?
Catalyzes synthesis of new DNA in the 5’ to 3’ direction.
How many origins of replication do humans have?
30000 origins of replication.
Fill in the blank: Eukaryotic DNA replication has ______ points of origin.
multiple
What is the significance of the Kozak sequence in eukaryotic translation initiation?
Helps recruit the ribosome to the mRNA for protein synthesis.
What is the function of the 5’ to 3’ exonuclease activity of DNA polymerase I?
Hydrolysis of terminal phosphodiester bond at the 5’ end of the DNA chain.
