DNA and Proteins Flashcards
What is DNA?
DNA, or deoxyribonucleic acid is the genetic material found mostly in the nucleus of a cell, that directs or controls the activities of the cell.
Function of DNA
Stores and transmits genetic information.
What is a chromosome?
A chromosome is an organised structure consisting of a singular piece of coiled DNA together with a protein and containing many genes.
Which two organelles have DNA resembling that of Prokaryotes?
Mitochondria and Chloroplasts.
What is the structure of DNA?
DNA is a double-stranded helical molecule composed of nucleotides. Each nucleotide contains a phosphate group, a sugar (deoxyribose), and a nitrogenous base (adenine, thymine, cytosine, or guanine). The two strands are antiparallel and held together by hydrogen bonds between complementary base pairs (A with T and C with G).
What is the shape of eukaryotic chromosomes?
Linear.
Where are eukaryotic chromosomes located?
In the nucleus.
What are eukaryotic chromosomes associated with?
Histone proteins.
What is the chromosome in Prokaryotes?
One single circular chromosome that floats freely in the cytosol (no protein attached).
What is a gene?
A gene is a segment of DNA on a chromosome that contains the complete sequence of bases required to direct the manufacture of a polypeptide or RNA molecule.
What is a protein?
A protein is a macromolecule composed of long chains of amino acids folded into unique shapes that give cells their structure and functions.
What is an exon?
Coding segment of DNA. Sequences that are translated (expressed) into a protein.
Introns
Non-coding segments of DNA. Sequences that are transcribed but then cut out of the mRNA, not being translated.
What are the three components of a DNA nucleotide?
A phosphate group, deoxyribose sugar, and a nitrogenous base (adenine, thymine, cytosine, or guanine).
What are the base-pairing rules in DNA?
Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).
What type of bonds hold the two strands of DNA together, and why are they important for replication?
Hydrogen bonds; they are weak enough to allow the strands to separate during replication.
Why is complementary base pairing (A-T and C-G) important in DNA replication?
It ensures accurate copying of genetic information, as each base on a template strand guides the addition of the correct complementary base on the new strand.
What does “semi-conservative” mean in DNA replication?
Each new DNA molecule consists of one original (parent) strand and one newly synthesized strand.
What enzyme unwinds the DNA double helix at the start of replication?
Helicase.
Which enzyme adds new nucleotides to form a complementary strand during DNA replication?
DNA polymerase.
How does the semi-conservative model of DNA replication help maintain genetic stability?
By conserving one original strand in each new DNA molecule, it ensures accurate transmission of genetic information to new cells.
Which enzyme joins the sugar-phosphate backbone of the free nucleotides?
DNA ligase.
What are enzymes?
Enzymes are proteins that speed up or slow down chemical reactions.
What are exons in eukaryotic genes?
Exons are the coding segments of a gene that contain sequences coding for amino acids and are translated into proteins.
What are introns in eukaryotic genes?
Introns are non-coding segments of a gene that do not code for amino acids and are removed during mRNA processing.
Are both exons and introns transcribed into RNA?
Yes, both exons and introns are transcribed into pre-mRNA.
What happens to introns during mRNA processing?
Introns are removed from the pre-mRNA through a process called splicing, leaving only exons in the mature mRNA.
How is RNA different to DNA?
The sugar is Ribose
It is single stranded
It uses Uracil instead of Thymine.
It is not confined to the nucleus.
What is gene expression?
The process where the genetic code, stored on the DNA is used to make gene products (proteins).
What is transcription?
The production of messenger RNA (mRNA).
What is translation?
Translation is the synthesis of a polypeptide using the genetic information on mRNA.
What is the role of DNA in protein synthesis?
DNA acts as the template for transcription, providing the genetic code that is transcribed into mRNA.
What is mRNA and its function in protein synthesis?
mRNA (messenger RNA) carries the genetic information from DNA to the ribosome, where it is translated into a protein.
What is tRNA and its role in translation?
tRNA (transfer RNA) brings amino acids to the ribosome and matches its anticodon with the mRNA codon to ensure correct amino acid sequencing.
What is rRNA and its role in translation?
rRNA (ribosomal RNA) forms the core structure of ribosomes, catalyzing the assembly of amino acids into a polypeptide chain.
What is a codon?
A codon is a three-nucleotide sequence on mRNA that codes for a specific amino acid.
What is an anticodon, and where is it found?
An anticodon is a three-nucleotide sequence on tRNA that pairs with the complementary codon on mRNA during translation.
What is the main purpose of transcription?
To copy DNA’s genetic code into mRNA, which will later be used to make proteins.
What enzyme is responsible for building the mRNA strand during transcription?
RNA polymerase.
What is the pre-mRNA?
The initial RNA strand produced from transcription, which includes both coding (exons) and non-coding (introns) regions.
What happens to introns during mRNA processing?
Introns are removed, and exons are joined together in a process called splicing.
Where does the mature mRNA go after processing?
It exits the nucleus and travels to the ribosome for translation.
What is the purpose of translation?
To use the mRNA sequence to build a protein.
Where does translation take place in the cell?
At the ribosome in the cytoplasm.
What is the start codon, and what does it signal?
The start codon (usually AUG) signals the ribosome to begin translation.
What is the role of tRNA in translation?
tRNA brings amino acids to the ribosome and matches its anticodon with mRNA codons.
How does the ribosome know which amino acid to add next?
Each mRNA codon pairs with a matching tRNA anticodon, which carries the correct amino acid.
What happens when the ribosome reaches a stop codon?
Translation ends, and the ribosome releases the completed protein.
What is a polypeptide chain?
A chain of amino acids linked together, which folds to become a functional protein.
What determines the way a protein will form?
The sequence of amino acids.
What are the four levels of protein structure?
Primary, secondary, tertiary and quaternary.