DNA, Genes and Chromosomes + Protein Synthesis. Flashcards
(19 cards)
Compare and contrast the DNA in eukaryotic cells and the DNA in prokaryotic cells.
- Their nucleotides both contain a deoxyribose sugar, a phosphate group and a nitrogen-containing base.
- Adjacent nucleotides are joined together by phosphodiester bonds.
- Eukaryotic DNA is longer compared to Prokaryotic DNA.
- Eukaryotic DNA is linear, and Prokaryotic DNA is circular.
- Eukaryotic DNA is associated with histones, and Prokaryotic DNA is not.
- Eukaryotic DNA contains introns, and Prokaryotic DNA does not.
What is a gene?
A sequence of bases in DNA that codes for a polypeptide or a fully functional RNA molecule.
What is a locus?
The fixed positions of a gene on a particular DNA molecule.
What is a codon?
A triplet of bases on mRNA that codes for a specific amino acid.
Why is the genetic code described as degenerate?
An amino acid can be coded for by more than one base triplet.
Why is the genetic code described as universal?
The same base triplets will code for the same amino acids in all organisms.
Why is the genetic code described as non-overlapping?
Each base is a part of only one triplet, so each triplet is read as a discrete unit.
What are exons?
Base sequence of a gene that codes for amino acids.
What are introns?
The base sequence of DNA that does not code for amino acids.
DNA and Protein Synthesis
Define the term genome.
The complete set of genes in a cell.
Define the term proteome.
The complete set of proteins that a cell can make.
What is transcription?
The production of mRNA from DNA, in the nucleus.
What is translation?
The production of a polypeptide from mRNA in the ribosomes.
What is the structure of mRNA?
- A polymer made of nucleotides.
- Adjacent nucleotides are joined together by phosphodiester bonds.
- Shorter than DNA, so it can leave the nucleus.
- Single-stranded.
- Complementary base sequence to DNA.
What is the structure of tRNA?
- A polymer made of nucleotides.
- Adjacent nucleotides are joined together by phosphodiester bonds.
- Single-stranded.
- Contain an anticodon, which is complementary to a specific codon on the mRNA, and allows the tRNA to bind to mRNA.
- Contains an amino acid binding site.
- Folded into a clover-like shape due to the formation of hydrogen bonds between complementary bases.
Compare and Contrast the Structure of mRNA and tRNA.
- They both are single-stranded.
- They are both polymers of nucleotides.
- Adjacent nucleotides are held together by phosphodiester bonds in both.
- mRNA is linear, and tRNA has a clover-like shape.
- tRNA contains hydrogen bonding between paired bases, and mRNA does not.
- tRNA contains anticodons and mRNA does not.
- tRNA contains an amino acid binding site, and mRNA does not.
Describe the process of transcription.
- DNA helicase breaks the hydrogen bonds between the DNA chains, causing the DNA to unwind.
- Only one strand is used as a template to make a pre-mRNA strand.
- Free nucleotides align next to their complementary bases due to specific base pairing.
- Adenine pairs with uracil. Cytosine pairs with Guanine.
- RNA polymerase joins adjacent nucleotides together by forming phosphodiester bonds between them.
- Pre-mRNA is spliced to remove the introns, forming mRNA.
Describe how translation leads to the formation of a polypeptide.
- mRNA attaches to a ribosome, and the ribosome moves to the start codon.
- The tRNA anticodon binds to the complementary codon on the mRNA.
- tRNA brings a specific amino acid with it.
- The ribosome moves over to the next codon, and another tRNA molecule binds to the mRNA.
- A peptide bond forms between the amino acids in a condensation reaction, using energy released by ATP.
- Once once amino acid is added to the polypeptide chain, a tRNA molecule is released.
- The ribosome moves along the mRNA until a stop codon is reached.
