DNA and Genetics Flashcards
Gene
A section of DNA nucleotides that codes for a specific protein.
Where is DNA found?
Nucleus of eukaryotic cells
Where are proteins made?
ribosomes within the cytoplasm of eukaryotic cells.
RNA structure and function
ribonucleic acid; single-stranded nucleic acid that contains the pentose sugar ribose. It is a polynucleotide (made up of mononucleotides which contain phosphate groups) and is involved in protein synthesis (making proteins via translation). Contains bases (G,C,A,U (uracil)). There are three versions of it (MRNA,TRNA,rRNA)
Genetic code
collection of codons of mRNA, each of which directs the incorporation of a particular amino acid into a protein during protein synthesis. (Adenine, uracil, guanine, cytosine).
Number of amino combinations
20 (2 bases)
Number of triplet combinations
64 (3 bases)
Protein synthesis
the formation of proteins by using information contained in DNA and carried by mRNA. (Translation and transcription)
Transcription definition
Process by which information on a DNA strand is transferred to an mRNA molecule. Occurs in the nucleus and is controlled by the enzyme RNA polymerase.
Transcription process
- occurs in the nucleus (controlled by RNA polymerase)
-DNA helicase unzips the double helix and breaks the hydrogen bonds between the base pairs.
-free nucleotides that are complementary to the exposed DNA bases on the template are joined by phosphodiester bonds.
-once made, the mRNA leaves the nucleus, through the nuclear pores, into the cytoplasm, onto a ribosome.
Translation definition
The process of converting mRNA into amino acids that form proteins. Happens in ribosomes in the cytoplasm.
Translation process
- amino acids in the cytoplasm are activated for protein synthesis
- ribosomes bind to the mRNA (messenger)
- in the cytoplasm there are free molecules of tRNA (transport) which have a triplet of unpaired bases at one end (anticodon) and a specific amino acid binding site at the other.
-There are at least 20 different tRNA molecules, each with a specific anti codon and specific amino acid binding site - tRNA transfers the amino acid to the ribosome
- the mRNA reads 3 bases at a time as each triplet is read a tRNA delivers the corresponding amino acid, which is added to a chain of amino acids, that once complete folds into a complex shape to form the protein’s secondary, tertiary (and quaternary) structure.
Allele
Alternative forms of the gene on the same position (loci) on a chromosome.
Phenotype
An organism’s physical appearance, or visible traits.
Genotype
genetic makeup of an organism/an organism’s combination of alleles.
Dominant
Alleles that can be express their phenotypic character with only one example in a body cell.
Recessive
Alleles which will be expressed only if homozygous in a body cell and dominant allele not present.
Where does transcription occur?
Nucleus
What does degenerate mean?
redundant code (codons that encode the same amino acid).
Describe the role of mRNA in protein synthesis
mRNA carries amino acids from the DNA in a cell’s nucleus to a ribosome in the cytoplasm, where the mRNA sequence is read three bases at a time and each codon is translated into its corresponding amino acid in a growing protein chain.
Compare and contrast the structure of a DNA double helix with the structure of tRNA
DNA contains a deoxyribose sugar, whereas tRNA contains a ribose sugar. DNA is a double stranded helix, whereas tRNA is a is single stranded and folded into a clover leaf structure. Both structure contain complementary base pairings but tRNA also contains an anticodon of 3 bases that codes for a specific amino acid. tRNA also contains an amino acid attachment site and DNA does not.
Sex linked trait
characteristics (or traits) that are influenced by genes carried on the sex chromosomes
Epigenetic
Nature vs nurture (how environment can affect genome)
Polygenic
Trait controlled by multiple genes (e.g height, eye colour)
Monogenic
Traits controlled by one gene (e.g dwarfism)
Lac operon stages
- Repressor attached to operator section of DNA stopping RNA polymerase from binding to the DNA.
- Lactose binds to the repressor (changing its shape) so it comes off the operator.
- This allows RNA to bind to the promoter region of DNA and so transcription can occur.
- mRNA will be translated and the enzyme to break down lactose will be made.
Lac operon definition
Prokarytoic example of controlled gene expression. When bacteria feed on lactose they will make an enzyme to break down the lactose. When they don’t feed on lactose the enzyme is not made.
