DNA, GENES AND PROTEIN SYNTHESIS Flashcards
Describe the structure of DNA
Made up of deoxyribose sugar, a phosphate group, and 1 of 4 nitrogenous bases (A G C T).
It is double-stranded, and hydrogen bonds between the bases form a helix shape
Describe the role of DNA
Carries genetic info
Determines our inherited characteristics.
Describe the structure of RNA
Made up of a ribose sugar, a phosphate group, and 1 of 4 nitrogenous bases (A G C U)
It is single stranded
Describe the role of RNA
Transfers genetic info from DNA to ribosomes for protein synthesis
PURINE vs PYRIMIDINE
PURES AS GOLD
CUT
How is DNA in eukaryotic cells different from in prokaryotic cells?
Euk.
- found in nucleus
- long & linear
- associated with histone proteins to form chromosomes
Pro.
- short & circular
- not associated with proteins
What is the genetic code?
The order of bases on DNA.
Consists of codons
Identify features f the genetic code
NON-OVERLAPPING - Each triplet is only read once
DEGENERATE - More than 1 triplet codes for the same aa
UNIVERSAL - same bases and sequenced used by all species
What is a gene?
A sequence of bases on a DNA molecule that codes for a specific sequence of aa to make a polypeptide.
Can also code for functional RNA
What is a locus?
The fixed position on a DNA molecule occupied by a gene
What is a locus?
The fixed position on a DNA molecule occupied by a gene
What is an allele?
Different versions of the same gene, found at the same locus on a chromosome
What are exons and introns?
EXONS = Regions of DNA that code for aa sequences. Separated by 1 or more introns.
INTRONS = Regions of DNA that do not code for anything
What are introns found?
Between exons
within genes
What is the genome?
The complete set of genetic info contained in the cells of an organism
What is the proteome?
The complete set of proteins that can be produced by a cell
Describe the structure of mRNA
A long, single strand.
Its base sequence is complementary to the DNA it was transcribed from
Suggest advantages of using mRNA rather than DNA for translation
- shorter & contains uracil = breaks down quickly so no excess polypeptide forms
- single-stranded and linear = ribosome moves along strand & tRNA bonds to exposed bases
- contains no introns
Describe the structure of tRNA
A single strand of around 80 nucleotides that is folded over into a clover leaf shape.
On one end is an aa binding site
What is produced by transcription?
mRNA
Where does transcription take place?
In the nucleus
Outline the process of transcription
- DNA uncoils into 2 strands with exposed bases. One used as a template.
- Free nucleotides line up next to their complementary bases, and r joined together by RNA polymerase
What happens to mRNA after transcription?
In eukaryotic cells, pre-mRNA must be spliced to remove introns, leaving only the coding regions.
Then it moves out of the nucleus and attaches to a ribosome.
What is produced by translation?
Proteins
