the amount of adenine equals the amout of thymine and the amount of guanine equals the amount of cytosine
50% of bases are purines and 50% are pyrimidines
purines-
A and G- 2 carbon rings
pyrimidines-
C and T- 1 carbon ring
Double Helix-
2 strands composed of a sugar and phosphate backbone with N-containing bases paired on the inside-2 strands spiral or twist around each other
adenine always pairs with_____
thymine
Guanine always pairs with _____
Cytosine
DNA replication-
During replication each old strand of the parent molecule serves as a template for a new strand in a daughter molecule
Steps of replication-
unwinding-the weak hydrogen bonds are broken
complementary base pairing- A pairs with T and C pairs with G
joining-nuckeotides join to form a new strand
semi-conservative replication-
because each daughter molecule has one old strand and one new strand
One Gene-One polypeptide-
each gene contains the info for making one protien
RNA-
Ribonucleic Acid
DNA-
Deoxyribose Nucleic Acid
Differences between DNA and RNA-
different sugar-ribose
different base-uracil replaces thymine
different number of strands-1 single straight strand
Messenger RNA-mRNA
takes a message fromt he DNA in the nucleus to the ribosomes in the cytoplasm
Ribosomal RNA-rRNA
along with protiens, makes up the ribosomes
transfer RNA-tRNA
carries amino acids to the robosomes
Gene expression-
the process by which a gene produces a product usually a protien
gene-
a sequence of nucleotide bases that codes for a product usually a protien
transcription-
occurs in the nucleus. process of making mRNA copy from DNA. similar to DNA replication bc one strand of DNA serves as the template for the mRNA formation
translation-
occurs in the cytoplasm. process by which the sequence of nucleotide bases in mRNA determines the sequence of the amino acids in a protein
genetic code-
consists of 64 three base "words" called codons.
codons-
3 nucleoitides of mRNA that code for a specific amino acid or the start/stop of translation
9 steps of gene expression-
1.DNA in nucleus serves as template for its own replication and for mRNA during transcription
2.mRNA is processed before leaving nucleus and the introns(portions dont leave nucleus) are removed
3.When mRNA is formed it has codons
4.mRNA moves to cytoplasm and becomes assoiciated with ribosomes
5.tRNA with anti codons carries amino acids to mRNA and ribosome
6.anticodon-codon complimentary base pairing occurs
7.peptide cahin is transferred from resident tRNA to new tRNA
8.tRNA departs and will soon pick up another amino acid
9.continues till reach a stop codon than releases a protien
polysome/polyribosome-
a string of robosomes simultaneously reading different regions of the smae mRNA strand