Micro Block 2 Flashcards
Define genome
entire complement of genes on all chromosomes found in an organism (hereditary info)
Define gene
What 3 functions is genetic code translated for?
segment of DNA containing the genetic code for a functional product.
structural, catalytic or regulatory functions
How is the genetic code carried?
As a sequence of nucleotide molecules in the nucleic acid macromolecule
Define genotype
total genetic makeup w/ potential properties
Define phenotype
the actual expressed properties of an organism
Define transcription
transfer of genetic code on DNA gene to mRNA by DNA dependent RNA polymerase
Define translation
the synthesis of a new polypeptide at the ribosomes by linking aa in sequence specified by mRNA
Define constitutive genes
Constantly expressed (transcribed and translated into functional units) accounts for 60-80% of genes
Define inducible genes
Genes that can be “turned on”
Define repressible genes
Genes that can be “turned off”
Define operon
Related genes that are regulated as a group/series
Define mutation
Changes (substitution or deletion) in the sequence of DNA bases which changes the genetic code
what are the molecular components of a nucleotide?
5 C sugar (ribose or deoxyribose)
N base- binds to 1’ prime of the 5C
P group- bound to 5’ C
What are the nitrogenous bases?
Purines- Adenine Guanine
Pyrimidine- Thymine Cytosine (Uracil)
A->T(U)
G->C
State the major structural components and characteristics of DNA
2 strands of paired nucleotides attached to deoxyribose
strand- long chain of nucleotides
Strand direction- end on which no P is bound to 3’ C, end with P bound ONLY to 5’ C is the 5’ end
Antiparallel- strands run in opposite directions (3’ nucleotide binds to 5’ nucleotide counter part)
Describe the steps of DNA replication
1- replication fork formation. DNA unwinding by helicase, DNA gyrase and topoisomerase by breaking H bonds between bases/strand.
2- DNA polymerase binds to DNA and inserts complementary nucleotides (always added to exposed 3’ end, strands grow in 5’ to 3’ direction) while also editing for error
3- leading strand has 3’ exposed/leading into replication fork. New strand grows towards replication fork and is continuously replicated.
- Lagging strand (discontinuous) has 5’ end exposed facing replication fork. RNA primer and polymerase are needed to initiate strand growth if nucleotide is missing 3’ binding site. DNA polymerase takes over for RNA primer down to the last/final nucleotide. DNA ligase takes over and inserts missing nucleotide to bind newly formed strand w/ existing strand.
- New double strand re-winds, parental strand unwinds to expose more nucleotides.
Entire process is semiconservative, each helix consists of one newly synthesized nucleotide and one original/parent nucleotide
What are the major components/characteristics of RNA?
Large, single stranded molecule of nucleotides (m,t,rRNA), U replaces T
Function of mRNA
Carries genetic code from DNA to ribosome
Function of RNA codon?
3 nucleotides on mRNA that specify AA to be placed in sequence on polypeptide.
3 nucleotides = 1 codon
1 codon = 1 aa
Function of tRNA?
transports aa to developing peptide chains
Function of Anticodon?
Site on tRNA that binds w/ mRNA codon (carries 3 bases that complement the codons).
Specifies which aa will be carried by tRNA.
Function of rRNA?
facilitator for mRNA and tRNA functions
What is the purpose of transcription?
transfer of genetic code on DNA into mRNA strand by means of DNA dependent RNA polymerase
What are the 4 steps of transcription?
1- DNA helix unwinds
2- RNA polymerase binds w/ DNA @ promoter site
3- Complementary RNA nucleotides joined in sequence by RNA polymerase
4- process ends when RNA polymerase reaches termination region. New single-stranded mRNA releases, DNA rewinds.