genetics Flashcards
gene
a heritable factor that consists of a length of DNA and influences characteristics
locus
position of a gene on a chromosome
Allele
A specific form of a gene
Types of dna
-introns
-exons
-highly repetitive sequences
-structural dna (telomeres, centromeres)
- inactive genes
Other
Short tandem repeats
In polymorphisms (areas of dna that are unique to each individuals)
A C G T U
adenine cytosine guanine thymine uracil
characteristics of dna
antiparallel strands double helix hydrogen bonds between two strands
A-T
two hydrogen bonds
C-G
three hydrogen bonds
nucleosome
8 histone proteins; help to organise DNA, prevent random transcription
Hershey and Chase experiment
radioactive S (protein coats) and P (DNA) in bacteriophages and after infecting bacteria found that genetic inf stored by DNA
DNA polymerase III
catalyses creation of covalent bonds between 3’ and 5’ ends of new nucleotide (5->3 direction)
DNA polymerase I
removes RNA primer of Okazaki fragments and replaces RNA nucleotides with DNA nucleotides
DNA ligase
catalyses formation of covalent bonds between Okazaki fragments
DNA helicase
unwinds the double helix by breaking hydrogen bonds
DNA primase
binds nucleotides of RNA primer together
DNA gyrase
prevents DNA from getting tangled by breaking it at strain points; relieves the strain on the “twisted side” by supercoiling
single strand binding proteins (SSBs)
prevents reformation of the double helix of the separated strands; prevents the strand from being digested; allows enzymes to work effectively
Okazaki fragments
from the lagging strand, 100-200 nucleotides; sticked together by DNA ligase
stopping DNA replication
dideoxyrybonucleoside replaces one nucleoside and next covalent bond can’t be formed
Meselson and Stahl’s experiment
N15 atoms (heavier) used to grow bacteria; provided proof that DNA replication is semi conservative
transcription
the process of obtaining mRNA from DNA template; takes place in the nucleus
Initiation of transcription
RNA polymerase binds to the promoter ( specific base sequence that is non coding)
Elongation of transcription
RNA polymerase unwinds the DNA strand (H bonds breaking) and attaches individual nucleotides together to form a single strand of RNA
termination of transcription
terminator transcribed, RNA fold back on itself and detaches
5’ cap
7-methylguanosine added after 5’ phosphate is removed; regulator function
poly(A) tail
multiple adenosine monophosphates added to 3’ end; enhance stability
splicing
removing introns, leaving exons; allows for multiple proteins to be created from the same DNA sequence
