Genetics Flashcards
DNA
deoxyribonucleic acid, form of genetic material in the nucleus
Histone
proteins that combine with DNA in eukaryotes to form chromatin
Nucleoid
A region of concentrated DNA in the cytoplasm of prokaryotic cells
Describe the location of DNA in prokaryotes
prokaryotic chromosomes are circular with far fewer associated proteins. there is also DNA in circular elements called plasmids
Nucleotide
a body consisting of a sugar (deoxyribose in DNA, a phosphate group and a nitrogen containing base
Nucleoside
A nucleotide without a phosphate group
what is the difference between deoxyribose and ribose
Deoxyribose lacks an oxygen ribose has on position 2 carbon, H instead of OH
what are the four N-bases and are they purines or pyrimidines
Adenine and Guanine (purines, 2 rings) cytosine and thymine (pyrimidines, 1 ring)
Phosphodiester bonds
phosphate binds to the 3 carbon on one sugar and the 5 carbon on the next
3’
the end of a DNA chain with nothing bonded on the 3 carbon
5’
the end of the chain with a phosphate bonded to the 5 carbon on the end
DNA measurements
diameter-2nm, distance between 2 bases-0.34nm, distance of 1 full turn-3.4nm
what are the differences between DNA and RNA
RNA has ribose instead of deoxyribose, uracil instead of thymine and exists in short one strand sections
Transcription
The synthesis of RNA through complementary pairings with a template strand
RNA polymerase
the enzyme that does transcription
in which direction does transcription occur
the template strand is read 3’ to 5’ and RNA is synthesized 5’ to 3”
describe the action of RNA polymerase
it causes localized unwinding and rewinding of DNA, binding at a promter site and moving along the chain until a terminator is reached.
template strand
the strand used by RNA polymerase to synthesize RNA
coding strand
the strand of DNA that isn’t the template strand
terminator
either a hairpin or a protein (rho) factor that causes the complex to fall apart
Protein rho
a protein that binds to DNA to stop transcription
mRNA
messenger RNA, codes for a protein
rRNA
ribosomal RNA, major parts of a ribosome
tRNA
transfer RNA, connects to an amino acid and brings it to the ribosome where tRNA decodes the mRNA
translation
the process of synthesizing proteins from mRNA
codon
a sequence of three bases that code for a specific amino acid
which direction does translation occur in
mRNA is read 5’ to 3’ proteins are synthesized N terminus to C terminus
tRNA structure
an amino acid binding site at the 3’ end and an anticodon loop to bind to the codon
Amino-acyl tRNA synthase
an enzyme that binds amino acids to their respective tRNA
ribosome structure
a small subunit of 1 rRNA and 21 proteins and a large subunit of 2 rRNA and 34 proteins
describe the process of translation
mRNA binds to the smaller subunit which binds to the first Amino-acyl tRNA. the large subunit then binds to the complex. When the stop codon is reached a release factor binds and causes the complex to fall apart.
A site
positions incoming Amino-acyl tRNA
P site
the second tRNA binding site
what post-transitional modifications can happen to proteins
the initiating Met is often removed, disulphide bonds form, amino acids are modified and some proteins are cleaved
Monocistronic
mRNA coding for one protein
Polycistronic
mRNA that codes for multiple proteins
DNA polymerase
enzyme catalyzing elongation of DNA hence causing replication
Describe the process of DNA replication
H bonds break and DNA unwinds allowing for each strand to be used as a template for a new strand through the matching of base pairs. This requires the presence of all nucleotides, magnesium ions and a primer.
what is the direction of replication
5’ to 3’ on new strand
leading strand
the strand on which replication occurs continually
Lagging strand
the strand on which replication occurs in small fragments called Okazaki fragments
DNA ligase
the enzyme responsible for stitching together Okazaki fragments
Mutation
physical changes introduced to DNA
Extragenic mutation
A mutation that doesn’t occur in a gene and hence has no effect
Intagenic mutation
mutation that occurs in a gene, may have an effect
Spontaneous Mutation
arises from damage from an unknown cause
Induced Mutations
Mutations as a result of exposure to known chemical, physical or biological mutagens
Somatic Mutations
Mutations to somatic cells
Germinal Mutations
Mutations to gametes
Broad types of Mutations
point (single base) and gross
INDEL
insertion or deletion of base pairs
Duplication
base pairs are duplicated
Inversion
A section of DNA is reversed in direction
Translocation
A section is moved from one region to another
Polyploidy
A change to the entire chromosome set
Aneuploidy
Change within the chromosome set
Transition
substuting A for G or C for T
Transversion
substituting a purine with a pyrimidine
Extragenic repeats
repeating base sequences, the number of repeats may increase every generation
Frameshift
addition or deletion that changes where codons are in the code
Missense
substitution of one base pair
Nonsense
mutation resulting in a early stop codon
silent mutation
point mutation with no effect
constitutive proteins
proteins always expressed
Regulated proteins
proteins expressed only when needed
Inducer
Molecule that induces synthesis
Induction
the process by which a molecule promotes protein synthesis
operator site
regulatory protein binding aite adjacent to a promoter
Promoter site
RNA polymerase binding site where transcription starts
negative regulation
regulator blocks RNA polymerase access at the operator site
Positive regulation
two distant promoter sites and a promoter (ex. cyclic AMP) needs to bring the sites together so RNA polymerase can bind.
