7.1 Flashcards
what did hershey and chase discover?
- they discovered that dna was the genetic material instead of protein
- proved that dna makes up genes within an organism
describe the 5 steps to hershey and chase’s experiment
- make (cultured) a virus in radioactive phosphorus (found in dna) and sulphur (found in protein coat)
- expose bacteria (e-coli) with this virus
- centrifuge to separate the protein coat to the top (fluid supernatant of matrix) and bacteria to the bottom (solid pellet of bacteria)
- measure the radioactivity with a geiger counter
- found that sulphur was mostly found in the supernatant and high phosphorus radioactivity is seen in the bottom (within cells), indicating dna, which must be the genetic material
how are nucleosomes bound together?
by a small length of dna and binding of the N-terminal tails of histone proteins
what is the function of the H1 histone protein?
its function is to hold the coiled dna in place around the histone protein core
how does dna supercoil?
by bunching up nucleosomes close together
in which direction does dna replication occur?
5’ to 3’
describe the 7 steps of dna replication
- a semi conservative process
1. dna gyrase unwinds dna
2. helicase splits the dna into 2 separate strands
3. dna primase adds rna primers on the lagging strand
4. dna polymerase III adds nucleotides in a 5’ to 3’ direction continuously on the leading strand but discontinuously on the lagging strand
5. okazaki fragments form on the lagging strand
6. dna polymerase I replaces rna primer with dna
7. dna ligase joins the okazaki fragments together
what is the function of dna gyrase during dna replication?
unwinding the 2 strands
what is the function of helicase in dna replication?
splitting the dna strand into 2 template strands
what is the function of the single stranded binding proteins during dna replication?
to hold the 2 template strands apart, and in place so they dont wind back together
what is the function of dna primase during dna replication?
to add rna primer to the lagging strand
what is the function of dna polymerase III during dna replication?
add nucleotides in 5’ to 3’ direction continuously on the leading strand and discontinuously on the lagging strand
what are okazaki fragments?
sections of replicated dna between rna primer formed as a result of discontinuous replication on the lagging strand
what is the function of dna polymerase I during dna replication?
to replace rna primer nucleotides with dna nucleotides
what is the function of dna ligase during dna replication?
to bind okazaki fragments together
what are ddNAs?
- dideoxyribonucleic acid
- nucleotides that do not follow further nucleotide addition due to their structure
describe the 4 steps of sanger sequencing
- replicate dna with ddNA nucleotides base A, normal nucleotides and dna polymerase
- repeat process for each remaining base (c, g and t)
- the ddNA blocks replication at varying lengths, so they can be separated by gel electrophoresis
- this forms a sequential banding pattern
what are the types of base sequences?
- coding
- non-coding
what are non-coding sequences useful in?
regulating gene expression, introns, telomeres, trna and rrna genes
how are non-coding sequences useful in regulating gene expression?
promotes or represses transcription of adjacent coding sequences
how are non-coding sequences useful in introns?
they aid mrna processing from within the coding sequence but are spliced out before translation
how are non-coding sequences useful in telomeres?
they are repetitive sequences at the end of chromosomes to make sure coding sequences aren’t lost during replication
how are non-coding sequences useful in trna and rrna genes?
they are sequences who’s transcription produces trna for translation or rrna to form ribosomes
what is the full name of rrna?
ribosomal ribonucleic acid
what did hershey and chase use in their experiment?
- by taking viruses that are known as ‘T2 bacteriophage’
describe the fucntion and structure of a T2 bacteriophage
- a protein coat
- a capsid head containing dna
- known to inject genes inside cells
why are some sulphur present in the solid pellet and some phosphorus present in the supernatant in hershey and chase’s experiment?
- agitation of the solution shakes of many of the protein coats into the supernatant
- but some may remain attached to bacteria and end up in the pellet
- some viruses may not inject their dna into the bacteria as well, meaning that it remains in the supernatant
what are the 2 groups of complementary bases?
- purine
- pyrimidines
which 2 bases are found under the purine group?
- adenine
- guanine
which 3 bases are found under the pyrimidine group?
- thymine
- cytosine
- uracil
what does eukaryotic dna wrapped around?
8 histone proteins
what does the rod histone do?
clamps the dna in position
what are the components of a nucleosome and what is the function of it?
- eukaryotic dna
- 8 histone proteins
- a rod protein
- fxn: allows dna to supercoil
why are prokaryotic dna ‘non-protein associated’ aka naked?
because it does not wrap around histones
what is dna profiling?
the process by which small repeat nucleotide sequences (coded for by a single allele named tandem repeats) are used to identify individuals
what are variable tandem repeats?
since tandem repeats repeat a varying number of times, in different individuals, it creates a unique dna pattern
describe the 4 steps of dna profiling
- collection and amplification of dna with PCR
- the strands are cut with restriction enzymes
- separated with gel electrophoresis
- pattern comparison for similarities
what can dna profiling be used for? give 2 examples
- paternity or maternity testing
- to assess the likelihood of their involvement in the crime
what is sanger sequencing?
the determination of entire dna base sequence
what is the difference between sanger sequencing and dna profiling?
sanger sequencing is…
- far more costly
- due to sequencing of entire genome instead of just the tandem repeats
what must not happen before sanger sequencing can occure?
- requires dna replication to be prevented, so it does not interrupt the process
how is dna replication prevented in the process of base sequencing?
- dna is mixed with ddNA nucleotides
- because ddNAs do not contain an OH carbon on the 3’ carbon
- meaning that no other nucleotides can attach to the 3’ end - therefore, it halts dna replication at ddNA bases
what is bioinformatic analysis?
large storage and analysis of gene sequences on computers
what are the several key advancements in medical science departments that bioinformatics analysis has helped with?
- identification of similarities within genes for people who suffer from genetic disorders informing diagnostic tests
- comparison of genes to other organisms with alternative forms of a disorder, despite similar genes despite mutation
