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Cell cycle of prokaryotes
They use fission to reproduce
Cell cycle of eukaryotes?
- Use Mitosis
- many do the processes of sex reproduction to allow more genetic varation.
Three different kinds of sexual life cycles in eukaryotes?
Any sexual life cycle has to have which two events.
- Mieosis-purpose is to reduce the chromosome number from diploid to haploid.
- Fertilization-purpose is to restore the chromosome number from two haploid gametes to one diploid zygote.
What the difference between a gamete and a spore?
- a gamete will not do mitosis it will only do fertilization.
- a spore will not do fertilization it will make more cells by mitosis.
a change in the DNA sequence.
- Bring together knew haploid genomes.
- EX. crossing over that happens between homologus chromosomes during mieosis, provides genetic varation.
those organisms that best adapt will reproduce causing that genetic combination to increase in the population.
any event that makes a new combination of DNA in a cell
Methodes by which genetic recombination accures in bacteria?
methodes by which genetic recombination occurs in a sexual life cycle?
- Crossing over-happens during meiosis
- Independent assortment-happens durin meiosis.
Who helped prove that DNA was the genetic material?
- Griggith-transformation expeirement.
- Avery-RNase-seperated components
- Hershey and Chase-Bacteriophage T2
Griffiths transformation expieremnet?
Mice injected with S strain died, where mice with either R strian or heat killed S bacteria servived, when injected with living R and heat killed S bacteria the mouse died because R was transformed to S killing the mouse.
seperated the major components of the S strain cell, subjected the R strain to the four major components, only transformed the nucleic acid portion showing DNA was the genetic material.
Hershy and Chase?
- bacteriophage T2
- Proteins contain sulfur, DNA contains phosphorus, they attached radio active markers to these. Then allowed there marker viruses to attack bacteria and then they looked at where they found the radio activity, They only found the radio active phosphorus inside the cell.
- Watson and Crick
- Made of nucleotides
- double stranded molecule
- two strand are complementary to eathother
- Strands are antiparrell to eachother
- Nucleotides are connected by phophodiester bonds
- Complimentary strands held by hydrogen bonds
Nucleotides are made of?
- nitrogenous base
- one or more phosphate groups
DNA is sythesized from?
- 5' prime end to 3' prime end
- only grows from 3' prime end
Viral chromosomes characteristics?
- They can do pretty much what ever they want.
- double stranded or single stranded
- linear or circular
- DNA or RNA
- single or multiple chromosomes
different kinds of DNA viruses?
- T even
- Lamda phage
They have linear DNA, when analyzed they have permutation, so it must form a circle sometime during replication
- single sranded
- Always circular
How do you know if a piece of DNA is circular or linear if you dont know the sequence?
By using exonucleases because they will only eat from the ends, so this unable to eat circular.
- Double stranded
- Linear when in viral partical
- Infect host cell becomes circular(becomes the COS sequence)
- genome when in its linear form has sticky ends(5' over hangs)
- Double stranded RNA
- In the partical form the genome is RNA
- When a retriovirus attacks a host cell that RNA is the reverse transcribed into DNA
- Carries reverse transcriptase, because the cell they infect dont carry it.
- tumor viruses
- nononcogenic viruses-Ex HIV
- RNA single stranded
- Never goes through DNA phase
- to replicate there genome they either code for or carry RNA dependent RNA polymerase(means makes more RNA)
Different kinds of nonretroviruses.
- Negitive strand-Influenza
- positive strand-polio viruses
- When the retrovirus inserts its DNA into the host cell DNA it causes a mutation because of where it inserted it.
- if it inserts close to one of the genes that controls the cell cycle, cell loses control of cell cycle and tumor developes.
What is the clue that a retrovirus has inserted itself?
A peice of DNA flanked by a long terminal repeat, flanked by a short terminal repeat.
when a retrovirus is carrying an onco gene?
- you will develope cancer
- its giving you a cancer gene
- MOst have single double stranded DNA circular chromosomes
- lots of extra DNA called plasmids or episomes about 500 base pairs.
- A single large chromosome about 5 million BP
- A piece of DNA that can exist in 2 states or conditions
- or they can insert themselves into large chromosomes and then pull themselves back out
bacterial DNA exist in
looped domains that are then supercoiled
- looped domains twist themselves up until they get closer to scafoltien protien
- you do that by inserting extra bases into the helix
on order to supercoil you have to have these to make and break phosphodiester bonds
- Most have double stranded DNA
- multiple chromosomes
- linear chromosomes
- dipliod in adult body form(exception fungi)
- Has a associated protien called Histone(chromotin)
- Archea have histone
- Highly conserved-when compared to different organisms the amino acid sequence and the nucliotide sequence are almost indentical
- Positively charged(other protien negative)
- bacteria dont have
- archea have
- Rap around cluster of histone twice, froms bead called Nucleosomes
- Nucleosomes coil up into a Soleniod(fromed by histone1)
- solenoid attaches to scaffoltien protien froming looped domains
- using topoisomerases looped domains begin to super coil
- SAR's attach DNA to scaffoltien protien(or MAR's)
What takes us from chromatin(cant see) to chromosomes
DNA plus its associated protiens specifically histones, not found in bacteria, found in archea
what are the 2 kinds of chromatin
- Loosley packed
- light stained
- transcriptionally active
- tightly packed
- dark stained
- transcriptionally inactive
heterochromatin has two types?
- constitutive-means its always heterochromatin structual part like centromere(tightly packed)
- faculative-sometimes heterochromatin, sometimes euchromatin which is a form of a gene expression regulation-EX Xchromosome of felame human
Sequence organization in eukaryotes
- single copy DNA-30% to 60% of genome
- repetitive DNA
- Spacer DNA
Repetitive DNA to
- Function DNA
- Sequences with no known function
Functional DNA to
- Family of coding genes
- Noncoding functional sequenses
Family of coding genes to
- Dispersed gene Family- globin genes, actin, Ig's, homologous genes pseydogenes
- Tandum genes-NO(nuclear organizers,rRNA genes)tRNA some histones.
- a)indentical copies
- b)Nucleolar organizere, satelites
Noncoding functional sequences
- telomers-repeditive sequences(good for unwanted shortening)
- centromeric DNA(10 to 12 repeats)-CsCI2 SAR's
sequences with no known function to
- STR(short tandem repeats)-micro setelite
- VNTR-mini satelite
- Transposed sequenses
- Transposons-they jump or move as DNA
- retrotransposons-they copy themselves as RNA the the RNA reverse transcribes back into DNA
- both of these have increased the rate of evolution.
two different kinds of retrotransoposones
- retriviral like-a DNA sequence in the middle then its flanked by by long terminal repeats and then flanked by short terminal repeats
- nonretroviral-at the end of the transposable sequence there is a polytail region(bunch of A's)
transposable sequences in mammals are called
- when a DNA molecule replicates you dont get one new molecule and one old molecule, you get one that is half old and half new and the other one is half new and half old
- Called Harlequin chromosome
who showed that DNA replication was semiconservetive
- Mesclsen and Stahl
- Labled nitrogen,CsCI2 centrifugation
- all DNA replicates from 5' to 3'
- replicon-all DNA that is under control of a single origin
- the squence of DNA where replication begins
- Bacterial chromosomes(circle) has one origin of replication
- Linear chromosomes have multiple origins of replication
Bacterial replication is described as (circular genome).
plasmid replication or viral replication
Rolling circle model
replication of eukaryotic chromosomes(linear)
The forked bubble pic shows
- semiconservitive replication
- bidirection replication-two forks move away from eachother