Sanandom Flashcards
Genome
The collection of genetic information
Chromosome
Storage unit of genes
DNA
A nucleus acid that contains the genetic instructions specifying the biological development of all cellular forms of life
Locus
Location of a gene on the chromosome
Allele
One variant form of a gene market at a particular locus
Genotype
At each locus there are 2 genes constituting the genotype at a locus
Phenotype
The expression of genotype
Dominant
Allele is expressed if paired with reassess ice allele
Recessive
Allele is only expressed when paired with another recessive allele
What was required to be found in search for genetic material?
- Stable source of information
- Ability to replicate accurately
- Capable of change
What was Griffiths DNA experiment?
Transformation experiment.
S and R strain
Incorrectly guessed protein
What was Oswald Averys experiment?
Transformation experiment. Treating with RNAase and DNAase when with RNAase s transformants were produced. Therefore DNA and not RNA is responsible
What was Hershey-Chase experiment?
Bacteriophage experiment. Labelling of the bacteriophage
Bacteriophage
Virus that attacks bacteria and replicates by invading a living cell by invading a living cell and using its machinery
What was Girer Conrat experiment
Demonstrated that it was RNA not pristine that is the genetic material of TMV. Shook of proteins
Why 3 additional information showed DNA is the genetic material
- Erwin chargaff reported DNA composition varies from one species to antother making it more credible as candidate for genetic material.
- DNA has equal number of AT CG residues
- by 1950s it was shown DNA is a polymer of nucleotides
What 2 sources of information showed double helix model
CHARGAFF RULES
X RAY DIFFRACTION of rosalind Franklin
What is DNA S structure
Helical with distinctive regularities 0.34nm and 3.4 no
What type of sugar is ribose
5 carbon so pentose
Difference between ribose and deoxyribose
Deoxy lacks hydroxyl on the 2’ carbon atom
Structure of a purine.
What bases are purines?
6 members prymidine ring and a 5 members imidazole ring. DOUBLE RING.
ADENINE
GUARNINE
Structure of prymidine
WhT bases are prymidine?
6 members rings.
CYTOSINE
THYMINE
URACIL (RNA ONLY)
What is a nucleoside?
Bases linked to ribose/deoxyribose via the 1’ carbon atom of deoxyribose
What is a nucleotide?
When a nucleoside is phosphorylated on the 5’ carbon atom of the ribose component.
How are nucleotides joined?
Condensation between adjacent deoxyribose sugars via a phosphodiester bond.
5’ carbon atom of one nucleotide condenses with the hydroxy group on the 3’ phosphodiester bond. Eliminating pyrophosphate and water.
It is a 5’ to 3’
Why 5’ to 3’ orientation
A string of nucleotides will this have a free 5’ phosphate and one free 3’ hydroxyl.
What is the common secondary structure of DNA
B-DNA. Favoured in aq solution
What is A DNA
Dehydrated forms. Still produces a right handed helix. But it is shorted and wiser than B DNA. This had a more open structure, and is the structure adopted by double stranded RNA. RNA cannot adopt the B structure due to the extra OH
What is the B DNA structure
2 spiral groves running up the helix, a wider major grove and narrower minor grove. These result from the glycosidic bonds to the bases not lying diametrically opposite eachother.
BDNA structure is stabilised in aq environment by a row of water molecules that fit into the minor groove
Gene
Basic unit of genetic information
How is DNA compacted
Supercoiling facilitates compaction of DNA of viral and bacterial chromosomes. Most closed circular DNA molecules are under would and supercooled.
What do topoisomerase do?
Cut one or both DNA strands and wind or unwind the helix before resealing the ends.
How does supercooling occur?
DNA double helix is twisted in space about its own axis, a process controlled by topoisomerases.
What is chromatin?
Complex of DNA and chromosomal proteins. 2x as much protein as DNA.
What are the 2 major types of proteins involved in the coiling process?
His tones
- abundant, basic proteins with postitive charge they bind to DNA. There are 5 types H1, H2A, H2B, H3, H4. They are evolutionarily conserved.
Non Histones
- differ markedly in type and structure
Explain step by step the packing of DNA into chromosomes.
Level 1
- Winding of DNA around histone proteins to create a nucleoside structure.
Level 2
- Nucleosomes are connected by strands of linker DNA like beads on a string. (A form of chromatin) 11nm wide
Level 3
- packing of Nucleosomes into 30nm chromatin fibre.
Level 4
-Formation of looped domains
What is Centromeric DNA?
Centre of chromosome specialised sequences function with the microtubules and spindle apparatus during mitosis and meiosis.
What is telomeric DNA
At extreme ends of the chromosome, maintain stability, and consist of tandem repeats. Play a role in DNA replication and stability of DNA.
What is polytene chromosome?
- have distinctive banding patterns
- represent paired homologise
- are composed of many DNA strands
- polytene chromosomes have PUFF regions where the DNA has uncoiled and are visible manifestations of a high gene activity.
What are lampbrush chromosomes?
Large and have extensive DNA looping.
Found in locates in the diplotene stage of meiosis.
Why is chromatin remodelling required?
To allow the DNA to be accessed by DNA binding proteins.
What are histone tails important for?
Important for histone modification, such as:
- acetylation (CH3COO-)
- methylation (CH3)
- phosphorylation (PO4)
How do histone modifications effect DNA?
Modifications are interactive and summative
- acyltation causes a shift from heterochromatin to euchromatin and AIDS gene expression.
- Methylation can silence gene expression.
- Phosphorylation is necessary for mitosis.
What are the differences between euchromatin or heterochromatin?
Euchromatin is uncoiled and active.
Heterochromatin is consented and is active.
Euchromatin changes between extended (30nm) fibre and highly condensed (mitosis) chromatin.
Heterochromatin remains highly condensed in all phases of cell cycle.
Heterochromatin is found only in Eukaryotes and prokaryotes.
How do enzymes interact with DNA?
Enzymes can access the base pairs in DNA to recognise the specific sequences via the major groove of B DNA
WhT is the TATA box binding protein?
A eukaryotic transcription factor that recognises promoter sequences and leads to initiation of transcription for most genes
How does the TATA protein interact with DNA
C terminal domain of protein interacts with AT rich regions of DNA via the minor groove resulting in the helix becoming unwound and bent
What cause denaturalising of DNA
Heat, extremes of pH or H bond breaking agents
What base pairs cause debaturation at higher temp
Higher GC content, 3H bonds
What is hybridisation?
Process by which separated DNA RNA strands reform a double helix.
Hybridisation can only occur between DNA strands with complementary sequences.
What secondary structures form in RNA?
Can form double helixs.
Stem and loop- formed by single strand base pairing between internally complementary sequences.
What are the major types of RNA in cells
All the following are single stranded.
Messenger RNA is copied from DNA constituting genes and acts as a template for protein synthesis or translation.
Transfer RNA- involved in protein synthesis as the adaptive molecule that fits between amino acid and messenger RNA
Ribosomal RNA- components of the ribosome
Eukaryotic cells also contain a variety of small nuclear RNAS which are involved in splicing mRNAs
What is the genome organisation of bacterial and viral chromosomes?
- a single nucleic acid
- largely devoid of associated proteins
- much smaller than eukaryotic chromosomes
