DNA chapter 7 Flashcards
(28 cards)
How are 2 strands of DNA linked ?
1) Nitrogenous bases
2) They are linked by means of H bonds.
Purines
A and G are double ringed
Pyrimidines
C and T are single ringed
Explain DNA packaging
1) DNA molecules of eukaryotes linked with histone protein
2) Packaging is essential because Nucleus is microscopic and DNA can be extremity long.
3) Nucleosomes are formed: DNA wraps twice around 8 histone proteins, 2 of each type.
3) between the nucleosomes there is a linker DNA
4) 5th type of histone attached to the linking string near each nucleosome
Why DNA is attracted to Histones ?
DNA is - cahrged and Histones are + cahrged
What function does DNA packaging serves
1) Wrapping allows certain areas of DNA to be available for protein synthesis
2) Regulation of transcription process
3) helps to super coil chromosomes
Whats Genome ?
complete sequence of DNA
What is DNA profiling ?
Obtaining a specific DNA pattern from an organism determining an individuals DNA characteristics.
What is satellite DNA ?
Highly repetitive DNA clustered in discrete areas \
1) These sequences can jump from one location to another on the chromosome.
What is structural DNA ?
1) Highly coiled DNA that does not have a coding function
2) Occurs around centro-mere
3) Near the ends of chromosomes
Polymorphism
Most of our DNA is similar to the DNA of other people
1) However specific regions that show significant variation are called Polymorphism
What are short tandem repeats
STRs are short sequences of DNA, normally of length 2-5 base pairs, that are repeated numerous times in a head-tail manner, i.e. the 16 bp sequence of “gatagatagatagata” would represent 4 head-tail copies of the tetramer “gata”.
only 1 point of origin in bacterial dna
Because DNA is much smaller
no histones
Where does the energy for DNA replication is derived from ?
Deoxynucleoside triphosphate molecule
contains 3 phosphate groups
2 phosphates are lost
provides energy for the nucleotides
What isi Central Dogma ?
Info passes from genes on DNA to RNA copy and the RNA copy then directs the production of proteins at the ribosomes by controlling the sequence of amino acids.
What re punctuation codons ?
Start and stop codons are called punctuation codons
Methylated DNA
Inactive DNA is highly methylated
For instance, In females, X chromosomes are highly methylated.
Methylated genes are not transcribed or expressed.
What are repressor proteins ?
Binds to the segment of DNA called silencers.Prevents transcription of the segment of that particular region.
What are transcription factors ?
Transcription factors are proteins that help turn specific genes “on” or “off” by binding to nearby DNA.
A typical transcription factor binds to DNA at a certain target sequence. Once it’s bound, the transcription factor makes it either harder or easier for RNA polymerase to bind to the promoter of the gene.
1) Activators
2) Repressor :his repression can work in a variety of ways. As one example, a repressor may get in the way of the basal transcription factors or RNA polymerase, making it so they can’t bind to the promoter or begin transcription.
Structure of Ribosomes
Ribosomal RNA+ Protein
Large subunit+ small subunit
Built in nucleolus of eukaryotic cells
Prokaryotic ribosomes are smaller thaneukaryotic ribosomes .
Between small and large sub unit, there is a binding site for mRNA.
Where does the amino acid attaches on the tRNA?
3 prime end of the tRNA
What is translocation
Movement of tRNA’s from one site to others.
What is the cause of sickle cell disease ?
Only one amino acid changes in the sequence of hemoglobin–Hemoglobin
how are the H bonds formed in secondary structure ?
Between Oxygen from the carboxyl group of one amino acid and the Hydrogen from amino group of the other.
1) it doesn’t involve the interaction of side chains.
