Chapter 16 Flashcards
(43 cards)
What did Morgan experiment show
-Th Morgan group showed that gene exist as part of chromosomes, the two chemical components of chromosomes-DNA and protein emerged as leading candidates of genetic material.
Transformation
Defined as a change in genotype and phenotype due to the assimilation of external DNA by a cell. American Maclyn MaCarry and Canadian Colin Macloed identified the transforming substance as DNA
Bacteriophage
Meaning bacteria-enter
Virus
A protein coat which has DNA inside, to produce more viruses, a virus must infect a cell and take over its metabolic machinery
What did Hershey and chase discover?
Hershey and chase found that phage DNA enter the host call but the phage protein did not. This result further showed that the DNA inside the cell played an ongoing role during infection process. Also concluded that DNA injected had genetic information that cell produce new virals.
What does DNA consist of ?
- a nitrogenous base containing adenine,thymine,guanine and cytosine
- a pentode sugar called deoxyribose
- phosphate group
Complementary base pairing
DNA base are complementary A binds to T and G bind to C. The number of A is equal to the number of T, and the number of g is equal c.
Chargoff rule
(1) DNA base composition varies between species,
(2) for each species, the percentages of A and T bases are roughly equal, as are those of G and C bases.
Franklin discovery
-Franklin discovered double helix model. Her model was appealing because it put the negative charged phosphate group facing the surrounding while relatively hydrophobic nitrogenous bases were hidden in the interior .
Antiparallel
Two sugar phosphate backbone are antiparallel- there subunit move in opposite direction constructing a ladder or rope like structure
Purine vs pyrimidines
Adenine and guanine are purine (pure as gold)
Cytosine and thymine are pyrimidine
No hydrogen bond between bases
- adenine can for for two hydrogen bonds with thymine
- guanine for, three hydrogen bonds with cytosine
What did Meselson-Stahi experiment showed ?
Showed that DNA replication is semi conservative= the parental molecules unwind,and each strand then serves as a template for the synthesis of a new strand according to base-pairing rule
Origin of replication
-the replication of chromosomal DNA begins at particular sites is called origin of replication. Protein recognises a DNA sequence and starts the process. This origin forms a double in strand prior to replication
Primer
The RNA chain
Primase
The enzyme used to synthesis RNA chain
Stages of DNaA replication
1) helically unwind the parental double helix
2)molecules of single strand binding protein stabilise the unfounded template
3) the easing strand is continuously synthesised in 5’ to 3’ direction by DNA polymerase 3
4)primase begin synthesis of the RNA primer on Okazaki fragment (lagging strand)
5) DNA pol 3 Is complete synthesis of fragment 4. When it reaches the RNA primer of fragment 3, it will detach and begin adding DNA nucleotide to the 3’ end of the fragment 5 primer in the replication fork.
6) DNA pol I removes the primer from the 5¿ end of fragment 2, replacing it with DNA nucleotides added one by one to the 3’ end of fragment 3. After the last addition, the backbone is left with
a free 3’
7)DNA ligand joins the fragment 3’dnd of fragment 2 to the 5’ end of fragment 1
Leading strand
Continuous strand
Lagging strand
Non continuous strand
Okazaki fragment
The segment of lagging stand
Helicase
An enzymes that unwinds the DNA strand at replication fork
Sing.e strand binding protein
Protein that binds to unpaired DNA strands
Topoisomerase
An enzyme that help relieve this strain by breaking, swivelling and rejoining DNA strand,
Protein involved in initial replication
- topoisomerase break, swivels and rejoin parental DNA ahead of the replication fork, reliving the strain to unwind the.
- primase synthesis RNA primer uses ping the parental DNA as template
- helicase unwinds and separates the parental DNA strands
- single strand binding protein stabilise the unfounded parental strand
