Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA +...
-
Upload
austen-richards -
Category
Documents
-
view
223 -
download
1
Transcript of Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA +...
![Page 1: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/1.jpg)
Chapter 16
Molecular Basis of Inheritance
![Page 2: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/2.jpg)
DNA genetic material
• Chromosomes composed of DNA + protein
![Page 3: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/3.jpg)
DNA base composition
Nucleotide base
GuanineCytosineThymineAdenine
Guanine, C5H5N5O
![Page 4: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/4.jpg)
DNA is a polymer of nucleotides
![Page 5: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/5.jpg)
Chargaff’s rules (1950)
[T] = [A] [G] = [C]
A certain chromosome is 19% A. What is the % of C?
![Page 6: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/6.jpg)
DNA structural model
Watson, Crick, Franklin 1953
X-ray crystallographyDNA is helicalSpacing of basesWidth of helix suggested 2 strands
![Page 7: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/7.jpg)
DNA double helix
Sugar-phosphate “backbone”
Anti parallel strands
![Page 8: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/8.jpg)
• Bases face inward
• Hydrogen bonds connect bases
![Page 9: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/9.jpg)
A - T (2 bonds)G - C ( 3 bonds)
![Page 10: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/10.jpg)
Original DNAcopied to new DNAhelix
Original DNA broken up and combined in new DNA
1 strand original DNA maintained in new DNA
![Page 11: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/11.jpg)
Meselson and Stahl 1950s
1. Label DNA (E. coli) with 15N in growth media
2. Transfer E. coli to 14N media for 1 generation (20 min)
![Page 12: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/12.jpg)
Results:The density of the DNA is
intermediate
Cells grown longer 14N, make lighter DNA
![Page 13: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/13.jpg)
What would the DNA density be after 20 more minutes of cell group?
15N DNA1.724 gm/cm3
14N DNA 1.710 gm/cm3
![Page 14: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/14.jpg)
DNA replication is semi-conservative
![Page 15: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/15.jpg)
DNA replication: mechanism (E. coli)
E. coli genome = 4 X 10 6 bp DNA1 circular chromosome1 origin of replication (ori)
![Page 16: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/16.jpg)
• Ori nucleotides– Replication proteins attach to ori– Forms a replication bubble
• Two strands of DNA open
![Page 17: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/17.jpg)
Replication fork in both directions
![Page 18: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/18.jpg)
Proteins in DNA replication Table 16.1
1. DNA polymerase (enzyme)Adds nucleotides 5’ 3’ direction only
![Page 19: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/19.jpg)
2. Helicase (enzyme) – unwinds double helix3. Single stranded binding protein (SSB) binds to
DNA strands to stabilize them
![Page 20: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/20.jpg)
4. Topoisomerase (enzyme) – breaks, rejoins DNA to relieve physical stress
5. Primase – synthesizes a primer
![Page 21: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/21.jpg)
Each strand is a template for new DNA
Leading strand is
Lagging strand is
![Page 22: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/22.jpg)
![Page 23: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/23.jpg)
DNA replication leading strand: steps
1. Primase (enzyme) – synthesizes primer complementary to leading strand– primer is ~10 bases
![Page 24: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/24.jpg)
2. DNA polymerase (pol III) synthesizes new strand 5’ 3’
G, A, T, C nucleotides complementary to template strand500 nuc/secContinuous elongation until end of chromosome
![Page 25: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/25.jpg)
DNA Synthesis steps: lagging strand1. Primase makes RNA primer2. DNA adds nucleotides to primer in 5’ 3’
direction only
![Page 26: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/26.jpg)
3. DNA pol III detaches
Okazaki fragment• ~ 1, 000 nucleotides
long
![Page 27: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/27.jpg)
4. Another primer added, another Okazaki fragment formed
Many primers needed
![Page 28: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/28.jpg)
5. Gaps between primers filled in
6. Ligase enzyme bonds fragments
![Page 29: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/29.jpg)
DNA replication Fig. 16.17
![Page 30: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/30.jpg)
Telomeres, the protective ends
![Page 31: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/31.jpg)
Linear DNA has telomeres• No genes• Repetitive DNA TTAGGG up to 1000 times
Human chromosomes capped by telomeres
5'...TTAGGG TTAGGG TTAGGG TTAGGG TTAGGG TTAGGG..3‘ 3'...AATCCC AATCCC AATCCC AATCCC AATCCC AATCCC..5'
![Page 32: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/32.jpg)
• Chromosomes shorten with each cell division
![Page 33: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/33.jpg)
• When telomeres are too short cell senescence(irreversible)
~ 125 cell divisions (humans)……life span?Telomeres shorten ~100 bp each time cell divides
Mouse fibroblasts in culture
![Page 34: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/34.jpg)
• Cells that do not divide often– Example: heart muscle
Telomeres do not shorten with age
![Page 36: Chapter 16 Molecular Basis of Inheritance. DNA genetic material Chromosomes composed of DNA + protein.](https://reader036.fdocuments.in/reader036/viewer/2022062305/5697c01e1a28abf838cd12d6/html5/thumbnails/36.jpg)
• Embryonic cells, some wbc, stem cells, cancer cells express telomerase
White blood cell cervical cancer cell embryo