Chapter 16: Molecular Basis of Inheritance Flashcards
Why did researchers originally think that protein was the genetic material?
Identified as a class of macromolecules with great heterogeneity and specificity of function
What are the two chemical components of chromosomes?
DNA and protein
Distinguish between the virulent and nonvirulent strains of pneumonia
Virulent: living s cells
Nonvirulent: living r cells and heat killed s cells
What was the purpose of griffiths studies
Find a vaccine for pneumonia
Define transformation
Defined as a change in genotype and phenotype due to the assimilation of external DNA by a cell
What did Avery determine to be the transforming factor?
DNA
Explain Avery’s experimental approach
Took out the contents of a heat killed pathogenic bacteria. Treated three samples with an agent that inactivated one type of molecule. Tested the sample for ability to transform live nonpathogenic bacteria. Only when DNA stayed did transformation happen
How does a bacteriophage destroy a bacterial cell
Attachment Entry Synthesis Assembly Release
How did Hershey and Chase label viral DNA and viral proteins so that they could be distinguished
They wanted to see which of these molecules entered the cells and could reprogram them to make more Phages
Describe the means by which Hershey and Chase established that only the DNA of the phages entered an E. coli cell. What conclusions did the scientist draw based on these observations
Phage DNA entered bacterial cells but phage proteins did not. Hershey and Chase concluded that DNA, not proteins, function as the genetic material of phage T2
What are chargaffs rules? How did he arrive at them?
The bass composition varies between species
Within a species the number of A and T bases are equal and the number G and C bases
He studied the ratios between the bases
This the three components of a nucleotide
Phosphate, deoxyribose, nucleic acid
Who built the first model of DNA and should the 1962 Nobel Prize for discovery of its structure
Watson and Crick
What was the role of Rosalind Franklin in the discovery of the double helix
X-ray crystallography
Do you distinguish between the structure of pyrimidines and purines. Explain why adenine bonds only to thymine
Pyrimidines have one organic green while purines have two organic rings
They fit together like a puzzle
How did Watson and crick’s model explain the basis of chargaffs rules
The model show that for DNA double helix structure to work. A -T and C-G
Adenine and guanine are both…
Purines
Cytosine thymine and Uracil are all
Pyrimidine
Explain the base pairing rule
A forms two hydrogen bonds with T
G forms three hydrogen bonds with C
Pyrimidines always bind to purines
Distance across molecule
Distance between nucleotides
Distance between turns
1nm
.34nm
3.4nm
Components of the backbone
Components of the rungs
Sugar (deoxyribose) and phosphate
Nitrogenous base
Explain what is meant by five’ and three’ ends of the nucleotide
Third carbon and deoxyribose close the phosphate group
Fifth carbon in the deoxyribose close to the OH group
What is a semi conservative model of replication
Double strand separate a new DNA forms old strand as template
Who performed experiments that elucidated the correct mechanism of DNA replication
Meselson and Stahl
How did Meselson and stahl create heavy DNA for their experiments
Marking with N15
Defined the origins of replication
Short stretches of DNA having a specific sequence of nucleotides
Distinguish between leading in the lagging strands during DNA replication
Leading: DNA pol 3 adds nucleotides to the new complementary 5’-3’
Lagging: DNA pol3 world along the other template in the othe direction 3’-5’
What is the direction of synthesis of the new strand
From 5’ to 3’
What are Okazaki fragments? How are they welded together?
The lighting is synthesized discontinuously as a series of segments
welded together by DNA ligase
Which enzyme untwists and separate strands
Helo case
Which enzyme holds DNA strands apart
Single-stranded binding protein
Which enzyme synthesizes RNA primer
Primase
Which enzyme ads DNA nucleotides to new strands
DNA polymerize three
Enzyme to relieve strain cause by unwinding
Topoisomerase
Which enzyme joins DNA fragments together
DNA ligase
Which enzyme removes are in a primary replaces with DNA
DNA polymerase one
Steps that occur in the synthesis of a new strand
Helicase unwinds the double helix
SSBP stabilizes
Leading strand synthesizes in 5’-3’ direction by DNA pol lll
Primase synthesizes RNA primer for Okaxaki fragments
DNA nucleotides added to RNA primer Okazaki fragments
DNA pol l removes RNA primer and adds DNA
DNA ligase bonds Okazaki fragments
What is the role of DNA pol
Adds new nucleotides
What is the role of the nuclease
Exices damage area of DNA
What is the role of ligase
Seals free ends of DNA
What is the role of repair enzymes
To repair a genetic damage
What is a thymine dimer? How might it occur? How is it repaired?
Covalent the linking of thymine is Thymine dimer
It is repaired by nucleotide exicion repair
It can occur by exposure of ultraviolet rays from the sun
Explain telomere erosion and the role of telomerase
Catalyzes the lengthening of telomeres and eukaryotic germ cells thus restoring their original length compensating for the shortening that occurs during DNA replication
Why are cancer cells immortal but most body cells have a limited life span
Cancer cells have the ability to stabilize the telomerase causing it to be able to live longer
Distinguish between heterochromatin and euchromatin
In heterochromatin it is more compact and in irregular clumps. In euchromatin it is more dispersed and can be expressed
