Chapter 24 Genes and Chromosomes Flashcards
Who was the father of genetics, what experiment did he perform that give him that title?
Gregor Mendel
“Factors/Merkmals” in his pea phenotypes experiment, that was passed on from one generation to the next was called genes.
He concluded that the 7 phenotypes in his plants were regulated by a single factor; genes
established the relationship between genes and phenotype
Explain the Griffith’s experiment with the rat
virulent form bacteria (S) and nonvirulent form (R)
When S form was headed and injected into rat it stayed alive
When S form was headed and mixed with living R form, rat died, inside tissues had S form
There was a transforming agent
What was the discovery made in the Avery, Macleod, and McCarty experiment?
They wanted to find the transforming agent.
They found that it was a cellular component and not the heat killed S-cells that transformed the R form.
Then they anted to see what is the chemical nature of the transforming agent.
The found that DNA was the transforming agent
What did Garrod research find?
he looked into a single gene disorder; alkaptonuria (black urine)
Alkaptonuria is inherited as a recessive Mendelian trait (implies a single gene defect)
Garrod suggested that metabolic pathway leading to the breakdown of alkapton into a colorless compound was blocked in alkaptonuria patients
he found that there was a relationship between gene and metabolism
What was Beadle and Tatum’s discovery? what did they proposed?
They looked into Neurospora, performed x-ray on the organism, and put into a minimum and complete medium. Minimun had no growth, but some of the complete did. Separated the complete medium into different components to see what is the chemical preference. Found that they can only survive on Niacin.
found the defect in each mutant, determined what pathway was used to bypass the defective enzyme, showed that each mutant phenotype is due to a defect of single enzyme along pathway.
proposed a 1 gene, 1 enzyme hypothesis
What was Pauling’s discovery? how did he make his discovery?
He proposed a 1 gene, 1 protein hypothesis.
Sickle cell anemia is inherited as a recessive Mendelian trait;
HH (normal), hh (sickle), Hh 1%
Pauling’s study clearly revealed a clear case of a change produced in a protein molecule by an allelic change in a single gene.
What did Ingram find by looking further into sickle cell anemia?
One gene determine the structure of one polypeptide chain.
Sequence of bases in DNA determines sequence of amino
acids in protein.
Hemoglobin A normal, Hemoglobin S sickle; single change in aa sequence
Before it was DNA –> Protein, but proposed that DNA –> messenger –> protein
The message coded in the bases of DNA in nucleus is carried to the cytoplasm by an intermediate
What was Jacob and Monod research and what did the find/proposed?
Jacob and Monod studied kinetics of enzyme induction in lac operon; with Lactose mRNA switched on, without it was off
Fast induction and repression kinetics suggested that template for protein synthesis must be short lived.
The messenger should be a polynucleotide.
The base composition of messenger should reflect the base composition of DNA that specifies it.
The messenger should be very heterogeneous in size.
The messenger should be synthesized and degraded very rapidly.
From what Jacob and Monod proposed what conclusion lead by Brenner, Jacob, Meselson?
Messenger is the short lived RNA different from stable rRNA
and tRNA known at that time. It was named mRNA.
Give/explain the steps in gene expression.
{Nucleus}
Chromatin control, transcriptional control; primary RNA transcript, RNA processing control (capping; 5’methyl, splicing, 3’ cleavage and polyaden); mRNA, mRNA leaves nucleus
{Cytoplasm}
translational control; protein, protein activity control; functional protein
protein expression truly occurs when functional protein is produced
What percent of human genome is actually coding sequences?
1.5%
What are the different levels of repeated DNA and what do they produce? spacers?
Nonrepeated (same for all of us) - proteins
moderate repeat - gene families, cluster pseudogenes, transposons
highly repeated (lower density) - satellite
spacers - inter-genetic regions, introns, regulatory elements (promotors, terminators, etc.)
What are nucleosome?
the units of chromatin: histone + linker/ wrapping of DNA
Wrapping of DNA in nucleosomes
induces ________ supercoils
negative
What are the components of a nucleosome?
DNA; 1.75 turns
2 H2A, 2 H2B, 2 H3, 2 H4
H1 is not a component
