Chapter 10- Biochemistry of the genome Flashcards
Friedrich Miescher
The first person to isolate phosphorus-rich chemicals from leukocytes from pus samples. These chemicals would later be known as DNA and RNA, but he named the chemicals “nuclein”. They were later called nucleic acid
Albrecht Kossel
Isolated and characterized the 5 different nucleotides bases composing nucleic acid (adenine, guanine, cytosine, thymine in DNA, and uracil in RNA).
Gregor Mendel
Demonstrated the basic patterns of inheritance using pea plants. Mendel performed hybridizations, which involve mating two true-breeding individuals (P generation) that have different traits, and examined the characteristics of their offspring (first filial generation, F1) as well as the offspring of self fertilization of the F1 generation (second filial generation, F2). He found that traits are transmitted from parents to offspring independently of other traits
Chromosomal Theory of Inheritance
Identifies chromosomes as the genetic material responsible for Mendelian inheritance. The theory was developed even before there was evidence that traits were carried in chromosomes
Thomas Hunt Morgan
Carried out crosses with fruit flies. They observed fly chromosomes microscopically and correlated the observations with the resulting fly characteristics. Their
work provided the first experimental evidence to support the Chromosomal Theory of Inheritance in the early 1900s
Barbara McClintock
Developed chromosomal staining techniques to visualize and differentiate between the different chromosomes of corn. She also found that certain loci could change position within the chromosome. These jumping genes are now called transposons and are mobile segments of DNA that can move within the genome of an organism. They regulate gene expression, protein expression, and virulence
Why are microbes and viruses good models for studying genetics?
They are propagated more easily in the laboratory and grow to high population densities in a short period of time. They can also be genetically manipulated. All organisms have the same underlying molecules responsible for heredity, so microbes can be studied regardless of their many differences between other organisms
Hammerling experiments
He studied large algal cells (Acetabacteria). These cells grow a “foot” that contain a nucleus and are used for substrate attachment. Hammerling removed either the cap or the foot of the cells and observed whether new caps or feet were regenerated. Only the cap could regenerate, which suggests that the hereditary information is found in the foot of each cell, which contains the nucleus. He also grafted head or tail portions of one cell onto another cell. The caps of the cells developed their morphology to the nucleus of each grafted cell
Red bread mold model (Beadle and Tatum)
Researchers irradiated the mold with X-rays to induce changes (mutations) to a sequence of nucleic acids. They mated the irradiated mold spores and attempted to grow them on both a complete medium and a minimal medium. Molds that grew on a complete medium but not not grow in the minimal medium lacking vitamins and amino acids theoretically contained mutations in the genes that encoded biosynthetic pathways. They were able to find these mutations and therefore demonstrated the relationship between genes and the proteins they encode
One gene-one enzyme hypothesis
Suggests that each gene encodes one enzyme. Demonstrated through work by Beadle, Tatum, and colleagues. They discovered mutations in the arginine biosynthesis pathway and supplemented these mutations with intermediates (citrulline or ornithine) in the pathway. The three mutants differed in their abilities to grow in each of the media
Griffith’s transformation experiments
Griffith was the first person to show that heredity information could be transferred from one cell to another between members of the same generation (horizontally) rather than vertically, between parents and offspring. He used a rough, nonpathogenic R strain of streptococcus bacteria and a pathogenic S strain. When mice were injected with the live S strain, they died. The mice survived when injected with the live R strain or the heat-killed S strain. But when he injected the mice with a mixture of live R strain and heat-killed S strain, the mice died. Upon isolating the live bacteria
from the dead mouse, he only recovered the S strain of bacteria. When he then injected this isolated S strain into fresh mice, the mice died. Griffith concluded that something had passed from the heat-killed S strain into the live R strain and “transformed” it into the pathogenic S strain; he called this the “transforming principle.”
Avery, MacLeod, and McCarty’s research (1944)
They further explored Griffith’s transforming principle. They isolated the S strain from infected dead mice, killed it using heat, and inactivated various components of the S extract. They used degrading enzymes that could destroy proteins, RNA, and DNA. They found that when DNA was degraded, the resulting extract was no longer able to transform the R strain. No other enzymatic treatment was able to prevent transformation, leading to the conclusion that DNA was the transforming principle and that genetic information could be transferred horizontally
Hersey and Chase
Provided evidence that DNA was the genetic material rather than protein. They studied a T2 bacteriophage virus that infected E. coli bacteria. They labeled the protein coat in one batch of phage using radioactive sulfur, because sulfur is found in the amino acids methionine and cysteine but not in nucleic acids. They labelled the DNA in another batch using radioactive phosphorus because phosphorus is found in DNA and RNA. The samples were centrifuged and placed in tubes- lighter phage particles remained in the supernatant and heavier bacterial cells remained at the bottom of the tube. In the protein tube, the radioactivity remained only in the supernatant. In the DNA tube, the radioactivity was detected only in bacterial cells. They concluded that it was the phage DNA that was injected into the cell that carried the information to make more phage particles, so DNA was the source of genetic material
Nucleic acids
Biological macromolecules that have monomers called nucleotides.
Base sequence
The order that nucleotides appear within a strand. The base sequence of DNA carries the hereditary information in a cell
Deoxyribonucleotides
Nucleotides that compose DNA
Nucleoside
Composed of the 5 carbon sugar and nitrogenous base
3 components of a deoxyribonucleotide
- Deoxyribose- a 5 carbon sugar
- A phosphate group
- A nitrogenous base- a ring structure that is responsible for complementary base pairing between nucleic acid strands
Purines
Bases that have a double ring structure with a 6 carbon ring fused to a 5 carbon ring. They include adenine and guanine
Pyrimidines
Bases that are smaller, and contain only a 6 carbon ring structure. Includes cytosine and thymine
Phosphodiester bonds
Covalent bonds that connect the nucleotides of the DNA molecule. The phosphate group attached to the 5’ carbon of the sugar of one nucleotide is bonded to the hydroxyl group of 3’ sugar of the other nucleotide
Sugar-phosphate backbone
The alternating sugar-phosphate structure that makes up the framework of a nucleic acid strand. It is held together by phosphodiester bonds
Chargaff’s rules
The idea that in DNA, the amount of adenine to close to equaling the amount of thymine, and the amount of cytosine is close to equaling the amount of guanine
Rosalind Franklin
Produced well-defined X ray images of DNA that clearly showed its double helix structure
Watson and Crick
Discovered the purine-pyrimidine pairing of the double helical DNA molecule. They proposed that the strands twist around each other to form a right handed helix and that the two strands are antiparallel
Antiparallel
The 3’ end of one DNA strand faces the 5’ end of the other strand
