Ch. 2 DNA: The Repository of Biological Information Flashcards
What did Mendel’s work with peas provide the basis for (3)?
Gene variants (alleles), diploid (body) and haploid (sex) cells, and the basics of inheritance.
What did Morgan’s work with fruit flies provide?
It provided evidence that genes are carried on large structures called chromosomes.
What is the process of cell division for gametes? Somatic cells? When were they discovered?
The processes of cell division were discovered early on. Gametes divide via meiosis and somatic cells divide via mitosis.
Were the molecules involved in cell division known early on?
No.
When were nucleic acids discovered in cells and when was their significance recognized?
Nucleic acids were discovered in cells in the 1800s, but their significance was not realized until the 1900s.
Why were proteins thought to be the more significant polymer in regards to inheritance?
Nucleic acids were a polymer of four repeating nucleotides while proteins were a polymer of 20 different amino acids.
Why do we now know that nucleic acids have more possible combinations than proteins?
While there are 20 amino acids, each polypeptide is only about 100 amino acids long, giving you 10⁵⁰ combinations. While there are only 4 nucleotides, each polymer has 3 billion bases giving you ∞ combinations.
Who were the first to demonstrate that DNA was the chemical of inheritance (3)?
Avery, MacLeod, and McCarty did in the 1940s.
What did they base their experiments on?
Griffith’s transformation experiment.
Who else helped solidify the recognition that DNA was the chemical of inheritance and how (2)?
Hershey and Chase studied viruses and supported the conclusion that DNA was the genetic material because radio-labeled viral DNA entered cells, not proteins.
Who linked DNA to proteins and how (2)?
Beadle and Tatum demonstrated that enzymes, and therefore proteins, were coded by DNA. They studied bread mold and proposed the “one gene, one enzyme” hypothesis.
What is the more correct version of Beadle and Tatum’s hypothesis?
“One gene, one polypeptide” is more correct because we now know that some enzymes are proposed of multiple polypeptides. This still isn’t 100% correct.
Who showed how DNA worked (2)?
Watson and Crick were the first to determine the chemical structure of DNA.
How did Watson and Crick determine the structure of DNA?
They figured it out based on the experimental results of their own labs, and other labs.
What did they determine the structure of DNA to be?
DNA is composed of two strands in a helix and the strands are antiparallel and complementary.
What did the identification of DNA’s structure allow for (2)?
The structure and chemistry of DNA immediately identified how DNA could be replicated. Genetics could now be studied at the chemical level = molecular genetics!
What’s Crick’s Central Dogma of Information Flow (3)?
- DNA acts as a template for its own synthesis
- DNA is the template for RNA synthesis
- RNA is the template for protein synthesis
How did Crick determine his “Central Dogma of Information Flow”?
In eukaryotes, DNA is in the nucleus, but protein synthesis occurs in the cytoplasm. There must be an intermediate chemical used to make this happen.
What did Crick think the intermediate chemical was?
RNA was believed to be this intermediate, and this was later proven to be the case.
Why is RNA important in molecular genetics, and life for that matter (4)?
- mRNA is the template for protein synthesis
- rRNA makes up part of the ribosome and creates peptide bonds in polypeptides
- tRNA brings aa’s to the ribosome to be added to the growing peptide (“reads” codons)
- there are many more roles of RNA, and probably some yet to be discovered
What do changes in DNA lead to?
Because proteins are based on information in DNA, changes in DNA information may lead to a change in protein.
What does the idea of DNA changes affecting proteins explain (3)?
- Explains why genes can have alleles that lead to phenotypic variation.
- Explains how genetic disorders can develop (i.e. sickle cell, cystic fibrosis, Huntington’s…).
- It also helps to explain how adaptations can evolve (i.e. mutation in CCR5 provides resistance to HIV and Smallpox, but has negative effects on T-cells).
