Summary
Summary MLB111 Units 8-10 Semester test 3 (updated 2024)
- Course
- Institution
- Book
Summary of units 8-10. Diagrams and images have been included. This is the scope for the 3rd Semester test.
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
More summaries for
-
Biology 8e Raven Chapter 1 Questions and Answers Graded A+ 2024 Reviewed
-
Summary Biology, Raven, MLB 111, Semester test 2
-
Summary of Membranes
1 review
By: juneduplessis • 2 year ago
By: claudiafreese • 1 year ago
Thank you!
Seller
Follow
claudiafreese
Reviews received
Content preview
Unit 10Genes and Gene Expression
Archibald Garrod
Garrod concluded that inherited disorders can involve specific enzymes. Certain diseases seemed to be more
prevalent in certain families. After studying the disorder, alkaptonuria, he suspected that disease was a result of
enzyme deficiencies.
Beadle and Tatum
Beadle and Tatum were able to change the genes of Neurospora
crassa using X-rays, making them non-functional. The specific defect
in each mutant was identified by growing on medium supplemented
with a carbon source (glucose), a vitamin (biotin) plus inorganic salt.
Any cell able to grow on this minimal medium must be able to
synthesize all necessary biological molecules to survive.
After exposing spores to X-rays they suspected that nutritional
mutants would result due to damaged genes which encoded functions
needed to make important biological molecules.
They first grew cultures on a rich medium, then placed subcultures of
individual cells onto minimal medium. This identified any cell that
had lost the ability to make compounds necessary for growth. They
concentrated on the ability to synthesise the amino acid arginine.
They were able to identify the biosynthetic pathway for arginine by
supplementing minimal medium with intermediates. They defined 4
genes they named argE, argF, argG and argH,
If the mutation affects the enzyme earlier in the pathway than the
supplement, then growth should be supported. They were able to
isolate a mutant strain defective for each enzyme.
They concluded that genes specify the structures of enzymes that
encodes the structure of one enzyme. One-gene/one-enzyme
hypothesis. Today many enzymes contain multiple polypeptide
subunits each encoded by a separate gene, the relationship is
generalized to the one-gene/one-polypeptide hypothesis.
Central Dogma
The conversion of genotype to phenotype requires info stored in DNA to be converted to protein. The central
dogma describes the info flow in cells from DNA to RNA to protein. DNA is transcribed to make mRNA and
then translated to make protein.
A class of viruses called retroviruses can convert RNA genome into a DNA copy
using viral enzymes reverse transcriptase. This conversion defies flow of the
, central dogma and therefore a “reverse” flow from RNA to DNA had to be incorporated into the possible flow
of information.
Transcription
Only one of the 2 DNA strands are copied, we call this the template strand or antisense strand. The strand that is
not copied is called the coding strand or sense strand.
The RNA transcribed is called messenger (mRNA) as it
carries the DNA message from the nucleus to the
ribosomes in the cytoplasm for processing.
RNA polymerase has no proofreading capacity, but RNA
is short lived, and therefore mistakes are not permanent
as in DNA replication.
Translation
RNA cannot be used as a direct template for a protein because there is no molecular basis for recognition
between amino acids and nucleotides. A transfer (tRNA) interacts with RNA by base-pairing and is covalently
bonded to an amino acid. Translation takes place on the ribosome and involved multiple kinds of RNA and
proteins:
Types of RNA
• mRNA to transport info from nucleus to cytoplasm.
• Ribosomal (rRNAs) are found in ribosomes and critical for their function.
• tRNA molecules have amino acids covalently attached to one end and an anticodon that can base-pair
with an mRNA codon at the other. The tRNA acts to interpret info in mRNA and help position the
amino acids on the ribosome.
• Small nuclear RNAs (snRNAs) are part of the machinery that is involved in nuclear processing of
eukaryotic “pre-mRNA”.
• Signal recognition particle (SRP RNA) contains both RNA and proteins. snRNAs mediate the process
whereby proteins are synthesized by ribosomes on the rough ER.
• Small RNAs include both micro-RNA (miRNA) and small interfering RNA (siRNA). These are
involved in gene expression control.
The Genetic Code:
Genetic code is read in groups of three called codons, each corresponding to an amino acid. With 4 nucleotides
(G,C,T and A) and 2 in each codon, this produces only 16 different codons which is not enough for 20 amino
acids. In the same way, using 4 nucleotides per codon would produce 256. Using 3 nucleotides results in 64
different codons which is enough.
Do genetic messages include spaces between codons or not?
Crick + demonstrated that there are not spaces. They created mutations causing a single base insertion or
deletion. They then demonstrated that combing a deletion with an insertion restored function. By selecting a
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller claudiafreese. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $5.04. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
82013 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now