BIO 143 Lecture Notes - Lecture 12: Cystic Fibrosis, Ribosomal Rna, Messenger Rna
16 Jun 2018
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Chapter 12
Gene Expression and Regulation
Cystic Fibrosis
Cystic fibrosis is an inherited genetic disease of the mucus glands that affects many body
systems
A common genetic disease that occurs in 1 in 2,500-3,500 Caucasian newborns; less
common in other groups affecting 1 in 17,000 African Americans and 1 in 31,000 Asian
Americans
Mutations in CFTR gene causes cystic fibrosis
-CFTR is a channel protein that is permeable to chloride and is found in many parts of the
body including glands, lungs and intestines
-Required for reabsorption of both chloride and sodium and for fluid secretion in the
airways
-Mutations in the CFTR gene produce defective CFTR proteins that prevent reabsorption of
chloride and sodium and also cause mucus in the airways of lungs, for instance, to be
dehdrated ad thik ad ilia a’t ove ateria out of lugs
-Causes airways of lungs to be partially clogged and bacteria multiply, causing chronic lung
infection
How is the Information in DNA Used in a Cell
The link between DNA and protein
-DNA contains the molecular blueprint of every cell
-Proteins are the construction workers of the cell
-Proteins control cell shape, function, reproduction, and synthesis of biomolecules
-Therefore, there must be a flow of information from DNA to protein
DNA provides instruction for protein synthesis via RNA intermediaries
-DNA in eukaryotes is kept in the nucleus
-Protein synthesis occurs at ribosomes in the cytoplasm
-DNA information must be carried by an intermediary, DNA, from the nucleus to the
cytoplasm
-RNA differs structurally from DNA in three ways
RNA is single stranded
RNA has the sugar ribose instead of deoxyribose
RNA has the base uracil instead of thymine
-There are three types of RNA involved in protein synthesis
Messenger RNA
Ribosomal RNA
Transfer RNA
Ribosomes
Messenger RNA: The base sequence of mRNA carries the information for the amino acid
sequence of a protein; groups of these bases, called codons, specify the amino acids
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Ribosomal RNA: rRNA combines with proteins to form ribosomes; the small subunit binds
mRNA; the large subunit binds tRNA and catalyzes peptide bond formation between amino
acids during protein synthesis
Transfer RNA: Each tRNA carries a specific amino acid to a ribosome during protein
synthesis; the anticodon of tRNA pairs with a codon of mRNA, ensuring that the correct
amino acid is incorporated into the protein
DNA provides instructions for protein synthesis via RNA intermediaries
-RNA occurs in many other roles besides protein synthesis
-RNA is used as the genetic material in some viruses, such as HIV
-Enzymatic RNA, called ribozymes, catalyzes various reactions, including the cutting apart of
other molecules of RNA
-Xist RNA prevents the genetic information in one of the X chromosomes of female
mammals from being used
-MicroRNA may play a role in regulating development and fighting disease
DNA provides instructions for protein synthesis via RNA intermediaries
-Messenger RNA carries the code for protein synthesis from DNA to the ribosomes
-Ribosomal RNA and proteins form ribosomes
-Transfer tRNA carries amino acids to the ribosomes for addition to the growing protein
Overview: Genetic information is transcribed into RNA and then translated into protein
-RNA directs protein synthesis in a two step process
1. Information in a DNA gene is copied into RNA in the process of transcription
2. Messenger RNA, together with tRNA, amino acids, and a ribosome, synthesizes a protein
in the process of translation of the genetic information contained in the mRNA
Genetic information is transcribed into RNA and then translated into protein
The Genetic code uses three bases to specify an amino acid
-The genetic code translates the sequence of bases in nucleic acids into the sequence of
amino acids in proteins
-Given that there are 20 amino acids but only four bases, statistically, the smallest number
of bases that could combine to yield a different sequence for each of the 20 amino acids is
three
:A two base code could produce only 16 combinations
:The three base code has the potential to create 64 combinations
The genetic code uses three bases to specify an amino acid
: The genetic code is usually written in terms of the base triplets in mRNA
: Each codon specifies a unique amino acid in the genetic code
: Each mRNA also has a start codon and one of three stop codons
: Each codon has only one specific amino acid; however, some amino acids are specified by
as many as six different codons
How is the Information in the Gene Transcribed into RNA
Overview of transcription
-The three steps of transcription correspond to the three major parts of most genes
:A promoter region at the beginning of the gene marks where transcription is to be initiated
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find more resources at oneclass.com
Document Summary
Cystic fibrosis is an inherited genetic disease of the mucus glands that affects many body systems. A common genetic disease that occurs in 1 in 2,500-3,500 caucasian newborns; less common in other groups affecting 1 in 17,000 african americans and 1 in 31,000 asian. Cftr is a channel protein that is permeable to chloride and is found in many parts of the body including glands, lungs and intestines. Required for reabsorption of both chloride and sodium and for fluid secretion in the airways. Causes airways of lungs to be partially clogged and bacteria multiply, causing chronic lung infection. How is the information in dna used in a cell. Dna contains the molecular blueprint of every cell. Proteins are the construction workers of the cell. Proteins control cell shape, function, reproduction, and synthesis of biomolecules. Therefore, there must be a flow of information from dna to protein. Dna provides instruction for protein synthesis via rna intermediaries.
