Chapter 12 Flashcards
We can look at gene function in two ways
Molecular function of the protein
Organisms trait
They are connected, the molecular function affects the structure and function of cells
Polysome
One mRNA and many ribosomes
Unit of heredity
Another name for a gene
Two things genes do
proteins, template for
Store the info to make proteins
Act as a template to make an RNA molecule
Mutations
Changes in genetic material that can be inherited. It may change genetic blueprint by altering gene function
Archinold garrod and the relationship between genes and enzymes
Studied the disease
What the disease causes
What he hypothesized the disease was the result of
Alkaptonuria which causes abnormal levels of homogentisic acid(alkapton)
Causes discoloration of skin and urine to be black
Due to a missing enzyme, called it an inborn error of metabolism which is
A mutation in a gene that’s inherited by one or both parents
Beasley and Tatum
Proposed WHAT hypothesis
Describe their experiment, with bread mold neurospora
One gene, one enzyme; genes carry the info to make enzymes so a mutation in a gene would cause a defect in an enzyme
The bread mold needs a carbon source(sugar) inorganic salts and biotin.
They found every mutation resulted in the need for a vitamin to be supplemented
Beadle and Tatum
Amino acid arginine Sequence of conversions Group 1 Group2 Group 3
Arginine needs 3 enzymes to grow,
Sequence of conversions
EnZyme 1 converts a precursor into”orinthine “, enzyme 2 converts to citrulline, and enzyme 3 converts to arginine.
Group 1 was missing the first enzyme. It would grow if o, c or a was added
Group 2 was missing enzyme 2. Wouldn’t grow if only orinthe was missing but would grow if c or a was added
Group 3 missing enzyme 3 could only grow if arginine was added
4 ways the one gene one enzyme hypothesis was modified
Modified slogan
- the info to make all proteins including enzymes is in genes
- some proteins are made of 2 or more polypeptides
- A single gene can encode more than 1 polypeptide. Sometimes due to the way rnas are spliced
- Some genes encode RNAs that form things other than protein, like ribosomes
One gene, one polypeptide
Polypeptide
Polypeptide denotes_____
Protein denotes —-
Protein activity determines
A linear sequence of amino acids. Polypeptide denotes structure, protein denotes function
The structure and function of cells
How proteins made of one polypeptide differ from those made with more
In those ones one gene contains all the info to make the whole protein
Hemoglobin
The protein that carries oxegyn in red blood cells. Made of 2 xglobin and 2 bglobin polypeptides
Central dogma ( steps of gene expression at molecular level)
- Transcription- messenger RNA (mRNA) specifies the amino acid sequence of a polypeptide.
Translation - uses mRNA template to make a polypeptide. Called translation because nucleotide sequence in mRNA is translated into an amino acid sequence of a polypeptide
DNA->RNA-> protein
Central dogma summary
The transcription of DNA into mRNA and the translation of mRNA into a polypeptide
mRNA is an example of a ____ gene
What do those genes do
Two important products of non structural genes
Structural gene
Code for polypeptides
Transfer RNA which translates the language of mRNA into amino acids
and ribosomal RNA which forms part of ribosomes where translation occurs
tRNA
rRNA
Transfer RNA translates mRNA into amino acids
Ribosomal RNA part of ribosomes
Stages of transcription
Prokaryotes
Initiation, recognition step
In bacteria sigma factor causes RNA polymerase to recognize promoter region
Stage completed when DNA strands separate near promoter to form open complex
Transcription second stage(prokaryotes)
Which strand is used
What base pair is subsitutied
Elongation RNA polymerase synthesizes RNA Template or coding strand used for RNA syntheses Synthesized to 5' 3' Uracil is substatitute for thymine
Transcription stage 3(prokaryotes)
Termination
RNA polymerase reaches the termination sequence
Causes both the polymerase and newly made RNA transcript to dissociate from the DNA
The main purpose of the genetic material is
To encode the production of proteins in the correct cell, at the right time, in the right amount
A gene at the molecular level is defined as
An organized unit of DNA to be transcribed into RNA and ultimately result in a functional product
In eukaryotic cells ( transcription)
Polymerase 1 and 3
Polymerase 2
Polymerase 1 and 3 transcribe nonstructural genes
Poly 2 transcribes structural genes, transcribes mRNA
RNA processing in eukaryotes How it's different from bacteria Intron Exon Splicing
Eukaryotic mRNAs have a pre mRNA form that requires processing into mature mRNA
Coding sequence in structural genes, they’re transcribed but not translated
Coding sequence found in mature mRNA
Removal of introns
What is a cap, when is it added, what’s it’s function
What’s a tail, when’s it added what’s its function for
Addition of tails and caps in RNA processing (eukaryotes)
A cap is a form of guanosine attached to the 5’ end
Added when pre mRNA is made
It’s function is to be recognized by the cap binding proteins which allow mRNA to exit nucleus and bind to ribosomes
A tail is 100-200 adenine nucleotides added to the 4’ ending . Added after pre mRNA is made
Aids in export of mRNA from nucleus and gives stability to mRNA
