module 6 gen 8-10 Flashcards
Why are recombination events considered rare?
Recombination events occur less frequently than mutations, especially within specific regions of DNA.
What is meant by “wild type”?
Wild type refers to the normal or most common phenotype or genotype found in a population.
What is the potential outcome of recombination between two independent mutations in the same gene?
The outcome could be the restoration of functional protein, leading to the wild-type phenotype
What is the significance of rare recombination events within a gene?
Rare recombination can restore the original wild-type sequence by swapping mutated segments with wild-type segments.
How is a gene defined in the context of mutations?
A gene is a linear arrangement of nucleotides that encodes for a specific protein or function.
What happens when two independent mutations occur in the same gene?
They may affect the gene’s function but can potentially be restored to wild-type through recombination.
seymor benzer did a
recombination analysis
seymor benzer proposed
if a gene is a inear set of nucleotides then recombination between
homologous chromosomes carrying different mutations within the
same gene should generate wild-type phage(
Benzer studied a mutation that
leads to
very rapid lysis of
bacteria
seymor benzer used ____ as an experimental system
T4 phage
T4 is _____ , but several different strains can infect E. coli
_______
haploid; simultaneously
Different viral genomes can ______
recombine
There is a large number of progeny to detect rare
recombination events (screening)
Only recombinant phages could
proliferate
Lytic Phage Life Cycle
1.phage injects dna into host cell
2.phage proteins made.dna replicated. host chromosome degrades
3.assembly of phages in host cell
4.lysis of host cell
the mutation seymor studied generated ______ (with sharper edges).
larger plaques
the mutation seymor studied also helped the viruses
lyse their hosts earlier.
benzor saw that II- mutants can infect E coli K but
cannot get that strain of bacteria to
make (more) viral particles
benzer concluded (3)
-A gene consists of different parts and each can mutate
-Gene is a linear arrangement of nucleotides and
recombination between different mutable parts can generate
a normal, wild-type allele
-A gene only performs its normal function if all components
are wild-type
How a Genotype Causes a Phenotype
Scientists learn about normal gene function by looking at
the disrupted, broken or diseased state
Archibald Garrod studied
a metabolic disease (alkaptonuria)
after studying alkaptonuria garrod determined
that the sick family members lack an enzyme due to a mutation
beadle and tatum proposed
One Gene, One Enzymes in 1940s
beadle and tatum proposed
isolated mutagen-induced mutants that disrupted synthesis of arginine, an amino acid required for Neurospora
crassa growth
Auxotroph
needs supplement to grow on minimal media
Prototroph
wild-type that needs no supplement; can synthesize
all required growth factors
beadle and tatum experiment setup
Several strains that could not
grow without arginine in the
medium were isolated
Beadle & Tatum Recombination analysis located ____
mutations
Beadle & Tatum located mutations
in four distinct
regions of genome
beatle and tatum had Complementation tests that showed each of four regions correlated
with different complementation group
since each region correlated with a different complementation group it meant
each was a different gene
what were the 4 different regions called
ARG-E, ARG-H, ARG-F, ARG-G
Beatle and Tatum experiment results (3)
Each mutation destroys the function of an enyzme
* Each gene controls the activity of an enzyme
* => One gene, one enzyme
what happened with beatle and tatum experiment results
one gene one enzyme had to be modified
beatle and tatum experiment setup
Organism: They used the bread mold Neurospora crassa.
Mutant Isolation: Spores were exposed to X-rays to induce mutations, creating strains with defects in nutrient synthesis.
Growth Conditions: Mutant strains were placed on minimal media with added specific amino acids to determine which nutrients allowed growth.
Analysis: If a mutant could only grow with a specific amino acid, it indicated a mutation affecting the enzyme responsible for its synthesis.
Proteins are linear polymers of
amino acids
proteins are linked by
peptide bonds
_____different amino acids are building blocks of proteins
20
each amino acid has
amino group, carboxyl group
amino group and carboxyl group attached to
core carbon
attached to core carbon is
R group
why is R group important
R is the side chain that distinguishes each amino acid
proteins have a
direction
left side of polypeptide bonds is the_______
right side of polypeptide bond is the_____
left- N terminus
right-C terminus
missense mutation can cause
sickle cell
Effect of a Sequence Change on Proteins
normal hemoglobin
3’CTGACTCCTG-A-GGAGAAGTCT5
3’CTGACTCCTG-T-GGAGAAGTCT5
what type of change is this and what does this cause
missense change, causes sickle cell
change in bases causes a change ______
amino acids
proteins primary structure is
the amino acid sequence
The amino acid sequence (primary structure) puts limitations on
the 3D structure of the protein
proteins second structure is normally a
alpha helix or a beta pleated sheet
secondary structure forms cause
interactions with side chains of amino acids
tertiary structure of proteins is formed by
folding of secondary structure
what type of structure does myoglobin have
tertiary
side chains help determine
protein structure
quaternary structure is when
more then one polypeptide forms to make a protein
