a+ --> a- mutation (forward mutation)

a- --> a+ reverse mutation (reversion)

Incomplete dominancethe term used to describe the general case

in which the phenotype of a heterozygote is intermediate between those of the two

homozygotes,on some quantitative scale of measurement

Presence of pink pigment- / +

Four-o’clock plants

Purine replaced by a different purine; pyrimidine replaced by a different pyrimidine: TRANSITIONS

Purine replaced by a pyrimidine; pyrimidine replaced by a purin :TRANSVERSIONS

Point mutations at the molecular level

Animation ed.9: 9.2&9.17

TRANSLATION

Animation ed.9: 9.2&9.17

TRANSLATION

Now, insertions and deletions of base pairs:

Forward mutation-A mutation that converts a wild-type allele into a mutant allele

Selection of auxotrophs by filter enrichment

Reverse mutation-The production of a wild-type gene from a mutant gene

Equivalent reversion

UCC (Ser) forward UGC (Cys) reverse AGC (Ser)Wild type Mutant Wild type

CGC (Arg, basic) forward CCC (Proline) reverse CAC (His, basic)Wild type Mutant Pseudo-wild type

Intragenic suppressor

Intragenic suppressor

Intergenic suppressor

Intergenic suppressor

Nonsense suppressor

Chromosome transmission fidelity (Ctf) assay

ade2-101

non-essential Chromosome FragmentM SUP11

WTade2-101

CIN mutant

ade1-101

ade2-101

kar3 sic1

rad50 xrs2

Animation ed9: 9.19a

Nonsense mutation

Animation ed9: 9.19b

Nonsense suppressor

Animation 9.19c

Nonsense suppression

rodns and suppressor-tRNA together give WT phenotype

Regulatory Coding

Using genomic sequence to find a specific gene

When doing GENETIC mapping,Molecular Markers can be used as a locus

Single Nucleotide Polymorphisms (SNPs)

AACGTCATCG vs. AACGTTATCG

Microsatellites (variable # of short repeats)

CGCGCG vs. CGCGCGCGCG vs. CGCG

Restriction Fragment Length Polymorphism (RFLP)

SNP leading to a loss/gain of a restriction cut site

When doing GENETIC mapping,Molecular Markers can be used as a locus

They are mile-markers ,not destinations!

אבני דרך, ולא יעדים!

Almost all SNPs, Microsatellites, etc. are SILENT,and there are millions of them

A specific gene, the breast cancer gene BRCA1 was foundBy using the genomic map at increasing levels of resolution

Is there linkage between a mutant gene/phenotype and a SNP?

USE standard genetic mapping technique, with SNP alternative sequences as “phenotype”

B= bad hair, Dominant

X

B/b b/b

B/b

B/b

b/b

b/b

1/1’ 25%

1/1 25%

1/1’ 25%

1/1 25%

1/1’ 1/1

SNP1 ..ACGTC..SNP1’ ..ACGCC..

SNP2 ..GCTAA..SNP2’ ..GCAAA..

SNP3 ..GTAAC..SNP3’ ..GTCAC..

2/2’ 47%

2/2 3%

2/2’ 3%

2/2 47%

2/2’ 2/2

3/3’ 25%

3/3 25%

3/3’ 25%

3/3 25%

3/3’ 3/3

SO…B is 6 cM from SNP2, and is unlinked to SNP 1 or 3

B 2’ / b 2

Is there linkage between a mutant gene/phenotype and a SNP?

USE standard genetic mapping technique, with SNP alternative sequences as “phenotype”

B= bad hair, Dominant

X

B/b b/b 1/1’ 1/1

SNP1 ..ACGTC..SNP1’ ..ACGCC..

SNP2 ..GCTAA..SNP2’ ..GCAAA..

SNP3 ..GTAAC..SNP3’ ..GTCAC.. 2/2’ 2/2 3/3’ 3/3

SO…B is 6 cM from SNP2, and is unlinked to SNP 1 or 3

We have the ENTIRE genome sequence of mouse, so we know where the SNPs are

Now-do this while checking the sequence of THOUSANDS of SNPs

The logic of creating sequence map of the genome

Physical maps are maps of the order, overlap, and orientation of physicallyisolated pieces of the genome-in other words, maps of the distribution of the cloned

genomic DNA from genomic clone libraries

Part of the automated production line of a major human genome sequencing center

A specific gene can be found in the genomic sequence bymatching linkage and cytological maps with the

Genome sequence

CGCGCG

vs. CGCGCGCGCG

vs. CGCG

Mutagenesis

Plate to select for phenotype of interest

Complementation groups

Complementation groups

First, we need to catalogue our mutants to complementation groups (Total of 138 mutants were isolated in the original CTF screen).

x xMate

xx

Diploid still shows CTF phenotype

Mutant#1 Mutant#2

Mutant#1 and Mutant#2are mutated in the same gene

Same complementation group

Diploid

x xMate

Mutant#3 Mutant#4 Diploid

xx

Diploid dont show CTF phenotype

Mutant#3 and Mutant#4are mutated in different genes

Different complementation groups

Complementation groups

Chromosome Transmission Fidelity (Chromosome Transmission Fidelity (ctfctf) Mutants) Mutants

Total # of mutant isolates:138

19 Complementation Groups10137 Undesignated (single member)37

Estimated total # of genes represented ~ 50 ctf genes

Complementation groups

WOBBLEA situation in which the third nucleotide

of an anticodon (at the 5’ end) can form two alignments.This third nucleotide can form hydrogen bonds not only with its

Normal complementary nucleotide in the third position butAlso with different nucleotide in the position.

I stands for inosine, one of the rare bases found in tRNA, often in anticodon

MESSAGE

The genetic code is said to be degenerate because in many casesmore then one codon is assigned to a single amino acid, and, in addition ,

several codons can pair with more then on anticodon (wobble)