Primary Mechanism of Duplication : Unequal Crossing Over
Download
1 / 24

Primary Mechanism of Duplication : Unequal Crossing Over - PowerPoint PPT Presentation


  • 70 Views
  • Uploaded on

Primary Mechanism of Duplication : Unequal Crossing Over. Crossing over Between Daughter Strands. Addition (duplication). Deletion. (tandom duplications). Crossing over Between Daughter Strands. Addition. Deletion. Polyploidization : complete genome duplication. Processed

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Primary Mechanism of Duplication : Unequal Crossing Over' - adie


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Primary Mechanism of Duplication : Unequal Crossing Over

Crossing over

Between Daughter

Strands

Addition (duplication)

Deletion

(tandom duplications)

Crossing over

Between Daughter

Strands

Addition

Deletion



Processed

Pseudogene

Creation of a processed pseudogene.


a

Duplication

TD

a

b

Speciation

TS

a

b

a

b

Species 2

Species 1

aandbare said to be paralogous genes

aspecies1andaspecies2are said to be orthologous genes



Fate of Duplicated Loci

  • Both copies retain original function

    e.g. rRNA genes

    (2) Gain new function through mutation and selection

    e.g. globin genes

    (3) Become functionless pseudogenes

    e.g globin genes


Time of duplication may be estimated by observing the

phylogenetic distribution of genes

All vertebrates but jawless fish have a and b

H1: Two independent gene losses

H2: Duplication




Point mutations generally arise

during DNA synthesis or repair

Error rate of DNA polymerases

and the

Efficiency of DNA repair

are heritable traits.


Chromosomes genes and alleles

Locus A

Many different genes (loci)

per chromosome

Locus B

Locus C

Different forms of a gene

are called alleles

Chromosomes, Genes, and Alleles

Traits are determined

to a great extent by genes




In humans 35,000?? different proteins are specified by the

simple linear arrangement

of four bases

The Watson-Crick Model of DNA


Nucleotide bases
Nucleotide Bases

Adenine

Guanine

Cytosine

Thymine

}

Purines

Complimentary

}

Pyrimidines


C T T G

| | | |

3’ OH---dR---P---dR---P---dR---P---dR---P 5’

Schematic Representation of DNA

G A A C

5’ P---dR---P---dR---P---dR---P---dR---OH 3’

| | | |

G A A C


Classes of gene
Classes of Gene

  • Protein-coding genes : transcribed and translated

  • RNA specifying genes : transcribed

  • Untranscribed genes


Schematic of Eukaryotic Protein-Coding Locus

5’ UTR

3’ UTR

Intron 2

Intron 1

5’

3’

Exon 1

Exon 2

Ex 3

GT AG

GT AG

Regulatory

Sequences

Initiation

codon

Stop

codon


How does mRNA specify the amino acid sequence of the protein?

Every three nucleotides forms a codon : each codon

codes for an amino acid


Figure 4.3 The Genetic Code (Codons of mRNA) protein?

Note : different codons specify the same amino acid

(i.e. Code is Degenerate)


Example of RNA specifying gene :rDNA array protein?

NTS

18S

28S

ITS-1

ITS-2

ETS

5.8S

1 array in Tetrahymena

19,300 copies in Amphiuma

200 copies in Human


28S protein?

ITS

NTS

ETS

18S

ITS

28S

NTS

c

b

a

d

c

28S

human

a

d

b

c

c

28S

chimp

a

d

b

c

c

28S

pygmy chimp

a

d

c

b

c

28S

gorilla

a BamHI

b HindI

c BgIII

d HpaI

Arnheim, 1983


ad