Chapter 6 Genome

8/8/2019 Chapter 6 Genome

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Genome:Allthe genetic information in a cell

Chromosome: Structure containing DNAphysically carries hereditary information;

the chromosomes contain the genes

Gene: A segment of DNA that encodes a functional product

Product: usually a protein

Genetics: The study of what genes are

how they carry information

how information is expressed

how genes are replicated

Genomics: The molecular study of genomes

Genotype: The genes of an organism codes for particular characteristics of an organism,potential properties

Phenotype: Expression of the genes (the actual expresses properties)

the manifestation of a genotype

Is

The complementary structure ofthe nitrogenous base sequence is the key to understanding

DNA replication.


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Polymer of nucleotides:

Adenine

thymine

cytosine

guanine

DNA polymer can add nucleotidesto the 3 end only!!

Double helix associated with proteins

"Backbone" is deoxyribose-phosphate

Strands are held together by:hydrogen bonds between AT and CG

DNA strands are antiparallel

Semiconservative Replication

New double strand

Ccc contains

thymine is present on theoriginal strand, only

adenine can fit into place

on new strand.guanine on original

strand, Only cytosine can

fit.

-Bases that r improperlypaired, are replaced by

replication enzymes.- Parental DNA continuesto unwind to allow

addition on the next

nucleiotide.Point @ which replication

occurs called replicationfork

New double strandedDNA molecules contain:

One original strand

One new stand

Paired DNA strands are

oriented on in opposite

directions of each other.Sugar phosphate upside

down

End having a

phosphate

attached to

the 5 carbon

is called

5 end

End having a

hydroxylattached tothe 3 carbon

is called3 end

Difference b/t ATP and adenine nucleotide

in DNA is Deoxyribose the sugar innucleotides that synthesizes DNA


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DNA Synthesis DNA Synthesis

DNA is copied by: DNA polymerase

(enzyme)In the 5'3' direction (new strand is

built in this direction)

Initiated by an RNA primer

Leading strand is synthesized

continuously

Lagging strand is synthesizeddiscontinuously

Okazaki fragments

RNA primers are removed and Okazaki

fragments joined by a DNA polymeraseand DNA ligase


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DNA Synthesis


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Replication of Bacterial DNA

Give a clinical application of genomics. 8-1

Why is the base pairing in DNA important? 8-2

Describe DNA replication, including the functions of DNA gyrase, DNA

ligase, and DNA polymerase. 8-3

Separate dark purple strand. Circular chromosome in bacteria

Goal : To take parent DNA and creating identical daughter DNA


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Transcription

DNA is transcribed to make RNA (mRNA, tRNA, and rRNA)

Genetic info stored in DNA is rewritten so the same information is in the

base sequence of mRNA DNA mRNA

G C

C G

T AA U

Transcription-begins (requires) when RNA polymerase binds to the site

promoter sequence, starts building (RNA Polymerase bound to DNA)

Transcription proceeds(like DNA, RNA) is synthesized in the 5'3'

direction (Process - RNA Polymearase (enzyme), bind s topromoter, DNA un-winds @ beginning of gene)

RNA is created by base pairing rules (complementery base pairing rules

Adine uricile No thymine in RNA

Makeing RNA only uses one (of the two) DNA stran, continue adding until

teminater

Transcription stops when it reaches theterminator sequence

mRNA carries the coded information for making specific proteins, From: DNA

ribosomes, where proteins are synthesized


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The Process of Transcription

Translation:

mRNA is translated in codons (grouping of three nucleotides) AUG initiates

protein synthesis.

Codons are written in their base sequence in mRNA- the sequence code on mRNA

molecules determines, the sequence of amino acids that will be in the protein synthesis

Translation ofmRNAbegins at the start codon: (AUG)

Translation ends at nonsense codons(do not code for amino acids):UAA, UAG, UGA-

end protein synthesis

Protein synthesis is called Translation

Involves: decoding nucleic acids Converting the information into proteins

The Genetic Code: 64 sense codons on mRNA encode the

20 amino acids

The genetic code is degenerateo-

allows it change(GUU/GUC/ so on)giving flexibility. Resulting the same DNA

or P protein

tRNA carries the complementary anticodon

anticodon a sequence of three bases that is complementary to a codon.


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Simultaneous Transcription & Translation The Process of Translation

The Process of Translation

Ribosomal RNA comes in two parts, Creating first amino acid (tRNA w/AUG & mRNA)This sets up the start codon (AUG) in the proper position to allow translation to begin.

After the ribosome joins the first 2 amino acids (w/ a peptide bond) the 1st tRNA leaves ribosome.

As amino acids are brought into line, peptide bonds are formed b/t them = polypeptide chainsAll of this happens in cytoplasm

Ends when nonsense codon in the mRNA is reached.Intact Ribosome: A P E

A arriving, deliver newly arriving amino acid, tRNA leaves exp w/ amino acidP- Pone, tRNA is going to transfer, shifts Placed to A cite leaving ? empty

Methine is being passed to Leu (A site) adding 1 amino acid at a time.


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What is the role of thepromoter, terminator, and

mRNA in transcription? 8-4

How does mRNA production in

eukaryotes differ from the

process in prokaryotes? 8-5


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Regulation of Gene Expression

Constitutive genes areexpressed at a fixed rate

Protiens that used all day longconstant supply of)

Other genes are expressedonly as needed

Repressible genes on,but can be turned off

Inducible genes off,but can be turned off

Catabolite repression form ofre ression determined b lucose

Induction

Respiration

Catabolt Respiration


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RNA Processing in Eukaryotes

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Chapter 6 Genome