Gene function convey information to the cell

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Gene function convey information to the cell
What is a gene? basic unit of inheritance contai
ns a packet of information a. information
to produce a protein determines the amino acid
sequence of a protein b. information to
control the production of a protein increase or
decrease the rate of protein synthesis
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Gene function convey information to the cell
Control production of a protein a two step
process Step 1 DNA ? RNA
transcription Step 2 RNA ? Protein
translation
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RNA structure comparison with DNA
DNA
RNA
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RNA structure comparison with DNA
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RNA structure There are three types of
RNA ribosomal RNA (rRNA) structural part of
the ribosome transfer RNA (tRNA) amino acid
carrier messenger RNA (mRNA) carries the
information for the amino acid sequence of a
protein
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RNA synthesis transcription occurs in the
nucleus RNA polymerase synthesis 5 ?
3 (template read 3 ? 5) pairing of bases
determines sequence A in template, U in RNA G
in template, C in RNA T in template, A in RNA C
in template, G in RNA
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Gene structure gene sequence of
nucleotides in DNA 1. may code for a protein
(mRNA) structural gene 2. may code for
an RNA molecule (rRNA, tRNA) 3. may control
expression of another gene regulatory
gene required for proper expression
when, amount, etc. may have positive effect
or a negative effect located at the 5 end
of the structural gene regulatory
genes promoter bind RNA polymerase
properly orient the polymerase, give start
point enhancer silencer locus control region
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Gene structure promoter bind RNA
polymerase properly orient the polymerase, give
start point located on 5 end of the
gene conserved region common to many
promoters same function regardless of the
gene promoter TATA box 25-30 bases to
the left of the transcription start site
rich in A T CAT box to the left of the TATA
box CCAAT common sequence
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Gene structure transcription alone does not
yield a functional mRNA! mRNA undergoes
modification after transcription splicing
removal of non-coding sequences introns
joining of coding sequences exons capping
addition to the 5 end polyA tail addition
200-300 A nucleotides
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Gene structure ß-globin gene as an example
three coding regions (red boxes), two
introns CAT box and TATA box bind and
orient the polymerase for proper transcription
white boxes transcribed regions which dont
code for the product
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Gene structure
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Gene families closely related DNA
sequences there is similarity in nucleotide
sequences there is similarity in amino acid
sequence in protein a-globin and ß-globin
genes on chromosome 16 and 11, respectively
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Gene families clusters of genes closely
related genes expressed at different
developmental stages genes are similar to one
another in cluster arose as a result of
gene duplication long ago intron-exon pattern is
similar some genes in the cluster dont
produce a mRNA pseudogenes pseudogenes
are very common in the genome believed to
have been functional at some point now
inactivated by mutation
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Gene families immunoglobulin superfamily
genes involved in cell recognition in the immune
system and the nervous system a. immunoglobulin
heavy and light chains chromosome 2, 14,
22 b. major histocompatibility complex (MHC)
chromosome 6 c. T cell receptor (surface
receptor) chromosome 7, 14 d. genes
expressed in neural tissue for cell adhesion