Download Gene Regulation Powerpoint[1]

Define the following terms:
Genetics
Gene
Gene expression
Cell Differentiation
Artificial Selection
Genetics Introduction
& Gene Regulation
Artificial Selection
• Selective breeding - allow the individuals
with desired traits to produce the next
generation.
• This takes advantage of naturally
occurring genetic variation.
• Ex. Breeds of dogs
cockapoo
puggle
Yorkie Pin
Artificial Selection
• Name a situation that humans have
selected for various characteristics.
• What are the advantages and
disadvantages of this type of selection?
Artificial Selection
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Agriculture
Livestock
Domesticated animals
Plants
Selective breeding
• Luther Burbank developed disease-resistant
potato that was exported to Ireland to fight the
potato blight.
• Hybridization - crossing dissimilar individuals
to bring together the best of both organisms.
– Ex. Burbank crossed a disease-resistant strain
with a strain that was high in food production.
Selective breeding
• Inbreeding - continued
breeding of individuals
with similar characteristics.
• This ensures that the
characteristics of each
unique breed are
preserved.
• Disadvantaged and
weaker species is created.
• All the individuals carry
similar genetic material
and have a higher chance
of contracting a disorder.
Amur Leopards only have
~40 individuals in the wild.
Human Genetics
• List all the features you share in common with
your parents.
• Turn to a neighbor to discuss which parent you
most resemble and share the traits that you
have in common with your parents.
• Why do some students not resemble either of
their parents?
Heritable traits
•
Completely (or nearly completely) heritable:
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Partially heritable:
–
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•
height
cognition
body mass
personality traits (at least many traits)
diabetes
asthma
schizophrenia
Not (or only very weakly) heritable:
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gender
eye color
skin color
cystic fibrosis
muscular dystrophy
deafness (many forms)
scurvy (vitamin C deficiency)
distance a student lives from school
The environment also affects how our genes
are expressed.
Gene Expression
•Humans have 25,000 genes within 46
chromosomes.
•How does a cell know which genes need
to be regulated (turned off and on)?
Gene Regulation
• Cells would waste a lot of energy if they
did not regulate the genes contained in
them.
• The organism would produce a lot of
waste product as well.
• Regulation allows the cell to control which
genes will be expressed and when.
Gene Expression
• Gene expression – the
activation of a gene that
results in the formation of a
protein
• Genome – the complete
genetic material of an
organism
• Karyotype – picture of
chromosomes
Prokaryotic gene regulation
• Francois Jacob and Jacques Monod
studied the regulatory elements in the DNA
of the bacterium Escherichia coli
• Studied how genes control the metabolism
of lactose.
•Lactose is a sugar found
in milk
•Can be broken down into
galactose and glucose
Gene Regulation
• Operon - A series of genes that code for specific
products and the regulatory elements that
control these genes.
– Structural genes –code for particular polypeptides
– Promoter – site at which polymerases attach to start
transcription
– Operator –binding site for an inhibitory protein that
blocks transcription from proceeding
lac Operon
Gene Repression
• Jacob and Monod found that the expression of
the genes were turned on only when lactose
was present.
• Repression – blockage of transcription by the
action of a repressor protein
• Repressor proteins – protein that stops a gene
from being expressed
– Regulator gene – codes for the repressor proteins
– DNA binding protein – protein that binds to DNA
– These proteins usually bind to the operator region of
the operon
Gene Repression
• Regulator protein is bound to operator
region preventing transcription of mRNA.
A repressor protein is coded for by a(n):
a. Structural gene
b. Regulator gene
c. Promoter
d. Enhancer
Gene Activation
• Activation – start of transcription
• Inducer – molecule that initiates
gene expression
– Binds to repressor and changes
conformation removing it from
operator
– Ex. Lactose in the lac operon
Define the following terms:
Character
Trait
Hybrid
Law of Independent Assortment
Gene Activation
1. Lactose, the inducer, turns on expression by binding
with the repressor protein.
2. This changes the repressors conformation and it is
removed from the DNA molecule.
3. Transcription of the necessary proteins proceeds
What is the purpose of the
operator?
a. Sequence of DNA that codes for the
repressor protein.
b. Talks to lactose to see when the operon
should be turned on.
c. Sequence that inducer binds to in order
to start translation.
d. Sequence of DNA that the repressor
protein binds to in order to stop
transcription.
Which of these are DNA-binding
proteins?
a.
b.
c.
d.
Repressor
Inducer
Operator
a&b
Eukaryotic Gene Regulation
• Most eukaryotic genes are controlled
individually.
• Regulatory sequences are much more
complex than the lac operon.
• Even though each cell in a multicellular
organism has the entire genome, only a
select few genes are expressed in a
particular cell.
Eukaryotic Gene Regulation
• Enhancer - a non-coding control sequence in a
eukaryotic gene
– Must be activated for transcription to take place
– Transcription factors - bind to enhancers and RNA
polymerase to facilitate transcription
• TATA box – region of “TATATA” or “TATAAA”
that is directly upstream of a coding sequence of
DNA.
– Helps to align the RNA polymerase on DNA molecule
Enhancer and TATA box
Eukaryotic Gene Regulation
• Histone – protein molecule around which DNA
is tightly coiled.
– For transcription to occur the histones loosen and the
coil relaxes, allowing the desired gene to be
transcribed into mRNA.
The control of gene expression enables
organisms to:
a. Reproduce more quickly
b. Remove mutations from their DNA
c. Produce proteins only when needed
d. Form new combinations of genes
Why is gene regulation in eukaryotes more
complex than in prokaryotes?
A. Prokaryotes have less chromosomes
than eukaryotes.
B. All the cells in a multicellular organism
cell can have a different function.
C. Prokaryotes are not multicellular
organisms.
D. All of the above.
Cell Differentiation
• Liver enzymes are not
expressed in nerve
cells.
• Keratin in skin cells is
not produced in blood
cells.
• Cell specialization, in
multicellular
organisms, requires
specific gene
regulation.
Cell Differentiation
• Homeotic gene – controls the
development of specific adult structures.
• Mutations in these genes have drastic
effects on the development of organisms
– Ex. Fly can grow appendage on head in place
of antennae.
How is the sex of an organism
determined?
• A human receives 23 chromosomes from
each parent.
• Autosomes – 22 non-sex chromosomes
• Sex chromosomes – determine an
individuals sex
• Females have two of the same sex
chromosomes (XX) and males have two
different sex chromosomes (XY).
Sex Chromosomes
• Thomas Hunt Morgan was a geneticist
from Columbia Univ. that began breeding
fruit flies, Drosophila.
• He noticed that one set
of the females
chromosomes were
different in shape and
size than the males.
Sex Chromosomes
• X-linked genes – genes found on the X
chromosome
• Y-linked genes – genes found on the Y
chromosome
• Sex linkage – the
presence of a gene on a
sex chromosome
•Ex. Colorblindness and
hemophilia
Keeping in mind that the gene for
colorblindness resides on the X
chromosome, why do males exhibit this
quality more than females?
a. Colorblindness is attached to the gene for
testosterone production.
b. Males only have one X chromosome and
therefore all the alleles are expressed.
c. Females do not inherit an X chromosome.
d. Males determine sex so they can chose which
offspring get the allele for colorblindness