Download 4.1.1- 4.1.4 | Chromosomes, genes, alleles and mutations

4.1.1- 4.1.4 | Chromosomes,
genes, alleles and mutations
Rania and Bryan
Eukaryote chromosomes are made up
of DNA and proteins…
• Eukaryotic chromosomes
consist of a DNA-protein
complex that is organized
in a compact way which
permits the large amount
of DNA to be stored in
the nucleus.
4.1.1
• A gene is a heritable
factor that controls a
specific characteristic.
• Alleles are one specific
form of a gene. They
differ from other alleles
by one or a few bases
only and occupy the
same gene locus as
other alleles of the gene.
4.1.2
• Genomes are the
whole genetic
information of an
organism.
• Eukaryote genomes
are contained in a
single, haploid* set
of chromosomes.
* Haploid - the number of chromosomes in a gamete of an
organism.
The human genome
is made up of about
35000 genes.
Gene Mutations
4.1.3
• Gene mutations are a change
to the base sequence of a gene.
 Mutations range in size from a single DNA base to a
large segment of a chromosome.
 Gene mutations occur in two ways: they can be
inherited by a parent or developed during a person’s
lifetime.
• Mutations also occur in an egg or sperm
cell, or those occurring right after
fertilization (de novo mutations).
Note: These types of
mutations can explain
genetic disorders in which
the child may have this
mutation in every cell, but
there is no history of this
disorder in the family.
• Acquired (somatic) mutations occur in the
DNA of individual cells during a person’s
lifetime.
 these changes can be caused by environmental factors such as
ultraviolet radiation from the sun, or when a mistake is made
in the replication during cell division.
Note: These types of
mutations cannot be
passed on to the next
generation.
4.2.1 – 4.2.2 | Mutations and Meiosis
Sickle Cell Anemia
4.1.4
• Sickle Cell Anemia is a good example of
a mutation.
• In sickle cell anemia the switch of just
one nucleotide causes glutamic acid to be
replaced by valine, which causes red
blood cells to become stiff and stick to
each other forming long fibers that
obstruct blood flow to other parts of the
body.
• The switch occurs
when the base code
CAG mutates to
CTG. That one
small change is
enough to cause
the disease.
• During Transcription there is a
mistake in the code and that
causes for the codon to be
misread, switching the amino
acid that normally pairs with
the base code causing the
sickle cell anemia.
Meiosis
• Meiosis is the division of
diploid cells into haploid
cells in order to create sex
cells.
• In meiosis the cell divides twice
without a DNA replication
between divisions.
• This creates Gene Variation
which is what allows us to evolve
as a species.
The reason we get a
haploid cell is so that
when the female and
male sex cell fuse we
have 46 chromosomes
instead of 92 if both cells
were diploid
Homologous Chromosomes
• Pairs of chromosomes that code
for the same gene but might have
different alleles.
For example: you can have two
chromosomes that code eye color
but one might code for blue eyes,
the other for brown eyes.
• Homologous chromosomes cross over during
division causing the genetic variation.
• Two chromosomes that code for the same gene
switch genetic code by tangling with one
another and keeping the code of the other.
Works Cited Page
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http://www.ndsu.edu/pubweb/~mcclean/plsc431/eukarychrom/eukaryo3.htm
http://hyperphysics.phy-astr.gsu.edu/hbase/biology/imgbio/cellhlabel.gif
http://www.dna-sequencing-service.com/wp-content/uploads/2010/06/gene-dna.jpg
http://www.anoleannals.org/wp-content/uploads/2011/04/sequencing-of-dna1.jpg
http://www.ibguides.com/biology/notes/chromosomes-genes-alleles-and-mutations
http://highered.mcgraw-hill.com/sites/dl/free/0072835125/126997/animation5.html
http://highered.mcgrawhill.com/sites/0072556781/student_view0/chapter11/animation_quiz_3.html
http://www.hhmi.org/biointeractive/media/DNAi_sicklecell-lg.mov
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter28/animation__how_meiosis_wor
ks.html