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Topic 3 Genetics
Genetics is the science of how _______
information is passed on from one
generation to the next, using the DNA in
_______.
3.1 Genes
• A gene is a _________ factor that consists of a
length of DNA and influences a specific
______________.
• Heritable means passed from ________ to
offspring, characteristic means a _____, like
eye or hair color.
• Humans have an estimated ________ genes,
organized into chromosomes.
Where genes are located
• A gene, for a particular trait, is always located at a
specific spot called its ______ (plural ____).
• Scientists are mapping the loci of all the genes.
• Scientists know that the gene for making the
protein _________ is located on chromosome 1.
• If you have the mutated version, you can’t see in
_____. There is only a single base difference.
Alleles
• Variations or versions of a gene. Usually different
by only a few _____ pairs.
• While there are different alleles, they are always
located at the some ______ on everyone's DNA.
• Example: _______________is a inherited disease
causes by a mutated gene on chromosome 7.
• The normal allele produces the correct amount of
______ in your body, the mutated allele
produced too much.
Base changes
• Just one base change can create a _________
that causes disease.
• Another example is a gene that determines
the type of ear wax you have (_________).
There are two versions (alleles) of this gene
(chromosome 16), one causing dry ear wax
and the other causing wax that is more fluid.
• Wet earwax is more common in __________
and ________, dry more common in _______
• This gene also is involved in the production of
______ ______with a possible link to breast
cancer.
• Different versions of genes, alleles, are created
by mutation.
• ________ _______disease is a good example.
Mutations
• A random, rare change in genetic material.
• A ____________ mutation would involve a wrong
base being substituted for the correct one, like in
sickle cell disease.
• Some mutations are _____. There is a mutation
that prevents people who have it from being able
to become infected by the ____ _______.
• Whether a mutation is good, bad or neutral
depends on what they are AND the __________.
• The gene that allows people to digest _______
is a mutation.
• Believed to have originated in ________, so
most Europeans and North Americans are not
lactose intolerant.
• Gene therapy involves putting a ______ gene
into someone who needs it. Dangerous,
ethical issues.
Sickle cell disease
• Caused by a single base substitution mutation.
• The gene is responsible for making the protein
_____________.
• The mutation causes the hemoglobin protein to
have a different ______, causing the red blood
cells it is located in to also have a different shape.
• Instead of _________ _____, valine is added to
the chain. _________ can’t be carried as
efficiently, the cell shape causes _______.
Sickle cell disease
• If the 2 _______ you have are both normal, you
have normal hemoglobin and normal shaped red
blood cells.
• If the 2 _______ you have are both the bad ones,
you have sickle cell disease.
• If you have one of each, you are said to have the
sickle cell ______ and do show some signs of the
disease but not nearly as severe.
• Having one or two sickle cell alleles prevents
________.
Genome
• The complete set of a organism’s base
sequences. In humans, about ________bases.
• Some organisms have been completely
sequenced, fruit fly and E. coli.
• How do geneticists figure out a genome?
• _______Sanger Technique – DNA samples are
chopped into pieces, and copies are made
(PCR)
• _________ added to start replication
• Each piece is put into DNA polymerase and
the 4 nucleotides so that replication can occur
• Each time, a special tagged _____base is
tested which, if added to the chain, will _____
replication.
• The pieces will all end with the tagged
nucleotide and all the pieces are run through
____ ______________.
Human Genome Project
• Began trying to sequence the human genome in
_____.
• In _____, they announced they had sequenced
the entire human genome.
• They are now working on what each gene does.
As this happens, scientists know the _____ of
individual genes and what they do.
• Before the Project, they knew where fewer than
____ genes were that caused disease, they now
know ______1400.
• Information learned from the Human genome
project can help scientists study __________
patterns and how we _________migrated over
the past.
• If we know where the genes are for making a
certain protein, we can then use that gene in the
lab to make molecules for people who can’t make
them due to genetic abnormalities.
• Carl ______ – Studying mutations in genes
discovered ____________
• You can’t _________ a gene
3.2 Chromosomes
• Because prokaryotes reproduce by binary
fission, they have only ____ chromosome
• Organisms that reproduce ________ will have
two of every chromosome because the
organism would get them from each ______.
• Some prokaryotes and archaea have a
________, eukaryotes don’t.
• Plasmids can ___________ independently
Eukaryote Chromosomes
• Chromosomes are made of ____ which is the
genetic material of the cell.
• The DNA is wrapped ______ around 8 histone
proteins (2 each of 4 diff types) forming an area
called a __________. Sometimes a ninth histone
• The DNA is attracted to the histones because
DNA has a ________ charge and the histones
have a _________ charge.
• The areas of nucleosomes won’t __________ so
the nucleosomes help to _________ the
transcription process.
Multiple Chromosomes
• Eukaryotes have more than one chromosome
(usually), and there will always be ____ of each
one.
• Humans have ___ chromosomes, 2 sets of 23.
• We get a set of 23 from each parent so we have 2
number one chromosomes, 2 number two
chromosomes, etc.
• These sets of two are called __________
chromosomes. The #1 from mom and the #1
from dad are homologous.
Homologous Chromosomes
• Same genes in the same locus (loci), but not
necessarily the same _______.
• _______ is a term used to describe a cell that has
2 of each chromosome. Most cells in our body
are diploid. (46 chromosomes)
• ________ is a term used to describe a cell that
only has 1 of each chromosome, the sex cells or
_________. (23 chromosomes)
• __ represents the haploid number and ___ the
diploid number
• Chromosome number is a defining feature of a
________.
• _____ cells in a species can be different (n).
• Some individuals can be born with less or
more (_________________)
• Some cells don’t have any chromosomes, like
____ _________cells.
Karyogram/Karyotype
• A karyotype is the specific number and
appearance of the ___________ of an individual.
• A karyogram is a ________ of the chromosomes.
Steps for making a karyogram
• Cells are _______ and put on a slide to look at
under a microscope
• A ________ is taken of a cell in __________
• Chromosomes are cut/pasted into order by
_____, largest to smallest, and position of
____________.
• Exception is the 2 ____ chromosomes which
are shown ______.
Sex Determination
• The sex chromosomes are X and Y.
• The X is _______ and contains many more genes
• Unlike the other 22 pairs, the sex chromosomes
can be very different.
• XX = ________ (physically) - gametes will all be X
• XY = _____(physically) - gametes will be X and Y
• ______ determines sex of child
• Any chromosome that is NOT a sex chromosome
is called an ____________.
• Humans have 22 pairs of autosomes and one pair
of sex chromosomes. (normally)
• Traits described as autosomal would have their
genes on one of the 22 pairs of autosomal
chromosomes.
• Traits described as _________would have their
genes on one or both of the 2 sex chromosomes.
Autoradiography
• X-rays use __________ to create an image of an
object.
• Autoradiography uses radioactivity being _____
_____by an object to create an image.
• Can be used to get images of DNA so its _______
can be measured.
• ________technique uses radioactive material
called radio markers. Radioactive form of
________ using 3H
• In 1962 used to prove bacteria DNA is a loop
3.3 Meiosis
• _______ have only one set of chromosomes
(n). That way, when an egg and a sperm
combine, you get 46 (2n).
• Meiosis is the process where a _______ cell
(2n), creates 4 ________ gametes (n).
• ________ is 46 (2n) nucleus creating two 46
(2n) nuclei.
• _______ is 46 (2n) nucleus creating four 23 (n)
_________ cells
• DNA is _________ prior to meiosis, so each of
the 46 chromosomes looks like an x , two
sister ___________ connected by the
centromeres.
• The parent cell must divide ______ during
meiosis, the first division creating 2 cells that
are ________ (n).
• The second division seeing the 2 haploid each
divide into 4 _________.
Crossing Over
• During the _____ division of meiosis, the
____________ chromosomes pair up side by
side.
• Crossing over allows the mothers DNA to mix
with the fathers DNA
• This increases _________ within the gametes
• The new chromatids are called ____________
chromatids.
Random Orientation
• During __________ of the first division, the
homologous chromosomes are going to line
up, ______________in the middle of the cell.
• How they line up is _______.
• This also increases variation
within the gametes
Division I
Prophase I
• Chromosomes _____ and become visible
• _________ membrane begins to break down
• Spindle fibers form, __________ disappears
These steps are exactly the same as __________
• ____________ chromosomes are attracted to
each other.
• ________ _______occurs
Division I
Metaphase I
• Homologous chromosomes line up along the
_________ by ________ orientation.
• Nuclear membrane is gone
• ________ _________grow toward the
chromosomes
Division I
Anaphase I
• Spindle fibers attach to ____________ of
chromosomes and pull them toward the ______.
Telophase I
• Spindle fibers ____________.
• Chromosomes _______, nuclear membranes form.
• Many ________ don’t have Telophase I
• ___________ occurs and created 2 haploid (n) cells
Division II
• Basically this is ___________
• Prophase II
DNA condenses into visible chromosomes
Spindle fibers are produced, nucleolus disappears.
• Metaphase II
Nuclear membrane gone
____________ chromosomes line up ___________
on the equator
Spindle fibers attach to the ____________
Division II
• Anaphase II
Centromeres split and ______
____________move toward the poles.
In animals, cell membrane begins to ______ in,
in plants, cell _______ begin to form
• Telophase
Chromosomes unwind, nuclear membranes
form.
Fertilization and variation
• Crossing over during ___________and
random orientation during Metaphase I create
___________ among gametes.
• ______ ___________also creates variation
because of which of the different sperm cells
______________ the egg cell.
• The number of different gametes a human
could produce is _____ or 8,388,608. That
doesn’t include _________ _______.
Extra or missing Chromosomes
• Sometimes organisms end up with less or more
chromosomes than normal.
• Example in humans is _____ ___________,
where a child is born with ___ chromosomes
instead of 46 because they have an _________.
• Caused by ________________, usually during
Anaphase I.
• Causes some eggs to have 2 #21 chromosomes
and others to not have any.
• Studies of families with children who have
Down Syndrome (________________ studies)
show that the _____ of the mother shows the
highest correlation.
• The older the mother is, especially after ___,
the greater the odds.
• A ____________ will show whether a child
has a chromosome issue or not.
Obtaining Cells for Karyotyping unborn
• Two different procedures
• ________________ uses a needle to extract
amniotic fluid which will contain cells
• _________ ______ __________obtains cells
from the placenta’s finger-like projections
called villi
• In both cases, the fetal cells are grown in the
lab and a karyotype is created.