Download Genetics

Unit 6 - Genetics
Introduction
http://www.exploringautism.org/g
enetics/images/overview.jpg
You look the way you do because of
the genes your parents passed on to
you at fertilization (the joining of the
sperm and the egg).
The transfer of genes from parents
to offspring gives you your unique
strand of DNA which every cell in
your body uses to function.
The scientific study of heredity is
called genetics.
What is a mutation?
TPS
 Think about the term “mutant”.
 On a note card, write what you think this means.
http://superherouniverse.com/other/turtles/images/teenage-mutant-ninja-turtles.jpg
DNA Mutations
 A change in the DNA
sequence that affects the
genetic information is
called a mutation.
 Sometimes the mistake is
caught and then corrected,
but sometimes the mistake
can be passed on to
offspring.
 Know that some mutations
can also be beneficial and
provide genetic variation
(differences) in organisms.
http://www.accessexcellence.org/RC/VL/GG/images/mutation.gif
Types of Mutations
 Point Mutations =
changes to one or a few
bases at a single point in
the DNA sequences
(usually one base is
changed to another
(inversion), one is
insertion, or one is
deletion).
http://ghr.nlm.nih.gov/handbook/illustrations/frameshift.jpg
 Frameshift Mutations = causes the codons read in the DNA
sequence to be completely altered; (create a protein unable to
perform normal functions).
Mutagen
http://www.hsesro.com/arti
cle_images/A47E64small.jpg
 A mutagen is anything that can cause a mutation in DNA.
 EX - UV radiation from the sun, chemicals found in asbestos (used
in construction) and cigarette smoke.
Genetic Disorders
 Mutations can be
natural.
 Sometimes, mutations
in the genetic code are
passed.
 Diseases found in
humans are related to
the DNA, called genetic
disorders.
 Cystic fibrosis, sickle
cell anemia, and
hemophilia are just
some examples of
genetic disorders.
http://www.humanillnesses.com/original/images/hdc_0001_0003_0_img0235.jpg
 The problems the people have are related to mistakes in
their genetic code. Common genetic disorders are listed on
pg. 345 – 348 and discussed in Ch. 14.
 Video Link
Introduction to Heredity
 The unique combination of
your parents genes which
they passed on to you is
what makes you look, and
to a certain extent, act the
way you do.
http://news.bbc.co.uk/media/images/38149000/jpg/_38149935
_cartoon_family300.jpg
 Heredity is the passing of traits from parents to
offspring.
 You might have blue eyes, even though both of your
parents have brown eyes. How does this happen?
 The specifics behind the scientific study of heredity, or
genetics, will be discussed in this chapter.
Gregor Mendel:
The Father of Genetics
http://mac122.icu.ac.jp/gen-ed/mendel-gifs/18mendel-cartoon.JPG
 An Austrian monk named Gregor
Mendel performed experiments
during the 1800s to understand
the process of traits.
 Traits are the specific
characteristics of an organism
(blue eyes, brown hair, etc).
 Mendel used pea plants from his
garden to study.
 He noticed that sometimes the
“parent” pea plants did not
match the characteristics in
“children.”
Mendel’s Experiments
 Mendel studied the plants and
found variations, or
differences.
 EX Purple or white flowers, tall
or short plants, and even
round versus wrinkled peas.
 He crossed (or pollinated)
plants with different traits and
observed the results.
http://www.micro.utexas.edu/courses/levin/b
io304/genetics/mendel.gif
Mendel’s Results
 He found that purple flowers,
round peas, and tall plants
were the MOST common.
(called the F1 generation or
first generation).
 In the second cross, the F2
generation, Mendel observed
differences (white flowers,
wrinkled peas, short plants).
 He concluded that some
traits only appear under
certain conditions.
http://www.groundscience.com/solutionsnewsletter/so
lutions15/pea.jpg
Alleles
http://biology.clc.uc.edu/graphics/bio105/all%20cats.jpg
 We now know that genes are responsible for coding for a specific
trait (EX blue eyes, brown hair).
 Genes are sequences of DNA that codes for a protein and
determines a trait (EX the protein for blue eyes).
 Every part of you, from your height to the color of your skin, is
related to your genes.
 The different forms of a gene are known as alleles.
 White flowers versus purple flowers are the same trait but
different alleles.
http://trc.ucdavis.edu/biosci10v/bis10v/week4/dihybridf1.gif
Dominant & Recessive
http://www.emc.maricopa.edu/faculty/farabee/biobk/mendel'str-1.gif
 The stronger trait that will
always appear is the
dominant allele (shown
with a capital letter).
 But what happened to the
white flowers?
 The wrinkled peas?
 The allele that did not
appear, sometimes called
the hidden trait, is called
recessive (shown with a
lowercase letter).
Homozygous: RR or rr
http://discover.edventures.com/images/termli
b/h/homozygous/support.gif
 These letters that we “GET” from our parents code for traits.
 EX the flower color trait (R or r).
 An organism can be homozygous dominant or homozygous recessive if
they have two identical alleles for a trait (Sketch it!).
 Homozygous dominant (RR) = Red
 Homozygous recessive (rr) = White.
 The recessive allele can ONLY be seen if it is in a homozygous pair
(remember it is normally HIDDEN).
Heterozygous: Rr
 An organism with a mixed
allele pair is heterozygous,
(Rr) has the opportunity of
having offspring with both
traits.
 If two heterozygous
organisms cross, you can
have offspring that exhibit
(or show) the recessive trait.
http://discover.edventures.com/images/termlib/h/hetero
zygous/support.gif
Chromosomes! Sketch it!
http://www.plant.uoguelph.ca/research/biotech/haploid/homo.gif
The Punnett Square
 Scientists have now
developed a system using
symbol combinations to
study heredity.
 A Punnett square is a chart
used to predict and
compare the genetic
combinations that will
result from a cross.
http://www.tea.state.tx.us/student.assessment/resources/onlin
e/2002/eoc/biology/p23no34.gif
 A capital letter represents the dominant trait while a
lowercase letter is the recessive trait.
 A plant that IS always tall would be TT while a plant
that is short would be tt.
The Punnett Square Cross
 In the Punnett square here,
you can visualize the genes
the parents are passing to
offspring.
 Each square of the box
represents one offspring (or
child).
 Each parent donates one
allele.
 The dominant (stronger)
allele will always go first,
and will always be seen in
the organism.
 Sketch it!
http://www.worldbuilders.org/lessons/less/les4/casino/casinogifs/pun2.gif
Studying the Cross
 If you look at the punnett
square, the top organism
is considered the male
while the organism on the
side is the female.
 One allele (or letter) from
each parent moves into
each square.
http://www.emc.maricopa.edu/faculty/farabee/biobk/mono2.gif
Remember if the organism has identical alleles (SS or ss)
it is said to be homozygous.
 An organism that has two different alleles for a trait it is
considered heterozygous (or Ss).

http://www.phschool.com/atschool/science_images/human_
punnett_square.jpg
Genotype & Phenotype
 The genetic makeup and inherited combination of
alleles is known as the offspring’s genotype, or “the
letters that you GET.”
• EX “Tt” or “tt”
 The physical characteristic and the appearance shown
in the organism (purple flowers, blue eyes, etc) is
called the phenotype.
 The phenotype is the “PROOF” of the allele that is
there and is what you “SEE”.
• EX “Tall plant” or “short plant”
Genotype & Phenotype
(the Right, the Left)
http://bio1151.nicerweb.com/doc/class/bio1151/Locked/media/ch14/14_06PhenotypeVsGenotype_L.jpg
Co dominance
 We now know that there are also instances of co
dominance, where there is none that is dominant or
recessive but a mixture of both alleles.
 An example of co dominance would be roses. A white
crossed with a red to produce a pink.
http://www.gwu.edu/~darwin/BiSc150/One/rose.GIF
Multiple Alleles
http://ghs.gresham.k12.or.us/science/ps/sci/soph/genetics/notes/bloodtype.htm
 Not all genes have
just two alleles for the
trait, but some can
have many alleles to
choose from and are
said to have multiple
alleles.
 Hair color, eye color,
and blood types are
all examples of human
traits where multiple
alleles are involved,
not just the standard
two often used in
punnett squares.
Multiple Alleles
 Shades of hair color represent the multiple alleles
of for possible combinations.
http://www.indiana.edu/~oso/lessons/Genetics/figs/HairColor/browns.jpg
Polygenic Traits
http://www.algebralab.org/img/4
9ab8f77-f675-423a-b8afd46874987ab3.gif
 Not every trait is controlled by a single gene. Traits that
are controlled by two or more genes are said to be
polygenic traits, which means “having many genes”.
 Human stature (or height) is controlled by multiple genes.
Where are those genes?
 Okay, so we understand that
each parent gives half of their
genes to each child, but where
are those genes located?
 The genes that make you tall
or can make you have curly
hair are located within the
chromosomes made of DNA in
the nucleus of every cell of
your body.
 Modern science allows us to
view all chromosomes in a
karyotype where they
arranged in pairs, one
chromosome from the mother
and one from the father.
http://www.genomenewsnetwork.org/gnn_image
s/whats_a_genome/karyotype.gif
http://ccr.coriell.org/nigms/genes/17gene.gif
Chromosome (Gene) Maps
 Mendel began studying genetics in
the 1820s, but science has
advanced and we know that DNA
carries genes in our
chromosomes.
 In 1911, the first gene map was
produced that showed the gene
locations on the chromosomes of
a fruit fly.
 The shaded areas represent a gene that controls a
specific trait(s).
 Gene maps are now widely used in understanding
genetic mutations, sickness, and the human genome
project.
Fruit Flies
 Fruit flies (as
shown here)
are used to
study genes
and genetic
relationships
because they
have a small
number of
chromosomes
and can
reproduce
quickly.
http://www-tc.pbs.org/wgbh/nova/allfours/images/gene-fruitfly-l.jpg
Sex Cells
http://www.dorlingkindersleyuk.co.uk/static/clipart/uk/dk/exp_humanbody/exp_human098.jpg
 Sperm and egg cells, known as sex cells (gametes), contain
all the genetic material needed to build an organism
• EX a cat, the zebra at the zoo, or even a little brother or
sister!
 A sperm is the male sex cell while an egg is the female sex
cell.
 Sex cells are haploid and have half the number of
chromosomes in a normal cell (diploid).
 Half of the genes in an organism are from the mother, the
other half from the father.
http://www.mcw.edu/cellbio/colorvision/images/pedigree.jpg
Pedigree
 Modern geneticists study the family history of persons using a
pedigree chart.
 A pedigree shows the relationships within a family and can
track the appearance of a genetic disease or disorder.
 Boxes represent males; circles represent females.
 A pedigree always has a key.
What is Heart Disease?
Is it related to genes?
 Today’s lab
investigates
how genes
relating to
heart disease
are inherited in
a family.
 Video
 How a heart
attack can
happen?
Pick the Risk:
Polygenic Pedigree Challenge
 Send one student to the
pick up a tray for each
group (beneath the
flag).
 Send another student to
the front to pick up a lab
packet for each group
member.
 Clear off the tables for
this activity.
 The bags represent the
female and male genes
inherited by the
offspring.
http://farm3.static.flickr.com/2465/3895583202_6c076d1837.jpg
My Family Pedigree
 Choose one trait from your family to study.
•
•
•
•
Eye color
Hair type (straight/curly)
Earlobes (attached/unattached)
Right handed/left handed.
 Create a key.
 Create a pedigree for your parents and your
siblings.
 Extra credit! Include your grandparents!!!!
Pedigree Review
 Examine the family below.
 What can you identify?
XX & XY
 Humans have 46
chromosomes total in
the body; 44 of them
are called autosomes.
 Two of the 46
chromosomes in
humans are known as
sex chromosomes
because they
determine an
individual's sex.
http://www.web-books.com/MoBio/Free/images/Ch1C4.gif
 Females most often have two copies of a large X
chromosomes (XX)
 Males most often have one X and one small Y chromosome
(XY).
Two Factor Punnett Square:
Dihybrid Cross
 We now understand how a simple Punnett
square works by outlining the possibilities for one
specific trait (eye color = E’s, skin color = G’s.)
 The two factor cross shows the possibilities
comparing TWO unique traits (using two
different letters).
 Male = Gg & Ee
 Female = GG & ee
Two Factor Punnett Square:
Dihybrid Cross




The sex cells for an organism (the sperm and the egg)
are known as gametes; these gametes contain the
chromosomes which contain the genes.
The first step in a dihybrid (two factor) cross is to
determine the gametes.
EX Gg (skin color) & Ee (eyes) in Martians. What
genes will be held in the gametes?
Step #1 – Creating the Gametes
1. Draw a box with 4 boxes.
2. Place the skin color genotype (Gg) on the top of
the box.
3. Place the eye genotype (Ee) on the side of the
box.
4. Fill in the four squares. These will be the sex cells
given to the children (gametes).
Two Factor Punnett Square:
Dihybrid Cross
E
e
G
GE
g
gE
Ge
ge
 Each of these boxes represents a single sperm cell
containing these specific genes. Repeat for the eggs.
Two Factor Punnett Square:
Dihybrid Cross
e
e
G
Ge
G
Ge
Ge
Ge
 Each of these boxes represents a single egg cell
containing these specific genes. Repeat for the eggs.
Two Factor Punnett Square:
Dihybrid Cross
Just as in a single trait Punnett
square, the male gametes go on the
top of the box and the female
gametes on the side of the box.
 Step #2 – Filling in the Punnett
Square
1. Draw a Punnett square with 16 boxes.
2. Place the gametes on the top and
sides (red & blue)
3. Always group the same genes
together (G’s with g’s, etc).

EX – in the first box, place a
GGEe.
4. Fill in the remaining boxes.
Fill in the Punnett Square
Dihybrid Cross
Ge
 Each of
these boxes
represents
the joining
of a sperm
and egg to
make
offspring.
Ge
Ge
Ge
sperm
GE
GGEe GGEe GGEe GGEe
gE
GgEe
Ge
GGee
ge
Ggee
eggs
 A dihybrid Punnett square shows 16 possible
genotypic combinations.
Ge
Ge
Ge
Ge
sperm
GE
GGEe GGEe GGEe GGEe
gE
GgEe
Ge
GGee
ge
Ggee
eggs
Conclusion:
Genetics and the Future
 Genetics and DNA
technology improves daily
in the scientific community.
 The entire human DNA
strand is mapped, many
genes are identified;
scientist are currently
discovering which genes
control which functions.
 In your journal, predict
what you think our
knowledge of our DNA and
genetics will have on the
future?
http://www.mcg.edu/news/2001NewsRel/images/poduslo1.jpg