Transcript Genetics & Heredity

Genetics & Heredity
An overview of the history &
principles of genetics
Mitosis/Meiosis
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Animations
Living things are composed of
cells.
Cells are specialized and can be
grouped into 2 main groups.
– 1.Somatic cells (body cells)brain cells, blood cells, skin
cells, etc.
– 2.Gametes (sex cells) – Sperm
(male) & Egg (female).
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Mitosis – somatic cell division. A
process that takes the original cell,
copies the genetic information and
ends up with 2 identical cells.
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Meiosis – sex cell division. A
process that takes the original cell
reproduces the genetic information
and divides twice producing 4 cells
each with 1\2 the original cells
genetic information.
What is genetics?
• Genetics is the study
of how organisms pass
on information to their
offspring
• It also explains
characteristics &
certain diseases.
What is a trait?
• A trait is a characteristic
that is passed on from
parent to offspring.
• Traits include eye color,
hair color, metabolism,
left or right hand.
• Acquired characteristics
like strength & education
are not passed on directly
as traits.
Who discovered genetics?
• Gregor Mendel was a monk
from Austria that is called the
“Father of genetics”.
• He worked with pea plants.
• He studied several traits in the
peas.
– 1.pod shape
– 2. Pod color
– 3. Seed shape
– 4. Seed coat color
– 5. Plant height
– 6. Flower position
• He was able to predict
outcomes & noticed patterns.
Mendel’s Findings
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He noticed that there were 2
versions of many traits.
He noticed that in certain crosses
1 of the traits showed up more
than the other.
He set up experiments to cross
plants to see if he could predict
the traits.
– Mendel crossed plants with
different traits to create a 2nd
generation of plants and all
2nd generation plants looked
exactly like the parent plant
with the dominant traits.
– Mendel also crossed 2nd
generation plants with each
other and the recessive trait
reappeared with a 3-1
dominant to recessive ratio.
– Finally Mendel did a few
backcrosses with the 2nd
generation plants and their
parent offspring to help
predict which traits were
dominant & recessive.
Mendel’s Findings (cont.)
• He called the trait that
showed up more a
dominant trait. The more
hidden trait he called a
recessive trait.
– Dominant trait – a trait
that seems to hide or
mask another trait.
• In a cross a dominant
trait is shown with a
capital letter.
– Recessive trait – a trait
that is masked or
hidden by a dominant
trait.
• A lower case letter in a
cross shows a recessive
trait
More of Mendel’s findings
• There are three possible
gene combinations.
• 1. Homozygous (pure)
dominant – 2 copies of
the dominant gene.
• 2. Homozygous recessive
– 2 copies of the recessive
gene.
• 3. Heterozygous
(Hybrid) – 1 copy of the
dominant gene & 1 copy
of the recessive gene.
What is a pedigree?
• A pedigree is a diagram
that shows the history of a
trait in a family.
• They are good indicators
that certain traits or
diseases are possible.
• Males are squares.
Females are circles. They
are usually in order from
oldest to youngest from
left to right.
• Colored parts show the
This pedigree show 3 generations
trait being looked at.
Punnett squares
• A Punnett square is a
method used to predict
possible gene
combinations.
• Dominant genes are given
capital letters.
• Recessive genes are given
lower case letters.
– Ex Tall (T) is dominant
over short (t)
– Possible combinations
TT,Tt,tt.
Genotype and Phenotype
• Phenotype – describes
the visible expression
of genes. (What you
see.)
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Genotype - shows
the actual gene
combinations. (What
you get).
• Online lab
How are traits passed on?
• Traits are passed from
parents to offspring.
• They are passed by objects
known as chromosomes.
• Chromosomes – structures
within the nucleus of a cell
that carry genes.
– *****Chromosomes
occur in pairs.
• Genes are specific locations
on chromosomes.
• Organisms receive 1 copy of
each gene for a trait from
each parent.
Co dominance and Incomplete
Dominance
• Incomplete dominance – a
Incomplete dominance
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Co dominance
Web lab
Blood type game
situation where an organism gets
2 genes that are not dominant
over each other. Both genes are
expressed.
– Ex. Cross a red flower & a
white flower & get a pink
flower.
– Sickle cell anemia – a
genetic disease that curves
red blood cells into a sickle
shape. It is very painful &
often deadly. It shows
incomplete dominance.
Co-dominance – a situation
where an organism has 2
dominant genes & both are
expressed.
– Ex. Two different colored
eyes or alternating white &
red flowers. Also blood
types.
Multiple Alleles/Co dominance and
Blood Types
• Multiple alleles - Any of
a set of three or more
alleles, or alternative
states of a gene, only two
of which can be present in
a diploid organism.
• Eye color, Hair color, &
blood types are all cases
of multiple alleles.
• Blood type is also co
dominance with A & B
being co dominant and O
being recessive.
What is DNA?
• DNA stands for
Deoxyribonucleic Acid
• It is a long thread – like
material located in the
nucleus of cells.
• It has a twisted ladder
shape called a double
helix.
• The shape was discovered
by James Watson &
Francis Crick.
The Genetic Code
• DNA is made of 4
nitrogen containing base.
• They are
adenine,guanine,cytosine
,& thiamine.
• The sequence of these
bases in triplet pairs
determine an individuals
genetic code.
• Example: TAG could
make left handed, TTG
could make right handed.
Human Genetics
Humans have 46
chromosomes (23
pairs)
1 pair is the sex
chromosomes.
Females have XX
Males have XY
Mutations
• Mutations are
changes in the genetic
structure.
• They can be DNA
mutations or
chromosome
mutations.
• Mutations may be
harmful, helpful or
neither.
Conjoined twins are caused by a mutation
which won’t allow fertilized eggs to split.
Gene Mutations
Gene deletion
Gene inversion
Gene duplication
Gene translocation
Chromosome Mutations
Trisomy:3 copies where 2
should be.
Monosomy: 1 copy where 2
should be
Genetic diseases
 SICKLE CELL ANEMIA
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TAY SACHS DISEASE
CYSTIC FIBROSIS
THALASSEMIA
DUCHENNE MUSCULAR
DYSTROPHY.
PHENYLKETONURIA (PKU)
MARFAN SYNDROME
PROGERIA
TRISOMY 21 OR DOWN
SYNDROME
SPINA BIFIDA
ACHONDROPLASIA(DWARFI
SM)
HUNTINGTON'S DISEASE
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FRAGILE X SYNDROME
HEMOPHILIA
KLINEFELTER SYNDROME
TURNER SYNDROME
TRISOMY 18 OR EDWARD
SYNDROME
CRI DU CHAT
CLEFT LIP/CLEFT PALATE
TRISOMY 13 OR PATAU
SYNDROME
Blue Rubber Bleb Nevus
Syndrome
Prader-Willi Syndrome
Waardenburg Syndrome
Retinoblastoma
Genetic Counseling
• If couples have a history
of genetic diseases they
may wish to see a genetic
counselor.
• They are specialized
doctors who use
pedigrees, Punnett squares
& genetic screenings to
determine probabilities of
disorders.
• They then advise the
couple of their findings &
their options.
Genetic Engineering
• Genetic Engineering
involves mapping the
genes of organisms &
manipulating them.
• Many of the ideas of
genetic engineering are
controversial because they
involve controlling traits.
• Cloning, gene splicing, &
gene therapy are part of
genetic engineering.
Gene Splicing
The animal in the front is a normal
angus cow. The animal in the rear is
an 8 month old Beefalo.
• Gene splicing involves
“cutting” an undesirable
gene out of one organism &
replacing it with a desirable
gene from another.
• The organisms must be
compatible.
• Examples: Frost & insect
resistant plants & Beefalos.
• A Beefalo is an angus cow
that has the size gene of the
American Bison (Buffalo)
Cloning
• Cloning is the process of
using DNA to produce a
genetic duplicate of an
organism.
• Not even identical twins
are genetic duplicates.
• Sheep & cows have been
cloned.
• Human cloning is illegal
in the US.
Click and clone mice