Download F 1 Generation

Genetics
What is Genetics?
• Branch of Biology that studies heredity
• Gene: Part of DNA that holds genetic
material
• DNA- “genetic code”
• Two factors that influence genetics
– Heredity: passing of traits from parent to
offspring
– Environment: all of the outside influences that
act upon an organism
Genetics Words to Know
• Dominant: The trait that is expressed (what you
see).
– Is always an upper case letter
– Ex: T=tall t=short
• Tt= Tall organism
• Recessive: The trait that is not expressed.
– Is always a lower case letter
– Ex: T=tall t=short
• tt= Short organism
• Homozygous: Having a pair of identical genes for
a trait (pure bred).
– Homo= same
– Example: TT or tt
• Heterozygous: Having two different genes for a
trait (hybrid)
– Hetero= different
– Example: Tt
• Allele: Each copy of a gene
• Phenotype: Physical appearance
– Remember Ph= Physical!
• Genotype: Genetic make up
– Remember Gene= Genetic!
Mendelian Genetics
Gregor Mendel
•
•
•
•
Father of genetics
He was a monk
Studied pea plants
Interested in why
some plants were different
colors and why their
seeds differed
Reasons for Mendel’s success:
1. He picked a organism that was easy to
grow (peas)
• short time for new generations
• he was able to control pollination
2. He studied one trait at a time
• 7 traits in all
3. Recorded data very carefully
• He analyzed his data with mathematical
reasoning
Mendel named offspring:
– P generation: Parent generation
– F1 generation: First filial generation (off spring
of the P generation)
– F2 generation: Second filial generation (off
spring of the F1 generation)
P generation-parents
F1 generation
F2 generation
Mendel's Laws of Heredity
•
Developed two laws that all genetics is
based upon.
1. Law of Segregation: When a gamete is
formed, each pair of alleles separate
– Each gamete gets a separate allele
2. Law of Independent Assortment: When a
gamete is formed, pairs of alleles separate
independent of one another
– One gamete may get a recessive allele while the
other gets a dominant allele
Predicting Heredity Outcomes
• Probability: The likelihood a specific event
will occur
Number of one type of possible outcome
Total number of all possible outcomes
Example: You have 4 red marbles and 6 blue
marbles in a bag. What is the probability of
pulling a blue marble from the bag?
6/10
Punnett Squares
• A diagram that helps
predict the probable
outcome of a genetic
cross
– Named for inventor
Reginald Punnett
– Uses Mendel’s
laws and probability
Monohybrid Cross
• A genetic cross that
involves one pair of
traits
REMEMBER
–
–
–
–
–
T= Dominant
t= Recessive
TT= Homozygous
Tt= Heterozygous
Phenotype (physical)
4:0
– Geneotype (genetic)
2:2 or 1:1
T
T
T
TT
TT
t
Tt
Tt
Punnett Squares
T
T
T
TT
TT
• F2 Generation: Cross
the results of the f1
generation
t
Ex: TT x Tt
Tt
Tt
• Parental : TT x Tt
• F1 Generation: TT,
TT, Tt, Tt
Punnett Squares
• Monohybrid Example
In guinea pigs, black coat is dominant to
white coat. Cross a heterozygous black
coated pig with a homozygous white pig
Step One:
Identify what genotypes you are working
with
B=black
b=white
Step Two
Set up your cross
Bb x bb
Step Four
Determine ratios
-Phenotype: 2:2
b
Step Three
Complete the Punnett
Square using the
genotypes from step
two
B
b
Bb
bb
or 1:1
-Geneotype: 2:2
or 1:1
b
Bb
bb
• Punnett Square example two:
In pea plants, wrinkled peas are dominant to
smooth peas. Cross a heterozygous
wrinkled pea with a homozygous smooth
pea
1. W=wrinkled
2. Ww x ww
w=smooth
w
W
w
Ww
ww
3. P: 1:1
G: 1:1
w
Ww
ww
Step Two
Set up your cross
Bb x bb
Step Four
Determine ratios
-Phenotype: 2:2
b
Step Three
Complete the Punnett
Square using the
genotypes from step
two
B
b
Bb
bb
or 1:1
-Geneotype: 2:2
or 1:1
b
Bb
bb
Dihybrid Punnett Square
• Dihybrid Cross: A
genetic cross that
involves two pairs of
traits
• Example:
– Looking at the
offspring of a white cat
with a long coat and a
black cat with a short
coat
• Dihybrid Cross Example:
– In snapdragons, red petal color is dominant
over white petal color and tall plants are
dominant over short plants. Cross a purebred
red tall plant with a white short plant.
Step One:
Identify what phenotypes you are
working with:
R=red
r=white
T=tall
t=short
• Punnett Square example two:
In pea plants, wrinkled peas are dominant to
smooth peas. Cross a heterozygous
wrinkled pea with a homozygous smooth
pea
1. W=wrinkled
2. Ww x ww
w=smooth
w
W
w
Ww
ww
3. P: 1:1
G: 1:1
w
Ww
ww
Step Two:
•Set up your cross
RRTT x rrtt
Step Three:
•Determine your F1 generation
RT
rt RrTt
Only do this step when
the P generation is
homozygous dominant x
homozygous recessive!
RRRTT x rrtt
Step Four
Cross your f1 generation to determine what
phenotypes to use in the Punnett square
RrTt
x
RrTt
RT
RT
Rt
Rt
rT
rT
rt
rt
Step Five
Complete the Punnett square using the F1 phenotypes
from step four
RT
RT
RRTT
Rt
RRTt
rT
RrTT
rt
RrTt
Rt
RRTt
RRtt
RrTt
Rrtt
rT
RrTT
RrTt
rrTT
rrTt
rt
RrTt
Rrtt
rrTt
rrtt
Step Six:
– Determine pheonotypical and geonotypical
ratios
• P- 9:3:3:1
• G-1:2:2:4:1:2:1:2:1
Example Two:
These each
add up to 16total number
of squares in
box!
In flies, double wings are dominant over
single wings and green body color is
dominant over black body color. Cross a
purebred double winged green fly with a
single winged black fly
1. D=double d=single
G=green g=black
2. DDGG x ddgg
DG
3.
4.
Do this step since homozygous
dominant x homozygous
recessive!
dg DdGg
DdGg x DdGg
DG
DG
Dg
Dg
dG
dG
dg
dg
DG
Dg
dG
dg
DG
Dg
DDGG
DDGg
DDGg
DDgg
DdGG
DdGg
dG
dg
DdGG
DdGg
DdGg
Ddgg
DdGg
ddGG
ddGg
Ddgg
ddGg
ddgg
• Incomplete Dominance: A trait
that is intermediate between
two parents
– Ex. A red snapdragon and a
white snapdragon produce a pink
snapdragon
• Codominance: Two dominant alleles are
expressed at the same time
– Ex: Roan coat in horses
REPRODUCTION
•
•
•
•
Sexual Reproduction
Gametes through meiosis
Genetic variability
Takes more time – growth
and development
Good if changing
environment
Asexual Reproduction
• Does not require a partner
• Genetically identical to
parent
• Short reproduction time
• Good if stable environment
not needing change
Meiosis (review)
• Increases genetic variability through
genetic recombination (re-assortment of
chromosomes)
– Crossing over – 2 chromosomes overlap and
exchange genetic material
– Independent assortment (remember)
Genetics and Humans
DNA Technology
• Biotechnology: Commercial application of
biological principles
• Recombinant DNA Technology: DNA of
an organism is cut into pieces to create
specific proteins.
– Is used in agriculture to improve crops
– Genetically altered crops can cause allergic
reactions
• GMO (genetically modified organism)
• GEO (genetically engineered organism)
• Biotechnology in Medicine:
– Used to make vaccines (Hepatitis B)
– Interferon: Used to fight cancer
– Gene Therapy: Bad gene is replaced with a
good gene
• Used to fight diseases such as cystic fibrosis and
sickle cell anemia.
• Stem Cell Research:
– Stem cells can be ANY type of cell, they are
not specialized
– Alzheimer's, Dementia, Parkinson’s
– Is VERY controversial
– Three sources of stem cells in humans:
• Adult bone marrow
• Umbilical cord blood
• Embryos
• Cloning:
– Making two genetically EXACT organisms
– Dolly the sheep was cloned in 1997
Other organisms such as a cat, mule and pig
have been cloned since
– Very controversial due to possible human
cloning
– May help with disease (cloning healthy tissue)
• DNA Fingerprinting:
– All DNA (except identical twins) is different
– Scientists look at a small piece of DNA to
determine a match
– Process that pulls “markers” out is called gel
electrophoresis
– Used in paternity testing and forensic science
• Human Genome Project:
– Genome: An organism’s complete set of DNA
– Humans have aprox. 3 BILLION base pairs
– 1990 scientists began mapping the genome to
find out which base pairs make up specific
chromosomes
– Completed in 2003
Sex Linked Traits
• Determined by a gene on the x
chromosome
• Colorblindness
Sex Influenced and Sex Limited
Traits
Sex Influenced
• Traits that are dominant in one sex but
recessive in the other
• Baldness in males
Sex Limited
• Traits that only appear in the presence of
estrogen or testosterone
• Beards in men
• Male or female body shape
Twins
• Fraternal Twins:
– Most common type
– Two eggs are fertilized by two sperm
– Genetically different
• Identical Twins:
– Are always the same sex
– One fertilized egg splits into two
– Genetically identical
Genetic Mutations
• Mutation: A change in the genetic code
• Point Mutation: One nitrogen base in the
sequence is altered
• Insertion Mutation: An extra nitrogen base
is added to sequence
• Deletion Mutation: One nitrogen base is
deleted from the sequence
• Substitution Mutation: Base pairings are
incorrect (ex: T&G pair or A&C pair)
What Can Cause Mutations?
• DNA Replication Errors:
– DNA polymerase misses an error when
proofreading new DNA strand
• Mutagens:
– Agents in the environment that can cause a
mutation
– Example: UV rays and chemicals
Disorders Caused By Genetic
Mutations
• Sickle Cell Anemia:
– Mainly occurs in the African American race
– Recessive gene
– Attacks red blood cells
– Crescent shaped cells rupture easily and get
lodged in circulatory system
– People with malaria are naturally resistant
• Hemophilia
– Blood does not clot
– Is called the “Royal Disease”
– Recessive gene
– Sex-linked trait
• Tay-Sachs Disease
– Attacks Nervous System
– Recessive trait
– Occurs mainly in Orthodox Jewish population
– Appears around 6 months of age, death
usually occurs by 4 years old
• Phenylketonuria (PKU)
– Causes mental retardation if left untreated
– Recessive gene
– Caused by a defective enzyme (can not
change phenylalanine into tyrosine)
– Tested for at birth
• Cystic Fibrosis
– Thick mucus covers lungs, liver and pancreas
– Recessive gene
– May cause secondary infections
– Occurs mostly in white race
• Huntington’s Disease
– Causes insanity
– Is usually fatal
– Dominant gene
– Deterioration of brain tissue in middle age
(begins 35-40 years old)
Nondisjunction
• Chromosomes do not separate during meiosis
• Down’s Syndrome
– Extra 21st Chromosome
– Autosomal nondisjunction
– Called Trisomy 21
• Trisomy: Diploid individual has an extra chromosome
Turner’s Syndrome
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•
•
•
•
In sex chromosomes
XO (no second sex chromosome)
Abnormally short female
No sex organs-sterile
Webbed neck
Trisomy X Syndrome
• Also called Triplo-X syndrome
• In sex chromosomes
• XXX
• Fertile
• Normal intelligence
Klinefelter’s Syndrome
• In sex chromosomes
• XXY
• Sterile male
• Does not mature
• Very tall with slight breast
development
XYY
• In sex chromosomes
• Fertile male
• Associated with criminal behavior
• Associated with aggression
Prenatal Testing
• Amniocentesis: Needle is used to remove
amniotic fluid from the placenta.
– A karyotype is then developed
– Tests for Huntington’s Disease, Down’s
Syndrome, Cystic Fibrosis, Tay-Sachs, Sickle
Cell Anemia
Prenatal Testing
• Fetoscopy: Tiny camera inserted into the
uterus
– Allows Dr. to see the baby
– Collection of umbilical cord blood (test for
genetic diseases)
• Ultrasound: High frequency sound waves
– Allows Dr. to see the development of the baby
Prenatal Testing
• Chorion Villi Sampling
– Collection of cells from the placenta
– Tests for genetic disorders
– Similar to an Amniocentesis, completed
earlier in the pregnancy
Blood Typing
• Type A:
– IA IA
– IA Io
• Type B:
– IB IB
– IB Io
•Type AB:
IA IB
•Type O:
i iO
O
• Endosymbosis:
– Mutalistic relationship between 1 organism
and another that lives within it.
– A small aerobic prokaryote entered and
began to live and reproduce in a larger
anaerobic prokaryote.
– The aerobic prokaryote evolved into the
mitochondria
– Ancestor to the modern eukaryotic cell
– The chloroplast followed a similar evolutionary
route.
• Mitochondrial DNA:
– Evidence that supports endosymbosis
– Replicates independently from the cell cycle
– DNA is circular in shape (prokaryotes)
– Contains some of its own genes which are
different than the rest of the cell’s.
Blood around the world
Where did these different blood groups come from? In the same way that people,
cultures and languages change from country to country, so do blood groups. This
means that some types are more common in certain ethnic and national groups and,
despite the fact these groups become more mixed as people move around the globe,
it's still possible to see how blood groups differ from population to population.
The O group is the oldest of the blood groups. Back in the Stone Age, everyone
would have been O - and today it's still the most common group in the UK, especially
in the North of England. Over in Central and South America and the USA most
people are O too. The fact that anyone can receive O blood reflects the fact that all
other blood groups are derived from it.
Group A is the second oldest blood group, appearing around 25,000 - 15,000BC,
when larger human settlements first appeared as farming developed. You'll find a lot
of A in Central and Eastern Europe. It's the commonest group in Norway, Denmark,
Austria, Armenia and Japan.
If you're looking for group B, then try the Chinese or Asian communities, where
around a quarter of all people share this blood group. It emerged between 15,000
and 10,000BC as tribes migrated from Africa to Europe, Asia and the Americas and
mingled with other populations.
The newest and rarest group, AB, only appeared between 1000 and 500 years ago,
and is believed to have occurred as a response to the mixing of existing blood
groups on a major scale. In Japan, China and Pakistan around 10% of the population
boast this rarest of blood groups. Amazing!
http://www.blood.co.uk/pages/world_blood.html
Body Type:
Large: BB or Bb
Small: bb
Legs:
Long and colored: FF or Ff
Short and not colored: ff
Eyes:
Large: EE or Ee
Small: ee
Antennae:
Shiny: AA or Aa
White: aa
Wings:
Waxy: WW or Ww
Shiny: ww