FUNDAMENTALS OF GENETICS Chapter 9 Lab Bio Chapter 12 Honors Bio
FUNDAMENTALS OF GENETICS
Chapter 9 Lab BioChapter 12 Honors Bio
Discussion about Lorenzo’s Oil
Brainstorm:- define genetics- define heredity
Anticipatory Set: How important is it to be able to find your own
answers to questions you may face? Does education and learning end with your
high school or college years? How do you plan to develop the skills to
become a life long learner?
Marfan Syndrome
Do you think he has Marfan Syndrome? Why?
Does Obama have Marfan Syndrome?
Abraham Lincoln had Marfan Syndrome.
Cyctic Fibrosis
Genetics
The study of how characteristics are transmitted from parent to offspring
What is HEREDITY?
The transmission of characteristics from parent to offspring
Vocabulary
Chromosome: structure within nucleus, made of DNA
Gene: unit of heredity found in DNA molecule (words)
Allele: symbols (letter) used to represent genes ex: T=tall, t=short
Dominant: trait/characteristic that are expressed – represented with capital letter
Recessive: trait/characteristic that may not be expressed (always lower case) ex: t=short
Continued Vocabulary
Homozygous/pure: both alleles are alike ex: TT or tt
Heterozygous/hybrid: alleles differ ex: Tt Genotype: genetic make up ex: (pure
homozygous) tall, hybrid (hetero.) tall Phenotype: what you see (physical
appearance) ex: tall, short Cross: symbolic of reproduction ____ X _____ P: parent generation F1: first generation
Where are the genes????
Can you see where the genes are?
NOW can you see where the genes are???
CHROMOSOMES AND GENES
A GENE is the segment of DNA on a chromosome that controls a particular trait.
Chromosomes are in pairs i.e. Genes occur in pairs (each of several
alternative forms of a gene is called an ALLELE
MENDEL’S FACTORS ARE NOW KNOW AS ALLELES!!!!!!
Letters used to represent alleles:
CAPITAL = Dominant alleles Lower case = recessive alleles Example: P = purple color (dom.) p = white color (rec.) When gametes combine in fertilization
offspring receive ONE ALLELE for a given trait from EACH PARENT!
Genetic Crosses
Helps us predict the likely outcome of offspring!!
1. genotype: genetic make-up, consists of alleles Ex: P=purple, p=white Pp = purple PP = purple White = pp
Continue…
2. Phenotype = appearance of an offspring (what you see)Ex: purple flowers, white flowers, hair color
Continue…
3. Homozygous = when both alleles of a pair are alike
Ex: tt, TT, PP, ppHomozygouse recessive = pp
Homozygouse dominant = PP
Continue…
4. Heterozygous = two alleles in a pair are different
Ex: Pp or Tt
Brainstorm/Anticipatory Set
Do you think that we could make as many discoveries in science if we didn’t use animals? Explain…..
Gregor Mendel
!
A little background…
Austrian Monk Studied garden pea plants
(Pisum sativum) 1842 he entered the monastery
in Austria 1851 enetered Univ. of Vienna
to study science and mathematics (statistics)
Mendel’s Pea Plants
Observed 7 characteristics each in 2 contrasting traits: Long short stems Axial terminal (flower position) Green yellow (pod color) Inflated constricted (pod appearance) Smooth wrinkled (seed texture) Yellow green (seed color) Purple white (flower color)
Pea Pods!!!
Some more pea plants…
Flowering Pea Plants!
Mendel’s Methods
He controlled how pea plants were POLLINATED!!! SELF POLLINATION=pollen is transferred from
anthers (male) of a flower to stigma (female) of same flower or flower on the same plant
CROSS POLLINATION=involves flowers of 2 separate plants
Flower!!
How to interrupt self pollination!
1. remove anthers from a flower
2. manually transfer the anther of a flower on one plant to stigma of a flower on another plant
Mendel’s Experiments:Pure Trait
P1 (cross) pure Purple x pure White Law of Dominance F1 ALL came out PURPLE
F1 (cross) Purple x Purple Law of Segregation F2 ¾ PURPLE, ¼ WHITE
Recessive & Dominant Traits
Mendel hypothesized that the trait appearing in the F1 generation was controlled by a DOMINANT FACTOR (allele) because it masked, or dominated, the other factor for a specific characteristic.
RECESSIVE is the trait that did not appear in the F1 generation but reappeared in the F2 generation.
The Law of Segregation
A pair of factors (alleles) is segregated (or separated) during the formation of gametes
Each reproductive cell (gamete) receives only one factor (allele) of each pair.
Crossed two heterozygous purple plants!
Test Cross- Unknown Genotype
Is the purple plant homozygous or heterozygous ?
Perform a test cross!
Always! Cross the unknown with a homozygous recessive
Test Cross
Practice!
g
g
G G
G G
g g
g g
P
F1
Key: G=greeng= yellow
Phenotype:100% green
Genotype:100% heterozygous
? x gg
Practice! ?
? x ggP
F1
Key: G=greeng= yellow
Phenotype:50% green50% yellow
Genotype:
INCOMPLETE DOMINANCE AND CO-DOMINANCE
Incomplete Dominance
Neither allele is dominant In some cases, an intermediate
phenotype is shown
Snapdragons
In snapdragons, flower color can be red, pink, or white. The heterozygous condition results in pink flowers
rr RrRR
Incomplete Dominance Cross
Key:R= Redr= White
F1 Phenotype:100% pink
F1 Genotype:100% heterozygous Rr
F1 Cross
Key:R= Redr= White
Phenotype: 1:2:125% Red25% White50% Pink
Genotype: 1:2:125% homozygous RR 25% homozygous rr50% heterozygous Rr
Other ways to represent incomplete dominance
Co-dominance Both alleles are expressed equally Neither allele is more dominant
than the other
Erminette chickens
Roan Cows
Co-Dominance Erminette Chicken
P generation Black chicken X White
chicken
F1 generation = erminette (checkered patterned)
Key:B =BlackB1 = White
B B
B1
B1
B
BB
B B1
B1
B1
B1
Phenotype: 4:0 or 1:0100% erminette
Genotype: 4:0 or 1:0100% heterozygous
Erminette chicken
BB BW
BB
BW
BB BB BB
BB BW
BW
BW BW
Key:B= BlackW= White
Key:BB =BlackBW = White
B1
B1
B2
B2
B1 B1
B1
B1 B2
B2 B2 B2
Key:B1 =BlackB2 = White
Do Now
1. What does recombination mean?
2. Do you know of any traits that seems to be inherited together? Ex: red hair and fair skin……
Anticipatory Set
Does anyone here look “nothing” like their parents?
If not do you know someone who looks nothing like their family members?
Can we explain this genetically?
Answer….
Traits are inherited independently of each other unless they are linked.
Random Assortment
Genetically Unique
Independent Assortment
Independent Assortment is the random assortment of chromosomes during the production of gametes, the result are genetically unique individual gametes.
The Law of Independent Assortment
He also crossed plants with 2 different characteristics Ex: flower color & seed color
FACTORS FOR DIFFERENT CHARACTERISTICS ARE DISTRIBUTED TO GAMETES INDEPENDENTLY.
Ex: Pure tall yellow x pure short green TTYY x ttyy
SEX DETERMINATION AND SEX-LINKED INHERITANCE
Sex Determination
Xy =
XX= female
male
Female karyotype
Male karyotype
X and Y chromosomes
Nondisjunction- Jigsaw
Nondisjunction: failure of chromosomes to separate during meiosis 1 or 2
Results in an extra chromosome or a missing chromosome
http://glencoe.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::550::400::/sites/dl/free/0078757134/383925/Chapter11_NGS_VisualizingNondisjunction_10_10_06.swf::Visualizing%20Nondisjunction
XO- Turner Syndrome XXX- Trisomy X XXY- Klinefelter Syndrome XYY- Jacob Syndrome
Very often, symptoms are slight due to X-inactivation and the small amount of genes found on the Y chromosome
SEX CHROMOSOMES CONTAIN GENES THAT CODE FOR TRAITS
=SEX LINKED TRAITS
Both Males and Females Inherit X Chromosomes: Males XY; Females
XX
X-LINKED GENES: Genes carried on the X chromosomeHemophilia
Color blindnessBaldness Muscular Dystrophy
Mother Without hemophilia = X X
Without hemophilia = X X
With hemophilia = X X Father
Without hemophilia = X y
With hemophilia = X y
H H
H h
h h
CARRIER
H
h
Key!
MULTIPLE ALLELES- BLOOD TYPING
How common is your blood type?
46.1%
38.8%
11.1%
3.9%
Genetics of Blood Types
Human blood type is determined by co-dominant alleles
Antigens-proteins-exist on the surface of all of your red blood cells.
Blood types
For simplicity
IA A
IB B
i O
Antibodies
Found in the plasma Specific to a single kind of
antigen Attack and kill that specific kind
of antigen
What are blood types?
http://learn.genetics.utah.edu/units/basics/blood/types.cfm
• There are 3 alleles for blood type: A, B, O
• Since we have 2 genes: 6 possible combinations
Blood Types
AA or AO = Type ABB or BO = Type B
OO = Type OAB = Type AB
RBC= Red Blood Cell = antibody
Antibody B- protects the body by attacking foreign B antigen blood
Scenario B
Scenario AB
Scenario O
Blood Transfusions
Blood transfusions – used to replace blood lost during surgery or a serious injury or if the body can't make blood properly because of an illness.
Who can give you blood?
TYPE O -Universal Donors
can give blood to any blood type
• No antigens present on RBC
TYPE AB- Universal Recipients
can receive any blood type
• No antibodies present in plasma
Universal Donor
Universal Recipient
Rh Factors Rhesus monkeys –contain certain
similarities with humans A blood protein was discovered and present
in the blood of some people The presence of the protein, or lack of it, is
referred to as the Rh (for Rhesus) factor.
Rh positive (Rh+) - contain the protein Rh negative (Rh-)- NOT contain the protein A+ A-
B+ B-AB+ AB-O+ O-
http://www.fi.edu/biosci/blood/rh.html
Rh factor Possible genotypes
Rh+ Rh+/Rh+
Rh+/Rh-
Rh- Rh-/Rh-
PEDIGREE ANALYSIS
Have you ever seen a family tree… do you have one??
Graphic representation of family inheritance.
Pedigree of Queen Victoria
What is a pedigree? Shows a pattern of inheritance in a family
for a specific trait (phenotype) Genotypes can usually be determined
Why would we want to use a pedigree in
genetics? Track the occurrence of diseases such as:
Huntington’s – simple dominant – lethal allele – causes breakdown of the brain
Cystic fibrosis – 1/2500 – mucus accumulates (white North Amer.)
Tay-Sachs disease – lipids accumulate in CNS (Jewish)
Phenylketonuria – missing enzyme causes problems in CNS (Nordic/Swedish)
The Symbols used:
Sample pedigree:• generations are numbered with Roman Numerals• oldest offspring are on the left
Inheritance patterns: Autosomal dominant:
–Examples: Polydactyly
–Huntington’s disease
The disease is passed from the father (II-3) to the son (III-5), this never happens with X-linked traits.
The disease occurs in three consecutive generations, this is rare with recessive traits.
Males and females are affected, with roughly the same probability.
Inheritance patterns: Autosomal recessive
– Cystic fibrosis– Tay-Sach’s disease
Males and females are equally likely to be affected.
The trait is characteristically found in siblings, not parents of affected or the offspring of affected.
Parents of affected children may be related. The rarer the trait in the general population, the more likely a consanguineous mating is involved.
Inheritance patterns: Sex-linked recessive conditions
– Examples:
– Color-blindness
– Duchenne Muscular Dystrophy
The disease is never passed from father to son.
Males are much more likely to be affected than females.
• All affected males in a family are related through their mothers.
Trait or disease is typically passed from an affected grandfather, through his carrier daughters, to half of his grandsons.
Method 1: Process of Elimination
• X-linked recessive
• Autosomal
dominant
• Autosomal
recessive
Method 2: Recognizing Patterns
• X-linked recessive
• Autosomal
dominant
• Autosomal
recessive
Practice!
• X-linked recessive
• Autosomal
dominant
• Autosomal
recessive
Mendel’s Rules Apply to:
Law of Dominance Law of Segregation Test Cross MENDEL’S RULES DO NOT APPLY TO: Incomplete dominance Multiple alleles Codominmanmce Polygenic inheritance Pleiotyropy Environmental influence
What you must know!
Law of dominance Law of segregation Test cross Incomplete dominance Codominance Independent assortment Sex determination Sex linkage Multiple alleles