Download Unit 6 Genetics and Heredity

Unit 6: Genetics & Heredity
Ch 8: Heredity & Ch 11: Human Genetics
• What is genetics?
– __________________ = the passing of traits
from parents to offspring
– Why is your combination of genes unique?
Gregor Mendel – the
Father of Genetics
1822-1884
Mendel’s Experiments
• Studied garden peas – _____ different traits
with clearly different forms
– Tried to determine how these traits were transmitted
from parent to offspring
Mendel’s Experiments
• Male & female parts
in same flower
–Normally
• Self pollinate
–Produce pure
offspring
» ______ parents
produce______
offspring
» ______ parents
produce _________
offspring
Mendel’s Experiments
• Cross pollination of pure
purple parent & pure white
parent (parent generation)
• Purple offspring (________
____________ generation)
• Hybrids (genes for both
purple & white in all offspring)
Mendel’s Experiments
• Offspring allowed to self pollinate
• New offspring (F2, second filial, generation) weren’t
all purple
Parent
– _______
– _______
First filial
Crossed 2
F1 plants
to get F2
Second Filial
Mendel’s Principle of Dominance
• Mendel noted that for each trait one form
dominates the other
– In other words, the __________ trait prevents
the expression of the _______________ trait.
• Ex. In peas, purple x white gives all purple
offspring
– ____________________
– ____________________
Punnett Squares
• Helps to predict the results of crosses
– all possible resulting offspring
• & the probability of each offspring’s genes
• Ea. parent can contribute 1 of 2 genes for a trait
(______)- found on homologous chromosomes
– Represent with letters
• ________________ = dominant gene
• ________________ = recessive gene
• ________________ – alleles same
– ex. AA or aa
• ________________ – alleles different
– ex. Aa
Genotype vs. Phenotype
• ____________________ = actual
genetic make-up of individual
– represented by letters
• __________ = outward (physical)
expression of the genotype
– (due to) the protein that is produced
• Ex. Let P = purple & p = white
– Genotypes PP & Pp both have the
same phenotype (purple)
• PP = ________________ dominant
• Pp = ________________________
– Genotype pp has (white) phenotype:
• pp = ________________ recessive
Mendel’s Principle of Segregation
• During gamete formation, the
pair of genes responsible for
each trait separates so that
each gamete receives only 1
gene for each trait.
– happens during meiosis I when
homologous chromosomes line up
(randomly) @ equator (metaphase
1) & separate (anaphase 1)
Draw diagrams
Mendel’s Principle of Segregation
Mendel’s Principle of Segregation
• tested segregation using
heterozygous purple
flower & homozygous
white flower
– Predicted _______ purple
& ____ white offspring b/c:
• P gene would combine w/
p gene _______ the time
– producing __________
_____________ flowers
• p gene would combine w/
p gene _______ the time
– producing ___________
_____________ flowers
Draw Punnett Square
Mendel’s Principle of Independent Assortment
• Genes for different traits segregate independently
during gamete formation when they are located on
different chromosomes…
– What if they are on the same chromosome?
Genes on same
chromosome
meiosis
Genes on same
chromosome
Probability
• The chance an event
will occur
• What is the chance of
getting heads? Tails?
– If you flip two coins, of
getting 2 heads?
2 tails?
– What is the chance of
a couple having a
boy? A girl? Of
having four boys?
Five girls?
Draw Punnett Square
Ratios
• _________________________= probable ratio
of genotypes in offspring of a cross
– Ex. If cross PP & pp
• 1PP : 2Pp : 1 pp
• _________________________= probable ratio
of phenotypes resulting from the genotypic ratio
• Ex. If cross PP & pp
• 3 purple : 1 white
• ________________________________ = ratio
expected based on probability (Punnett Square)
• ___________________ = what actually occurs
– Why would these be different?
Phenotype
genotype
Pp
Pp
Phenotype
genotype
Pp
Pp
Monohybrid Cross
• a cross where __________________________
________________________ (gene) is studied
– ex. only height, flower color, eye color, etc...
Draw Punnett Square
T
t
Dihybrid Cross
• involves study of inheritance patterns for
organisms differing in _______ (ea. w/ 2 forms).
– Mendel  determine if different traits of pea plants,
such as flower color & seed shape, were inherited
independently.
Dihybrid Cross Animation
Dihybrid
Cross
2 traits
with 2
forms
Test Cross
• Used to determine
__________________
of dominant phenotype
– Cross ______________
phenotype w/ ________
phenotype
Show as P_
• If any offspring show
recessive trait, unknown
parent  ____________
• If all show dominant trait,
then parent  ________
____________________
Draw Punnett Squares
Dominant/Recessive is Not
Always the Mode of Inheritance
• Traits are not always as clearly defined as
the 7 pea plant traits Mendel studied
– Incomplete dominance
– Codominance
– Multiple alleles
– Sex-linked inheritance
– Polygenic inheritance
• Continuous variation
Incomplete Dominance
• No allele is ________
__________________
– results in _ phenotypes
– ________________,
___________ (mixed),
__________________.
• Genotypic & phenotypic
ratios same
– ___________________
– ___________________
– Ex. Pink four o’clock
flowers
Draw Punnett Square
Codominance
• heterozygote
displays the protein
products of both
alleles __________
– Ex. Roan cow has
a mixture of both
red & white hairs.
Multiple Alleles
• More than _______________ different forms of
an allele exist, but individual still has just 2.
• Ex. alleles that code for human blood types
– A = _____
– B = _____
– O = _____
– exhibit both codominance
& multiple alleles
• (______= ______ ) > ______
•How many possible genotypes are there?
•How many phenotypes?
•Can you spot the blood type that is a product of
codominance?
Copy Chart
antigen
antigen
antigens
No antigens
Multiple Alleles
• Agouti rabbits
– 4 alleles: C, cch, ch, c
– w/ dominance relationship to one another:
_________________________________
• agouti rabbit (wild type)
– Phenotype: brown, Genotype: CC, Ccch, Cch, or Cc
• “Chinchilla” (mutant)
– Phenotype: silvery gray, Genotype: cchcch, cchch, or cchc
• “Himalayan” (mutant):
– Phenotype: white w/ black points, Genotype: cchcch chch or chc
• “Albino” (mutant)
– Phenotype: white, Genotype: cchcch cc
Sex Determination
• In humans chromosomes:
– Pairs 1 – 22 = ____________________
– 23rd pair determine gender = __________________
• __________ = female
• __________= male
Draw Punnett Square
What is the probability of having a son?
A daughter?
Sex-linked Inheritance
• X & Y chromosomes not fully homologous
– X is bigger & carries more genes
• Males will have _____________________
for traits carried only on X
– called _______________________________
• Ex.:
– In Drosophila (fruit flies) eye color
– In humans  _______________________________
___________________________________________
– X-linked traits more common in males
• Why???
Sex-linked Inheritance
• Predictions made using Punnett square
– Include sex of each parent
– Consider the sex chromosomes & genes they
carry together as a unit…
• ex. XG (= dominant gene), Xg (= recessive gene),
Y (= no gene)
XG female Xg
XG
Male
Y
Complete Punnett Square
Sex-linked Inheritance
• Ex. In Drosophila (fruit flies)  eye color
– What are the sex, genotype, & phenotype of each
F2 offspring?
• Are there any female carriers for the white eye gene?
P generation
genotypes were XRXR
& XwY
red-eyed
Heterozygous redeyed
carrier for white eye
allele
Sex-linked Inheritance
•Hemophilia is X-linked recessive
– If mother is carrier &
father has hemophilia:
• genotypic ratio?
• phenotypic ratio?
Draw Punnett Square
– If mother is carrier &
father is normal:
• Make a Punnett square
– genotypic ratio?
– phenotypic ratio?
Sex-linked Inheritance
• pedigree
chart showing
inheritance of
hemophilia
– Does
hemophilia
affect one
gender more
often?
• Why?
Sex-linked Inheritance
• Colorblindness is X-linked
recessive
– In this Punnett square, what are
the genotypes & phenotypes of
the parents?
Ishihara
test for
redgreen
color
blindness
Polygenic Inheritance
• ______________
______________
affect a single trait
– shows range of
phenotypes from
one extreme to
another (_______
______________)
• Ex. in humans:
hair color, height,
skin color
Expression of Genes
• Genes can _______________________ to
control various other patterns of inheritance
– Most characteristics that make up individual’s
phenotype not inherited in Mendelian patterns
• Ex. Modifier genes affect eye color
– influence amount, intensity, & distribution of melanin (color
pigment) in eye cells
Expression of Genes
• ____________________________ in which organism
develops is another factor that affects expression
– Probably due to how enzymes (proteins) operate at different
temperature
• Higher temps may “deactivate” enzyme & prevent a reaction form
occurring (therefore, changing phenotype)
• Examples:
– temp & size of fruit fly wings: Warmer temps = larger wings
& colder temps = smaller wings
– __________: Low altitudes = taller & high altitudes = shorter
– ____: Poor soil or drought may produce shorter (or no) ears
– _______ seedlings: Green (dominant) & albino (recessive)…
• however green color is also affected by environment
– No sunlight green color cannot be expressed due to lack of chlorophyll production
– Put in light green will appear b/c chlorophyll being produced
Human Genetic Disorders
Pedigree Charts
• A ____________________________
______________________________
of family over several generations
–Scientist or a genetic counselor would
find out about your family history &
make this chart to analyze.
• used to find out probability of a child having
a disorder in a particular family
–To begin to interpret a pedigree, determine if
the disease or condition is autosomal or Xlinked and dominant or recessive.
Pedigree
Chart
Square = ___________________________
Circle = ____________________________
Shaded = __________________________
Marriage = _________________________
Offspring = _________________________
Human Genetic Disorders
• Due to DNA mutation (usually recessive) or
chromosome abnormalities (# or structure)
– Causes production of abnormal proteins
• Examples:
– ______________________________ (***most genetic disorders)
» Cystic Fibrosis
» Sickle-cell Anemia
» Tay-Sachs Disease
– _________________________________________________________
» Huntington’s Disease
– _____________________________________________________
» Hemophilia
» Color Blindness
– _________________________________________________________
» Down Syndrome (trisomy 21)
» Klinefelter’s Syndrome
Autosomal Recessive
• Must be _____________ b/c allele
needed to produce trait is _______
– Cystic Fibrosis
– Sickle-cell Anemia (A normal,
S sickle-cell trait)
– Tay-Sachs Disease
Complete
Punnett
Squares
A
Male
S
A female S
Autosomal Dominant
• Can be homozygous or heterozygous b/c allele
needed to produce trait is dominant
– Huntington’s Disease
Draw Punnett Square
Sex-linked Disorders
•Hemophilia
•Color blindness
Complete
Punnett
Squares
Chromosomal Abnormalities
• Affects ________
____________ of
chromosomes
– #:
• Down Syndrome
(____________ …
_______ copies of
chromosome # __)
– Cause  _______
______________
(failure of paired
chromosomes to
______________
during meiosis 1
or meiosis 2)
Detecting Abnormalities
• Klinefelter’s Syndrome
– Sex chromosome disorder
» Males have ________
__________________
_______ chromosome
*XXY (or 47, XXY b/c 47
total chromosomes)
» Cause  __________
__________________
(failure of paired
chromosomes to
__________________
during meiosis 1 or
meiosis 2)
Chromosomal Abnormalities
• Affects # or
structure of
chromosomes
– Structure:
• Added,
deleted,
inverted, or
translocated
pieces
Detecting Abnormalities
• ______________
– “picture of human
chromosomes”
• From blood
sample
– Can detect _____
______________
______________
______________
______________
(additions,
deletions,
inversions,
translocations)
Detecting Abnormalities
• _________________
– sample of fluid
surrounding fetus
(karyotype then made)
• Can detect _________
__________________
– 14th + week of preg.
• _________________
_____ sample of cells
from chorion (part of
structure by which
fetus linked to mother)
– 9th + week of preg.
Review & Animations
• Vocab interactive
– http://nortonbooks.com/college/biology/animations/ch10a02.htm
• Crosses
– http://www.sonefe.org/online-biyoloji-dersleri/grade-12/monohybridcross/
• Drag & drop genetics
– http://www.zerobio.com/drag_gr11/mono.htm
• Various
– http://www.abpischools.org.uk/page/modules/genome/dna4.cfm?coSiteN
avigation_allTopic=1
• Pedigrees
– http://www.learnerstv.com/animation/animation.php?ani=13&cat=biology
• Genetic disorders
– http://www.humanillnesses.com/original/Gas-Hep/Genetic-Diseases.html