unit 6: genetics & heredity ch 12 and 13: heredity & human genetics
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Unit 6: Genetics & Heredity Ch 12 and 13: Heredity & 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. - PowerPoint PPT PresentationTRANSCRIPT
Unit 6: Genetics & HeredityCh 12 and 13: Heredity & 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
• Male & female parts in same flower–Normally
• Self pollinate–Produce pure
offspring» ______ parents
produce______ offspring
» ______ parents produce _________ offspring
Mendel’s Experiments
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)
• Offspring allowed to self pollinate• New offspring (F2, second filial, generation) weren’t
all purple– _______– _______
Mendel’s Experiments
Parent
First filial
Second Filial
Crossed 2 F1 plants to get F2
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 samechromosome
Genes on samechromosome
meiosis
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?
Phenotypegenotype
Phenotypegenotype
Pp
Pp
Pp
Pp
P p
p P
Monohybrid Cross• a cross where __________________________
________________________ (gene) is studied– ex. only height, flower color, eye color, etc...
T t
Draw Punnett Square
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
• If any offspring show recessive trait, unknown parent ____________
• If all show dominant trait, then parent ________ ____________________
Show as P_
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
• 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
Multiple Alleles
Sex Determination• In humans chromosomes:
– Pairs 1 – 22 = ____________________– 23rd pair determine gender = __________________
• __________ = female• __________= male
What is the probability of having a son? A daughter?
Draw Punnett Square
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???
• 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)
Sex-linked Inheritance
XG female Xg
Complete Punnett Square
• 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?
Sex-linked Inheritance
Heterozygous red-eyed
carrier for white eye allele
red-eyed
P generation genotypes were XRXR & XwY
Sex-linked Inheritance
– If mother is carrier & father has hemophilia:
• genotypic ratio?• phenotypic ratio?
– If mother is carrier & father is normal:
• Make a Punnett square– genotypic ratio?– phenotypic ratio?
•Hemophilia is X-linked recessive
Draw Punnett Square
• 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?
Sex-linked Inheritance
Ishiharatest forred-greencolorblindness
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
• ____________________________ 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
Expression of Genes
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 X-linked and dominant or recessive.
Pedigree Chart
Square = ___________________________
Circle = ____________________________
Shaded = __________________________
Marriage = _________________________
Offspring = _________________________
• 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
Human Genetic Disorders
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 A female S
Complete Punnett Squares
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)
• 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)
Detecting Abnormalities
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)
• _________________– 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.
Detecting Abnormalities
Review & Animations• Vocab interactive
– http://nortonbooks.com/college/biology/animations/ch10a02.htm
• Crosses– http://www.sonefe.org/online-biyoloji-dersleri/grade-12/monohybrid-
cross/
• Drag & drop genetics– http://www.zerobio.com/drag_gr11/mono.htm
• Various– http://www.abpischools.org.uk/page/modules/genome/dna4.cfm?
coSiteNavigation_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