Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
Unit 8: Genetics & Heredity & Unit 9: Human Genetic Disorders
Ch. 26: Inheritance of Traits & Ch. 27: Human Genetics
Genetics & Heredity
• What is genetics?
– The study of _________________________
• ____________________________________ from parents to offspring
Chromosomes in Cells
• Remember…
– Body cells are ________________________________
• _________ of each chromosome
– 1 from mom & 1 from dad
– Gametes (sperm & eggs) are ______________________
• _________________ of each chromosome
– Why?
• _________________________________________________
Genes
• Why is your combination of genes unique?
– _______________ … don’t know
______________________________________
• get ½ of your chromosomes from mom & ½ from dad
• ____________________________
– crossing over during
_______________________________________
– _______________ of chromosomes during _____________________
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
Genes & Alleles
• What is a "gene"?
– section of ___________________________________________________
___________________________________________________________
• & determines a specific __________ (ex. hair color, eye color, etc.)
– genes are ___________________________________________________
• different forms of genes for the same trait are called
“________________”
Dominant & Recessive Alleles
• Each parent contributes __________________________________________
_____________________________________________________________
– What is a dominant allele?
• allele that _______________________________________________
– What is a recessive allele?
• allele whose trait can _______________________ when the organism is
_____________________________________________ for that trait
• How are alleles represented?
– with _____________________________
• usually the _______________________ of the
____________________________
– If the same letter is used for dominant & recessive, how do we know
which allele is which?
• CAPITAL = ___________________________
• lowercase = ___________________________
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
Allele Combinations
• What does "homozygous" mean?
– both alleles are ____________________________
• _____________________________________ (pure) dominant (ex. AA)
• _____________________________________ (pure) recessive (ex. aa)
• What does "heterozygous" mean?
– both alleles are _______________________________
• ___________________________________________ (hybrid) (ex. Aa)
Genotype vs. Phenotype
• What is "genotype"?
– organism's actual _____________________________________________
___________________________________________________________
• What does the genotype do?
– codes for ___________________________________________________
• How do we represent an organism's genotype?
– ___________________________________________________________
• one from mom & one from dad
– ex. ___________________________________________________
• What is "phenotype"?
– the _______________________________ of the genotype ("trait we see")
• What actually causes the "phenotype" (trait) we see?
– the ______________ that is __________________ (due to the organism's
genotype "code"/alleles)
• How do we represent an organism's phenotype?
– usually an __________________________
• ex. __________________________________________________ etc.
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
Genotype is Expressed as a Phenotype
• Ex. Let P = purple & p = white
– homozygous (pure) dominant
• genotype _________
• phenotype = _________
– heterozygous (hybrid)
• genotype _________
• phenotype = _________
– ___________ trait "masks/ hides"
____________ trait
– homozygous (pure) recessive
• genotype _________
• phenotype = _________
Predicting Traits in Offspring
• What are Punnett Squares?
– a way to ____________________________________________________
• letters outside represent ____________________________________
________________________________________________________
– top = _______________________ & side = ____________________
• letters inside boxes represent ________________________________
________________________________________________________
________________________________________________________
– can be used to determine ___________________________________
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Making a Punnett Square
Date __________
Period _________
Making a Punnett Square
• Parents are Tt & tt genotypes…
1. Determine the genotypes of the parent
– So… Tt x tt is our cross
organisms.
2. Write down your "cross" (mating).
3. Draw a Punnett square.
4. "Split" the letters of the genotype for
each parent & put them "outside" the
Punnett square (one on left & one on top)
to represent the possible alleles in the gametes.
5. Determine possible genotypes of the offspring by filling in the Punnett square.
6. Summarize results (genotypes & phenotypes of offspring)
 Parent Pea Plants ("P" Generation)
o Genotypes: __________________________
o Phenotypes: __________________________
 Offspring ("F1" Generation)
o Genotypes: __________________________
o Phenotypes: __________________________
Passing Traits to Offspring & Probability
• What is probability?
– ______________ 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 five girls?
• 1/2 x 1/2 x 1/2 x 1/2 x 1/2 = ______________
– or (1/2)5 = ___________
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
Passing Traits to Offspring & Ratios
• What is "genotypic ratio"?
– probable ratio of _______________________
____________________________________
• Ex. If cross Pp & Pp
– _______________________________
• What is "phenotypic ratio"?
– probable ratio of _______________________
____________________________________
• Ex. If cross Pp & Pp
– _______________________________
• What is an "expected ratio"?
– ratio we _______________________ based on probability (Punnett Square)
• What is an "observed ratio"?
– ratio we ____________________________________________________
• Why would these be different?
– fertilization is ______________________________
– some embryos _______________ during early stages
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
Gregor ______________
• Father of Genetics
– 1822-1884
• Studied garden _________________________________________________
– 7 different traits with clearly different forms
• tried to determine how these traits were passed from parent to offspring
Mendel’s Experiments
• What happened when Mendel mated pure purple parent
(_____) & pure white parent (_____)?
– All offspring had:
• _______________________________ phenotype
• ________________________________ genotype
– ___________
• What happened when Mendel let the heterozygous (hybrid)
offspring from his first experiment self- pollinate?
– So… __________ x ____________
• New offspring ____________________________
Mendel’s Principle of Dominance
• What did Mendel notice from his experiments?
– that one form ______________________ over the other
• ...__________ trait __________ the expression of the _________ trait
– What is the dominant trait in these plants?
• ____________________ = DOMINANT
– What trait was recessive?
• ____________________ = recessive
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
Dominant/Recessive is Not Always the Method of Inheritance
• Traits are not always as clearly defined as the 7 pea plant traits Mendel studied
– Examples of non-dominant/recessive inheritance
• ________________________________________
• ________________________________________
• ________________________________________
• ________________________________________
Sex Determination
• How many chromosomes do humans have in body cells?
– _______ ... _______ pairs
• Pairs 1 – 22 = ______________________________________________
• 23rd pair determines gender = _________________________________
– __________ = female
– __________ = male
• Which parent’s chromosomes determines if the offspring will be a
boy or girl???? _____________ Why?
– ______ b/c _____ is only one who can give ______; ______ always gives ___
Sex-linked Inheritance
• X & Y chromosomes are _________ fully ________________________. Why?
– ______ is bigger & carries more genes
• How many alleles will a male have for traits that are carried only on the X
chromosome?
– ___ b/c only have ________________ chromosome (___ doesn't have allele)
• What is this called?
– ________________________ or ___________________________
• Ex.: ________________________________________________
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
– X-linked traits & disorders are more common in males. Why???
• b/c female has ______, more likely she will have a copy of ____________
allele... males = ______... can only get _________________ allele on X (&
only have _____ X)
• How do we make predictions made using Punnett Squares for sex-linked traits?
Sex-linked Inheritance
– consider the _________________________ & __________ for the trait it
• Predictions made using Punnett square
carries ("exponent") ___________________
as a unit…
– Consider the sex chromosomes (X or Y) & genes
they____
carry (shown
as superscript/exponent)
• ex. ____ (= X w/ __________ allele),
(= X w/
___________ allele),
together as a unit…
• ex. XG (= dominant gene), Xg (= recessive gene), Y (= no
_______ (= Y w/ ___________ allele)
gene)
• What if a female is heterozygous (XGXg)?– If a female is heterozygous,
she does not show the
G
trait/have the disorder, X
Male
_____________________________ but is a carrier
– she does not show the trait/have the disorder, but is a
• can pass gene
• & can ________________________ toto
offspring
offspring
Y
XG female Xg
XG X G
XG X g
XG Y
Xg Y
• Can a male be a carrier?
– _________, b/c only _________________________________________…
so ________________________________________________________
• Drosophila (fruit fly)  ________________________ is sex-linked
– What are the sex, genotype, & phenotype of each offspring? Are there any
carriers for the white-eye gene?
• Left picture: 2 __________ w/ __________ eyes = XRXr (carrier)
& 2 ___________ w/ ____________ eyes =
XrY
• Right picture: ______ w/ _______ eyes =
XRXR, __________ w/ __________ eyes = XRXr (carrier),
_________________ w/ _________________ eyes =
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
XRY, & _________________ w/ _________________ eyes = XrY
Multiple Alleles & Codominance
• What is meant by multiple alleles?
– _______________ different forms of an allele exist
• but individual ____________________________
– Ex. ___________________________________
• _______________ multiple alleles
– ________________
– ________________
– ________________
• What is meant by codominance?
– both alleles are _____________________________________________
– ex. ___________________________ also exhibit codominance (as well as
multiple alleles)
• ____________ are __________________ and are "expressed" equally
– _______ = ______ (codominant)
– _______ (recessive)
– So… (________ = ________) > ________
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
Human Genetic Disorders
• What causes genetic disorders?
– ____________________ (usually recessive) or chromosome abnormalities
(in # or structure) that causes production of ______________________
• How can we group genetic disorders?
1.
disorders (*most genetic disorders)
• allele is ______________ & found on a chromosome from pairs ________
(autosomes or body chromosomes)
– cystic fibrosis, sickle-cell anemia, Tay-Sachs disease
2.
disorders
• allele is ______________ & found on a chromosome from pairs ________
(autosomes or body chromosomes)
– Huntington’s Disease
3.
disorders
• allele (which is usually recessive) is found on the ________ of
chromosomes (_____________ chromosomes)… Usually on the
__________ chromosome
– hemophilia
– color blindness
4.
disorders
• result from errors in ________________________________________
– Down Syndrome (trisomy 21), Klinefelter’s Syndrome (XXY)
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
Autosomal Recessive Disorders
• What genotype(s) must a person have to be affected?
– ____________________________________________
• ____________________________
• ____________________________
• ____________________________
• Can someone be a carrier? Why/why not?
– __________________
• b/c if ____________________, person carries gene, but isn’t affected
– due to having the ________________________________________
Autosomal Dominant Disorders
• What genotype(s) must a person have to be affected?
– can be ____________________________________ or
________________________ b/c allele is __________
• ____________________________
• Can someone be a carrier? Why/why not?
– _________
• b/c even if person is heterozygous (Gg), person ____________________
– due to _________________________________________________
______________________________________________________
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
Sex-linked Disorders
• Remember from earlier… hemophilia is X-linked & recessive
– What are the possible genotypes & phenotypes? Can someone be a carrier?
• ____________ = __________________________________________
• ____________ = __________________________________________
• ____________ = __________________________________________
• ____________ = __________________________________________
• ____________ = __________________________________________
– Why can’t a male be a carrier?
• b/c only has ___________________________________________… so
either has it or doesn’t
– Ex. mom = carrier & dad = normal:
• Make a Punnett square
– genotypic ratio? ______________________
___________________________________
– phenotypic ratio? _____________________
___________________________________
• Remember from earlier… colorblindness is X-linked recessive
– What are the possible genotypes & phenotypes? Can someone be a carrier?
• ____________ = __________________________________________
• ____________ = __________________________________________
• ____________ = __________________________________________
• ____________ = __________________________
• ____________ = __________________________
– In this Punnett square, what are the genotypes &
phenotypes of the parents?
• father: genotype = _______ & phenotype = __________
Name ____________________________________
Mrs. Geithner-Marron Bio 200
Date __________
Period _________
• mother: genotype = _______ & phenotype =
__________
Chromosomal Abnormalities in Number
• What causes an abnormal number of chromosomes?
– ________________________
• failure of paired chromosomes to _________
during _____________ or _____________
Disorders Due to Abnormal Chromosome Number
• What is Down Syndrome (trisomy 21)?
– when person has ______________ of chromosome _______
• What is Klinefelter’s Syndrome?
– a _______________________ disorder in which males
have _____________________________ chromosome
• _______ (or 47, ______ b/c 47 total chromosomes)
• What causes Down Syndrome (trisomy 21) & Klinefelter’s Syndrome?
– _________________________________________________
• failure of paired chromosomes to ________ during ________ or _______
Chromosomal Abnormalities in Structure
• What causes structural abnormalities in chromosomes?
− pieces are _________________________________
_________________________________________