1. Genetic inheritance x

2. Mendelian Genetics
Gregor Mendel (late 1800's)
Austrian monk
Trained in math & chemistry
Experimented with plants at monastery
Controlled their __________
Studied inheritance of ______ traits
E.g., flower color, seed shape
Now called ______ inheritance

3. Traits are inherited characteristics Can have alternative forms
E.g., brown versus red hair
Some forms can dominate over others
Dominant versus ________ traits
Mendel had no knowledge of chromosomes or DNA
Recognized “_______” that control inheritance
Now recognized as genes & alleles
Genes are the molecular code for genetic ______
Alleles are _________________ of a gene
Occur at ________ on chromosomes
Inheritance > genes

4. Recessive allele = ____ flowers
Homologous pair
of chromosomes
Gene locus
(e.g., for
flower color) P P p
One from mom,
one from dad
Dominant allele
= _____ flowers
Recessive allele = ____ flowers
Inheritance > genes

5. Mendel observed inheritance over generations
Studied ____________ crosses:
Parents have different forms of a single trait
E.g., purple versus white flower color
Observed _________: outward appearances
Inheritance > mono-hybrid cross

6. E.g., mono-hybrid cross of purple and white peas
Parents: x
F1 hybrids:
____ offspring are _______
Called first or ___ (hybrid) generation
Inheritance > mono-hybrid cross > F1

7. Produces 3 purple & 1 white offspring
Breeding of 2 purple F1s
Produces 3 purple & 1 white offspring x
F1 generation:
F2 generation:
Called second or ___ generation
Inheritance > mono-hybrid cross > F2

8. How did white re-appear in the F2 generation?
Was present in F1 hyrbids, but dominated by purple
Key points:
1. Offspring inherit _______ of a trait
One from each parent, which can differ
2. Recessive not expressed if coupled with ______ E.g., dominant produces pigment, recessive doesn’t
3. Traits re-occur through _________
Separation of ___________ chromosomes during gametogenesis (________)
Inheritance > mono-hybrid cross > segregation

9. To understand segregation, track _________
The actual alleles an individual carries
In mono-hybrid crosses:
1. Parental genotype is homozygous PP pp X
Homozygous
_________
Homozygous
_________
Inheritance > mono-hybrid cross > segregation

10. 2. Parental alleles segregate during meiosisPP pp
female
male X
meiosis
Eggs
Sperm P P p p
Inheritance > mono-hybrid cross > segregation

11. 3. F1 generation is heterozygous
A dominant allele gets paired with recessive allele
female
male pp PP
Parents: x
meiosis P P p + p +
fertilization Pp Pp
Heterozygous
condition
F1:
Only the ________ allele is expressed

12. ? ? ? ? 4. F2 generation will occur in 3:1 ________ ratio female malePp Pp
F1: x
Segregation: p ? ? P Pp ?
Gametes: ? P ? p ? PP ? pp
______
square
F2: Pp ?
Genotypic ratio is
_____ (1 PP, 2Pp, 1pp)
Inheritance > mono-hybrid cross > phenotypic ratio

13. Complex inheritance patterns
1. Incomplete dominance
Heterozygotes are __________ in form (________)
E.g., heterozygous snapdragons are _____
Co-dominant allele also influences phenotype
Apostrophe indicates co-dominant
(subdominant) rather than recessive
Inheritance > complex crosses

14. Gene for blood antigen has __ alleles: A, B, & O
2. One gene with multiple alleles:
Human blood types (more in lab)
Gene for blood antigen has __ alleles: A, B, & O
Blood type Genotype Glycoprotein
A AA or AO
B BB or BO
AB AB
O OO
Inheritance > complex crosses

15. 3. A single trait influenced by ____ genes
Phenotypes usually vary along a _________
Most common kind of inheritance in humans
Human skin, eye, & hair color
Mendel purposely _________ such traits
Human eye color:
2 genes, each
with 2 alleles
Inheritance > complex crosses

16. 4. Sex-linked inheritance Gene is located on a ___ chromosome, X or Y
X and Y are homologous chromosomes (__rd pr.)
But are quite different
Y is smaller & lacks some ________ X Y
Inheritance > complex crosses

17. Must first discuss Sex determination
___ System of sex determination:
Male Female
Adults: XY XX
Gametes:
Gametes: X Y X
Offspring: XY XX
Only _________ contribution (Y) determines sex
___ gene on Y chromosome codes for ‘_______’
Starts a cascade of fetal ________ changes
Inheritance > sex determination

18. In birds, females have the unusual sex chromosome
In bees:
Males develop from unfertilized eggs; _____
Females developed from fertilized eggs; ______
In some reptiles, sex is determine by incubation ____.
Appears to influence hormones
Actual mechanism not well-understood

19. Back to sex-linked inheritance:
E.g., Hemophilia: a recessive ________ disease
Causes non-stop bleeding
Defective blood-clotting _______
Severe forms can be ______
Mothers can be heterozygous _______ (Hh): H h X
Carriers (Hh) ______ suffer from the disease

20. Males that inherit recessive allele ______ sufferX Y
Y chromosome lacks corresponding locus
Not possible to be ____________ (carrier)

21. Females suffer only when homozygous _______X
Rare: father must be ________ (h on X)
Why rare?
Male sufferers of severe forms ___ young