1. Chapter 9 Fundamentals of Genetics
Genetics- the branch of biology that studies how traits are transmitted from parents to offspring
Gregor Mendel

2. Section 1 Mendel’s Legacy
Heredity- the transmission of characteristics from parents to offspring
Mendel studied 7 traits in pea plants:
Plant height (tall, short)
Flower position (axial, terminal)
Pod color (green, yellow)
Pod appearance (smooth, constricted)
Seed texture (round, wrinkled)
Seed color (yellow, green)
Flower color (purple, white)
Trait-a contrasting form of a hereditary characteristic

3. Mendel’s Methods
1st: allowed plants to self-pollinate in order to produce true- breeding plants
2nd: cross- pollinated plants that were true-breeding for contrasting traits (he called these his P generation)
3rd: The results of crossing the P generation gave him his F1 generation
4th: allowed F1 offspring to self-pollinate to produce F2 offspring

4. The ratio that he always got from his F1 generation was 4:0.
YY x yy
= all green
(4:0)

5. The ratio that he always got in his F2 generation was 3:1
Yy x Yy
= 3 green and
1 yellow
(3:1)

6. He called the controls that determined how traits were transmitted, factors
We call them “alleles” or “genes”
Gene- a segment of DNA that controls a particular hereditary trait
Allele- alternative form of a gene

7. Recessive and Dominant Traits
Dominant- the allele that is expressed
AA or Aa
Recessive- the allele that is masked; the only way for a recessive trait to be exhibited is if 2 recessive alleles are present aa
Free-dominant
Dimples - dominant
Attached- recessive
Widow’s peak-dominant

8. Tongue rolling-dominant
* sex-linked characteristic
Tongue rolling-dominant
DOMINANT TRAITS
RECESSIVE TRAITS
eye coloring
brown eyes
grey, green, hazel, blue eyes
vision
farsightedness normal vision normal vision normal vision
normal vision nearsightedness night blindness color blindness*
hair
dark hair non-red hair curly hair full head of hair widow's peak
blonde, light, red hair red hair straight hair baldness* normal hairline
facial features
dim ples unat tach ed earl obes frec kles broa d lips
no dimples attached earlobes no freckles thin lips
appendages
extra digits fused digits short digits fingers lack 1 joint limb dwarfing clubbed thumb double-jointedness
normal number normal digits normal digits normal joints normal proportion normal thumb normal joints
other
immunity to poison ivy normal pigmented skin normal blood clotting normal hearing normal hearing and speaking normal- no PKU
susceptibility to poison ivy albinism hemophilia* congenital deafness deaf mutism phenylketonuria (PKU)
Hitchhiker’s thumb-recessive
Albinism-recessive

9. The Law of Segregation
Factors separate during gamete formation; each gamete only receives 1 factor from every pair
This occurs during meiosis

10. The Law of Independent Assortment
Two traits, although present in a parent are not necessarily transmitted together in the offspring
For example if a yellow, smooth pea is crossed with a green, wrinkled pea, will all offspring be either yellow and smooth or green and wrinkled?

11. No, because genes for each of those traits become separated during the formation of gametes