Transcript Chapter 9-

Chapter 9
Fundamentals of Genetics
Page 164
• Look at the photo and answer the
following questions in complete sentences!
• How is this alligator different from other
alligators you have seen?
Background Vocab
• Genetics:
– Field of biology to understand how
characteristics are given from
parents to their children
• Heredity:
– The sending of characteristics
from parents to children
• Gregor Mendel:
– Person who did much of the work
to create genetics as a topic to
study
Mendel’s Peas
• Mendel looked at 7 characteristics.
• Each characteristic had 2 options.
– Height—tall or short
– Seed color—yellow or green
– Texture—smooth or wrinkled
– Flower color—purple or white
• He collected seeds from his pea
plants and planted them the
next year.
• Seeds from a purple flower plant…
Purple Flower & White Flower Plants
• Seeds from a tall plant…
Tall & Short Plants
• P1 Generation:
– Parents
• F1 Generation:
– 1st set of children
• F2 Generation:
– 2nd set of children
For Example…
P1
F1
F2
Tall X Short All Tall
Most Tall
Some Short
Purple X
White
Most Purple
Some White
All Purple
Mendel’s Conclusions
• A pair of factors must control each trait
(ex. Tall vs. Short).
• One factor must prevent the other from
being seen. (In F1 only saw tall plants.)
• Dominant:
– Trait that is seen
• Recessive:
– Trait that does NOT appear
• Law of Segregation:
– A pair of factors is separated when eggs and
sperm are made
• Example—
Sperm  tall factor
Egg  short factor
Baby is…tall or short
WHY?????
• Law of Independent Assortment:
– Factors are given to the gametes (?)
independently
• Allele:
– New name for forms of a gene (Mendel’s
factors)
– Use letters
– CAPITAL LETTERS = dominant alleles
– Lowercase letters = recessive alleles
For Example…
• Seed Color
• Green is dominant
–G
• Yellow is recessive
–g
• Genotype:
– Genetic make-up
– Ex: Gg
• Phenotype:
– Appearance of an organism
– Ex: Green
9.2
Genetic Crosses
• Homozygous:
– Both alleles are alike
– Homozygous dominant = TT = tall
– Homozygous recessive = tt = short
• Heterozygous:
– The two alleles are different
– Tt = tall
• Probability:
– How likely it is for something to occur
– Often written in the form of a fraction
• Monohybrid cross:
– A cross using one pair of traits
– Ex: cross between a pure purple flowering
plant and a pure white flowering plant
How do you show a cross?
• Punnett Square:
– A diagram to predict
how traits are inherited
p
P
P
p