Transcript Ch. 9 + 10 [genetics]

Mendelian Patterns of Inheritance
Chapter 9
Gregor Mendel
 Monk
who lived in early 1860’s.
 Wanted to know how heredity was passed on from
generation to generation.
 1800’s theory: Blending Concept
 Both
parents contribute equally to offspring.
 EX:
red flower + white flower = pink
Mendel’s Experiment

Worked with PEA plants

Why:
1. Easy to cultivate
2. Has a short generation time
3. Easily cross pollinated
4. Many varieties
Pea Plant Traits
Mendel’s Final Theory
 Particulate Theory
of Inheritance:
Inheritance is based on the existence of minute particles
called genes; these genes are reshuffled from
generation to generation.
One-Trait Inheritance




Chose plants that differed only in ONE trait
Parent Generation : P
1st Generation : F1
2nd Generation : F2
 Alleles:
different forms of genes
 Letters
are assigned for different alleles (traits)
 Y = yellow
y = green
 Dominant (Y) – visible trait
 Recessive (y) – hidden trait
 Homozygous – a trait where 2 alleles are the same (yy
or YY)
 Heterozygous – a trait where 2 alleles are different (Yy)
 Genotype – the alleles the individual receives
 Phenotype – the physical appearance
Punnett Square
 Represents
a cross between 2 parents, showing all
possible offspring.
Practice Problem

In rabbits, if B = black hair, and b= white hair.
When two heterozygous parents are crossed,
B
b
what are the offsprings?
B
BB
Bb
b
Bb
bb
-one trait cross-
Practice Problem
 What
is the phenotypic ratio??
B
b
B
BB
Bb
b
Bb
bb
3:1
3 = black
1 = white
Practice Problem

In pea plants, if Y = yellow, and y = green peas,
and T = tall plant, and t = short plant. When two
heterozygous parents are crossed, what are the
offsprings?
YT
-two trait cross-
YT YYTT
Yt
yT
yt
YYTt
YyTT
YyTt
Yt
YYTt
YYtt
YyTt
Yytt
yT
YyTT
YyTt
yyTT
yyTt
yt
YyTt
Yytt
yyTt
yytt
Practice Problem
 What
is the phenotypic ratio??
9:3:3:1
9 = yellow & tall
3 = yellow & short
3 = green & tall
1 = green & short
YT
YT YYTT
Yt
yT
yt
YYTt
YyTT
YyTt
Yt
YYTt
YYtt
YyTt
Yytt
yT
YyTT
YyTt
yyTT
yyTt
yt
YyTt
Yytt
yyTt
yytt
DNA Structure
Chapter 10
History


Mendel knew that inheritance was passed on, but
he didn’t know what!
Two molecules that were thought to pass on
inheritance – DIDN’T KNOW WHICH ONE
1.
2.
Proteins
DNA
DNA Structure

Watson and Crick – 1962

Nucleotides bonded together in a double helix

1.
2.
3.
4.
4 different ones
A = adenine
T = thymine
G = guanine
C = cytosine
A=T
G=C
Replication of DNA
Eukaryote
Prokaryote