Download GENETICS

GENETICS
The study of Heredity!
• Heredity- Deals with inherited traits
• Traits- Inherited characteristics
• (ex. Eye color)
– Our DNA determines our traits (genes)
• Genetics- The study of heredity
Gregor Mendel
• 1st person to study how traits were inherited
• He found that traits were passed from a
parent to the offspring by studying a garden
pea
• He was the 1st to succeed in predicting traits
• Example: He crossed a tall pea plant with a
short pea plant and found that all of the
offspring were tall (TT x tt)
How are things inherited?
• When fertilization occurs, there are 2
traits given to the offspring
– (1 from the mother and 1 from the father)
• Each parent contributes a trait
– (1 trait is called an allele)
– Ex. Dad may contribute a dark hair trait
and the mother a light hair trait
2 kinds of traits:
Dominant trait- strong trait- represented
by a capital letter (ex. T)
– The dominant trait will win out (show up)
Recessive trait- weaker trait- represented
by a lower case letter (ex. t)
• During fertilization,
alleles will randomly pair
which will produce 4
different combinations
called the Law of
Segregation
• We use the punnett
square to show the 4
different possible
combinations that the
offspring may get
Solving genetics problems
• Use the punnett square
Terms used in genetics
problems:
1. Genotype- Shows the different gene
combinations an offspring may have (example
Bb)
2. Phenotype- The physical appearance of the
offspring – ex. black hair
3. Homozygous allele- Both alleles are the
same (ex. HH or hh)
4. Heterozygous allele- Both alleles are
different (ex. Hh)
Terms contd.
5. Monohybrid cross- Cross of 1 trait (ex.
Eye color)
6. Dihybrid cross- Cross of two traits (ex.
eye color x hair color)
We will be working with monohybrid
crosses only!
Genetic problems—copy problems
Must use punnett square and show letter of
dominant/recessive
• 1. A homozygous dominant man with nonattached eyebrows crosses with
a woman that has attached eyebrows.
– What is the phenotype? Genotype? Percent attached eyebrow?
• 2. A woman that is heterozygous for dimples crosses with a man who is
heterozygous for dimples.
– What are the genotypes? Phenotypes? Ratio of dimples to no dimples?
• 3. A man who is heterozygous for freckles crosses with a woman who lacks
freckles.
– What are the phenotypes? Genotypes? Percent that do not have
freckles?
• 4. A woman with a square face crosses with a man that is homozygous
dominant for a round face.
– What are the genotypes? Phenotypes? Ratio of round to square?
• 5. A woman who has heterozygous almond shaped eyes crosses with a
man that is homozygous dominant for almond eyes (round is recessive)
– What are the phenotypes? Genotypes? Percent of almond shaped?
• A heterozygous man with normal joints
marries a woman that is recessive for
double joints.
• What are the genotypes?
• What are the phenotypes?
• What percent are double jointed?
Problems
• 1. A woman that is
heterozygous for a
big mouth crosses
with a man that has
a small mouth
• A. genotype?
• B. phenotype?
• C. ratio large to
small
• 2. A homozygous
dominant man for cleft
chin crosses with a
woman that lacks a
cleft chin.
• A. phenotype
• B. genotype
• C. Percent non cleft
• 3. A homozygous
dominant bushy eye
browed crosses with a
woman that is
heterozygous bushy
eyebrowed.
• A. genotypes?
• B. phenotypes?
• C. percent bushy?
drawing
• 1. Go to microsoft word
• Click on insert, then pictures, then
autoshapes
• 2. When you have finished your drawing
• Save as:
• Shared drive (F), click on osborn, your
period, file name should be your name
• Do not print!!!
• Probability—likelihood of an event
occuring
• Example: probability of inheriting a
disease
pedigree