Transcript Human Genetics

Aim: How do your genetics
play a role in the person
you are today?
 Do Now: What similarities do you
have with your parents or
siblings?
 Homework:Textbook 126-132 #1-5
Human Genetics
What is Heredity?
 The transfer of characteristics from one
generation to the next
What are Traits?
 A characteristic that is determined by
your genes
 A pair of genes will determine the trait
 Examples:
 Tongue rolling
 Earlobes
 Widow’s Peak
 Hair Whorl
 Dimples
What is genetics?
 The science of how traits are inherited
Where do our genes come
from?
• We had said that a pair of genes determines which traits
we will inherit from our parents
• Why would it be a pair of genes?
•Each parent provides a sex cell in order for fertilization
to occur
•The father will provide a sperm cell that has 23
chromosomes
•The mother will provide an egg cell that has 23
chromosomes
•When these two cells merge and become one,
fertilization has occurred, and as a result, the new
fertilized egg has 46 chromosomes (23 + 23 = 46)
+
23 chromosomes
23 chromosomes
46 chromosomes
How are traits determined?
 Dominant Genes – the traits that will
usually appear in the individual
(represented by an uppercase letter)
 If an organism has a gene for blue or
brown eyes, usually it will have brown
eyes because in is the dominant gene
 Recessive Genes – The gene hidden by
the dominant gene
(represented by a lowercase letter)
 Blue-eyed people need two recessive
genes to show the blue-eyed trait
Who is Gregor Mendel?
 “Father of Genetics”
 Studied pea plants
 He crossed pea plants with different
characteristics and studied their offspring
 He was able to determine how
traits get passed on from
generation to generation
What is a Punnett Square?
 A table that shows
the possible results
when the genes of
two parents are
crossed
 It shows the
probability of a trait to
be expressed in the
offspring
B
B
B
BB
BB
b
Bb
Bb
B – Brown Eyes
b – Blue Eyes
What is a genotype?
 The genetic code or make up of the
individual
 Examples: BB, Bb, bb
What is a genotype?
 Homozygous dominant
– a pair of dominant genes (BB)
 Homozygous recessive
– a pair of recessive genes (bb)
 Heterozygous or hybrid
– a mixed pair of one dominant gene and
one recessive gene (Bb)
What is a phenotype?
 The way an organism looks or behaves
 Examples:
Genotype Phenotype
BB
Brown Hair
Bb
Brown Hair
Lets try some Punnett Squares!
B = Brown Eyes
b = Blue Eyes
What we are looking for:
1. Genotypes
2. Phenotypes
3. Percentage Brown
eyes
4. Percentage Blue Eyes
Examples:
 BB x bb
 Bb x bb
 Bb x Bb
 bb x bb
 BB x BB
 BB x Bb