Download Basics Of Genetics - Fall River Public Schools

Basics Of Genetics
B.M.C. Durfee High School
Objectives
• Describe genetics role in evolution
• Describe how genetic traits are passed from
one generation to the next
• Identify the difference between genotype and
phenotype
• Describe the different types of inheritance
patterns
Genetics and Evolution
• Genetics are important to our understanding
of evolution.
• Genetics is the key to understanding how
variation arises.
• Genetics is the study of heredity (transmission
of genetic information from parent to
offspring)
Basics of Genetics
• Genes are parts of the DNA that code for
certain traits.
• DNA is packaged as chromosomes (DNA and
proteins)
• We have 46 chromosomes in our somatic cells
• These cells are diploid: 2 copies of each
chromosome (one from each parent)
How are Traits Passed
Down?
• Gamete cells (eggs and sperm) are haploid
(half of the genetic information)
• Our gametes have 23 chromosomes
• These cells fuse together during fertilization to
make a zygote
• Meiosis is the process of making gametes
• Mitosis is when we copy cells
Types of Chromosomes
• There are two types of chromosomes:
o Autosomes: 22 pairs/ 44 chromosomes that
code for traits
o Sex chromosomes: 1 pair/2 chromosomes
that code for sex
 XX: female
 XY: male
Alleles
• Alleles are different forms of the traits (i.e..
Purple flowers, blue eyes)
• Dominant alleles mask the expression of
recessive alleles
o Dominant alleles are written with capital
letters
o Recessive alleles are written with lowercase
letters
Genotypes
• Genotype is the genetic makeup of the
individual
o Homozygous: both alleles are the same
 BB: homozygous dominant
 bb: homozygous recessive
o Heterozygous: both alleles are different
 Bb: heterozygous
Phenotype
• Phenotype is the expression of the trait
o BB: Brown eyes
o Bb: Brown eyes
o bb: blue eyes
Other Inheritance Patterns
• Co-dominance: both dominant alleles are
expressed in the heterozygote
• Incomplete dominance: middle between two
alleles are expressed in heterozygote
• Sex Linked Traits: On X chromosome, are they
usually expressed in males or females? Why?
Genetics and Environment
• Genes are influenced by the environment:
o Height
o Diseases
• Reaction Norm:
oG+EP
o Genotype interacting with the environment
yields the phenotype
What Is Phenotype Video
What is phenotype
Sociobiology
• Idea that your behavior is determined by your
biology
• Genetics provides range of possibilities and
Environment selects
• Determinists:
o Biological Determinist: Biology determines
behavior
o Cultural Determinist: Culture determines
behavior
Review
• Describe genetics role in • Genetics is the key to understanding how variation
evolution:
arises
• Describe how genetic
traits are passed from
one generation to the
next:
• We get our genetic traits from our parents
• Gamete cells (eggs and sperm) are haploid (half of
the genetic information)
• During sexual reproduction, the gametes join to
form a fertilized egg (zygote)
• Identify the difference
between genotype and
phenotype
• Genotype is the genetic makeup of an organism
• Phenotype is the physical expression (what is
shown) of the genotype
• Describe the different
types of inheritance
patterns
• Co-dominance: both dominant alleles are expressed
• Incomplete dominance: middle between two alleles
are expressed in heterozygote
• Sex Linked Traits: trait is found only on the X or Y
chromosome
Learn Long
Live Long