Transcript Chapter 7 – Are You Only as Smart as Your Genes

Chapter 7 – Are You Only as
Smart as Your Genes
Genetics:
Genetic Heredity
– Organisms have two
sets of chromosomes
(1 set from each
parent)
– Alleles: genes that
code for different
traits (ex. height)
• Alleles are represented
by a letter
• Dominant (capital) trait
appears over the
recessive (lowercase)
trait
Differentiation
• Differentiation – same
genetic information,
different look & function
• All your cells have the
same genetic information
– Criminal cases use any
tissue sample to collect
DNA; investigations can
use DNA from different
tissues to identify
someone at a crime scene
• Why are cells different?
– The genetic information is
‘read’ and expressed
differently
Segregation & Independent Assortment
• Each gamete gets half of a persons
chromosomes
• Segregation: All genes (chromosomes) don’t
always go to the same gamete, they have to
go through:
– Segregation: genes may split into different
gametes
– Independent Assortment: genes go to gametes
independently (not always with the same genes)
Gene Expression
• Genotype (Genetic makeup)
Types of Genotypes
– Homozygous Dominant: two capital letters
– Homozygous Recessive: two lowercase letters
– Heterozygous: one capital, one lowercase letter
• Phenotype (Physical traits)
– Expression of alleles
Predicting Offspring Traits
• Punnett Squares are
used to predict the
likelihood of an offspring
acquiring a trait
• For one trait, a four
square Punnett Square is
used
– Each square represents a
25% chance
Why do phenotype & genotype have different ratios?
Quantitative Traits
• Quantitative traits do not go
through these yes-or-no or onor-off characteristics
• Quantitative traits are
continuous traits that show inbetween characteristics
– Ex. Height, weight, skin color,
susceptibility to cancer
• Factors determining the
phenotype of quantitative
traits
– Inheritance: traits are
influenced by many genes
– Environment: environmental
factors determine traits
Heritability
• Estimating heritibility:
researchers use
correlations between
individuals with varying
degrees of genetic
similarity
– Heritability in humans is
measured by examining
correlations between
groups
– Comparisons between
parents and children are
used
Misconceptions of High Heritability
• Similarities & differences between groups may
be environmental because of environmental
factors
– Parents & children with similar features may have
been raised in the same environment
– For some traits, there is no way of knowing how
much of it is a result of genetic factors and how
much of it is a result of environmental factors