Transcript DO NOW - Maria Regina School

DO NOW
The allele B carries the trait for blue body color.
The allele b carries the trait for pink body color.
Cross Bb and BB
Heredity
• The passing of traits from parents to offspring
– Genes on chromosomes control the traits that
show up in organisms
Gregor Mendel
• The father of genetics
• First to use
mathematics of
probability to explain
heredity and to trace
one trait for several
generations
Alleles
• Different forms of a trait
that a gene may have are
alleles.
• During meiosis, a pair of
chromosomes separates
and the alleles move into
separate sex cells.
• Each sex cell now
contains ONE allele for
each trait.
• The study of how traits
are inherited is genetics.
Alleles
• Dominant allele- covers up or dominates
other allele
• Recessive allele- the trait seems to disappear
unless the organism has TWO copies
Hybrids
• Hybrids receive DIFFERENT genetic
information for a trait from each parent
Punnett Square
• Upper case letters- dominant alleles
• Lowercase letters- recessive alleles
Genotype and Phenotype
• Genotype- the genetic
makeup of an organism
– Homozygous- an organism
with two alleles for one
trait that are the SAME
– Heterozygous- an organism
with two alleles for one
trait that are the
DIFFERENT
• Phenotype- the way an
organism looks and
behaves as a result of its
genotype
DO NOW
Incomplete dominance
• When the offspring of two homozygous
parents show an intermediate phenotype
– Such as flower color in some plants, coat of some
horse breeds
Chesnut horse
Cremello horse
Palomino horse
Multiple Alleles
• Many traits are
controlled by more than
one allele
• Traits controlled by
multiple alleles produce
more than 3
phenotypes of that trait
– Ex: blood type in
humans
Blood Type
• Alleles are A, B, and O
• O is recessive to both A and B
• If a person inherits both A and B, both are expressed, creating
genotype/phenotype AB
• Genotypes AA and AO are phenotype A
• Genotypes BB and BO are phenotype B
• Genotype OO are phenotype O
Polygenic Inheritance
• Occurs when a group of gene pairs act
together to produce a trait
• The effects of many alleles produce a wide
variety of phenotypes
– Ex: height, eye and skin color
Environmental Impact
• Environment plays a role in how genes are
expressed
– Ex: some people have genes that make them at
risk for developing skin cancer, but if they limit
their exposure to the sun, they may never get
cancer
Mutations
• Genes that are altered or copied incorrectly
– Can be harmful, beneficial, or have no effect
– Can be caused by x-rays or radioactive substances
Bruce Banner was exposed to Gamma Radiation, turning him into the Hulk.
Chromosome Disorders
• Mistakes in meiosis can result in new
organism with more or fewer chromosomes
than normal
– Usually fatal to unborn fetus, but not always
– Ex: Down Syndrome
Recessive Genetic Disorders
• Some recessive genes are result of a mutation
• These disorders occur when both parents
have a recessive allele responsible
– Because parents heterozygous, they don’t show
symptoms
• Ex: cystic fibrosis
Cystic Fibrosis
• Most common genetic disorder leading to death
among Caucasian Americans
• People with disease produce thick mucous instead of
thin fluid which normally lines lungs
• The mucus builds up, making it hard to breathe, and
results in bacterial infections and prevents flow of
substances necessary for digesting food
Sex Determination
• Chromosomes that determine the sex of an
organism are XX in females and XY in males
• Females produce eggs with X chromosome
only and males produce sperm with X or Y.
Sex Linked Disorders
• Sex-linked gene- an
allele inherited on a sex
chromosome
– Ex: color blindness
trait for color blindness
recessive on X
chromosome. Because
men only have one X
chromosome, a male
with this allele is color
blind.
Pedigree
• A visual tool for following a trait through
generations of a family
Genetic Engineering
• When scientists experiment with biological
and chemical methods to change the
arrangement of DNA that makes up a gene
– Can be done to find new ways to improve crop
production and quality, including the development
of plants that are resistant to disease
Methods of Genetic Engineering
• Recombinant DNA- made by inserting a useful
segment of DNA from one organism into a
bacterium
– ex: large quantities of human insulin are made by
genetically engineered organisms
• Gene therapy- a normal allele is placed in a virus.
The virus then delivers the normal allele when it
infects target, and the normal allele replaces
defective one.
– Used to test ways of controlling cystic fibrosis and
cancer
Genetically Engineered Plants
• In the past,
improvements to plants
were result of selecting
plants with most
desirable traits and
breeding them, or
selective breeding.
• NOW, we can find the
genes that produce
desirable trait in one
plant and then insert
those genes into another
plant
Genetically Engineering Plants
Genetically Modified Organism (GMO)
Benefits
Risks
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• Modified plants or animals may
have genetic changes that are
unexpected and harmful.
• Modified organisms may
interbreed with natural
organisms and out-compete
them, leading to extinction of
the original organism or to
other unpredictable
environmental effects.
• Plants may be less resistant to
some pests and more
susceptible to others.
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More nutritious food
Tastier food
Disease- and drought-resistant plants
that require fewer environmental
resources (water, fertilizer, etc.)
Decreased use of pesticides
Increased supply of food with
reduced cost and longer shelf life
Faster growing plants and animals
Food with more desirable traits, such
as potatoes that absorb less fat when
fried
Medicinal foods that could be used as
vaccines or other medications