Transcript DO NOW - Maria Regina School

• The passing of traits from parents to offspring
– Genes on chromosomes control the traits that
show up in organisms
Heredity
• The father of genetics
• First to use
mathematics of
probability to explain
heredity and to trace
one trait for several
generations
Gregor Mendel
• Different forms of a trait
that a gene may have
Alleles
• The study of how traits are inherited is
genetics
• covers up or dominates other allele
Dominant allele
• the trait seems to disappear unless the
organism has TWO copies
Recessive allele
• receive DIFFERENT genetic information for a
trait from each parent
Hybrids
Punnett Square
• the genetic makeup of
an organism
Genotype
– an organism with two alleles for one trait that are the
SAME
Homozygous
– an organism with two
alleles for one trait that
are the DIFFERENT
Heterozygous
• the way an organism looks and behaves as a result
of its genotype
Phenotype
Cross Bb and BB
Cross Bb and BB
B
B
B
b
BB Bb
BB Bb
What Percentage of Offspring are
Homozygous recessive?
BB Bb
Bb bb
25%
If B is allele for pink flowers, and b is
the allele for white, what is the
probability of having offspring that are
pink?
BB Bb
Bb bb
75%
B and b show incomplete dominance.
If B is allele for red flowers, and b is
the allele for white, what is the
probability of having offspring that are
pink?
BB Bb
Bb bb
50%
B and b show codominance. If B is
allele for pink flowers, and b is the
allele for white, what is the probability
of having offspring that are pink?
BB Bb
Bb bb
25%
• 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
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
• 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
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
• 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
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
• 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.
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.
• 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
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
• These disorders occur when both parents
have a recessive allele responsible
– Because parents heterozygous, they don’t show
symptoms
• Ex: cystic fibrosis
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
• 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 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.
• an allele inherited on a sex chromosome
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.
• A visual tool for following a trait through
generations of a family
Pedigree
• A visual tool for following a trait through
generations of a family
• 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
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
• 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
Recombinant DNA
• 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
Gene therapy
• In the past, improvements to plants were result of
selecting plants with most desirable traits and
breeding them
Selective Breeding
Genetically Modified Organism (GMO)
Benefits
Risks
•
•
•
• 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.
•
•
•
•
•
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