the passing of traits from parents to offspring – genes on chromosomes control the traits that...
TRANSCRIPT
• 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
BB BbBB Bb
B b
B
B
What Percentage of Offspring are Homozygous recessive?
BB BbBb 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 BbBb 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 BbBb 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 BbBb 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• 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
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.