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Genetics: The Science of Heredity

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Julie Southwood

on 16 December 2013

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Transcript of Genetics: The Science of Heredity

12.4: Chromosomes and Inheritance
12.5: Advances in Genetics
12.3: Patterns of Inheritance
12.2: Probability and Heredity
Genetics: The Science
of Heredity

12.1: What is heredity?
What Did Mendel Observe?
Experimented with pea plants
Father of genetics
Genetics: The study of heredity
Heredity: the passing of physical characteristics from parents to offspring.
Study traits found in pea plants
F1:
P generation
F2:
Purebred: offspring of many generations that have the same form of a trait.
Purebred: offspring of many generations that have the same form of a trait.
First generation
F1 x F1
In all his crosses, the F1 generations had the same trait but in the F2 generation the "lost" trait reappeared in about 1/4 of the plants.
How Do Alleles Affect Inheritance?
Genes: factors that control a trait.
Alleles: the different forms of a gene
An organism's traits are controlled by the alleles it inherits from its parents
Some alleles are dominant, while others are recessive.
Dominant vs. Recessive
One whose trait always shows up
Hidden when paired with a dominant allele. Only shows with another recessive allele.
Shown with a capital letter
Shown with a lowercase letter.
Tall = T
Short = t
Green = G
Yellow = g
Round = R
Wrinkled = r
TT : Purebred
tt : Purebred
Tt : Hybrid
Tt : Hybrid
TT
Tt
Tt
tt
How Is Probability Related to Inheritance?
Probability: how likely it is that an event will occur.
Example: Tossing a coin
Heads:
Tails:
1/2 or 50%
1/2 or 50%
Punnett squares: a chart that shows all the possible ways alleles can be combined.
(parent 2)
(parent 1)
Parent 1: Gg
Parent 2: Gg
G
g
G
g
G
G
G
G
g
g
g
g
Probable offspring:
GG
Gg
gg
1/4
25%
1/2
50%
1/4
25%
Dominant
Recessive
3/4
75%
1/4
25%
What Are Phenotypes and Genotypes?
Phenotype: physical appearance (what you see)
Genotype: genetic makeup (alleles)
Homozygous: two identical alleles for a trait. ex: two dominants (TT) or two recessive (tt).
Heterozygous: Two different alleles for a trait. ex: Tt
How Are Most Traits Inherited?
Most traits are the results of complex patterns of inheritance.
Codominance and Incomplete Dominance
Occurs when one allele is partially dominant
NOT BLENDING!!!!!!
Occurs when both alleles for a gene are expressed equally
Multiple Alleles and Polygenic Inheritance
Three or more alleles determine the trait.
Occurs when more then one gene affects a trait.
Alleles for these genes work together to form a single trait.
How Do Genes and the Environment Interact?
Inherited vs. Acquired Traits
Traits you are born with
EX: Eye color, skin color
Traits that are developed over time.
EX: Skills learned (riding a bike), physical changes (hair dye)
Language
Acquired
Leaf Shape
Inherited
Freckles
Inherited
Hedge Shape
Acquired
Athletics (swimming)
Inherited and Acquired
Genes and the Environment
Environment can influence how genes are expressed.
Some factors can change the genes.
EX: tobacco smoke
Changes in body cells cannot be passed on. Only changes in sex cells (egg and sperm) can be passed on.
Producing Desired Traits
Selective breeding
Process of selecting organisms with desired traits to be parents of the next generations.
Inbreeding
Breeding organisms that are vary similar genetically
Found a lot in breeding animals
Increased chance of inheriting a recessive allele
Increase chance for genetic disorders
Hybridization
Crossing two genetically different organisms
Two different alleles for a trait
Bred to have the best traits from both parents
Producing Desired Traits
Cloning
Organisms that are exactly the same genetically
Dolly
Genetic Engineering
Genes from one organism are transferred into the DNA of another organism.
According to the chromosome theory of inheritance, genes pass from parents to their offspring on chromosomes
Sexual vs. Asexual Reproduction
Sexual:
Two sex cells
Sex cells go through meiosis
Produces variations
Asexual:
One parent cell
Offspring are identical
Ex: sponges, jellyfish
Full transcript