Download Mendelian Genetics (powerpoint view)

Genetics: the branch of biology that
studies heredity
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Heredity: Is the passing on of characteristics from
parents to offspring
camel
llama
?
cama
Trait: A characteristic coded for by a gene.
˃ Height (tall or short)
˃ Color (purple or white)
˃ Shape (smooth or wrinkled)
Inherited traits: Characteristics that are inherited or passed
on from parents to offspring
Early principles of inheritance 2.25
Acquired traits: characteristics that you get as you go
through life (not inherited)
Gregor Mendel: the father of genetics.
˃ Mendelian Genetics
˃ He worked with garden pea inheritance in the 1800’s.
˃ His ideas were not accepted widely until the 1900’s
» States that every individual has two alleles of each gene
and when gametes are produced, each gamete receives
one of these alleles
Pollination: (plants)Is the transfer of pollen from anther
(male) to stigma (female)
Gamete: Sex cell (sperm or egg) produced by an organism
˃ The sperm in the pollen grain fertilizes the egg in the female
part of the flower (pistil)
Zygote: A fertilized egg; formed when a sperm unites with
an egg.
Self Pollination: The transfer of pollen from anther to
stigma on the same flower
Cross Pollination: The transfer of pollen from the anther
of one flower to the stigma on a
different flower
Chromosome: Dark rod-shaped bodies (coiled up
chromatin) inside a cell’s nucleus
made of DNA
Autosome: A chromosome that does not code for gender
Sex Chromosome: A chromosome that codes for gender
# of autosomes
# of sex chromosomes
Body cells: 44
Gametes: 22
Body cells: 2 (XX)
Gametes: 1 (X)
Body cells: 44
Gametes: 22
Body cells: 2 (XY)
Gametes: 1 (X or Y)
Gene: A segment of DNA on a chromosome that directs
protein production for a trait
˃ located on the chromosome
˃ exist in alternative forms
Allele: alternate forms of a gene
Genetic work of Mendel 4.31
Dominant allele: a gene that expresses itself in the
presence of a weaker form of the gene
(capital letter- example T = tall)
Recessive allele: a gene that is masked in the presence of
a dominant allele
(lowercase letter –example t = short)
Intro to Genetics and Heredity .52
Phenotype: the way an organism looks & behaves.
Genotype: the alleles (letters) that determine how an
organism looks or behaves.
Are these three tall plants genetically the same?
Height
Homozygous: purebred; having 2 identical alleles
˃ TT – homozygous dominant
˃ tt – homozygous recessive
Homozygous dominant
Homozygous recessive
Heterozygous: hybrid; having 2 different alleles
˃ Tt – heterozygous dominant
Punnett Square: Shorthand
way of finding the expected
proportions of possible
genotypes in the offspring of a
cross.
˃ Devised by Reginald Punnett in
1905
Probability: The chance that an event will occur
˃ Determined by dividing the desired outcomes by the total
number of possible outcomes
˃ Expressed as a fraction or a percent
Two sides
Heads – ½ (50%)
Tails – ½ (50%
Monohybrid: Crosses that involve only 1 trait
Pure (homozygous) parents
gametes
Hybrid (heterozygous) offspring
» P1 = original parents
Your Grandparents
» P1 x P1 = F1 (F = offspring)
Your parents
» F1 x F1 = F2
You
» Cross a heterozygous tall plant with a heterozygous tall parent.
Tt x ____
Tt
____
» (T= tall) (t=short)
» Genotypic ratio: _________
» Phenotypic ratio: _________
TT
tt
» Cross a homozygous tall plant with a short plant. _____
x _____
» (T= tall) (t=short)
» Genotypic ratio: __________
» Phenotypic ratio: __________
Cross a plant that is pure tall with a plant that is heterozygous tall.
TT x _____
Tt
_____
» Genotypic ratio: ___________
» Phenotypic ratio: ___________
» States that the genes for different traits are inherited
independently of each other.
Dihybrid cross: involve two traits
RRYY
rryy
Gamete
RY
Gamete
ry
RrYy
R
r
RY
Y
y
RY
Ry
rY
ry
Ry
rY
ry
HhTt X ______
hhtt
» ______
HT
Ht
hT
ht
HhTt
Hhtt
hhTt
hhtt
ht
HhTt
Hhtt
hhTt
hhtt
ht
HhTt
Hhtt
hhTt
hhtt
ht
HhTt
Hhtt
hhTt
ht
hhtt