heredity : the passing of traits from parent to offspring
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Heredity : the passing of traits from parent to offspring Traits are controlled by genes , SO what is GENETICS ? Genetics: The study of how traits are inherited . GREGOR MENDEL. First known geneticist and “ father of genetics” Was an Austrian monk and was born in 1822 - PowerPoint PPT PresentationTRANSCRIPT
• HeredityHeredity : the passing of traits from
parent to offspringparent to offspring
Traits are controlled by genes genes, SO what is GENETICS?
Genetics: The study of how
traits are inheritedinherited.
GREGOR MENDELGREGOR MENDELo First known geneticist and
“father father of genetics”
o Was an Austrian monk and was born in 18221822
o Did most of his genetic studies on peapea plants
o He performed cross-pollinationo He became the pollinatorpollinator himselfo He controlled which plants mixed.
o Some traits Mendel worked with were shapeshape of pea pea and it’s pod, colorcolor and shape of seedsseeds, plant heightheight, flower positionposition and flower color.
WHAT ARE ALLELES?WHAT ARE ALLELES?o Are ONE FORM FORM of a gene (there can be
more than one form)
o Body cells have two two forms or ALLELES for a single gene (you got one from Mom and one from Dad)
o One may be dominantdominant over another. If this happens, the dominant gene is the one expressed. If not, the recessive trait is expressed.
DOMINANT AND RECESSIVEDOMINANT AND RECESSIVE
o A Dominant trait: will always be expressed and will “maskmask”
a recessive trait
o A recessive trait can only be expressed if there are no dominant dominant alleles present.
ExampleExample: Eyecolor—Brown color is dominantdominant
and blue is recessive. A person can have a brown allele and
a blue allele but still have brownbrown eyes because the brown allele is dominant and “hideshides” the blue allele.
Example:RR= dominant rr = recessive
• Generally, dominant alleles are represented with a capitalcapital letter, and recessive alleles are represented with a lower caselower case letter.
Each organism is represented
by TWOTWO letters, one
for each allele.
o “Purebred” species have two alleles of the same same traito Represented by two of the same letters. This
is called homozygoushomozygous. For instance: BB For instance: BB or bb.or bb.
o Species with two different alleles or two different forms of the gene would be “hybrid”o Represented by two different “lettersletters” and
by called “heterozygous”. For instance: BbFor instance: Bb
o The alleles present in the organism are referred to as its genotypegenotype. For instance, BB, Bb, or bb.BB, Bb, or bb.
o The PHYSICALPHYSICAL trait that shows, regardless of genotype is called a PHENOTYPEPHENOTYPE.
o For instance, BlueBlue or BrownBrown Eyes.
Mom has blue eyes (bb)
Dad has brown eyes (BB or Bb)
Daughter has blue eyes (bb)
Therefore, Dad must have the Bb genotype, because he must have given her the “b” allele. His “b” allele is masked by his “B”/dominant allele.
Genetics by Brainpop
PROBABILITYPROBABILITYo Helps predict the chance chance that
something will happen
o ExampleExample: the probability of throwing heads or tails on a coin is 50% 50% (1/2 chances)
o Your predictions become more accurateaccurate with the more trials you run!
Using a Punnett Square…Using a Punnett Square…
o Used to help predict Mendelian genetics
Steps for using the Punnett square:
1) One parent’s alleles (genotype) (genotype) go along the top
2) The other parent’s alleles go down the side.
3) You fill in the squares like doing the communicative property of multiplication.
B bB
b
BB
bbBb
Bb
Steps for using the Punnett square:Steps for using the Punnett square:
Let’s say the parents are Bb and Bb (the same
genotype). What would be their phenotype?
Brown EyesBrown EyesB bB
b
So you would predict: ¼ offspring to be BB, or Brown Eyes 2/4 or 1/21/2 to be Bb, or BrownBrown Eyesand ¼ to be bb or BlueBlue eyes
BB
bbBb
Bb
So, if Miss Hemphill had children with her husband to be …what color eyes would they have?
Mr. EllingerBlue eyes
(bb)
Miss HemphillBlue eyes
(bb)
All of their kids would have blue eyes!
bb bbbb bb
b b
b
b
Let’s try some practice Let’s try some practice problems…problems…
Practice Problem #1Practice Problem #1
• Predict the fur color of the offspring of a brown heterozygous hamsters and a white homozygous hamster. Brown is dominant. White is recessive.
• Use any letter you like.
Practice Problem #1Practice Problem #1
Bb bbBb bb
B bbb
Practice Problem #2Practice Problem #2
• Predict the offspring of 2 white homozygous cows. Black is dominant over white.
• Use any letter you like.
Practice Problem #2Practice Problem #2
bb bbbb bb
b bbb
Practice Problem #3Practice Problem #3
• Predict the offspring of 2 Grey Heterozygous rats. Gray is dominant over white, which is recessive.
• Use any letter you like.
Practice Problem #3Practice Problem #3
GG GgGg gg
G gGg
Practice Problem #4Practice Problem #4
• Predict the pea shape of the offspring of one Heterozygous Round Pea plant and one homozygous wrinkled pea plant. Round is dominant over wrinkled.
• Use any letter you like.
Practice Problem #4Practice Problem #4
Rr rrRr rr
R rrr