why is everyone so different? why do some people look the same, like family members?
TRANSCRIPT
Why is everyone so different?
Why do some people look the same, like family members?
Even in animals?
Why do some Larkeys have red or gray eyes?
Why do some Larkeys have long or short legs?
GREGOR MENDELGREGOR MENDEL
o First known geneticist and “father father of genetics”
o Was an Austrian monk and was born in 18221822
o Was a gardner and a beekeeper as a young man
The Pea StudiesThe Pea Studies
o Did most of his genetic studies on peapea plants
o He made careful observations, and strictly adhered to the scientific scientific methodmethod
o He performed cross-pollination by becoming the pollinatorpollinator himself, and controlling which plants mixed.
o Studied 29,000 pea plants (That’s some dedication)
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.
HIS WORKHIS WORK
• At first, his findings were rejected….
• Until 40 years later it was rediscovered
• He was correct with his discovery of traits being passed on by the parents to the offspring
Heredity & Genetics
o The passing of traits from parent parent to offspringto offspring
o Traits are controlled by genes genes, so therefore, GENETICS is the study of how traits are inheritedinherited through the action of alleles
ALLELES
o Are ONE FORM FORM of a gene (there can be more than one form)
o Sex cells have one one form of a gene on their chromosomes- (structure that transfers heredity information)
ALLELES
o Sex cells have one one form of a gene on their Body cells have twotwo 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 recessiverecessive trait is expressed.
DOMINANT 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 alleles present.
o 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.
Her Mom has blue eyes (bb)
Her Dad has brown eyes (BB or Bb)
Miss Hemphill has blue eyes
(bb)
Therefore, her 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.
Genes by Brainpop
Why is it that if a couple has 2 Why is it that if a couple has 2 children, they don’t always children, they don’t always have one boy and one girl?have one boy and one girl?
2 is a really small trial #…so won’t always “see” the ratio!
…we will investigate this more later on!
PROBABILITY
o Helps predict the chance chance that something will happen
o Example: 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
o Used to help predict Mendelian genetics
o In Punnett squares, dominant traits are represented with a CAPITAL letter, and recessive traits represented by a LOWER CASE letter. Take for instance, eye color. Choose to represent eye color with the letter b. Big B or “B” for dominant and little b or “b” for recessive.
o Each organism is represented by TWO letters, one for each allele.
o “Purebred” species have two alleles of the same trait, and therefore would be represented by two of the same letters. This is called homozygoushomozygous. For instance: BB or bb.
o Species with two different alleles or two different forms of the gene would have two different letters and by called heterozygousheterozygous. For instance: Bb
o The alleles present in the organism are referred to as its genotypegenotype, the genetic makeup. For instance, BB, Bb, or bb.
o The alleles present in the organism are referred to as its genotypegenotype, the genetic makeup.
o For instance, BB, Bb, or bb.
o The PHYSICAL trait that shows, regardless of genotype is called a PHENOTYPEPHENOTYPE.
o For instance, Blue or Brown Eyes; Red hair or Blonde hair;
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.
4) See Below:
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 Eyes
BBBB BbBb
BbBb bbbb
B b
B
b
So you would predict:
¼1/41/4 offspring to be BB, or Brown Eyes
2/4 or 1/2½1/2½ to be Bb, or BrownBrown Eyes
and ¼1/41/4 to be bb or BlueBlue eyes
So, if Miss Hemphill married and had children with her boyfriend …what color eyes would they have?
Blue eyes (bb)
Blue eyes (bb)
All of thier kids would have blue eyes!
bb bb
bb bb
b b
b
b
