Transcript Mendel - Powerpoint

Mendel
THE FATHER OF THE GENETICS
Do Now
Look at your parents. What color hair do they have? What
color eyes do they have? What shape of ears do they have?
Now look at you. Which “traits” did you get from each of
your parents? Which traits did your brothers or sisters get?
Why don’t you look EXACTLY like one of you parents?
Next….
Taste Lab!!!!
Vocabulary
◦Heredity – passing of traits from one parent to the
next
◦Genetics – the study of how traits are passed from
parents to offspring
◦Dominant trait – a genetic factor that blocks the
appearance of another trait
◦Recessive trait – A genetic factor that is blocked by
the presence of a dominant trait.
Vocabulary Cont.
◦Gene – a section on a chromosome that has
genetic information
◦Allele – the different forms of a gene
◦Phenotype – how a trait appears to the
observer
◦Genotype – the two alleles that control the
phenotype of a trait
Mendel, the father of genetics
◦ Born Johann Gregor Mendel, in
what is now the Czech Republic.
◦ Was a poor farmer, but an awesome
students
◦ His parents spent all of their money
on his education, but when dad got
injured, Mendel had to find other
ways to get his education
◦ Became a monk (out of necessity)
and went to school for free.
What is up with Mendel?
◦ We now credit this monk as the
father of Modern genetics
◦ You’all, as sixth graders, know more
about modern genetics than he did
when he finished his work.
◦ You all know that there’s DNA, and
our traits reside on that DNA
◦ You also have seen how cells divide,
and he didn’t know things like that.
Well, what did he discover?
◦ Mendel used the humble pea plant to help him discover and write
his three major laws
◦ Law of segregation – Each organism has two copies of one allele,
and that they pass one copy randomly to their offspring.
◦ Law of independent assortment – Separate genes of separate traits
are passed down independently to the next generation.
◦ Law of Dominance – That recessive alleles will always be masked
by dominant alleles.
Whoa Whoa Whoa, What does that
mean?
◦ Law of segregation
◦ States that each organism has two
copies of one allele, and that they
pass one copy randomly to their
offspring.
◦ Remember Allele is a trait on a
gene that is expressed
◦ And remember a gene is genetic
information on a chromosome
Think of it like a bracelet
◦ This group of bracelets is all of
the DNA in one of your cells
◦ One of the bracelets is a
chromosome in your cell’s
nucleus
◦ The beads on the bracelet are
the genes in your
chromosomes
◦ The alleles are the code for
what color, material, or size
beads they are.
Law of independent assortment
◦ This states that each gene is passed on
independently of each other
◦ If we look at Mendel’s peas that he worked
with, there are many traits he saw, for
instance
◦ Pea color
◦ Flower color
◦ Pea shape
◦ Pea pod shape
◦ Etc.
◦ Each of these physical traits were passed on
to its offspring without influencing another
trait
He studied these peas for 8+ years!
(Talk about Dead!)
◦ But he got really good at his
observations.
◦ He found that there were even ways
to predict what type of peas he
would have after he crossed
offspring from pure bred parents (he
could predict the ratio of what the
grandkids would look like)
◦ That ratio, for each allele was 3:1, as
shown in the Punnett square to the
right
Third Law
◦ Law of Dominance
◦ A dominant allele always
masks a recessive allele
◦ If a rabbit that’s dominant for
black fur mates with a rabbit
that’s recessive for white fur
what Will the baby rabbit look
like?
◦ The baby will be Black, not gray
One more thing!!!!
◦ We’ll be talking a lot about genotypes and
phenotypes in this unit. You’ll need to know the
difference between them
◦ A genotype is the two alleles that control the
phenotype
◦ The phenotype is what we observe the organism
to look like / sound like / smell like / taste like /
Etc.
Exit Slip!
◦ How many laws did Mendel publish?
◦ If a pea with dominant purple flowers is crossed
with another pea with recessive white flower,
what color will the flower be?
◦ Will the flower color for the above question
affect the shape of the pea seed? What law tells
us this?
◦ What is the difference between phenotype and
genotype?