graded notes. review meiosis 2 mitosises, chromosomes replicated in interphase 1, homologous pairs,...
TRANSCRIPT
Review Meiosis
2 mitosises, chromosomes replicated in interphase 1, homologous pairs, crossing over, 4 haploid daughter cells
Pea plants(1st Mendel did this: )
True-breeding: if self-pollinate, produce offspring identical to themselves
Cross pollinate: male sex cells in pollen from one plant fertilize egg cells of flower in another plant(Then he tested flowers together w/2 different characteristics; purple/white)
Traits: specific characteristics (seed color, height, texture)
Monohybrid Cross
Mono = one trait (flower color)
Hybrid = Offspring of two different breeding varieties
Mendel reasoned that F1 plants carried two factors for the flower color trait (Purple and White).
“Factors” called genes
Mendel’s crosses:
P: Parental generationF1: Offspring or 1st generationHybrids: Offspring of crosses between parents with different traits
Testing of other traits…one trait disappears in F1, Reappears in F2
Conclusions of Mendel’s crosses:
Genes: Chemical factors that determine traits passes on from one generation to another
Alleles: Different forms of genes for trait
Ex. Plant height has two forms produces tall plants & short ones
Principle of Dominance: states that some alleles are dominant and other are recessive
Dominant: Trait will always show up; Shown with capital letters
Recessive: Trait does not show up; Shown with lower case letters
Homozygous: (TT) organism has 2 identical alleles for particular trait
Heterozygous: (Tt) organism has 2 different alleles for particular trait
Phenotype: physical characteristics you see (yellow, round)
Genotype: genetic makeup (Tt); what we write
What are alleles?
Since one allele is inherited from each parent,two letters are needed to represent the alleles of a gene
Different forms of gene
Where do alleles come from?
One from each parent
GENOTYPE?
Don’t Copy
-two letters that represent the alleles of a geneEX. RR, Rr, rr
Phenotype?
the outward appearance of an organism (what it looks like)
If a farmer has a red flower (RR) give genotype and phenotype
- the genotype is RR- the phenotype is red
Don’t copy
1. A brown dog (bb)
the genotype ________
the phenotype _______
2. A long haired cat (Hh)
the genotype _______
the phenotype _______
(Review)
Mendel learned that the alleles of each individual separate and end up in gametes because of
MEIOSIS!!MEIOSIS!!
Replication of chromosomes
If a male red flower (Rr) and a female pure white (rr) flower from above got their
gametes together (fertilization)
What kind of combinations could be formed?
X
Practice on own paper before showing next slide! Write out male=Rr, female=rr.
Which is dominant, recessive? What are we crossing? (Write Genotypes)
Male red flower (Rr) Female white flower (rr)
Rr
Sperm 1 Sperm 2
rr
Egg 1 Egg 2
Answers? Write out alleles for each gamete of cross.
R r r r
+
+
+
+
=
=
=
=
1 1
1 2
2 1
2 2
Genotype Phenotype
Show possible offspring of crossing different alleles.
R
r
r
R
r
r
r
r
A punnet square is a chart that helps us predict the probability that an offspring with a particular genotype and phenotype will be produced
Punnett Squares show the chances that one male’s
sperm & one female’s eggs can make certain offspring
Create a punnett square using male red (Rr) and female white (rr) flowers.
To Make a punnet square there are a few simple steps to follow:
1) Draw a box and divide it into four parts
4) In the middle boxes place 2 alleles. One letter comes from the left side and one from the top
R
r
r r
Rr
r r
Rr
r r
You have predicted what kind of
offspring these 2 parents could
have!!!
R= Red r= White
Red______% White______%
You now know the possible genotypes for the offspring of these two parents.
• The genotypes of the offspring are:
R
r
r r
Rr Rr
r r r r
2: Rr, 2: rr Red=50% White=50%
2: Red, 2: White
•The phenotypes of the offspring are:
1. A cross between a female with straight hair (SS) and a male with curly hair (ss). Draw out punnett square:
genotypes_____________
phenotypes______________
Straight______% Curly_______%
2. A cross between a black dog (Bb) and a brown dog (bb). Draw out Punnett Square.
genotypes_____________phenotypes_______________Black_______% Brown________%Ratio_____:______