tuesday, april 24, 2012
DESCRIPTION
Tuesday, April 24, 2012. Punnett Square checkup (end of) Block Day. MendelSim Data Review. Goes in entry from Friday- Entry 39: MendelSim Simulation - 4/20/12. Data Table 1: Pure Red X Pure Blue. Red. Blue. 0. 50. Data Table 2: Cross of Two Red Offspring. This one varied. 38. 12. - PowerPoint PPT PresentationTRANSCRIPT
Parent 1 Parent 2 Offspring (after 50 crosses)
Red Blue
Data Table 1: Pure Red X Pure Blue
Parent 1 Parent 2 Offspring (after 50 crosses)
Red Blue
Data Table 2: Cross of Two Red Offspring
Data Table 3: Cross of Two Blue OffspringParent 1 Parent 2 Offspring (after 50 crosses)
Red Blue
Red Blue
Red Red
Blue Blue
50 0
38 12
This one varied
0 50
PARENT 2BLUE
X 50 (ALL) RED OFFSPRING
=
PARENT 1RED
PARENT 2RED
X =
38 RED 12 BLUE
X = 50 (ALL) BLUEOFFSPRING
PARENT 1RED
PARENT 1BLUE
PARENT 1BLUE
TAPE in these questions and answer them in your logbook
1. What is the trait we observed?2. What are the results of crossing the red
flowers with the blue flowers?3. Based on the results, what do we know about
the flower color gene?4. What are the results for the second crossing
—red crossed with red?5. The flowers in the second crossing look red—
but what do we know about their genetics?6. What happened to the blue trait and how did
it show up again in the third generation?
Chromosome structure - genes
Human chromosome # 7
• Contains about 1,800 genes
• Contains over 150 million nucleotides
Link to view genes and DNA sequence
• Parts of chromosomes that code for proteins are called genes
• Genes, and specifically the proteins made from them, help determine your characteristics RGene for
RED flowers
How does your DNA determine your traits?
DNA mRNA protein Observed trait
transcr
iption
transla
tion
Example1: A person has DNA that has instructions to make LACTASE (a protein) which allows them to digest milk
Example 2: The Labrador Retriever has DNA that has the instructions to make TRP-1 which converts brown pigment to black—so they have black fur.
Trait – a characteristic of an organism– Example: “flower color”
Gene – part of a chromosome that helps determine a specific trait– Example: “flower color gene”
Allele – a form of a gene – Example:• One allele is the “blue” form of the gene• One allele is the “red” form of the gene
• Humans = 23 chromosome pairs, or 46 total. We have about 24,000 genes.
Some other examples: (do not need to memorize)
• Pea flower = 7 chromosome pairs (14 total)• Fruit fly = 4 chromosome pairs (8 total) 13,601
genes identified so far!• Potato = 24 pairs (total 48)• Horse = 32 pairs (total 64)
How many chromosomes?
Chromosomes come in pairs (one from Mom and one from Dad)
• This pair of chromosomes is called a “homologous pair” because they have the same genes on them -
Flower chromosome 3
(from computer simulation)From Dad
From Mom
flower color gene
IMPORTANT: homologous pairs are NOT IDENTICAL, but they have the same genes, – Alleles can be different
flower color gene
From Dad
From Mom
“Blue” alleleof flower colorgene
“Red” alleleof flower colorgene
The combination of alleles determines the observed characteristics
Chromosomecombination
Allelecombination
Observedcharacteristic
REDallele
RED allele
REDallele
BLUE allele
BLUEallele
BLUE allele
red, red red, blue(or blue, red)
blue, blue
RED RED BLUE
Dominant and recessive allelesOnly one red allele is needed for the flower to look
red.• Scientists call this a DOMINANT allele
Two blue alleles are needed for the flower to look blue.
• Scientists call this a RECESSIVE allele
Symbols used for alleles• The traditional symbols used for alleles are
big and small letters• The letter chosen usually refers to the
dominant alleleExample: R = Red allele
r = Blue allele
The combination of alleles determines the observed characteristics
Chromosomecombination
Allelecombination
Observedcharacteristic
REDallele
RED allele
REDallele
BLUE allele
BLUEallele
BLUE allele
red, red red, blue(or blue, red)
blue, blue
RED RED BLUE
The combination of alleles determines the observed characteristics
RChromosomecombination
Allelecombination
Observedcharacteristic
RR Rr rr
RED RED BLUE
R R r r r
Genotype – the two alleles that an organism has for a trait (genetics)
Phenotype – the observed (or measurable) trait of an organism that relates to one gene (physical)
Example: Trait = “flower color”Genotype = “RR” or “Rr” or “rr”Phenotype = “RED” or “BLUE”
The combination of alleles determines the observed characteristics
RChromosomecombination
GENOTYPE
PHENOTYPE
RR Rr rr
RED RED BLUE
R R r r r
Representing genotype and phenotype based on DNA/genes
DNA mRNA protein Observed trait
transcr
iption
transla
tion
GENOTYPE for flower type 1:
Allele of chromosome 2A= Y1 (functional enzyme)
PHENOTYPEof flower type 1:
nucleus
Y1 Y1
Draw the enzymes and pigment molecules present in the cells of each type of flower below.
Yes or no, is any functional enzyme Y in the cell?
Allele of chromosome 2B= Y1 (functional enzyme)
2A
2B
1B
1A
YES
RED
RR
Draw the enzymes and pigment molecules present in the cells of each type of flower below.
GENOTYPE for flower type 2:Allele of chromosome 2A= Y1 (functional enzyme)
PHENOTYPEof flower type 2:
nucleus
Y1
Y2
Yes or no, is any functional enzyme Y in the cell?
Allele of chromosome 2B= Y2 (non-functional enzyme)
2A
2B
1B1A
GENOTYPE for flower type 3:Allele of chromosome 2A= Y2 (non-functional enzyme) PHENOTYPE
of flower type 3:
nucleus
Y2
Y2
Yes or no, is any functional enzyme Y in the cell?
Allele of chromosome 2B= Y2 (non-functional enzyme)
2A
2B1B
1A
YES
RED
NO
BLUE
Rr
rr
• ATB: NEW LOGBOOK ENTRY “HEREDITY AND GENETICS 2”• PLANNER: SHORT CHECKUP ON
PUNNETT SQUARES/HEREDITY AT END OF BLOCK DAY• MAKE UP ANY MISSED WORK!
Homozygous – the two alleles are the same • RR and rr are homozygous genotypes
Heterozygous – the two alleles are different• Rr is a heterozygous genotype
Draw the enzymes and pigment molecules present in the cells of each type of flower below.
GENOTYPE for flower type 2:
Allele of chromosome 2A= Y1 (functional enzyme)
PHENOTYPEof flower type 2:
nucleus
Y1
Y2
Yes or no, is any functional enzyme Y in the cell?
Allele of chromosome 2B= Y2 (non-functional enzyme) 2A 2B
1B
1A
YES RED
WHAT DOES Rr ACTUALLY MEAN?Rr
Possible combinations of inherited chromosomes/genes
R rR r
Dad Mom
R
r
Parents
PossibleOffspring r
r
R
R
r
R
X
Order doesn’t matter, these two are the same (Rr)
What are all possible genotypes produced from the parents?
RR, Rr, rr
1 out of 4 possibilities is rr = What is probability of Rr?• How many out of 4 are red? • What is the probability of red? • What is the probability of blue?
R r
R RR Rr
r Rr rrGenotypic ratio = 1RR: 2Rr:1rr
25 %50 %
3/475 %
25 %
R= red flower alleler= blue flower allele
Phenotypic ratio = 3 Red:1 blue
Your turn:• What are all possible genotypes and phenotypes
produced by crossing Rr with rr?
Complete the Punnett Square
r r
R Rr Rr
r rr rr