Post on 12-Jan-2016
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CONTENTS
• Vocabulary• Asexual Reproduction• Sexual Reproduction• Mitosis vs. Meiosis• The Gene• Genotypes and Phenotypes• Punnett Square – Predicting Offspring• Practice Problems• Review Quiz
VOCABULARY YOU NEED TO BE ABLE TO SPEAK “GENETICS”
• Asexual reproduction• Sexual reproduction• Mitosis – normal cell division
• Meiosis• Gamete• Fertilization• Pollination• Gene• Trait
• Allele• Dominant• Recessive• Genotype• Phenotype• Homozygous• Heterozygous• Punnett Square
Asexual Reproduction
• The gene is a strand of DNA that makes a particular protein, enzyme, or pigment.
• In asexual reproduction, all of the DNA comes from your 1 parent.
• If an asexually reproducing plant had yellow flowers, what percentage of its offspring will have yellow flowers?
• Answer: 100% of the offspring will have yellow flowers.
Contents
The Gene and Sexual Reproduction
• The gene is a strand of DNA that makes a particular protein, enzyme, or pigment.
• ½ of your DNA comes from the mother’s egg.
• ½ comes from the father’s sperm.
• These half cells are produced by the process of meiosis.
• Each of these ½ cells (egg, sperm or pollen) is called a gamete.
• When the two halves combine (fertilization) you have a complete set of DNA. (½ + ½ = 1)
• Thus you actually have two of each gene. Vocabulary
Plants and Sexual Reproduction• Plants usually reproduce sexually, too.
• The female half of the DNA is found in the egg.
• The male half comes from the pollen.
• Insects or wind carries the pollen from one flower to another. This pollination leads to fertilization of the egg.
• This fertilized egg is called a zygote. The zygote has a complete set of DNA.
VocabularyContents
Mitosis vs. Meiosis
• Go to the following PBS website listed below. Either run the flash animation, or use the non-Flash version.
• Answer: how is meiosis different from mitosis?
• Link: PBS Meiosis/Mitosis Site
Mitosis vs. Meiosis
• How is meiosis different from mitosis?
• Answer: In the beginning, they are the same, one cell dividing into two complete cells. In meiosis the two cells then each divide into 2 half cells.
• If you missed this, go back (hit “P”), and run the animation again.
Comparison of meiosis and mitosis
Normal Cell Division
All the DNA is found in each cell.
½ of the parent DNA is found in gamete.
Makes eggs, sperm, pollenMakes 2 copies of any cell
Produces two cells Produces four gametes
46 chromosomes
23 pairs
23 chromosomes
1 from each pair
Mitosis Meiosis
Makes gametes
Let’s See if We’ve Got it All Straight.• Question: What is the process that produces normal cells?
• Answer: Mitosis
• Question: What is the process that produces eggs, sperm, and pollen?
• Answer: Meiosis
• Question: What is a gamete?
• Answer: a sex cell: egg, sperm, or pollen
• Question: How much DNA does a pollen or egg have?
• Answer: ½ of the normal DNA
• Question: How much DNA does a zygote have?
• Answer: full amount of DNA
The Gene
• Let’s see how genes work.
• Let’s look at human eye color.
• The gene is represented by the letter B.
• There are 2 alleles for this gene; that means that there are 2 ways that eye color can be.
• Eye color can be brown; we show this gene with a B.
• Eye color can also be blue; we show this gene with a b.
• Remember: You get a gene from each parent; so you have 2.
VocabularyContents
Which Gene Does Your Cell Listen to?
• If you have 2 brown genes (BB), your eyes are obviously brown.
• If you have 2 blue genes (bb), your eyes are obviously blue.
• But what happens if you have one of each gene?
• The dominant gene wins out.
• Brown (B) is the dominant gene; that’s why it is represented with a capital letter.
• Thus a person with Bb genes has brown eyes.
• The blue gene (b) is recessive; that means it is hidden or masked by the dominant gene, BUT it can be passed on to the offspring.
VocabularyContents
Genotypes and Phenotypes
• Let’s show this in a chart.
• Trait: Eye color
• Alleles: B and b
Genotype(the genes)
Phenotype(what it looks like)
BB Brown
bb Blue
Bb Brown
VocabularyContents
Genotypes and Phenotypes• Let’s look at another trait.
• Trait: Height of a pea plant
• Alleles: T and t
• T – gene for tallness t – gene for short plant
Genotype(the genes)
Phenotype(what it looks like)
TT Tall plant
tt Short plant
Tt Tall plant
Let’s Review
• Question: What is the trait?
• Answer: height of pea plant
• Question: What are the alleles for height?
• Answer: T and t
• Question: What is the dominant allele?
• Answer: T
TT Tall plant
tt Short plant
Tt Tall plant
Let’s Review
• Question: What is genotype for a short plant?
• Answer: tt
• Question: What is the phenotype for TT?
• Answer: tall
• Question: What is the phenotype for Tt?
• Answer: tall since T is dominant
TT Tall plant
tt Short plant
Tt ???? plant
Contents
Genotype and Phenotype Practice
Genotype
Phenotype
Gg
gg
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Let’s do some practice using the 4 pairs of pea plant genes shown at the right. For each genotype listed, give the phenotype (what it looks like).
green leaves
yellow leaves
Genotype and Phenotype Practice
Genotype Phenotype
Pp
rr
Rr
TtGg
Pprr
TTggppRr
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
purple flowers
wrinkled peas
round peas
tall plants with green leaves
purple flowers and wrinkled peas
tall plants, yellow peas, white flowers, and round peas
Contents
Homozygous and Heterozygous
• Let’s add 2 more words to the mix.
• Homozygous means both genes are the same.
• Heterozygous means both genes are different,
• “Homo” = the same “Hetero” = different
• “zygous” refers to the zygote, the first cell formed from the fertilization of the egg by the sperm.
• Another word for a heterozygous (Tt) is hybrid, one of each gene).
TT (homozygous) Tall plant
Tt (homozygous) Short plant
Tt (heterozygous) Tall plant
Vocabulary
Contents
Putting it All Together
• What is the homozygous genotype for a tall plant?
• Answer: TT
• What is the heterozygous genotype for a tall individual?
• Answer: Tt
• What is the heterozygous genotype for a short individual?
• Answer: impossible; Tt is can’t be short.
TT Tall plant
tt Short plant
Tt Tall plant
Monohybrid inheritanceLet the allele for round seeds be: R (dominant allele)Let the allele for wrinkled seeds be: r (recessive
allele)
Parents phenotype round seeds x round seedsgenotype RR RR
Gametes (pollen, eggs)
OffspringGametes
Gametes
R R R R
We call this a Punnett Square.
We’ll use this to show the 4 ways that the gametes from the 2 parents can combine.
Monohybrid inheritance• Let’s watch this in action.• With these gametes, there are 4 possibilities;
that’s why there are 4 boxes in the Punnett Square.
Gametes
Gametes
R
R
R R
Possibility # 1
Monohybrid inheritance• Let’s watch this in action.• With these gametes, there are 4 possibilities;
that’s why there are 4 boxes in the Punnett Square.
Gametes
Gametes
R
R
R R
Possibility # 2
Monohybrid inheritance• Let’s watch this in action.• With these gametes, there are 4 possibilities;
that’s why there are 4 boxes in the Punnett Square.
Gametes
Gametes
R
R
R R
Possibility # 3
Monohybrid inheritance• Let’s watch this in action.• With these gametes, there are 4 possibilities;
that’s why there are 4 boxes in the Punnett Square.
Gametes
Gametes
R
R
R R
Possibility # 4
Monohybrid inheritanceLet the allele for round seeds be: R (dominant allele)Let the allele for wrinkled seeds be: r (recessive
allele)
Parents phenotype round seeds x round seedsgenotype RR RR
Offspring
Offspring phenotypes 100% plants producing round seeds
Offspring genotypes 100% heterozygotes RR
Gametes
Gametes R R
R RR RR
R RR RRAll possibilities are the same: RR.
Monohybrid inheritance – Part 2
Let the allele for round seeds be: R (dominant allele)Let the allele for wrinkled seeds be: r (recessive
allele)
Parents phenotype wrinkled seeds x wrinkled seedsgenotype rr rr
Gametes (eggs, pollen)
Offspring
Gametes
Gametes
r r r r
Offspring phenotypes 100% plants producing wrinkled seeds
Offspring genotypes 100% heterozygotes rr
Gametes
Gametes r r
r
r
Gametes
Gametes r r
r rr rr
r rr rr
Monohybrid inheritance – Part 3
Let the allele for round seeds be: R (dominant allele)Let the allele for wrinkled seeds be: r (recessive allele)
Parents phenotype round seeds x wrinkled seedsgenotype RR rr
Gametes
OffspringGametes
Gametes
R R r r
Offspring phenotypes 100% plants producing round seeds
Offspring genotypes 100% heterozygotes Rr
Gametes
Gametes r r
R
R
Gametes
Gametes r r
R Rr Rr
R Rr Rr
Heterozygous Cross
Let the allele for round seeds be: R (dominant allele)Let the allele for wrinkled seeds be: r (recessive allele)
Parents phenotype round seeds x round seedsgenotype Rr Rr
Gametes
Offspring
Gametes
Gametes
R r R r
Offspring phenotypes 75% plants producing round seeds
25% plants producing wrinkled seeds
Offspring genotypes 50% Rr 25% RR 25% rr
Gametes
Gametes R r
R
r
Gametes
Gametes R r
R RR Rr
r Rr rr
Contents
Prediction vs. Actual
Predicted Offspring phenotypes 75% plants producing round seeds
25% plants producing wrinkled seeds
Ratio 3:1 Round seeds: wrinkled seeds
• This is what we predict, just like we predict that 1 out of 2 coin flips will be heads.
• Actual results can be different.
• If we bred the plants above many times, we would at least get close to a 3:1 ratio.
Gametes
Gametes R r
R RR Rr
r Rr rr
Contents
Prediction vs. Actual
Contents
• To see how predicted can vary from what actual happens. Let’s look at coin flips.• Because there is a 50:50 chance of heads turning up, ½ or 50% of coin flips will be heads.• This obviously doesn’t happen, but if you flip the coin enough, you will approximate 50%.• Go to the website below, and flip coins different numbers of time. Notice that when you flip 10,000 times, you will always get close to 50%.• Return here when you’re done.
Go to Coin Toss Probability
How can you tell if a parent is RR or Rr?To test whether a plant producing round seeds is homozygous RR or heterozygous Rr it can be crossed with a homozygous rr plant
If plant is homozygous dominant RR
Parents phenotype round x wrinkledgenotype RR rrgametes
Offspring
If plant is heterozygous Rr Parents phenotype round x wrinkledgenotype Rr rrgametes
OffspringR R r r
R r r r
gametesgametes R R
r Rr Rrr Rr Rr
gametesgametes R r
r Rr rrr Rr rr
Offspring
phenotype 100% round
Genotype 100% Rr
Offspring
phenotype 50% round/50% wrinkled
genotype 50% Rr 50% rr
Let’s Try a Couple Problems!
Gametes
Gametes g g
Gg
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Two plants are cross pollinated: Gg and gg. What will the resulting offspring look like? Work out the problem using a Punnett Square like the one below on scrap paper.
1. What percentage of the plants will be yellow?
2. What is the ratio of green to yellow plants?
Let’s Try a Couple Problems!
Gametes
Gametes g g
G Gg Gg
g gg gg
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Two plants are cross pollinated: Gg and gg. What will the resulting offspring look like? Work out the problem using a Punnett Square like the one below on scrap paper.
1. What percentage of the plants will be yellow? 50%
2. What is the ratio of green to yellow plants?1:1 ratio of green: yellow
Practice Problem #2
Gametes
Gametes
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Two plants are cross pollinated: Gg and Gg. What will the resulting offspring look like? Work out the problem using a Punnett Square like the one below on scrap paper.
1. What percentage of the plants will be green?
2. What is the ratio of green to yellow plants?
Practice Problem #2
Gametes
Gametes G g
G GG Gg
g Gg gg
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Two plants are cross pollinated: Gg and Gg. What will the resulting offspring look like? Work out the problem using a Punnett Square like the one below on scrap paper.
1. What percentage of the plants will be green? 75%
2. What is the ratio of green to yellow plants?3:1 ratio of green: yellow
Practice Problem #3
Gametes
Gametes
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Two plants are cross pollinated: GG and gg. What will the resulting offspring look like? Work out the problem using a Punnett Square like the one below on scrap paper.
1. What percentage of the plants will be yellow?
Practice Problem #3
Gametes
Gametes G Gg Gg Gg
g Gg Gg
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Two plants are cross pollinated: GG and gg. What will the resulting offspring look like? Work out the problem using a Punnett Square like the one below on scrap paper.
1. What percentage of the plants will be yellow? 0%
Practice Problem #4
Gametes
Gametes
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Two plants are cross pollinated: Pp and Pp. What will the resulting offspring look like? Work out the problem using a Punnett Square like the one below on scrap paper.
1. What percentage of the plants will be white?
2. What is the ratio of purple to white flowers?
Practice Problem #4
Gametes
Gametes P p
P PP Pp
p Pp pp
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Two plants are cross pollinated: Pp and Pp. What will the resulting offspring look like? Work out the problem using a Punnett Square like the one below on scrap paper.
1. What percentage of the plants will be white? 25%
2. What is the ratio of purple to white flowers?3:1 ratio of purple: white Contents
Review Questions
• Number a ¼ sheet of paper from 1 to 15.
• Answer the questions with no assistance.
• Score your paper with the key; consider 11 or more correct as OK.
• Go back into the PowerPoint to correct your errors.
Review Questions
1. What process produces the gametes?
A. fertilizationB. mitosisC. conjugationD. meiosis
Review Questions
2. In asexual reproduction
A. Gametes are produced.B. Fertilization occurs.C. An identical cell is produced.D. A cell with ½ of the DNA is
produced.
Review Questions
3. In sexual reproduction, meiosis produces
A. A zygote.B. A cell with ½ of the DNA C. A cell with double the DNAD. A cell with the same DNA as the
parent’s cell.
Review Questions
4. A plant with Tt genes reproduces asexually. What will its offspring look like?
A. None will be tall.B. 50% will be tall. C. 75% will be tall.D. 100% will be tall.
Review Questions
5. What is the genotype of a homozygous tall plant?
A. TTB. TtC. ttD. None of the above
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Review Questions
6. What is the phenotype of a Gg plant?
A. Green leavesB. Yellow leavesC. Green and yellow leavesD. It depends on who gave
the G gene.
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Review Questions
7. Which of the below could be the genotype for a plant with purple flowers?
A.PPB.Pp
C. Either PP or Pp
D. Neither PP or Pp
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Review Questions
8. Which of the below could be the genotype for a short plant with purple flowers?
A.TtPPB. ttPpC. TTppD. Ttpp
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Review Questions
9. A cutting is taken from a pea plant. Thus the plant reproduces asexually. The parent has TtGg genes. What percentage of the offspring will be tall with yellow leaves?
A. 100%B. 50%C. 25%D. 0%
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Review Questions
10. If a homozygous tall and heterozygous tall plant are cross pollinated, what percentage of the offspring will be short?
A. 0%B. 25%C. 50%D. 75%
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Review Questions
11. What will be the ratio of round peas to wrinkled peas if a Rr plant is bred with a rr plant?
A. 4:1B. 3:1C. 2:1D. 1:1
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Review Questions
12. Predict the result of breeding: Gg and Gg
A. 100% will be green.B. 25% will be yellow.C. 50% will be green.D. None will be yellow.
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Review Questions13. If you breed a Rr plant with a
RR plant,
A. You will get all homozygous offspring.
B. You will get no wrinkled plants since round is dominant.
C. 75% of the offspring will be round since wrinkled is recessive.
D. You will get all heterozygous offspring.
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Review Questions14. Which of the below gene
set represents a gamete?
A. TtGgB. TtC. TTD. T
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas
Review Questions15. Challenge Question: How
many tall and green plants will result from breeding Ttgg with TTgg?
A. 100%B. 50%C. NoneD. Depends on other
variables
T = tall
t = short
G = green leaves
g = yellow leaves
P = purple flowers
p = white flowers
R = round peas
r = wrinkled peas