FUNDAMENTALS OF GENETICS
description
Transcript of FUNDAMENTALS OF GENETICS
![Page 1: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/1.jpg)
FUNDAMENTALS OF GENETICSModern Biology
Chapter 9Pages 164 - 182
![Page 2: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/2.jpg)
Objectives:•Describe how Mendel’s results can be explained by the scientific knowledge of genes and chromosomes.•Differentiate between a monohybrid cross and a dihybrid cross.•Predict & perform results of monohybrid and dihybrid crosses
Fundamentals of Genetics
![Page 3: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/3.jpg)
![Page 4: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/4.jpg)
SOOKIE
![Page 5: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/5.jpg)
Do Now• What is the genetic code?• What molecule carries the genetic code?• What is genetics?
![Page 6: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/6.jpg)
K – W - LWhat do you know about inheritance?
What do you want to know about inheritance?
What have you learned about inheritance?
![Page 7: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/7.jpg)
Fundamentals of GeneticsAll of your characteristics or traits are unique to you.Parents may pass many of their own traits to their children, or offspring.For example, the color of your hair, the size of your feet and the shape of your nose are some ofyour traits.
![Page 8: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/8.jpg)
The passing of these traits from parents to offspring is called heredity. The study of heredity is called genetics. Biologists who study heredity are calledGeneticists.
Fundamentals of Genetics
![Page 9: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/9.jpg)
Fundamentals of Genetics
• Look at the photographs to the right.
• What traits have these babies inherited from their parent?
![Page 10: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/10.jpg)
Gregor MendelThe Father of Genetics
•Genetics was founded with the works of an Austrian Monk, scientists and mathematician Gregor Johann Mendel.•He experimented with garden pea plants.
rpee Seeds and Plants Home> Vegetables > Peas > Pea, Easy Peasy
![Page 11: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/11.jpg)
Gregor Mendel•His task of tending the garden gave him time to observe the passing of traits from parentpea plants to their offspring.•He became interested in whycertain patterns oftraits showed upin living things.
![Page 12: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/12.jpg)
• Mendel began his experiments by collecting seeds from his pea plants, carefully recording the traits of each plant.
• Seeds from tall plants usually produced tall plants but sometimes produced short plants.
• Seeds from short plants only produced short plants.
• …but, “WHY?”
![Page 13: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/13.jpg)
He studied 7 different characteristics in his pea plants, each with 2 contrasting traits.–CHARACTERISTIC-a distinguishing quality that an organism exhibits.•Ex: height, hair color, eye color, skin color.–TRAIT- specific hereditary options available for each characteristic.•Ex: tall height/short height, smooth/ blonde hair, brown/blue eyes, Dark/light skin.
Mendel’s Experiments
![Page 14: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/14.jpg)
CHARACTERISTICS
TRAIT
1. Plant Height Tall vs. Short2. Seed Color Yellow vs. Green 3. Seed Shape Round vs. Wrinkled4. Pod Color Green vs. Yellow5. Pod/Flower Location
Axial vs. Terminal
6. Pod Shape Inflated vs. Constricted
7. Flower Color Purple vs. White
![Page 15: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/15.jpg)
• He decided to grow plants that were purebred - having a trait that will always be passed to the next generation
• The term strain denotes all plants that are pure for a trait.
Mendel’s Methods
![Page 16: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/16.jpg)
• He produced 14 strains (one for each of the 14 traits he observed) by allowing the plants to self-pollinate for several generations
• This became his Parent generation or his
“P1 Generation”
Mendel Controlled Pollination
![Page 17: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/17.jpg)
• Pollination-transfer of pollen from anther (male flower part) to stigma (female flower part)
• Self–Pollination – occurs on same plant
• Cross Pollination – occurs between different plants
Mendel Controlled Pollination
![Page 18: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/18.jpg)
•Then, Mendel cross pollinated plants that had contrasting traits to see what the offspring would look like. (P1 X P1- i.e. pure tall x pure short)•Would the offspring (F1 Generation – offspring of P1) be tall, short, or medium ?
Mendel’s Methods
![Page 19: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/19.jpg)
•In his first crosses, Mendel found that only one of the two traits appeared in the offspring plants – (F1 generation).•For example, when he crossbred tall pea plants with short pea plants, the offspring (F1) were always tall.
Mendel’s Results
![Page 20: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/20.jpg)
•After his first crosses, Mendel took those offspring plants (F1) and crossed them.•In these second crosses, both traits showed up again in the F2 generation.(F2 GENERATION-offspring of crosses between the F1 generation).•He observed that ¾ of the plants had the same trait as the F1 generation.
![Page 21: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/21.jpg)
•The same results happened in every experiment. One trait, like being tall, was always there in the first generation (F1).•The other trait, like being short, seemed to go away; only to reappear again in the second generation (F2).
This happened with every set of traits that Mendel studied.
![Page 22: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/22.jpg)
EXAMPLES:Plant
Height Cross
Seed Color Cross
Seed Shape Cross
Parent P1 x P1
Tall x Short
All Tall Plants
Tall x Tall
¾ Tall¼ Short
Yellow x Green
All Yellow Plants
Yellow x Yellow
¾ Yellow¼ Green
Round vs. Wrinkled
All Round Plants
Round X Round
¾ Round¼ Wrinkled
First Generation
F1 x F1
Second Generation
F2
![Page 23: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/23.jpg)
• Mendel hypothesized that something in the pea plants was controlling the characteristics that came through
• He called these controls “factors”
(We now know that these factors are really traits controlled by Genes)
![Page 24: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/24.jpg)
• Because each characteristic had two forms, he said there must be a pair of “factors” controlling each trait.
• Each pair consists of alternate forms (we now call alleles) of the same trait; one from mother and one from father.
![Page 25: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/25.jpg)
MENDEL’S 3 CONCLUSIONS:
Based on his findings, Mendel formulated three laws or principles of heredity:1. Principle of Dominant and Recessiveness2. Principle of Segregation3. Principle of Independent Assortment
![Page 26: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/26.jpg)
Through crossing thousands of pea plants, he was able to conclude that that both of these factors (alleles) together controlled the expression of a trait.Dominant traits were controlled by dominant alleles and recessive traits were controlled byrecessive alleles.
Principle of Dominant & Recessiveness
![Page 27: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/27.jpg)
DOMINANT-can mask or dominate the other ‘factor’ and is displayed most often.
RECESSIVE-the ‘factor’ that can be covered up; is displayed less often.• Ex: the ‘factor’ (allele) for tall is
dominant over the ‘factor’ (allele) for short, so the short allele would be the recessive allele.
Principle of Dominant & Recessiveness
![Page 28: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/28.jpg)
•Letters are used to represent the alleles that carry the trait found on genes
•If the gene that controls the trait is dominant, the letter is written in uppercase.If the gene is recessive, the letter is written in lowercase.
–i.e. T- represents a dominant trait for tallness; t – represents a recessive trait for lack of tallness, or shortness
Principle of Dominant & Recessiveness
![Page 29: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/29.jpg)
•T – dominant allele for tallness•t – recessive allele for lack of tallness or shortness.•W – dominant allele for round or smooth seeds•w – recessive allele for wrinkled seeds•P – dominant for flower color (purple)•p – recessive allele for white flower
![Page 30: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/30.jpg)
GENE- a segment of DNA that codes for a specific characteristic.• Ex: height
ALLELE-the different forms of a gene (Mendel’s “factor”)Ex: allele for brown eyes is B/ allele for
blue eyes is bSO…if BB is a brown eyed person
and bb is a blue eyed person, what color eyes does someone with Bb have?
Vocabulary Review
![Page 31: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/31.jpg)
Principle of Segregation• Each parent has two factors
(copies of each trait) and they segregate, or separate into different sex cells (gametes)
• Each gamete gets only 1 factor (allele)of each trait
![Page 32: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/32.jpg)
![Page 33: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/33.jpg)
Principle of Independent Assortment
• Mendel also crossed plants that differed in 2 characteristics, such as flower height and flower color.
• The data from these crosses showed that dominant traits do not always appear together
ttP?
![Page 34: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/34.jpg)
Principle of Independent Assortment
• The alleles for different genes on different chromosomes are not connected.
• The alleles for different traits are distributed into gametes independently (randomly) from each other.
![Page 35: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/35.jpg)
Principle of Independent Assortment
![Page 36: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/36.jpg)
![Page 37: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/37.jpg)
Gregor Mendel and his pea plants experiments (1857-1865)
![Page 38: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/38.jpg)
Do Now• Who is the father of genetics?• What type of organism did he
work with?• What are dominant and
recessive traits?
![Page 39: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/39.jpg)
Vocabulary Review• Chromosomes – made of DNA• Gene – segment of DNA that
controls a specific hereditary trait.
• Because chromosomes occur in pairs, genes occur in pairs
• Allele - (Mendel’s “factor”) – contrasting form of a gene– Dominant allele – capital letter– Recessive allele – lowercase
letter
![Page 40: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/40.jpg)
AFTER MENDEL• Today, Geneticists rely on
Mendel’s work to predict the likely outcome of genetic crosses.
• Why would geneticists want to predict the probable genetic make up and appearance of offspring resulting from specified crosses?
![Page 41: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/41.jpg)
GENOTYPE & PHENOTYPE• GENOTYPE-the genetic makeup
of an organism (the combination of alleles an organism inherits).– Use 2 letters together to represent
genotype.• PHENOTYPE-the trait displayed
based on the genotype.Ex: BB – Brown eyes– bb – Blue eyes– Bb – Brown eyes
![Page 42: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/42.jpg)
GENETIC CROSSES
![Page 43: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/43.jpg)
b b
Blue alleles
Genotype
Phenotype
![Page 44: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/44.jpg)
•Organisms with different genotypes may have the same phenotype.
•For example, a brown-eyed organism (BB) and a brown eyed organism (Bb) have different genotypes.
•However, they have the same phenotype, which is brown eyes
GENOTYPE & PHENOTYPE
![Page 45: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/45.jpg)
b
Brown AllelesBrown Alleles
One pair of chromosomesfor eye color
One pair of chromosomesfor eye color
BBB
![Page 46: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/46.jpg)
AFTER MENDEL
![Page 47: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/47.jpg)
•HOMOZYGOUS- organism has 2 of the same alleles for a trait.•Homozygous Dominant-has 2 dominant alleles; dominant trait is displayed
–Ex: BB = Brown-eyed organism•Homozygous Recessive-has 2 recessive alleles; recessive trait is displayed
–Ex: bb = blue-eyed•HETEROZYGOUS-organism has 1 dominant and 1 recessive allele; the dominant trait is displayed.
–Ex: Bb = brown eyes
GENOTYPE & PHENOTYPE
![Page 48: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/48.jpg)
b b b B
Blue Allele Brown AlleleBlue alleles
Homozygous – alleles are the same
Heterozygous – alleles are different
![Page 49: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/49.jpg)
Do Now• What are Mendel’s Laws of
Inheritance? • What is an allele? What is
homozygous vs. heterozygous?• What is genotype vs.
phenotype?
![Page 50: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/50.jpg)
Probability• In order to understand genetics
you need to have some basic concepts concerning probability.
• Probability – the likelihood that a specific event will occur
• Can be expressed as a decimal, percentage, ratio or fraction.
P= number of times an event is expected to happen
number of opportunities for an event to happen
![Page 51: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/51.jpg)
ProbabilityIf you flip a coin once, what is the probability that it will land on heads?P(Event)= 1 (Heads)
2 (Heads or Tails)P= 1 2 ; .5; or 50%; 1:2If you flip a coin twice, what is the probability that it will land on heads twice?
P = 1 (Heads) 4 (Heads, Tails; Tails, Heads; Tails, Tails; Heads, Heads)P = ??¼
![Page 52: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/52.jpg)
•Remember, probability is the likelihood that a chance event will occur.•The value of studying genetics is in understanding how we can predict the likelihood of inheriting particular trait.
Predicting the Results of Genetic Crosses
![Page 53: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/53.jpg)
•MONOHYBRID CROSS – a genetic cross between 2 individuals involving 1 pair of contrasting traits.
Predicting the Results of Genetic Crosses
![Page 54: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/54.jpg)
•One of the easiest ways to calculate the mathematical probability of inheriting aspecific trait wasinvented by an early 20th
century English geneticist, Reginald Punnett .
Predicting the Results of Genetic Crosses
![Page 55: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/55.jpg)
Predicting the Results of Genetic Crosses
His technique employs what we now call a Punnett square.
A Punnett square is a chart that shows possible gene combinations of offspring of two parents whose genotypes are known.
![Page 56: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/56.jpg)
HOW TO DRAW A PUNNETT SQUARE
• 1. Write what each allele means.
• 2. Write the genotypes of the parents.
• 3. Draw a grid.• 4. Put the alleles for one parent
along the top; put the alleles for the other parent along the side.
• 5. Fill in the grid.
![Page 57: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/57.jpg)
EXAMPLE 1:HOMOZYGOUS X HOMOZYGOUS
T= tall plant TALL X SHORT t = short plant (TT x tt)
Genotype = 4 TtPhenotype = 4 tall plants
Probability = number of times an event(tall) is expected to happen
number of opportunities (total) for an event to happen
Probability Ratio : 4/4 Probability percent: 100%
TTt
Ttt
Tt
TtT
tTt
![Page 58: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/58.jpg)
EXAMPLE 2:HOMOZYGOUS X HETEROZYGOUS
T= tall plant TALL X SHORT t = short plant (Tt x tt)
Genotype = 2 Tt, 2 ttPhenotype = 2 tall, 2 short
Probability = number of times an event(tall/short) is expected to happen number of opportunities (total) for an event to happen
Probability: 2/4 tall plants; 50% tall plants; 2:4 2/4 short plants; 50% short plants; 2:4
TTt
ttt
Tt
ttTt
tt
![Page 59: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/59.jpg)
EXAMPLE 2:HOMOZYGOUS X HETEROZYGOUS
T= tall plant TALL X TALL t = short plant (TT x Tt)
Genotype = 2 TT, 2 TtPhenotype = 4 Tall
Probability = number of times an event(tall/short) is expected to happen number of opportunities (total) for an event to happen
Probability: 4/4 tall plants; 100% tall plants; 4:4 0% short
TTt
TTt
TTTt
TTTt
![Page 60: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/60.jpg)
EXAMPLE 2:HETEROZYGOUS X HETEROZYGOUS
T= tall plant TALL X TALL t = short plant (Tt x Tt)
Genotype = 1 TT, 2 Tt, 1 ttPhenotype = 3 Tall, 1 short
Probability = number of times an event(tall/short) is expected to happen number of opportunities (total) for an event to happen
Probability: ¾ tall plants; 75%; 3:4 ¼ short plants; 25%; 1:4
TTt
tTt
TTTt
Tttt
![Page 61: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/61.jpg)
TESTCROSS• TESTCROSS - Cross to
determine genotype of parent with dominant phenotype.
• Use to determine if the unknown is heterozygous or homozygous dominant genotype.– Ex: A plant with green seed pods
could have a genotype of GG or Gg.
• Cross the unknown parent with a homozygous recessive.
![Page 62: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/62.jpg)
EXAMPLE 2: ? ? X HOMOZYGOUS
T= tall plant TALL X SHORT t = short plant (T? x tt)
If Phenotype = 4 TallGenotype of Unknown = TT
TTt
?tt
TtTt
? t? t
TT tT t
![Page 63: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/63.jpg)
EXAMPLE 2: ? ? X HOMOZYGOUS
T= tall plant TALL X SHORT t = short plant (T? x tt)
If Phenotype = 3 Tall, 1 shortGenotype of Unknown = Tt
TTt
?tt
TtTt
? t? t
t t tt t
![Page 64: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/64.jpg)
![Page 65: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/65.jpg)
The way genes control traits can be complex and interact in different ways.
More Complex Patterns of Heredity
![Page 66: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/66.jpg)
•All of these crosses we just did were examples of COMPLETE DOMINANCE.•COMPLETE DOMINANCE-one allele is totally dominant over the other allele.–EXAMPLE: PP and Pp = purple flower plants
![Page 67: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/67.jpg)
When one gene for a certain trait is not completely dominant over the other gene, a blending effect occurs.INCOMPLETE DOMINANCE is a type of inheritance in which one allele (dominant) for a specific trait is not completely dominant over the other (recessive) allele. This results in a combined phenotype (expressed physical trait).
Incomplete Dominance
![Page 68: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/68.jpg)
Incomplete Dominance
R R
r
r R r
R r
R r
R r
EXAMPLE:Four o’clocks (flowers)RR = red rr =
white Rr = pink
RED (RR) X WHITE (rr)
Genotype = 4RrPhenotype = 4 pink
![Page 69: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/69.jpg)
Incomplete Dominance
R r
r
R R R
r rR r
R r
EXAMPLE:Four o’clocks (flowers)RR = red rr =
white Rr = pink
PINK (Rr) X PINK (Rr)
Genotype = 1 RR;2Rr;1rr
Phenotype = 1 red, 2 pink, 1 white
![Page 70: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/70.jpg)
Codominance•Another pattern of heredity can occur when two dominant genes are present for a certain trait.•This pattern of heredity is called co-dominance (both variations of the gene appearing at the same time).•Neither allele is dominant or recessive, nor do they blend.
![Page 71: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/71.jpg)
CodominanceR R
R’
R’ R R’
R R’
R R’
R R’
EXAMPLE:roan horse:RR – red coat colorR’R’ – white coat colorRR’ – roan coat – both
red and white hairs
Genotype = 4 RR’Phenotype = 4 Roan
![Page 72: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/72.jpg)
•Many traits are controlled by one gene that has more than two possible variations. •These traits are controlled by multiple alleles.• Human blood groups are controlled by multiple alleles.
Codominance & Multiple Alleles
![Page 73: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/73.jpg)
•There are 3 alleles for the gene that determines blood type. A, B, O•(Remember: You have just 2 of the 3 in your genotype - 1 from mom & 1 from dad). •With three alleles, we have a higher number ofpossible combinations in creating a genotype.There are 6 differentgenotypes and four differentphenotypes blood type.
Codominance & Multiple Alleles
![Page 74: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/74.jpg)
Blood Type A (IAIA) X Blood Type B (IBIB)
Genotype = 4 IAIB
Phenotype = 4 Blood Type AB
IA
IBIB
IAIAIB IAIB
IAIB IAIB
![Page 75: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/75.jpg)
Possible Blood Type Combinations
![Page 76: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/76.jpg)
The A and B alleles are equally dominant.A child who inherits and A allele from one parent and a B allele from the other parent will have type AB blood.
What type of dominance is this?co-dominance
The O allele is recessive to both A and B alleles. A child who inherits an A allele from one parent and an O allele from the other parent will have a genotype of AO and a phenotype of Type A blood.
A child who inherits on O allele from one parentand an O allele from the other will have:Genotype?Phenotype?
FYI
![Page 77: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/77.jpg)
Predicting the Probability of a Dihybrid Crosses
• Cross between individuals studying one trait is Monohybrid Cross
• Cross between individuals studying two traits is Dihybrid Cross
![Page 78: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/78.jpg)
Predicting the Probability of a Dihybrid Crosses
• A DIHYBRID CROSS is more complicated than monohybrid because there are more possible combinations.
• MONOHYBRID CROSS = 2 traits/4 possible offspring
• DIHYBRID CROSS = 4 Traits/ 16 possible offspring
![Page 79: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/79.jpg)
Predicting the Probability of a Dihybrid Crosses
• Example: AA or Aa = purple; aa = whiteBB or Bb = tall; bb = short
• AaBb x AaBb (Purple Flower, Short Plant x Purple Flower, Short Plant)
![Page 80: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/80.jpg)
FYI• One really important thing that Mendel
noticed from this type of cross was that traits (like flower color, height) are inherited independently - not together as a unit.
• This is type of cross helped Mendel develop the Law of Independent Assortment.
• REMEMBER - Law of Independent Assortment - Genes for various traits assort into gametes independently (due to homolouges lining up randomly at the metaphase plate.)
![Page 81: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/81.jpg)
Dihybrid Cross Example:Homozygous x Homozygous
Tall, Round Plant (TT RR) X Tall, Round Plant (TT RR)
• First, we need to determine what alleles each parent could possibly give - all possible combinations of the alleles from each trait.
• TTRR
• TTRR
TR, TR, TR, TR
TR, TR, TR, TR
![Page 82: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/82.jpg)
Tall, Round Plant (TT RR) X Tall, Round Plant (TT RR)
TR TR TR TRTR
TRTR
TR
TTRR
TTRR
TTRRTTRR
TTRR
TTRR
TTRR
TTRR
TTRR
TTRR
TTRR
TTRR TTRR
GENOTYPE: 16 TTRR
Dihybrid Cross Example:Homozygous x Homozygous
PHENOTYPE: 16 Tall, Round Plants
TTRR
TTRR
TTRR
![Page 83: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/83.jpg)
Dihybrid Cross Example:Heterozygous x Homozygous
LET’S TRY IT !!Cross Tall, Round Plant (TtRr) X Short, Wrinkled Plant (ttrr)• Determine what alleles each
parent could possibly give - all possible combinations of the alleles from each trait.
• TtRr
• ttrr
TR, Tr, tR, tr
tr tr tr tr
![Page 84: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/84.jpg)
LET’S TRY IT !! Cross Tall, Round Plant (TtRr) X Short, Wrinkled Plant (ttrr)
tr tr tr trTRTrtRtr
TtRr
TtrrTtRrTtrr
ttRrttRr
ttrrttrr ttrrttRr
ttrrttRr
Ttrr Ttrr
TtRr TtRr
GENOTYPE: 4TtRr, 4 Ttrr, 4 ttRr, 4 ttrr
PHENOTYPE:4 Tall, Round4 Tall, Wrinkled4 Short, Round4 Short, Wrinkled
Dihybrid Cross Example:Heterozygous x Homozygous
![Page 85: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/85.jpg)
Dihybrid Cross Example:Heterozygous x Heterozygous
Cross Tall, Round Plant (TtRr) X Tall, Round Plant (TtRr) • Determine what alleles each
parent could possibly give - all possible combinations of the alleles from each trait.
• TtRr
• TtRr
TR, Tr, tR, tr
TR Tr tR tr
![Page 86: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/86.jpg)
Tall, Round Plant (Tt Rr) X Tall, Round Plant (Tt Rr)
TR Tr tR trTRTrtRtr
TTRRTTRr
TTRrTTrr
TtRrTtRR
TtrrTtRr ttRrttRR
ttrrttRr
TtRr Ttrr
TtRR
TtRrPHENOTYPE:9 tall, round3 tall, wrinkled3 short, round1 short, wrinkled
Phenotypic Ratio= 9:3:3:1
Dihybrid Cross Example:Heterozygous x Heterozygous
GENOTYPE: 1 TTRR, 2TTRr, 2TtRR, 4TtRr, 1 TTrr, 2 Ttrr, 1ttRR, 2ttRr, 1 ttrr
![Page 88: FUNDAMENTALS OF GENETICS](https://reader036.fdocuments.in/reader036/viewer/2022062323/56816356550346895dd401ec/html5/thumbnails/88.jpg)