Genetics.

Genetics

Genetics: what is it? What is the study of genetics?
“Genetics is the study of heredity, the process in which a parent passes certain genes onto their children.” What does that mean? Children inherit their biological parents’ genes that express specific traits, such as some physical characteristics, natural talents, and genetic disorders. Conduct a brief class discussion to assess students’ knowledge and assumptions about genetics, while providing the information to those students who may not have any prior knowledge.

Word Match Activity base pair cell chromosome
Match the genetic terms to their corresponding parts of the illustration. base pair cell chromosome DNA (Deoxyribonucleic Acid) genes nucleus Hand out the Word Match Activity worksheet and ask students to work in pairs to complete the worksheet. * Tell students that “double is paired with another term, and that both terms should be placed in one of the six areas indicated on the illustration.

Word Match Activity cell genes nucleus base pair chromosome
DNA (Deoxyribonucleic Acid) genes nucleus cell base pair (double helix) DNA Have students volunteer the answers and clarify that “double helix” is the structure of DNA. genes

The History of Genetics
Genetics is the study of genes. Inheritance is how traits, or characteristics, are passed on from generation to generation. Chromosomes are made up of genes, which are made up of DNA. Genetic material (genes,chromosomes, DNA) is found inside the nucleus of a cell. Gregor Mendel is considered “The Father of Genetics"

Gregor Johann Mendel Austrian monk Called the “Father of Genetics"
Mendelian Genetics 4/27/2017 Gregor Johann Mendel Austrian monk Called the “Father of Genetics" Studied the inheritance of traits in pea plants Developed the laws of inheritance. Mendel's work was not recognized until the turn of the 20th century Between 1856 and 1863, Mendel cultivated and tested some 28,000 pea plants He found that the plants' offspring retained traits of the parents

Site of Gregor Mendel’s experimental garden in the Czech Republic
Mendelian Genetics 4/27/2017 Site of Gregor Mendel’s experimental garden in the Czech Republic Fig. 5.co

What did he actually do to the plants?

Mendelian Genetics Genotype- the types of genes (Alleles) present.
Dominant traits- traits that are expressed. Recessive traits- traits that are covered up. Alleles- the different forms of a characteristic. Punnett Squares- show how crosses are made. Probability- the chances/ percentages that something will occur. Genotype- the types of genes (Alleles) present. Phenotype- what it looks like. Homozygous- two of the same alleles. Heterozygous- two different alleles.

Genotype Phenotype the types of genes (Alleles) present
what it looks like

Mendel’ Pea Plants Mendel based his laws on his studies of garden pea plants. Mendel was able to observe differences in multiple traits over many generations because pea plants reproduce rapidly, and have many visible traits such as: Pod color Green Yellow Seed Shape Round Wrinkled Plant Height Tall Short Seed Color Green Yellow Pod Shape Smooth Pinched

Mendel’s Experiments X X
Mendel noticed that some plants always produced offspring that had a form of a trait exactly like the parent plant. He called these plants “purebred” plants. For instance, purebred short plants always produced short offspring and purebred tall plants always produced tall offspring. X Purebred Short Parents Short Offspring Purebred Tall Parents X Tall Offspring

Mendel’s First Experiment
Mendel crossed purebred plants with opposite forms of a trait. He called these plants the parental generation , or P generation. For instance, purebred tall plants were crossed with purebred short plants. Parent Tall P generation Parent Short P generation X Offspring Tall F1 generation Mendel observed that all of the offspring grew to be tall plants. None resembled the short short parent. He called this generation of offspring the first filial , or F1 generation, (The word filial means “son” in Latin.)

Mendel’s Second Experiment
Mendel then crossed two of the offspring tall plants produced from his first experiment. Tall F1 generation X 3⁄4 Tall & 1⁄4 Short F2 generation Parent Plants Offspring Mendel called this second generation of plants the second filial, F2, generation. To his surprise, Mendel observed that this generation had a mix of tall and short plants. This occurred even though none of the F1 parents were short.

Mendel’s Law of Segregation
1. Plant traits are handed down through “hereditary factors” in the sperm and egg. 2. Because offspring obtain hereditary factors from both parents, each plant must contain two factors for every trait. 3. The factors in a pair segregate (separate) during the formation of sex cells, and each sperm or egg receives only one member of the pair.

Dominant and Recessive Genes
One factor (gene) in a pair may mask, or hide, the other factor. For instance, in his first experiment, when he crossed a purebred tall plant with a purebred short plant, all offspring were tall. Although the F1 offspring all had both tall and short factors, they only displayed the tall factor. He concluded that the tallness factor masked the shortness factor. Today, scientists refer to the “factors” that control traits as genes. The different forms of a gene are called alleles. Alleles that mask or hide other alleles, such as the “tall” allele, are said to be dominant. A recessive allele, such as the short allele, is masked, or covered up, whenever the dominant allele is present.

Homozygous Genes What Mendel referred to as a “purebred” plant we now know this to mean that the plant has two identical genes for a particular trait. For instance, a purebred tall plant has two tall genes and a purebred short plant has two short genes. The modern scientific term for “purebred” is homozygous. X Short Offspring short-short Short Parents Law of Segregation each parent donates one height gene to the offspring. Since each parent had only short genes to donate, all offspring will also have two short genes (homozygous) and will therefore be short.

Hybrid (Heterozygous) Alleles
In Mendel’s first experiment, F1 offspring plants received one tall gene and one short gene from the parent plants. Therefore, all offspring contained both alleles, a short allele and a tall allele. When both alleles for a trait are present, the plant is said to be a hybrid for that trait. Today, we call hybrid alleles heterozygous. Parent Tall P generation Parent Short P generation X Offspring Tall F1 generation short-short short-tall tall-tall Offspring have both a tall and a short allele, only the tall allele is expressed and is therefore dominant over short.

Dominant and Recessive Genes… The Law of Dominance
Gene that prevents the other gene from “showing” – dominant (there are a few exceptions to this …) Gene that does NOT “show” even though it is present – recessive Symbol – Dominant gene – upper case letter – T Recessive gene – lower case letter – t Recessive color Dominant color

Dominant vs Recessive Alleles
Mendel observed a variety of dominant alleles in pea plants other than the tall allele. For instance, hybrid plants for seed color always have yellow seeds. Green & Yellow Allele Yellow Seed However, a plant that is a hybrid for pod color always displays the green allele. Green & Yellow Allele Green Pod Round seeds are dominant over wrinkled seeds, and smooth pods are dominant over wrinkled pods.

Alleles – different genes (possibilities) for the same trait
Chromosomes come in homologous pairs, thus genes come in pairs. Homologous pairs – matching genes – one from female parent and one from male parent Example: Humans have 46 chromosomes or 23 pairs. One set from dad – 23 in sperm One set from mom – 23 in egg Alleles – different genes (possibilities) for the same trait ex: purple or white flowers

To be purebred or not to be purebred that is the question…
An organism that always produces an offspring with the same physical / genetic characteristic(s). 1. P Generation – Parents 2. F1 Generation – Offspring from parents 3. F2 Generation – Offspring from F1

Law of Segregation Each gamete only donates one allele for each gene.

Law of Independent Assortment: each pair of genes separate independently of each other in the production of sex cells. Gene pairs will separate during the formation of egg or sperm cells. Plant will donate one allele from each pair Plant will donate either a yellow or green seed allele, either a yellow or green pod allele, and a wrinkled or round seed allele Plant will always donate a wrinkled pod shape The donation of one allele from each pair is independent of any other pair. Ex: if the plant donates the yellow seed allele it does not mean that it will also donate the yellow pod allele.

(Always use the same letter for the same alleles—
Example: Straight thumb is dominant to hitchhiker thumb T = straight thumb t = hitchhikers thumb (Always use the same letter for the same alleles— No S = straight, h = hitchhiker’s) Straight thumb = TT Straight thumb = Tt Hitchhikers thumb = tt * Must have 2 recessive alleles for a recessive trait to “show”

The Punnett Square

Probability - The likelihood an event will or will not occur. Ex. What is the probability of flipping heads? Ex. What is the probability of pulling an ace out of a deck of cards? The prior occurrences have no effect on future results – it is all chance and it starts over each time. , ½, 50% , 1/13, 7.7%

Punnett Squares The Punnett square is the standard way of working out what the possible offspring of two parents will be. It is a helpful tool to show allelic combinations and predict offspring ratios.

Types of Genetic Crosses
Mendelian Genetics 4/27/2017 Types of Genetic Crosses Monohybrid cross - cross involving a single trait (We will cover these first.) e.g. flower color Dihybrid cross - cross involving two traits e.g. flower color & plant height

How to set up a Punnett Square…
Begin by constructing a grid of two perpendicular lines.

How to set up a Punnett Square…
One parents traits go on top  One parents traits go on the side 

For this example lets consider a genotype of BB crossed with bb.
Notice only one letter goes above each box It does not matter which parent’s genotype goes on either side. B B b

Next, fill in the boxes by copying the column and row head-letters down and across into the empty spaces. Notice how the capitol letter is always first. B B b B b B b b B b B b

Punnett Squares Now that we have learned the basics of genetics lets walk through some examples using Punnett Squares.

W w W W W W w W w w w w heterozygous (Ww).
Usually write the capital letter first W Lets say: W- dominant white w- recessive violet W W W w w W w w w heterozygous (Ww). Parents in this cross are __________________________ Note: Make sure I can tell your capital letters from lowercase letters. What percentage of the offspring will have violet flowers? _____________________________________________ ANSWER: 25% (homozygous recessive)

Red hair (R) is dominant over blond hair (r)
Red hair (R) is dominant over blond hair (r). Make a cross between a heterozygous red head and a blond. R r r Rr rr 50% What percentage of the offspring will have red hair?

0% Which is good because red eyes are creepy…
Black eyes (E) is dominant over red eyes (e) in rats. Make a cross between a homozygous rat with black eyes and a rat with red eyes. E E What is the possibility of a red eye off springs? Ee e 0% Which is good because red eyes are creepy… Discuss with students other possible answers

Studying the inheritance of two characters simultaneously
THE DIHYBRID CROSS Studying the inheritance of two characters simultaneously

Mendel’s peas Character Trait Allele Seed shape Round R Wrinkled r
Pea color Yellow Y Green y

Combinations Genotype Phenotype RRYY Round Yellow RRYy RrYY RrYy RRyy
Round Green Rryy rrYY Wrinkled Yellow rrYy rryy Wrinkled Green

Is the inheritance of one character affected by the inheritance of another?
P Phenotypes Round Yellow x Wrinkled Green (Pure Bred) F1 Phenotypes All Round Yellow (Selfed) F2 Phenotypes Seed color Yellow Green TOTAL RATIO Round 315 108 423 shape Wrinkled 101 32 133 416 140 556

Is the inheritance of one character affected by the inheritance of another?
P Phenotypes Round Yellow x Wrinkled Green (Pure Bred) F1 Phenotypes All Round Yellow (Selfed) F2 Phenotypes Seed color Yellow Green TOTAL RATIO Round 315 108 423 3.18 shape Wrinkled 101 32 133 1 416 140 556 2.97

A dihybrid cross can be treated as two separate monohybrid crosses
A dihybrid cross can be treated as two separate monohybrid crosses. The expected probability of each type of seed can be calculated: How would you do this? Probability of an F2 seed being round = Probability of an F2 seed being wrinkled = Probability of an F2 seed being yellow = Probability of an F2 seed being green =

A dihybrid cross can be treated as two separate monohybrid crosses. The expected probability of each type of seed can be calculated: How would you do this? R r

A dihybrid cross can be treated as two separate monohybrid crosses. The expected probability of each type of seed can be calculated: How would you do this? R r RR Rr rr

A dihybrid cross can be treated as two separate monohybrid crosses. The expected probability of each type of seed can be calculated: How would you do this? Probability of an F2 seed being round =75% or ¾ Probability of an F2 seed being wrinkled = Probability of an F2 seed being yellow = Probability of an F2 seed being green =

The expected probability of each type of seed can be calculated:
A dihybrid cross can be treated as two separate monohybrid crosses The expected probability of each type of seed can be calculated: Probability of an F2 seed being round = 75% or ¾ Probability of an F2 seed being wrinkled = 25% or ¼ Probability of an F2 seed being yellow = 75% or ¾ Probability of an F2 seed being green = 25% or ¼

Or together…Therefore
Probability of an F2 seed being round and yellow = ¾ x ¾ = 9/16 = % Probability of an F2 seed being round and green = Probability of an F2 seed being wrinkled and yellow = Probability of an F2 seed being wrinkled and green =

Therefore Probability of an F2 seed being round and yellow = ¾ x ¾ = 9/16 = % Probability of an F2 seed being round and green = ¾ x ¼ = 3/16 = % Probability of an F2 seed being wrinkled and yellow = ¼ x ¾ = 3/16 = % Probability of an F2 seed being wrinkled and green = ¼ x ¼ = 1/16 = %

We could expect What Mendel observed 556 x 9/16 round yellow 313 315
Predicting how many seeds we could expect to get in a sample We could expect What Mendel observed 556 x 9/16 round yellow 313 315 556 x 3/16 round green 108 556 x 3/16 wrinkled yellow 101 556 x 1/16 wrinkled green 32

Predicting how many seeds we could expect to get in a sample
What Mendel observed 556 x 9/16 round yellow 313 315 556 x 3/16 round green 104 108 556 x 3/16 wrinkled yellow 101 556 x 1/16 wrinkled green 35 32

REMEMBER  THE LAW OF INDEPENDENT ASSORTMENT
It appears that the inheritance of seed shape has no influence over the inheritance of seed colour The two characters are inherited INDEPENDENTLY The pairs of alleles that control these two characters assort themselves independently

Mendel & Meiosis: The pairs of chromosomes could orientate in different ways at Anaphase 1

Dihybrid cross genetic diagram
P Phenotypes Round Yellow seed X Wrinkled Green seed (Pure bred) Genotypes RRYY rryy meiosis Gametes RY ry fertilisation F1 RrYy (Selfed) Round Yellow Proportions 100%

F1 Phenotypes RrYy (Selfed) Genotypes Round Yellow Proportions 100% meiosis Gametes Y y R RY Ry r rY ry

Gametes Y y R RY Ry r rY ry fertilisation F2 Genotypes RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy rryy

Dihybrid cross proportions
Phenotypes Proportions Round Yellow 9/16 or 56.25% Round Green Wrinkled Yellow Wrinkled Green

Dihybrid cross proportions
Phenotypes Proportions Round Yellow 9/16 or 56.25% Round Green 3/16 or 18.75% Wrinkled Yellow Wrinkled Green 1/16 or 6.25%

Dihybrid test cross In monohybrid crosses, to know if a dominant trait is homozygous (RR) or heterozygous (Rr) it is necessary to carry out a test cross. This is done with a homozygous recessive (rr) individual The same is true for a dihybrid cross where the test cross is made with an individual which is homozygous recessive for both characters (rryy).

Dihybrid test cross Phenotypes Round Yellow X Wrinkled Green Genotypes
RrYy rryy Gametes RY, Ry, rY, ry ry Genotypes RY Ry rY ry RrYy Rryy rrYy rryy Phenotypes Round Yellow Round Green Wrinkled Yellow Wrinkled Green Proportions 1/4 or 25%

Dihybrid Crosses Use the FOIL method!
- To get the proper segregation of alleles for the parents in a dihybrid cross, use the FOIL method: First, Outer, Inner, Last (Bb)(Tt) BT, Bt, bT, bt - There are a lot of genotypes, we only record the phenotypic ratio like this: Dom, Dom: Dom, Rec: Rec, Dom: Rec, Rec 9: : : (It needs to add to 16!)

So Remember…. Dihybrid Crosses are:
- A cross involving two traits. - Create a table with 4 columns & 4 rows. Example 1: Black hair is dominant to blonde hair. Being tall is dominant to being short. What would be the possible phenotypes of a cross between a heterozygous black-haired, tall female with a male who is homozygous for having black hair and being short? Parent Genotypes?

On the Review Worksheets…
Now you try some… On the Review Worksheets…

Sometimes the laws are violated…

What we already know about Dominant/Recessive
One allele is dominant over the other (capable of masking the recessive allele) PP = purple pp = white Pp = purple

What we already know about Dominant/Recessive
In pea plants, purple flowers (P) are dominant over white flowers (p) show the cross between two heterozygous plants. P p GENOTYPES: P p PHENOTYPES:

Are there always dominants and recessives?
Not all traits are purely dominant or purely recessive. Can you think of one that we discussed being this way? In some cases, neither are dominant. When this happens it is known as ________________________ Incomplete dominance

So what do you think? If neither trait is dominant, what do you think happens? Do they both show? Neither? A Mixture? Well, in actuality, there is a ________ of traits mixture

Blending of the Traits The blending gives intermediate expression
What is intermediate expression? New phenotypes that are shown when incomplete dominance of genes occurs What sorts of genotype is needed for this? Only happens in ____________ individuals. Why? Heterozygous

Why only in heterozygotes
We know that homozygous individuals have the same allele for both trait (BB or bb). Heterozygous individuals have _________ alleles for both traits and therefore both of the traits ______ in expression levels producing some _______ traits different show New

Incomplete Dominance A third (new) phenotype appears in the heterozygous condition ONLY!!! CRCR = red CWCW = white CRCW = pink

Example Cross CR CW CR CW CRCW CRCR CWCW

Real Life Examples Roses Carnations Snapdragons

Problem: Incomplete Dominance
Show the cross between a pink and a white flower. GENOTYPES/ PHENOTYPES CR CW CW CWCW CRCw CRCW

* Individuals that are white produce no red pigment
Why does it happen? * Individuals with a single CR (ie., CR CW) allele are unable to make enough red pigment to produce the red flowers * Individuals that are white produce no red pigment * So the resulting flowers are pink.

What have we seen? We have seen now that some alleles can be dominant, others recessive, and some are not, and we call these _________________ Are there any other combinations of alleles that we may be interested in looking at? Incomplete dominance

What about this… Is there a possibility that two alleles for the same trait can both be dominant? ___________________ But what does this mean for expression? Are the individuals going to take one over another Neither? Both? Co-dominance

Expression When we have two alleles that are both dominant we actually get expression of both We will use the example of chickens Some chickens are black Some chickens are white

Expression

Examples

What about in Humans?

Co-dominance in Humans
The heterozygous condition, both alleles are expressed ____________________ Sickle Cell Anemia in Humans HbAHbS HbAHbA = normal cells HbSHbS= sickle cells HbAHbS = some of each sick

Human Example – Electron Micrograph
Individuals with HbAHbS are also called carriers This means that they carry the gene for sickle cell anemia, but it is not expressed to its fullest extent

Think Back Harder to get Malaria
Could changes in an individual be good for an individual in some cases? Yes! Of course they could What is an advantage of having sickle cell anemia? _____________________________________ Harder to get Malaria

Problem: Co-dominance
Show the cross between an individual with sickle-cell anemia and another who is a carrier but not sick. GENOTYPES/ PHENOTYPES:

Problem: Co-dominance
Show the cross between an individual with sickle-cell anemia and another who is a carrier but not sick. HbS HbS HbS HbS HbS HbA HbS HbS GENOTYPES/ PHENOTYPES: HbS HbA HbS HbA

Another Tally So far we have looked at dominance, recessiveness, Incomplete dominance and Co-Dominance But what do all of these have in common despite their differences They all use ____________ possible allele types Two

Karyotype Picture of homologous chromosomes that are arranged in order of size A normal human Karyotype has 44 autosomal chromosomes and 2 sex chromosomes

Karyotypes: can help determine chromosomal abnormalities

Chromosomal Disorders
Nondisjunction – means “not coming apart” – results in abnormal numbers of chromosomes in gametes Monosomy – when there is a chromosome missing Trisomy- when there is an extra chromosome

Sex – linked Traits Genes for these traits are located only on the X chromosome (NOT on the Y chromosome) X linked alleles always show up in males whether dominant or recessive because males have only one X chromosome

Sex-Linked Inheritance
- Sex-linked genes are found on the X chromosome - Because males have only one X chromosome, males are more likely than females to receive & express a recessive trait. - A person is a carrier if they have one recessive allele “and” one dominant allele for a trait.

Examples of recessive sex-linked disorders:
colorblindness – inability to distinguish between certain colors You should see 58 (upper left), 18 (upper right), E (lower left) and 17 (lower right). Color blindness is the inability to distinguish the differences between certain colors. The most common type is red-green color blindness, where red and green are seen as the same color.

hemophilia – blood won’t clot

Examples: Down’s syndrome – (Trisomy 21) 47 chromosomes, extra chromosome at pair #21

Turner’s syndrome – only 45 chromosomes, missing a sex chromosome (X)
Girls affected – short, slow growth, heart problems

Klinefelter’s syndrome – 47 chromosomes, extra X chromosomes (XXY)
Boys affected – low testosterone levels, underdeveloped muscles, sparse facial hair

Having an extra set of chromosomes is fatal in animals, but in plants it makes them larger and hardier. Hardier

XN Xn XNXN XNXn XNY XnY XN Y
Example: A female that has normal vision but is a carrier for colorblindness marries a male with normal vision. Give the expected phenotypes of their children. N = normal vision n = colorblindness XN Xn X XN Y XN Xn XNXN XNXn XNY XnY XN Y Phenotype: 2 normal vision females 1 normal vision male 1 colorblind male

Autosomal Inheritance
- Traits not located on the sex chromosomes. Autosomal Recessive - Equal numbers of males & females affected. - Can skip generations. i.e. Cystic Fibrosis & Sickle Cell Anemia Problem: A female homozygous dominant for C.F. marries a man who is a carrier for C.F. What are their chances of having a child with C.F.?

Autosomal Dominant / Lethal Alleles
- One dominant allele leads to death. - Seen in every generation. i.e. Huntington’s Disease Problem: A female heterozygous for Huntington’s disease marries a man who does not have the disorder. What are the chances their child will have Huntington’s disease?

PEDIGREES Chart that helps track which members of a family express a trait.

Interpreting Pedigrees
STEPS: Determine if its Autosomal or Sex-Linked? - If “most” affected individuals are XY, then it is most likely X-Linked. - If there is a 50:50 ratio of affected males to females, than it is most likely Autosomal. 2. Is it dominant or recessive? - If dominant, one parent must have the trait and it will be seen in every generation. - If recessive, neither parent has to have it and it can skip generations.

Pedigrees Graphic representation of how a trait is passed from parents to offspring Tips for making a pedigree Circles are for females Squares are for males Horizontal lines connecting a male and a female represent a marriage Vertical line and brackets connect parent to offspring A shaded circle or square indicates a person has the trait A circle or square NOT shaded represents an individual who does NOT have the trait Partial shade indicates a carrier – someone who is heterozygous for the trait

Can pass trait to offspring
Example: Make a pedigree chart for the following couple. Dana is color blind; her husband Jeff is not. They have two boys and two girls. HINT: Colorblindness is a recessive sex-linked trait. XnXn XNY Has trait Can pass trait to offspring

Multiple Alleles Two - When there are more than ______________ possible alleles for a gene. - Along with having multiple alleles, a gene may also show incomplete or co-dominance.

More Two More variety What does that mean?
Many genes that control specific traits have _______________ than _____________ alleles This means that there are far more possibilities for different Phenotypes _______________________________ More Two More variety

Multiple Alleles Example
Blood Types Possible Alleles: (IA, IB, i) IA = Type A (IAIA or IAi) IB = Type B (IBIB or IBi) i = Type O (ii) IAIB = Type AB

What possible blood type(s) could a child have from the result of a cross between a mother who is heterozygous Type A blood and a father who is homozygous Type B blood. A i B i AB Bi Ai Bi

D. BLOOD TYPE NOTES

A and B are dominant over O
A and B are co-dominant AA BB AB A and B are dominant over O AO BO OO

Blood Transfusion

How does this account for bloods alleles?
* A, B, and O are the alleles * If A and B are co-dominant, then when they are both present they will be represented with A and B giving us blood type AB * When A and O and B and O are present you get AO and BO but because A and B are dominant over O, you get blood type A and blood type B * O blood is known as the Universal Donor.

- A trait controlled by two or more genes.
POLYGENIC TRAITS - A trait controlled by two or more genes. Examples: Height, Eye Color & Skin Color Example Genotype: EeBbYy = Hazel Eyes

XN Xn XNXN XNXn XNY XnY XN Y
Example: A female that has normal vision but is a carrier for colorblindness marries a male with normal vision. Give the expected phenotypes of their children. N = normal vision n = colorblindness XN Xn X XN Y XN Xn XNXN XNXn XNY XnY XN Y Phenotype: 2 normal vision females 1 normal vision male 1 colorblind male

Pedigrees Graphic representation of how a trait is passed from parents to offspring Tips for making a pedigree Circles are for females Squares are for males Horizontal lines connecting a male and a female represent a marriage Vertical line and brackets connect parent to offspring A shaded circle or square indicates a person has the trait A circle or square NOT shaded represents an individual who does NOT have the trait Partial shade indicates a carrier – someone who is heterozygous for the trait

Can pass trait to offspring
Example: Make a pedigree chart for the following couple. Dana is color blind; her husband Jeff is not. They have two boys and two girls. HINT: Colorblindness is a recessive sex-linked trait. XnXn XNY Has trait Can pass trait to offspring

Review

Genetic Vocabulary Genetics: The scientific study of heredity
Genes: Point on a chromosome that controls the trait. Allele: Alternate forms of a gene/factor. A or a Genotype: combination of alleles an organism has. (genetic traits) Phenotype: How an organism appears. (physical traits) Dominant: An allele which is expressed (masks the other). Recessive: An allele which is present but remains unexpressed (masked) Homozygous: Both alleles for a trait are the same. Heterozygous: The organism's alleles for a trait are different.

Genetic Vocabulary Probability : The mathematical chance that an event will happen. Meiosis :The cell division that produces sex cells. Mutation : A change in the type or order of the bases in an organism DNA: deletion, insertion or substitution. Natural Selection : The process by which organisms with favorable traits survive and reproduce at a higher rate than organisms without favorable traits. Evolution :The process by which population accumulate inherited changes over time.

Summary of Mendel’s laws
Mendelian Genetics 4/27/2017 Summary of Mendel’s laws LAW PARENT CROSS OFFSPRING DOMINANCE TT x tt tall x short 100% Tt tall SEGREGATION Tt x Tt tall x tall 75% tall 25% short INDEPENDENT ASSORTMENT RrGg x RrGg round & green x round & green 9/16 round seeds & green pods 3/16 round seeds & yellow pods 3/16 wrinkled seeds & green pods 1/16 wrinkled seeds & yellow pods copyright cmassengale

Mendelian Genetics 4/27/2017 Dihybrid Cross RY Ry rY ry RY Ry rY ry

Dihybrid Cross RY Ry rY ry Round/Yellow: 9 Round/green: 3
Mendelian Genetics 4/27/2017 Dihybrid Cross RY Ry rY ry Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 phenotypic ratio RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy rryy

copyright cmassengale
Mendelian Genetics 4/27/2017 Dihybrid Cross Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 copyright cmassengale

Mendelian Genetics 4/27/2017 Test Cross A mating between an individual of unknown genotype and a homozygous recessive individual. Example: bbC__ x bbcc BB = brown eyes Bb = brown eyes bb = blue eyes CC = curly hair Cc = curly hair cc = straight hair bC b___ bc copyright cmassengale

Mendelian Genetics 4/27/2017 Test Cross Possible results: bC b___ bc bbCc C bC b___ bc bbCc bbcc or c copyright cmassengale

Incomplete Dominance and Codominance
Mendelian Genetics 4/27/2017 Incomplete Dominance and Codominance copyright cmassengale

Mendelian Genetics 4/27/2017 Incomplete Dominance F1 hybrids have an appearance somewhat in between the phenotypes of the two parental varieties. Example: snapdragons (flower) red (RR) x white (rr) RR = red flower rr = white flower r R copyright cmassengale

Mendelian Genetics 4/27/2017 Incomplete Dominance r R r All Rr = pink (heterozygous pink) produces the F1 generation Rr copyright cmassengale

Mendelian Genetics 4/27/2017 Codominance Two alleles are expressed (multiple alleles) in heterozygous individuals. Example: blood type 1. type A = IAIA or IAi 2. type B = IBIB or IBi 3. type AB = IAIB 4. type O = ii copyright cmassengale

Mendelian Genetics 4/27/2017 Codominance Problem Example: homozygous male Type B (IBIB) x heterozygous female Type A (IAi) IB IA i IAIB IBi 1/2 = IAIB 1/2 = IBi copyright cmassengale

Another Codominance Problem
Mendelian Genetics 4/27/2017 Another Codominance Problem Example: male Type O (ii) x female type AB (IAIB) i IA IB IAi IBi 1/2 = IAi 1/2 = IBi copyright cmassengale

Mendelian Genetics 4/27/2017 Codominance Question: If a boy has a blood type O and his sister has blood type AB, what are the genotypes and phenotypes of their parents? boy - type O (ii) X girl - type AB (IAIB) copyright cmassengale

Mendelian Genetics 4/27/2017 Codominance Answer: IB IA i IAIB ii Parents: genotypes = IAi and IBi phenotypes = A and B copyright cmassengale

Mendelian Genetics 4/27/2017 Sex-linked Traits Traits (genes) located on the sex chromosomes Sex chromosomes are X and Y XX genotype for females XY genotype for males Many sex-linked traits carried on X chromosome copyright cmassengale

Mendelian Genetics 4/27/2017 Sex-linked Traits Example: Eye color in fruit flies Sex Chromosomes XX chromosome - female Xy chromosome - male fruit fly eye color copyright cmassengale

Sex-linked Trait Problem
Mendelian Genetics Sex-linked Trait Problem 4/27/2017 Example: Eye color in fruit flies (red-eyed male) x (white-eyed female) XRY x XrXr Remember: the Y chromosome in males does not carry traits. RR = red eyed Rr = red eyed rr = white eyed XY = male XX = female XR Xr Y copyright cmassengale

Sex-linked Trait Solution:
Mendelian Genetics 4/27/2017 Sex-linked Trait Solution: XR Xr Y 50% red eyed female 50% white eyed male XR Xr Xr Y copyright cmassengale

Genetic Practice Problems
Mendelian Genetics 4/27/2017 Genetic Practice Problems copyright cmassengale

Mendelian Genetics 4/27/2017 Breed the P1 generation tall (TT) x dwarf (tt) pea plants t T copyright cmassengale

Mendelian Genetics 4/27/2017 Solution: tall (TT) vs. dwarf (tt) pea plants T t All Tt = tall (heterozygous tall) produces the F1 generation Tt copyright cmassengale

Mendelian Genetics 4/27/2017 Breed the F1 generation tall (Tt) vs. tall (Tt) pea plants T t T t copyright cmassengale

Mendelian Genetics 4/27/2017 Solution: tall (Tt) x tall (Tt) pea plants T t produces the F2 generation 1/4 (25%) = TT 1/2 (50%) = Tt 1/4 (25%) = tt 1:2:1 genotype 3:1 phenotype TT Tt tt copyright cmassengale

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Genetics.

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Presentation on theme: "Genetics."— Presentation transcript:

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