Chapter 11 Introduction to Genetics Pg. 262 What

Chapter 11 Introduction to Genetics Pg. 262 What

Chapter 11 Introduction to Genetics Pg. 262 What makes you unique? Sure, were all humans, but what makes you different from others in the room. o Your talents, interests or dreams? o Your personality, looks or clothes?

Actually, one of the reasons youre unique is because of the genes you inherited from your parents. o Your genes make you unique, they have a hidden potential that can make you excel at things others can not. Seek out your potential and you will find it, otherwise it will be wasted. Genetics Genetics is the

study of how traits are passed from one generation to the next. o Traits are specific characteristics that vary from one individual to another. Examples: hair color, height, intelligence

Lets check out our traits! Take out a piece of paper to keep track of your traits. The first trait well do together. Are you colorblind? o There are three main kinds of color vision defects. Red-green color vision defects are the most common. This type occurs in men more than in women. The other major types are blue-yellow color vision defects and a complete absence of color vision. Most of the time, color blindness is genetic.

I will show you a series of slides. On your paper write down the number you see or the word spots if you dont see a number. o DO NOT SAY ANYTHIG OUT LOUD! QUIETLY, write down what you see. QUIETLY, write down

what you see. QUIETLY, write down what you see. QUIETLY, write down what you see. QUIETLY, write down what you see.

QUIETLY, write down what you see. How did you do?

Slide Slide Slide Slide Slide Slide 1 2 3 4

5 6 showed showed showed showed showed showed an orange # 25

a red # 29 an orange # 45 a red # 56 a green # 6 a green # 8 You may be red-green colorblind if you only saw the numbers 25 and 56. All of the other slides would have appeared to have only had spots. On your paper identify if you are color blind or if you have normal color vision.

Now for the rest Individually complete the worksheet given to you. As a class we will then collect and analyze our trait data o http:// ofMyTraits.pdf Take a moment and clasp your hands together so that they are on the desk.

o Look at your hands o Which finger is on top? Note this on your sheet. The following slides will have pictures to help you determine if you and your partner have the various traits well be looking at. Detache d Earlobe s

Tongue roller Non roller Attache d Earlobe s Widows Peak Dimples

Straight Hair Line Cleft Chin Lets see the class results.. Lets calculate the frequency of each trait for our class: Number of students with the trait

x 100 = ________ % Number of students in the class Example: Hitchhikers thumb (Class size =21) 5 x 100 = 24% 21 Lets compare the frequency of traits in the classroom population with the frequency in the general population.

The Father of Genetics Gregor Mendel 1822-1884 o After becoming a priest, Mendel spent several years studying science and math. o He spent 14 years working in the monastery and teaching at the high school. o Mendel was also in charge of the monastery garden. It was in this garden that Mendel did work that would change biology forever! What did Mendel do?

Gregor Mendel discovered how traits get passed on from one generation to the next. He discovered how heredity works! How did Mendel achieve such a feat? PEAS! please Mendel knew that pea plants can selfpollinate, meaning they

had both pollen (sperm) and seeds (eggs) in the same flower. This means that seeds produced by peas inherit all of the characteristics from the parent plant. True-breeding plants like peas produce offspring identical to

themselves. Mendel wanted to cross pollinate the plants with different traits. This meant that he had to prevent self-pollination by removing the male parts and physically dusting the female parts with the desired pollen. This allowed Mendel to

cross breed plants with different traits and study the results. Genes and Dominance Mendel studies the following pea traits. The offspring of parents with different traits are called hybrids. Parents and Offspring

We call the original pair of breeding plants the P (parental) generation. The offspring of the P are called the F1, or first filial generation (filius means son and filia means daughter in Latin) P What did the F1 hybrid plants look like? To Mendels surprise, all of the offspring had the characteristics of only one of the parents. The other one seemed to have

disappeared. The F2 Generation Mendel then allowed the F1 generation to selfpollinate to create the F2 generation. Mendel discovered that the trait that disappeared in the F1 showed up again in the F2. Two Conclusions Mendels first conclusion from this set of experiments was that biological inheritance is

determined by factors that are passed from one generation to the next. o Today we call these chemical factors that determine traits genes. o Each of these traits is controlled by one gene that has two different forms. The different forms of a gene are called alleles. Example: there is one gene for plant height with two alleles, tall and short. http:// The Principle of Dominance The principle of dominance states that some alleles are dominant and others are recessive. Dominant Alleles An organism with a dominant allele for a trait will always show that trait.

o Dominant alleles are represented with the capital letter of the dominant trait. o Example: T is for tall, R is for round, Y is for yellow, etc. o If you see a capital letter for an allele, it WILL show that trait. TT or Tt are tall RR or Rr are round YY or Yy are green

Recessive Alleles An organism with a recessive allele for a trait will only show that form if the dominant allele for the trait is absent. For a recessive trait to show, there must be two recessive alleles, NO DOMINAT. o Recessive alleles are represented with the lower case letter of the dominant trait. o Example: t is for short, r is for wrinkled, y is for green, etc.

You try it Take out the trait activity we recently did. Write the allele combination you may have for each of the following traits. Lets do the first couple together. Unattached earlobes are dominant and attached earlobes are recessive. Straight thumb is dominant and hitchhikers thumb is recessive. The ability to roll the tongue a dominant trait and the lack of tongue rolling ability a recessive trait. Dimples dominant and a lack of dimples recessive.

Right handedness dominant and left handedness recessive. Freckles is dominant, the absence of freckles is recessive. Cleft chin dominant and a smooth chin recessive. Widows peak dominant and a straight hairline recessive. Explaining the F1 cross Remember that when Mendel allowed the F1 generation to self-pollinate that the recessive trait showed up in 25% of the population.

This reappearance indicated that at some point the allele for yellow separated from the allele for green. Segregation Mendel realized that alleles separate when gametes or sex cells (sperm and eggs) form. During gamete formation, alleles separate from each other so that each gamete carries only one allele.

Vocabulary Homozygous: organisms that have two identical allelles for a trait. Example: TT or tt (true breeding) o HOMO means same Heterozygous: Organisms that have two different alleles for a trait. Example: Tt (hybrids) o HETERO means different Phenotype: The physical characteristics (what we see). Example: tall, short, round

Genotype: The genetic make-up (combination of alleles). Example: TT, aa, Rr Vocabulary Review For each genotype, indicate whether it is heterozygous (HE) or homozygous (HO) AA ____ Bb ____ Cc ____ Dd ____ Ee ____

ff ____ GG ____ HH ____ Ii ____ Jj ____ kk ____ Ll ____ Mm ____ nn ____

OO ____ Pp ____ For each of the genotypes below, determine the phenotype. Purple flowers are dominant to white flowers Brown eyes are dominant to blue eyes PP __________________ Pp _________________ pp __________________

BB ___________________________ Bb ___________________________ bb ___________________________ Round seeds are dominant to wrinkled Bobtails are recessive (long tails dominant) RR ___________________________ Rr ___________________________

rr ___________________________ TT ___________________ Tt ___________________ tt __________________ For each phenotype, list the genotypes. (Remember to use the letter of the dominant trait) Straight hair is dominant to curly. ____________ straight

____________ straight ____________ curly Pointed heads are dominant to round heads. ____________ pointed ____________ pointed ____________ round Probability and Punnett Squares

The likelihood of something happening is called probability. o When you flip the coin what is the probability of flipping a head? o When you roll the dice, what is the probability of getting a two? When talking probabilities, past outcomes DO NOT affect future ones. The principle of probability can be used to predict the outcome of genetic crosses. Genetics with a Smile Now for an activity to see how probability plays a role in genetic crosses. Punnett Squares Gene combinations that could result from a genetic cross (breeding) can be determined by drawing a Punnett Square. o A Punnett Square demonstrates how alleles segregate in the gametes and

the possible combinations of them coming together again in the offspring. o The Punnett Square is a guide to possible results, not a guarantee of results. Punnett Squares Probabilities predict averages!

Remember that probabilities predict the average outcome of a large number of events. o Probability does not predict the precise outcome of an individual event. The same is true of genetics. The larger the number of offspring, the closer the resulting numbers will get to expected values.

Monohybrid Cross Studying the inheritance of a single trait is called a monohybrid cross. In humans, acondroplasia dwarfism (D) is dominant over normal (d). A homozygous dominant (DD) person dies before the age of one. A heterozygous (Dd) person is dwarfed. A homozygous recessive individual is normal.

A heterozygous dwarf man marries a dwarf heterozygous woman.. What is the probability of having a normal child? What is the probability of having a child that is a dwarf? What is the probability of having a child that dies at one from this disorder? Lets sum it up. Section 11-3 Exploring Mendelian Genetics After showing that alleles segregated during the formation of gametes, Mendel wondered if certain alleles traveled together or if they separated independently from each other.. o Example: Does the gene that determines a seeds shape (round or wrinkled) have anything to do with the seeds color (yellow or green)? Must a round seed also be yellow?

The di-hybrid cross R = round Y = yellow r = wrinkled y = green

Dihybrid Practice A tall green pea plant (TTGG) is crossed with a short white pea plant (ttgg). TT or Tt = tall tt = short GG or Gg = green gg = white ___________ X ___________ Now you try A tall green pea plant (TTGg) is crossed with a tall green pea plant (TtGg) TT or Tt = tall tt = short

GG or Gg = green gg = white ___________ X ___________ Independent Assortment The principle of independent assortment states that genes for different traits do not travel together. o We now know that if genes

are located on the same chromosome, they can travel together. Its this independent assortment that gives us the many genetic variations we observe in plants, animals and other organisms.

A Summary of Mendels Principles The traits we inherit come from our genes. Genes are passed from parents to offspring. Some alleles are dominant and others are recessive. Each organism receives an allele from each parent to make their genes. These genes are segregated when gametes are formed. Alleles for different genes segregate independently of one another.

Beyond Dominant and Recessive We now know that there are many exceptions to Mendels principles. o The majority of genes have more than two alleles. o Many traits are controlled by more than one gene. Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or genes.

Incomplete Dominance A cross between some individuals causes a trait to blend together. When one allele is not completely dominant over another it is called incomplete dominance. Red (RR) + White (WW)= pink (RW) Example: A cross between A red flower (RR) and a white flower (WW) creates Pink flowers (RW)

Codominance When both alleles are dominant and both show up in the offspring, its called codominance. o Examples: Roan Cows Erminette Chickens Blood Type AB Multiple alleles

Many genes have more than two alleles that exist in a population. o An individual will still only have two alleles for the trait. One example is coat color in rabbits. A rabbits coat color is determined by a single gene that has at least four different alleles. What color eyes What color eyes would your children have? o

change Baby eyes: Eye color changes in children are usually due to a delay in the production of melanin. The greater amount of melanin present in the eye usually denotes a more brown tint. Pupil size: Eye color can also change as the pupils dilate and shrink. As the pupil dilates, the melanin pigments in

the iris are pushed together causing a darker looking eye. As the pupil shrinks, the melanin pigments spread out making the eyes appear lighter in color. Eye color change Disease: some diseases can cause dramatic changes in eye color. For example, some diseases may change one eye color from brown to blue resulting in heterochromia (two different colored eyes).

o Horner syndrome, some forms of glaucoma, and Fuch's disease can cause a change in eye color. Age: Between 10 and 15 percent of the Caucasian population will experience a change in eye color as they age. This is usually due to a degradation of the color of the pigments in the eye, or a loss of melanin granules in the eyes over time. Polygenic Traits Many traits are produced by the

interaction of many genes. o Traits controlled by two or more genes are polygenic traits. For example, the wide range of skin color in humans comes about partly because more than four different genes control the trait. Principles In the 1900s a scientist, Thomas Morgan, wanted to

find an organism that could help advance the study of genetics. He decided on the fruit fly Drosophila because o It could produce lots of offspring very quickly (up to 100 offspring per pair) o Its easy to keep in the lab o Its small He discovered that Mendels principles apply to all organisms, not just plants.

Genetics and the Environment The characteristics of any organism are not determined only be the genes it inherits. They are determined by interactions between genes and the environment. o Example: Genes may affect a sunflowers height and the color of its flowers, but these characteristics are also influenced by climate, soil and water. Genes provide a plan for development, but how

that plan unfolds also depends on the environment. Section 11-4 Meiosis Mendel did not know where the genes he had discovered were located in the cell. o We now know that genes are located on

chromosomes in the cell nucleus. o http:// Chromosome Number Remember that offspring inherit a single copy of each gene from each parent, or half the number of chromosomes. This means that when gametes (sex cells) form, the two sets of genes must be separated so each

gamete ends up with only one set. Vocabulary Homologous chromosomes: The matching chromosomes that come from each parent. Diploid: A body cell with both sets of chromosomes (2N)

Haploid: sex cells with only one set of chromosomes (N) Meiosis Meiosis turns a diploid cell into a haploid cell. o 2N Into N Recall that mitosis clones a cell.

2N makes another 2N Meiosis 1 Prior to meiosis 1, each chromosome is replicated. In meiosis 1 each chromosome pairs with its homologous partner to form a tetrad (4 chromatids). This pairing is KEY to understanding meiosis.

As tetrads are formed, they exchange portions of their chromatids in a process called crossing over (prophase I) prophase, metaphase, anaphase, telophase Next The homologous chromosomes separate and two new cells are formed.

The chromosomes have been sorted and shuffled like a deck of cards. VERY IMPORTANT to diversity. These new cells now have chromosomes and alleles that are different from each other and from the parent cells! Meiosis 2

Now one more division to half the genetic material in each cell. We now have 4 genetically different cells! (mitosis creates 2 genetically identical cells)

11-5 Linkage and Gene Maps Mendel concluded that alleles assort independently from each other, but he didnt know genes were on chromosomes. Do genes on the same chromosome travel together? Well, when Morgan was studying his fruit flies in 1910 he discovered that the answer was yes. Every chromosome is

actually a group of linked genes. This means that Mendels conclusion still holds true only its chromosomes that assort independently and not every allele. Genetic Diversity Sometimes crossing over separates the genes

that are on a chromosome and can produce a new combination of alleles. This helps create genetic diversity! Lets try it out Everyone come up and get a cell division set. If you do not have one partner with someone who does. Meiosis 1 is similar to mitosis, lets review. Now

The End!

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