Genetics - Pottsgrove School District

Genetics - Pottsgrove School District

Genetics 11.1 Gregor Mendel Heredity Inheritance Genetics of traits - study of heredity Genetics

Gregor Mendel Suggested that paired factors, or genes, carry inherited traits. Predicted how traits were inherited by studying pea plants The Role of Fertilization Fertilization - During sexual reproduction, male and female reproductive cells join to produce a new cell. The Role of Fertilization

The Role of Fertilization Mendel had several truebreeding plants Trait - a specific characteristic of an individual

Self-pollinating and produce offspring identical to parent Ex) Seed color and shape. Varies The Role of Fertilization Mendel studied traits of pea plants. Hybrids - Offspring between parents with different traits.

Quick Graded Review Two Options 5 minutes 1. Stand and speak Summarize the notes in 15 seconds. Spend the next 3 minutes preparing what

youll say. 2. Schoology discussion Go to Schoology your class Unit 7 11.1 Summary First Half Write a summary of the notes so far in at least 3 sentences.

Do not respond to anyone yet. Genes and Alleles P gen Parents - Original pair of plants F1 - Offspring of P generation. In each cross, the nature of the other parent, with regard to each trait, seemed

to have Genes and Alleles Mendels first conclusion - An individuals characteristics are determined by factors that are passed from one parental generation to the next.

Genes - Factors that are passed from parent to offspring. Dominant and Recessive Traits Mendels second conclusion Principle of Dominance

Some alleles are dominant, others are recessive. If an organism has at least one dominant allele for a trait, it will exhibit the dominant trait. If an organism has a recessive allele for a trait, it will exhibit the recessive trait only when there are no dominant alleles present. Alleles Different forms of a gene Organisms have two alleles, or genes, for each trait.

One allele from the female gamete (egg). One allele from the male gamete (sperm). Segregation What happened to the recessive alleles? Mendel allowed F1 hybrids to self-pollinate. The

offspring of an F1 cross are called the F2 generation. The F1 Cross When Mendel saw the F2 plants, he observed the recessive traits reappeared. About of the F2 plants showed the recessive trait.

Explaining the F1 Cross Alleles had segregated. Mendel suggested the alleles for tallness and shortness in the F1 plants segregated from each other during formation of the sex cells, or gametes. Seed Seed shape color

Flower color Flower position Pod color Pod shape Plant height

purple axial (side) green inflated tall white terminal (tips)

yellow constricted short Dominant trait round yellow wrinkled

green Recessive trait Quick Graded Review Two Options 5 minutes 1. Stand and speak

Summarize this part of notes in 15 seconds. Spend the next 3 minutes preparing what youll say. 2. Schoology discussion Go to Schoology your class Unit 7 11.1 Summary Second Half Write a summary of this part of notes in at least 3

sentences. Or respond and add on to someone elses response from First Half with information from notes. Recessive attached ear lobes Tongue Roll Dominant trait Dominant Free Ear Lobes Hitch hikers

thumb Dominant Regular thumb Recessive Other examples Chin cleft Dominant Bent pinky finger Dominant

Dimples Blue Dominant eyes Recessive Hand clasp Left thumb dominant Widows peak - Dominant

11.2 Applying Mendels Principles Dominant gene (allele) Stronger of two genes Represented Written by capital letter

first Example: T for tall plant height Recessive gene (allele) Weaker Can of two genes be hidden by dominant genes.

Represented Example: with lower case letters t for short plant height Pure (Homozygous) Two of the same genes (alleles) for a trait Example: TT (homozygous dominant) or tt (homozygous recessive)

Hybrid (Heterozygous) Two different alleles for a trait Example: Tt Tall or short? Probability Probability The likelihood that a particular event will occur.

Example: Flipping a coin Probability 1 of flipping heads? Number of desired outcomes 2 Number of total possible outcomes

Probability Example: Flipping a coin Probability of flipping heads three times? x x = 1/8 Genotype Combination of alleles or genes

for a certain trait Example: Tt, TT, tt Phenotype Physical, how visible traits it looks Determined by looking at

organism Example: tall, short Genotype or Phenotype? Tt Genotype Round Phenotype Black Phenotype

BB Genotype Smoot Phenotype h rr Tall Genotype Phenotype

In pea plants, green (G) pods are completely dominant over yellow (g). What are the genotypes? Homozygous gg yellow Heterozygous green Gg GG Homozygous dominant Hybrid Gg

In pea plants, green pods are completely dominant over yellow. Pure yellow gg Homozygous Pure recessivegg green GG Heterozygous Gg

Yellow gg In guinea pigs, short hair is dominant over long hair What hair length will be represented by a capital S? Short What hair length will be represented by a lower case s? Long

What phenotypes would result from the following genotypes? SS Short hair ss Long hair Ss Short hair

What are the phenotypes of the parent plants? Tall plant Short plant If both parents are pure, what are their genotypes? Which gene or allele can each parent pass on to the offspring? What is the phenotype of the offspring? What is the genotype of

the offspring? T T t t T t All tall plants

T t In pea plants, round pea pod texture is dominant over wrinkled texture. What is the genotype of the following? homozygous roundRR heterozygous Rr wrinkled rr

pure dominant RR hybrid round Rr In pea plants, round pea pod texture is dominant over wrinkled texture. What is the genotype of the following? pure rr recessive heterozygous round Rr pure wrinkled rr hybrid Rr

pure round RR Punnett Squares Punnett squares used to predict and compare the genetic differences that will result from a cross. Monohybri

d crosses Heterozygous tall parent Heterozygous tall parent T t T T t t

T TT Tt t Tt tt How To Make a Punnett Square for a OneFactor Cross

Write the genotypes of the parents in a cross. Ex) Cross a male and female bird that are heterozygous for large beaks. They each have genotypes of Bb. Bb and Bb How To Make a Punnett Square

Draw a Punnett square. Put one parent on the top, one parent on the left. Put one allele from each parent on each side of each section. How To Make a Punnett Square

Fill in the table by combining the gametes genotypes. Mom Dad How To Make a Punnett Square -Determine the genotypes and phenotypes of each offspring. Probability of having A large beak?

A small beak? Homozygous 3:4 1:4 1:4 dominant? Heterozygous? 2:4

Homozygous recessive? 1:4 Independent Assortment Principle of independent assortment genes for different traits can segregate independently during the formation of gametes. Dihybrid Cross Two factor cross Two traits involved. The Two-Factor Cross: F1

Mendel crossed two true-breeding plants: One produced only round yellow peas One produced only wrinkled green peas.

The Two-Factor Cross: F1 The round yellow peas had the genotype RRYY, which is homozygous dominant. The Two-Factor Cross: F1 The wrinkled green peas had the genotype rryy, which is homozygous recessive.

The Two-Factor Cross: F1 All F1 offspring were round yellow peas. Shows yellow and round alleles are dominant over the alleles for green and wrinkled. Punnett square shows genotype of F1 offspring as RrYy, heterozygous for both seed shape and seed

color. The Two-Factor Cross: F2 Mendel then crossed the F1 plants to produce F2 offspring. Crossed RrYy RrYy with

Dihybrid cross instructions Cross the parent alleles. Make sure each box has two of each letter, one from each

Mom Dad The Two-Factor Cross: F2 Alleles for shape segregated independently of those for color. Genes that segregate

independently do not influence each others inheritance. The Two-Factor Cross: F2 Results were close to the 9:3:3:1 ratio the Punnett square predicts. Mendel discovered the principle of

independent assortment genes for different traits segregate independently during gamete formation. 11.3 Other Patterns of Inheritanc Incomplete dominance Alleles BLEND (mix)

Neither gene is dominant Heterozygous phenotype is a blend of the dominant and recessive phenotypes. Think Red about colors of paint + White = Pink Incomplete Dominance R

R W RW RW RW RW W www.nerdscience.com 11-3

Codominance Both alleles are dominant Heterozygous expresses both phenotypes together. There is NO blending Red + White = Red and White Red cow crossed with white cow results

in roan cattle. Roan cattle have both red and white hairs. Codominance Codominance Example: White chicken (WW) x black chicken (BB) = black and white checkered

chicken (BW) Codominance Incomplete or Codominance? A white cow and a red cow produce a roan cow, one that has both white and red hairs. Codominance A red flower and a white flower

produce pink flowers. Incomplete A black cat and a tan cat produce tabby cats, cats where black and tan fur is seen together. Codominance Incomplete or Codominance? A blue blahblah bird and a white blahblah bird produce offspring that

are silver. Incomplete A certain species of mouse with black fur is crossed with a mouse with white Incomplete fur and all of the offspring have grey fur. A woman with blood type A and a man

with bloodCodominance type B have a child with blood type AB. Multiple Alleles Single gene with more than two alleles. example: type

human blood Blood Types (codominant) Blood type is codominant IA and IB are dominant. i is recessive 4 different blood types Phenotype Genotype (Blood

(Alleles or type) genes for blood type) A IAIA, IAi B IBIB, IBi AB

I AI B O ii Polygenic Traits Traits controlled by two or more (many) genes Polygenic traits often show a wide range of phenotypes.

example: human skin color employs more than four different genes Skin color genes: AaBbCcDd Genes and the Environment The characteristics of any organism are not determined solely by the genes that organism

inherits. Genes provide a plan for development, but how that plan unfolds also depends on the environment. Both nature and nurture 14.1 Human Chromosom

es Karyotype Chart of chromosome pairs arranged by decreasing size. Shows unusual number of chromosomes Can detect trisomy 21 (Down syndrome) Identifies male or female Shows genome full set of genetic information. Karyotype

Normal Female Karyotype Female with Down Syndrome Sex Chromosomes X and Y chromosomes Determine the sex of the offspring Females are XX Males are XY Sex Chromosomes All

other chromosomes are autosomes. Everyone has 46 chromsomes: 2 sex chromosomes and 44 autosomes. Sex-linked Traits Traits inherited on X and Y chromosomes. Most

are on the X chromosome (because its bigger) Example) Color blindness is a recessive sex-linked trait on the X-chromosome Males show recessive sex-linked traits more than females Why?

Sex-linked Traits Males get only one X chromosome Therefore, males show all recessive sex-linked traits on X chromosome. Females have a second X chromosome that carries another

allele that can hide recessive traits Sex-linked Traits Females who have recessive alleles but show the dominant trait (heterozygous) are called carriers A woman can have normal vision but carry the recessive allele for colorblindness X-Chromosome Inactivation

If just one X chromosome is enough for male cells, how does the cell adjust to the extra X chromosome in female cells? In female cells, one X chromosome is randomly switched off, forming a Barr body. Barr bodies are generally not found in males because their single X chromosome is still active.

Pedigree Study Method of determining the genotype of individuals by looking at inheritance patterns Male Parents Female

Siblings Affected male Affected female Mating Known heterozygotes for recessive allele Death

Pedigrees illustrate inheritance Human Pedigrees This diagram shows what the symbols in a pedigree represent. Human Pedigrees This pedigree shows how one human trait a white lock of hair just above the forehead

passes through three generations of a family. The allele for the white forelock trait is dominant. Human Pedigrees Top of the chart is grandfather with the white forelock trait.

Two of his three children inherited the trait. Three grandchildren have the trait, but two do not. Human Pedigrees Because the white forelock trait is dominant, all family members lacking this trait must have homozygous recessive alleles.

One of the grandfathers children lacks the white forelock trait, so the grandfather must be heterozygous for this trait.

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