Chapter 10.2 and 10.3 (biology)

What is the genotypic ratio and phenotypic ratio for dihybrid crosses

1 do not do a genotypic rato for dihybrid or two factor crosses because their are 9 genotypes 2. Do a phenotypic ratio since their is only 4 phenotypes a) DOMINANT/DOMINANT: DOMINANT/RECESSIVE: RECESSIVE/DOMINANT: RECESSIVE/RECESSIVE example: RrYy: Rryy: rrYy; rryy 3. ALWAYS HAVE 4 NUMBERS IN THE RATIO THAT ADD TO UP 16 a) REMEMBER THAT EVEN ONE CAPITAL LETTER IS IN THE COMBINATION IT IS DOMINANT

F1 generation

1. Always heterozygous a) a cross of two F₁'s gives you the F₂ generation 2. Stands for Filial generation

P generation

1. Both parents are purebreads or homozygous for the two forms of the trait a) a cross of the P generation gives you the F₁ generation 2. P stands for parent generation

What happens to genes that are located close together

1. Chromosomes contain multiple genes that code for proteins 2. GENES THAT ARE LOCATED CLOSE TO EACH OTHER ON THE SAME CHROMOSOMES ARE SAID TO BE LINKED AND USUALLY TRAVEL TOGETHER DURING GAMETE FORMATION a) Genes that are linked together on the same chromosome usually travel together in the gamete 3. The linkage of genes on a chromosome results in an exception to Mendel's law of independent assortment because linked genes usually do not segregate independently 4. First studied using the fruit fly a) thousands of crosses confirmed THAT LINKED GENES USUALLY TRAVELED TOGETHER DURING MEIOSIS b) SOME RESULTS REVEALED THAT LINKED GENES DO NOT ALWAYS TRAVEL TOGETHER DURING MEIOSIS 5. Scientists concluded that linked genes can separate during crossing over

What happens to genes that are farther apart to each other during a cross

1. In a cross, the exchange of genes is directly related to the cross over frequency between them 2. This frequency correlates with the relative distance between the two genes a) One chromosome map unit between two genes is equivalent to 1% of the crossing over occurring between them 3. GENES THAT ARE FARTHER APART WOULD HAVE A GREATER FREQUENCY OF CROSSING OVER

What were the results and conclusions of Mendel's experiment

1. Inherited characteristics in pea plants are controlled by FACTORS THAT OCCUR IN PAIRS a) we now know these factors are genes(allele) and you get one from each parent which is how they ed up in pairs b) the gene for yellow seeds and the gene for green seeds are each different forms of a single gene 2. The traits that appeared in the F₁ generation was the DOMINANT TRAIT because it masked the other form of the trait, THE RECESSIVE TRAIT which reappeared in the F₂ generations a) in the cross between yellow-seed plants and green seed plants, the yellow seed was the dominant form of the trait and the green seed of the recessive form of the trait 3. Mendel concluded that the PAIR OF GENES FRO A TRAIT SEPARATE DURING MEIOSIS, so each reproductive cell gets only one gen of the pair, and when fertilization occurs the offspring again have a pair of genes for a trait a) CALLED THE LAW OF SEGREGATION 4. Mendel also concluded that the green-seed form of the trait did not show up in the F₁ generation because the yellow seed form of the trait is dominant and masks the allele for the green-seed of the trait a) The green-seed is masked but it does not disappear

How do you tell one factor crosses apart?

1. MENDELIAN DOMINANT/RECESSIVE: a) obeys the same principal of dominant ex; R= round r= wrinked, Rr is round 2. INCOMPLETE DOMINANCE: a) two alleles create 3 different phenotype (2 homozygous and 1 heterozygous) ex: R= red W= white, RW is pink 3. CODOMINANCE: a) both forms of the trait show up ex: F(exponent B)= black feathers F(exponent W)= white feathers, F(exponent B)F(exponent W) has both black and white feathers

Mendel's experiment

1. Mendel allowed pea plants to self-pollinate for many generations to ensure THEY COULD ONLY PRODUCE ONE FORM OF THE TRAIT a) True breeding or pure bred plants always produce offspring with the trait they have b) yellow seed plants always produce offspring with yellow seeds c) CALLED THESE PLANTS THE P GENERATION (P= PARENT) 2. Mendel performed cross-pollination by transferring male gametes from the flower of a true breeding green seed plant to the female organ of a flower from a true-breeding yellow seed plant a) to prevent self fertilization, Mendel removed the male organs from the flower of the yellow seed plant 3. A cross in the P generation produces the F₁ (first filial) generation a) THE F₁ ALWAYS SHOW ONLY ONE FORM OF A TRAIT b) His cross of the P generation produced ALL YELLOW PEAS c) Decided to investigate whether th trait was no longer present or whether it was hidden or masked 3. The F₂ (send filial) generation is produced by allowing the F₁ generation to self fertilize or by crossing two members of the F₁ a) of the seed Mendel collected, 6022 were yellow and 2001 were green a) BOTH FORMS OF THE TRAIT REAPPEAR IN THE F₂ GENERATION IN A 3:1 RATIO of yellow to green seeds 4. He did seven different experiments with the same results every time (F₂ GENERATION PLANTS FROM DIFFERENT TRAIT CROSSES ALSO SHOWED A 3:1 RATIO a) a big sample takes out chance and proves that something is occurring

What are the types of analyses with Punnett squares

1. PHENOTYPIC RATIO: 3:1 a) # that look dominant: # that look recessive 2. GENOTYPIC RATIO: 1:2: 1 a) # of homozygous dominant: # of heterozygous: # of homozygous recessive b) always 3 numbers when you are dealing with 1 factor

Why is the pea plant an ideal organism to study heredity with

1. Pea plants are true breeding 2. Mendel observed that the had characteristics that were displayed in one form or the other a) tall or short b) purple or white flowers 3. Easy to grow and reproduce quickly 4. Pea plants usually reproduce by self-fertilization a) Mendel discovered that pea plants could easily be crossed pollinated by hand b) He was able to make plats with specific traits by interrupting self pollination and transferred a male gamete from the flower of one pea plant to the female reproductive organ in a flower of another pea plant c) He was able to observe how traits were passed by carefully controlling how plants were pollinated (fertilized) d) he analyzed the results of his experiments and formed hypotheses concerning how the traits were inherited

F2 generation

1. Second filial generation 2. All possible genotypes will show up in a 1:2:1 ratio 3. all possible phenotpyes will be expressed always 3:1 ratio 4. The product of a cross of two F₁

What different traits did Mendel examine

1. Seed/pea color a) yellow or green 2. Flower color a) purple or white 3. Seed pod color a) green or yellow 4. Seed shape/texture a) round or wrinkled 5. Seed pod shape a) inflated or constricted 6. Stem length a) tall or dwarf 7. Flower position a) axial or terminal

What are the different types of the one factor crosses

1. Test crosses 2. Incomplete dominance 3. Codominance

How do you model inheritance

1. There is a dominant allele, which is represented BY A CAPITAL LETTER a) Y= yellow seeds 2. There is a recessive allele REPRESENTED BY A LOWER CASE LETTER a) the lowercase version of the letter in the dominant allele b) y=green seeds 3. In F₁ cross, the dominant allele is writtten first, whether it came from the male or female gamete

How do you make a Punnett square for dihybrid crosses?

1. their are 16 squares with 4 alleles in each one 2. The alleles are spread out in pairs of two a) follow the arrow method to find the options at the top and side 3. Put them together normally a) Make sure that to put capitals BEFORE the lower case letters in the combination

Monohybrid cross

A CROSS THAT INVOLVES HYBRIDS FOR A SINGLE TRAIT 1. Only one trait is tracked 2. Cross of two F₁ 3. HETEROZYGOUS ALWAYS (Yy)

Chromosome maps

A DRAWING THAT SHOWS THE SEQUENCE OF GENES ON A CHROMOSOME AND CAN BE CREATED BY USING CROSSOVER DATA 1. Crossing over occurs more frequently between genes that are far apart than those that are close together 2. The very first chromosome maps were published in 1913 using data from thousands of fruit fly crosses 3. CHROMOSOME MAPS PERCENTAGES ARE NOT ACTUAL CHROMOSOME DISTANCES, BUT THEY REPRESENT RELATIVE POSITIONS OF THE GENES

Dihybrid cross

A cross between two organism from the F₁ generation that are heteroygous for both of the two traits that are being tracked 1. Mendel crossed plants that differed in 2 characteristics AND FOUND THAT IN THE F₂ GENERATION, ALL POSSIBLE COMBINATIONS OF THE PARENT CHARACTERISTICS ARE SHOWN example: crossing homozygous yellow, round seed pea plants with homozygous green, wrinkle seed pea plants a) the P cross could be represented by RRYY x rryy a) the F₁ generation would be all hybrid and the genotype is heterozygous, RrYy and the phenotype is the dominant, yellow and round 1. In the dihybrid cross, when the F₁ generation is crossed, four types of alleles from the male and four types of alleles from the female gametes can be produced a) CROSSING RrYy x RrYy AND YOU GET 4 PHENOTYPES (ALL POSSIBLE COMBINATIONS OF THE PARENTS CHARACTERISTICS 1. round, yellow 2. round, green 3. wrinkled, green 4. wrinkled, yellow MENDEL DID THIS WITH A COMBINATION OF ALL 7 DIFFERENT TRAITS AND ALWAYS GOT 4 PHENOTYPES AND THE SAME CHARACTERISTIC RATIO

allele

ALTERNATIVE FORM THAT A SINGLE GENE MAY HAVE FOR A PARTICULAR TRAIT 1. The alternate forms of a gene

genotype

AN ORGANISM'S GENOME (total DNA in each cell nucleus of an organism) a) an organism's allele pairs example: YY or yy or Yy

In the trait flower position, what is the dominant and recessive genes

Axial is dominant Terminal is recessive

What cross would result in 1/2 offspring having green pods and 1/2 of the offspring having yellow pods

Cross Tt and tt

Find the Genotypic and phenotypic ratio for this cross: cross a plant that is heterozygous for inflated pods with a plant that has constricted pods

Genotypic ratio: 0:2: 2 Phenotypic ratio: 2:2 constricted pod is recessive

Find the Genotypic and phenotypic ratio for this cross: cross a plant that is heterozygous for axial flowers with a plant that has terminal flowers

Genotypic ratio: 0:2:2 Phenotypic ratio: 2:2

Find the Genotypic and phenotypic ratio for this cross: Aa x aa

Genotypic ratio: 0:2:2 Phenotypic ratio: 2:2

Find the Genotypic and phenotypic ratio for this cross: Cross a homozygous tall plant with a short plant

Genotypic ratio: 0:4:0 Phenotypic ratio: 4:0 both are homozygous so they make heterozyogous

Find the Genotypic and phenotypic ratio for this cross: Tt x Tt

Genotypic ratio: 1:2:1 Phenotypic ratio: 3:1

Find the Genotypic and phenotypic ratio for this cross: cross two plants that are heterozygous for green pods

Gentotypic ratio: 1:2:1 Phenotypic ratio: 3:1

In the trait pod color, what is the dominant and recessive genes

Green is dominant Yellow is recessive

polyploidy

HAVING ONE OR MORE EXTRA SETS OF ALL CHROMOSOMES, WHICH IN POLYPLOID PLANTS CAN OFTEN RESULT IN GREATER SIZE AND BETTER GROWTH AND SURVIVAL 1. Most species have diploid cells, but some have polyploid cells 2. Occur rarely in animals a) IN HUMANS, POLYPLOID IS ALWAYS LETHAL 3. Roughly one in three species of known flowering plants are polyploid a) polypoid plants are selected by plant growers for their desirable characteristics b) increase in vigor and size EXAMPLES: 1. A triploid organism (3n or it has 3 complete sets of chromosomes) 2. Commercially grown bread wheat (6n) 3. Oats (6n) 4. Sugar cane (8n) 5. Coffee (4n) 6. Strawberries (8n)

Punnett Squares

ILLUSTRATE GENETIC CROSSES a) visual summary of the possible combinations for the alleles 1. A way to predict the outcome of crosses 2. Dr. Reginald Punnett developed the Punnett square to predict the possible offspring of a cross between two known genotypes 3. Allow genticists to predict the possible genotype and phenotypes of the offspring from a genetic cross 4. SHOW PROBABILITIES 5. There are four different possible crosses in the inside squares from the F₁ generation in monohybrids 6. The outside has the two genotypes from the P generation 7. MENDEL'S DATA CLOSELY MATCHED THE OUTCOME PREDICTS BY THE PUNNETT SQUARES

In the trait pod shape, what is the dominant and recessive genes

Inflated is dominant Constricted is recessive

recessive

MENDEL'S NAME FOR A SPECIFIC TRAIT HIDDEN OR MASKED IN F₁ GENERATION

dominate

MENDEL'S NAME FOR A SPECIFIC TRAIT THAT APPEARED IN THE F₁ GENERATION

law of independent assortment

MENDELIAN LAW STATING THAT A RANDOM DISTRIBUTION OF ALLELES OCCURS DURING THE FORMATION OF GAMETES a) Alleles for different characteristics, located on different chromosomes are distributed to gametes independently (describes meiosis) b) Genes on separate chromosomes sort independently during meiosis 1. Developed from the calculation of the genotypic and phenotypic ratios of the offspring of F₁ pea plants that self fertilized in a dihybrid cross in both the F₁ and F₂ generations 2. Form four possible gametes and there is an equal chance that any of these gametes will form

law of segregation

MENDELIAN LAW STATING THAT TWO ALLELES FOR EACH TRAIT SEPARATE DURING MEIOSIS 1. Both homologous chromosomes have the same trait, so when the pairs separate, the genes are on those chromosomes 2. During gamete formation in the YY or yy plant, the two alleles separate resulting in Y or y in the gametes a) During fertilization, two alleles for that trait unite

genetic recombination

NEW COMBINATION OF GENES PRODUCED BY CROSSING OVER AN INDEPENDENT ASSORTMENT 1. The possible combinations of genes due to independent assortment can be calculated using the formula 2n (exponent n), where n is the number of chromosomes pairs a) this number does not include the amount of genetic recombination produced by crossing over EXAMPLE: Pea plants have 7 pairs of chromosomes a) for seven pairs of chromosomes, the possible combinations are 2⁷ or 128 combinations

Phenotype

OBSERVABLE CHARACTERISTIC THAT IS EXPRESSED AS A RESULT OF AN ALLELE PAIR a) an organism's observable characteristics or outward expression of an allele pair example: yellow seeds or green seeds 1. The outward appearance of an organism does not always indicate which pair of alleles is present

hybrid

ORGANISM HETEROZYGOUS FOR A SPECIFIC TRAIT

Heterozygous

ORGANISM WITH TWO DIFFERENT ALLELES FOR A SPECIFIC TRAIT 1. The F₁ generation are all heterozygoous or hybrid because they get a dominant allele from one parents and a recessive allele from the other a) Yy= yellow 2. When alleles are present in the heterozygous state, the dominant trait will be observed

Homozygous

ORGANISM WITH TWO OF THE SAME ALLELES FOR A SPECIFIC TRAIT 1. The pair of alleles for each parent in the P generation match a) Yellow seed parent= YY (HOMOZYGOUS DOMINANT) b) the green seed parent= yy (HOMOZYGOUS RECESSIVE) A) Only way the recessive trait will be expressed 2. THE P GENERATION IS ALWAYS HOMOZYGOUS

3/4 of the plants by a cross between two unknown pea plants have axial flowers and 1/4 have terminal flowers. What are the genotypes of the parent plants

Parent genotypes: Aa and Aa

when a tall plant is crossed with a short plant, some of the offspring are short. What are the genotypes of the parents and the offsprings? What is the phenotypic ratio of the offspring

Parent genotypes: Tt and tt Offspring genotypes: Tt and tt Phenotypic ratio: 2:2

In the trait flower color, what is the dominant and recessive genes

Purple is dominant White is recessive

In the trait seed shape , what is the dominant and recessive genes

Round is dominant Wrinkled is recessive

Gregor Mendel

THE FATHER OF GENETICS 1. An Austrian monk and a plant breeder who studied science and mathematics 2. First person to systematically study heredity 3. Published his findings (in a book) in 1866 a) this happened a year after Darwin's evolution so it was largely ignored b) when his work was rediscovered, it laid the ground work for heredity 4. He was successful in sorting out the mystery of inheritance because of the organism he chose for his study, THE PEA PLANT

genetics

THE SCIENCE OF HEREDITY 1. Began with Mendel's experiment

probabilities

The likelihood of an event or outcome 1. represented as a fraction or a percentage ex: 1/4 will look recessive or 25% 2. Actual data might not perfectly match the predicted ratios a) the larger the number of offspring involved in a cross, the more likely it will match the results predicted by the Punnett square

cross

The mating of two organisms 1. represented by x ex: YY x yy

Test cross

USED TO DETERMINE THE GENOTYPE OF AN INDIVIDUAL WHOSE PHENOTYPE IS DOMINANT a) unlike a recessive phenotype, dominant phenotypes have two different possible genotypes that would create it 1. To determine the genotype, cross the unknown with a recessive individual 2. If any resulting offspring exhibit the recessive phenotype, then the unknown individual was heterozygous a) if the resulting offspring exhibit all dominant phenotypes, you know the unknown individual is homozygous

Codominance

WHEN BOTH ALLELES FOR A GENE ARE EXPRESSED EQUALLY IN A HETEROZYGOUS OFFSPRING a) both colors are shown in the offspring, nothing is hidden EXAMPLE: Roan (mix of red and white) H(exponent R)H(exponent R)= red H(exponent W)H(exponent W)= white OFFSPRING GENOTYPE: H(exponent R)H(exponent W) a) MUST BE WRITTEN LIKE THIS: TRAIT(option as exponent) Trait (option as exponent) Penotype: roan, both red and white EXAMPLE 2: Human blood types

Incomplete dominance

WHEN NEITHER ALLELE IS DOMINANT OVER THE OTHER ALLELE, RESULTING IN A PHENOTYPE IN THE HETEROZYGOTE THAT IS A BLEND OF THE TWO HOMOZYGOUS PHENOTYPES a) think blended offspring 1. EXAMPLE: four o'clock flowers RR= red WW- white RR x WW= RW (all pink) a) GENOTYPIC RATIO: 1RR: 2RW: 1WW b) PHENOTYPIC RATIO: 1 red: 2 pink: 1 white c) 3 numbers in the ratio because no trait is dominant (3 different possible outcomes that are needed in the ratio) EXAMPLE 2: human facial features

self pollination

WHEN POLLEN IS TRANSFERRED FROM THE ANTHERS TO THE STIGMA a) occurs when a male gamete within a flower combines with female gamete in the same flower

In the trait seed color, what is the dominant and recessive genes

Yellow is dominant Green is recessive

true breeding

an organism that consistently produce off spring with only one form of a trait

What is the phenotypic ratio that the traits show up in the F2 generation in both monohybrid and dihybrid crosses

phenotypic ratio for monohybrid crosses: 3:1 phenotypic ratio for dihybrid crosses: 9:3:3:1

In the trait stem length , what is the dominant and recessive genes

tall is dominant dwarf is recessive

heredity

the tendency for traits to be passed from parent to offspring AKA INHERITANCE