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Vocabulary Genetics C12L03C12

Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

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Page 1: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Vocabulary

Genetics

C12L03C12

Page 2: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Allele - alternative form that a single gene may have for a particular trait (dominant & recessive)

Dihybrid – a genetic cross to examine the possible inheritance of two specific alleles (traits) (e.g. flower color & plant height)

Dominant - stronger of two genes expressed in the hybrid; represented by a capital letter (R). Masks recessive alleles.

Codominance – Pattern where phenotypes of both homozygous parents are produced in heterozygous offspring so that both alleles for a gene are equally expressed. (e.g. a cross between a red cow (RR) and a white cow (WW) produce red a white (RW) spotted cows)

Genetics Vocabulary

Page 3: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

F1 generation - the first-generation offspring in a breeding experiment. (1st filial generation, your parents)

F2 generation - the second-generation offspring in a breeding experiment. (2nd filial generation, you)

Gene - a unit of heredity; a sequence of DNA nucleotides that determines a single characteristic.

Genetics - science of heredity

Genetics Vocabulary

Page 4: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Genotype – gene or allele combination for a trait. This is the letter combination for the genes. (e.g. RR, Rr, rr)

Heredity - passing of traits from parent to offspring

Heterozygous or Hybrid - gene combination of one dominant & one recessive allele    (e.g. Rr)

Homozygous or true breeding (pure) -gene combination involving 2 dominant or 2 recessive genes (e.g. RR or rr)

Genetics Vocabulary

Page 5: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Incomplete Dominance – Pattern where one allele is not completely dominant over the other. Generally displays a new trait. (Parents = Red Flower (RR), and White Flower (rr); Offspring are all Rr with Pink flowers)

Law of Independent Assortment - Mendelian law stating that a random distribution of alleles occurs during the formation of gametes.

Law of Segregation - Mendelian law stating that two alleles for each trait separate during meiosis

Monohybrid – a genetic cross involving a single trait e.g. flower color

Genetics Vocabulary

Page 6: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Parental P1 Generation - the parental generation in a breeding experiment.(your grandparents)

Pedigree – Graphic representation of genetic inheritance used by geneticists to map genetic traits.

Phenotype – Physical expression of the gene. The observable characteristic that is expressed as a result of genotype (e.g. red, white)

Polygenic Traits – traits controlled by two or more genes; genes may be on the same or different chromosomes

Genetics Vocabulary

Page 7: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Punnett Square - a diagram used to analyze the possible gene combinations of the offspring between two individuals. ( genotypes and phenotypes)

Recessive - gene that shows up less often in a cross; represented by a lowercase letter (r). Is not seen if a dominant allele is present.

Sex Linked Traits – traits controlled by genes located on sex chromosomes ( X and Y chromosomes)

Trait — characteristic that is inherited; can be either dominant or recessive

Genetics Vocabulary

Page 8: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Mendelian Genetics

Genetics

Page 9: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Known as the “father of genetics”Austrian MonkStudied the inheritance of traits in

pea plantsDeveloped the rule of dominance

and laws of inheritanceMendel's work was not recognized

until the turn of the 20th century

Gregor Johann Mendel(1822 -1884)

Page 10: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Can be grown in a small area

Produce lots of offspring very quickly

Produce pure plants when allowed to self-pollinate several generations

Can be artificially cross – pollinated

Why Peas, Pisum sativum?

Page 11: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Eight Pea Plant Traits

Page 12: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

1. Seed shape --- Round (R) or Wrinkled (r)2. Seed Color ---- Yellow (Y) or  Green (y)3. Pod Shape --- Smooth (S) or Wrinkled (s)4. Pod Color ---  Green (G) or Yellow (g)5. Seed Coat Color ---Gray (G) or White (g)6. Flower position ---Axial (A) or Terminal (a)7. Plant Height --- Tall (T) or Short (t)8. Flower color --- Purple (P) or white (p)

He studied only one trait at a time to control variables, and he analyzed his data

mathematically.

Eight Pea Plant TraitsPhenotype

Genotype

Page 13: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Pollen contains sperm which is produced by the stamen Ovary (found inside the flower) contains eggs

Reproduction in Flowers

stamen pistol

ovary

• Pollen carries sperm to the eggs for fertilization• Self-fertilization can occur in the same flower• Cross-fertilization can occur between flowers

Page 14: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Mendel’s Experiments

Mendel cross-pollinated flowers using a paintbrush

He could snip the stamens to prevent self-pollination

He traced traits through the several generations

Page 15: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Mendel’s Experiment

Mendel produced pure strains by allowing the plants to self-pollinate for several generations

Page 16: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Mendel’s first experiments are called monohybrid crosses because mono

means “one” and the two parent plants differed from each other by a

single trait like height

Mendel’s Monohybrid Cross

Page 17: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Used to help solve genetic problemsPunnett Squares

Page 18: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Punnet SquaresWhen recording the

results of crosses, it is customary to use the same letter for different alleles of the same gene.

An uppercase letter is used for the dominant allele and a lowercase letter for the recessive allele.

The dominant allele is always written first.

Tall plantT T

T

T

Short plantt t

t

t

Page 19: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Mendel cross-pollinated a tall pea plant with pollen from a short pea

plant

Generations (P1 generation; both true

breed)

T T

t

t

Shortpea plant

Tallpea plant

Page 20: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

All of their offspring were as tall or taller than the parent plants.

Generations (F1 generation)

T T

t

t

Tt Tt

Tt Tt

Shortpea plant

Tallpea plant

Page 21: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

These plants were allowed to self pollinate

Generations (F1 generation)

T t

T

t

Tallpea plant

Tallpea plant

Page 22: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Three-fourths of the plants were as tall as the tall plants in the parent and first

generations and One-fourth of the offspring were as short as the short

plants in the parent generation.

Generations (F2 generation)

T t

T

t

T T T t

T t tt

Tallpea plant

Tallpea plant

Page 23: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Generations Summary

P1

Short pea plant

Tall pea plant

F1

All tall pea plants

F2 3 tall: 1

short

• Parent generation (P1) produced all tall pea plants. (F1)• Short phenotype

disappeared• First generation

(F1)• A cross of two

offspring from P1• Produce F2

• Second generation (F2)• Short phenotype

reappears

Page 24: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

In every case, he found that one trait of a pair seemed to disappear in the F1 generation, only to reappear unchanged in one-fourth of the F2 plants.

Mendel concluded that each organism has two factors that control each of its traits.

We now know that these factors are genes and that they are located on chromosomes.

Mendel’s Conclusions

Page 25: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

An organism’s two alleles are located on different copies of a chromosome—one inherited from the female parent and one from the male parent.

Mendel called the observed trait dominant and the trait that disappeared recessive.

The Rule of Dominance

Page 26: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Mendel’s experiments helped him formulate the 2 laws of

inheritance.

1. The law of segregationAnd

2. The law of independent assortment

Mendel’s Laws of Inheritance

Page 27: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

States that every individual has two alleles of each gene and when gametes are produced, each gamete receives

one of these alleles.

During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other.

Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring.

Law of Segregation

Page 28: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Applying the Law of Segregation

TALLSHOR

T

Tt

TtTt

TtTT

tt

T

T

t

t

Female Parent

Male Parent

Male Gametes

Female Gametes

Page 29: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

An Example: Your mother has the recessive gene for a

unibrow (uu), Your father has the dominant gene for two eyebrows (UU)MOM DAD

Genotype: Uu

Phenotype: two eyebrows

YOU

Page 30: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

States that genes (traits) for different traits—for example, seed shape and seed color—are inherited independently of each other.

This law can be illustrated using dihybrid crosses.

Law of Independent Assortment

Page 31: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Monohybrid Crosses

Genetics

Page 32: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

Genotypes VS. Phenotypes

Genotype Possibilities: RR, Rr, rrPhenotype Possibilities: Red or White

Red (R) Dominant – White (r) Recessive

Page 33: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

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Trait: Seed ShapeAlleles: R – Roundr – WrinkledCross: Round seeds x Wrinkled

seeds RR x rr

P1 Monohybrid Cross

R

R

rr

Rr

RrRr

Rr

Genotype: Rr

Phenotype: Round

GenotypicRatio: All alike

PhenotypicRatio: All alike

Page 34: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

P1 Monohybrid Cross Review

Homozygous dominant X Homozygous recessive

Offspring all Heterozygous (hybrids)

Offspring called F1 generationGenotypic & Phenotypic ratio is ALL ALIKE

Page 35: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

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Trait: Seed ShapeAlleles: R – Roundr – WrinkledCross: Round seeds x Round seeds

Rr x Rr

F1 Monohybrid Cross

R

r

rR

RR

rrRr

Rr

Genotype: RR, Rr, rr

Phenotype: Round & wrinkled

G.Ratio: 1:2:1

P.Ratio: 3:1

Page 36: Vocabulary C12L03C12. dominant & recessive Allele - alternative form that a single gene may have for a particular trait (dominant & recessive) e.g. flower

F1 Monohybrid Cross Review

Heterozygous X HeterozygousOffspring:25% Homozygous dominant RR50% Heterozygous Rr25% Homozygous Recessive rr

Offspring called F2 generationGenotypic ratio is 1:2:1Phenotypic Ratio is 3:1