Pattern Of Inheritance

Review

Define the Following

• Gene • Alleles• Locus• Homozygous• Heterozygous• Dominant• Recessive• Phenotype• Genotype• Monohybrid cros

Definition• A. gene - the unit of heredity; a section of DNA sequence encoding a single

proteinB. alleles - two genes that occupy the same position on homologous chromosomes and cover the same traitC. locus - a fixed location on a strand of DNA where a gene or one of its alleles is locatedD. homozygous - having identical genes (one from each parent) for a particular characteristicE. heterozygous - having two different genes for a particular characteristicF. dominant - the trait that appears in the heterozygous condition G. recessive - the trait that is masked in the heterozygous condition H. phenotype - appearanceI. genotype - genetic makeupJ. monohybrid cross - cross involving a single pair of genes, one trait

Useful Links

• http://www.life.umd.edu/classroom/bsci124/lec10.html

Which of the following is a heterozygous genotype? (1 point)

•a) HHbb

• B) HH• C) Hh• D) hh

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• If black hair (B) is completely dominant over brown hair (b), which of the following will produce brown hair? (1 point)A) BB

• B) Bb• C) bb • D) Both A and B

In a plant, the tall characteristic (T) is dominant over the short (t). In a monohybrid cross, two tall plants produce 3 tall and 1 short offspring.

What are the genotypes of the parents?

• (A) TT, tt• (B) TT, Tt • (C) Tt, Tt • (D) tt, tt

With incomplete dominance, when a red flowered plant is crossed with a white flowered plant, the offspring will be

• (A) red • (B) pink • (C) white• (D) all of these

State the Laws of Mendel

• The inheritance of one pair of factors (genes) is independent of the inheritance of the other pair.

• Law of Independent assortment

The "father of genetics" is (1 point)

• Gregor Mendel. • Isaac Newton. • Carl Sagan.• Charles Darwin.

Hint: Think of a test cross• Tongue rolling (the ability to roll your tongue) is a dominant trait

in humans. A woman who CAN roll her tongue is married to a man who CANNOT roll his tongue. They have four children, only two of whom CAN roll their tongues. Which of the following describes the genotypes of the parents (woman x man)? (1 point)

a) Rr x rr • B) RR x rr• C) Rr x RR • D) Rr x Rr

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• What are the chances of a child being homozygous recessive for a trait if both parents are heterozygous? (1 point)

a) 25% • B) 50% • C) 75% • D) 100%

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• Which of the following crosses will only produce homozygous recessive offspring? (1 point)

a) RRYY x RRYY • B) RRYY x rryy • C) RrYy x rryy • D) rryy x rryy

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• In leopard frogs, black spots (B) are dominant over brown spots (b). A homozygous recessive male frog mates with a heterozygous female frog. What percentage of the offspring will have black spots? (1 point)

a) 0% • B) 25% • C) 50% • D) 100%

-• In Australian Shepherds (a breed of dog), black fur (FB) is

codominant with white fur (FW). The heterozygous phenotype is spotted fur--both black and white. A homozygous male with black fur mates with a spotted female. What percentage of the offspring from this cross are expected to be white? (1 point)

a) 0% • B) 25% • C) 50% • D) 75%

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• Which of the following correctly lists all of the possible gametes that could be produced by a parent with the genotype BbNn? (1 point)

a) Bb, Nn • B) BN, Bn • C) BN, Bn, bb, nn • D) BN, Bn, bN, bn

Pedigree analysis

Multiple alleles

• A man with blood type O marries a woman with blood type A. All of there seven children have blood type A. What is the woman's most likely genotype? (1 point)

a) IAIA

B) IAIB c) IAi d) ii

-• In pea plants, round peas (R) are dominant over wrinkled peas

(r). A cross between two plants yielded the following results: ROUND: 148WRINKLED: 51

• Based on this information, which of the following crosses represents the most likely genotypes of the parents? (1 point)

a) RR x RR• b) RR x Rr • C) Rr x Rr • D) Rr x rr

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• The sex-linked allele for colorblindness is located on (1 point)a) chromosome 21.

• B) the X chromosome only. • C) the Y chromosome only.• D) both the X chromosome and the Y chromosome.

-• Colorblindness is more common in males than in females

because (1 point)

a) fathers pass the allele for colorblindness to their sons only. • B) the allele for colorblindness is located on the Y

chromosome.• C) males who are colorblind have two copies of the allele for

colorblindness. • D) the allele for colorblindness is recessive and located on the

X chromosome.

• The genetic make up of an organism _________

• The physical characteristics of on organism _____

Practice Genetics Problems

• Solve the genetics problems in the following slides based on the concepts of monohybrid cross, dihybrid cross, incomplete dominance, multiple alleles, sex-linked inheritance, autosomal dominant and recessive inheritance.

Genetic Problems

• Most individuals of a certain wild flower have white petals, but a few are blue. Crosses have shown that the blue color is due to a recessive allele. Use "W" for white and "w" for blue.

• a. What is the genotype of a blue-flowered plant and what gametes would it produce as a result of meiosis?

d. If a blue-flowered plant is crossed with its white-flowered parent, what fraction of their offspring would have the genotype "ww"?

•e. If two blue-flowered plants cross, what fraction of their offspring will be blue? White?

Incomplete Dominance

• Four o'clocks exhibit incomplete dominance. Thus, if a plant with red flowers is crossed with a plant with white flowers, the offspring will all produce pink flowers.

• What offspring would you expect if you crossed a red-flowered plant with a pink-flowered plant?

Dihybrid Cross

• In peas, the gene for tall plants (T) is dominant over the gene for dwarf plants (t) and round seed (R) is dominant over wrinkled seed (r). If one crosses a homozygous tall, wrinkled-seeded plant with a homozygous dwarf, round-seeded plant, what is the phenotype of the F1? The genotype of the F1? The phenotypic ratio of the F2?