Repressors bind to specific sites on the DNA. In bacterial cells, such binding sites, called operators

Regulation by means of a repressor protein that blocks transcription is referred to as negative regulation. Activators provide a molecular counterpoint to repressors; they bind to DNA and enhance the activity of RNA polymerase at a promoter; this is positive regulation.Repressor binding to DNA is regulated by a molecular signal called effector

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#Unit 8. Inheritance Biology

The exchange of bacterial genes clearly required direct contact, between the bacterial cells

TLS Online TPP Program

#Id: 6753

#Unit 8. Inheritance Biology

Lederberg and Tatum’s experiment demonstrated that bacteria undergo genetic exchange.

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#Unit 8. Inheritance Biology

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#Unit 8. Inheritance Biology

Autosomal Recessive Trait

a. Usually appears in both sexes with equal frequency.

b. Tends to skip generations.

c. Affected offspring are usually born to unaffected parents.

d. When both parents are heterozygous, approximately one-fourth of the offspring will be affected.

e. Appears more frequently among the children of consanguineous marriages.

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#Unit 8. Inheritance Biology

Autosomal Dominant Trait

a. Usually appears in both sexes with equal frequency.

b. Both sexes transmit the trait to their offspring.

c. Does not skip generations.

d. Affected offspring must have an affected parent unless they possess a new mutation.

e. When one parent is affected (heterozygous) and the other parent is unaffected, approximately half of the offspring will be affected.

f. Unaffected parents do not transmit the trait.

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#Unit 8. Inheritance Biology

X-Linked Recessive Trait

a. Usually more males than females are affected.

b. Affected sons are usually born to unaffected mothers; thus, the trait skips generations.

c. Approximately half of a carrier (heterozygous) mother’s sons are affected.

d. Never passed from father to son.

e. All daughters of affected fathers are carriers.