Test 2 Flashcards by Chelsea Hayes

Prevalent alleles in a population are termed..

Wild-type alleles

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___ ___ can produce more than one wild-type in large populations.

Genetic polymorphism

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Alleles that have been altered by mutation are termed..

Mutant alleles

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Gain-of-function

Protein encoded by the mutant gene is changed so it gains a new or abnormal function

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Dominant-negative

Protein encoded by the mutant gene acts antagonistically to the normal protein

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Haploinsufficiency

Loss of function

Heterozygote does not make enough product to give the wild type phenotype

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Incomplete penetrance

In some instances, a dominant allele does not influence the outcome of a trait in a heterozygote individual

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Expressivity

The degree to which a trait is expressed

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Incomplete dominance

The heterozygote exhibits a phenotype that is intermediate between the corresponding homozygotes

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Overdominance

Heterozygote is more vigorous than both of the corresponding homozygotes

Heterozygote advantage

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At the molecular level, overdominance is due to..

Two alleles that produce slightly different proteins

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Three possible explanations for overdominance at the molecular level

Disease resistance
Homodimer formation
Variation in functional activity

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Type O blood people can only accept what type of blood?

Type O

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Who can type O blood donate to?

Anyone

Universal donor

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Sex-linked genes

Found on one of the two types of sex chromosomes, but not both

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Pseudoautosomal inheritance

Very few genes found on both X and Y chromosomes

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Sex-influenced traits

Involve an allele that is dominant in one sex but recessive in the opposite sex

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Lethal allele

One that has the potential to cause of death of an organism

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Essential genes

Those that are absolutely required for survival

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Nonessential genes

Those not absolutely required for survival

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Conditional lethal alleles

May kill an organism only when certain environmental conditions prevail

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Semilethal alleles

Kill some individuals in a population, not all of them

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Pleiotrophy

Multiple effects of a single gene on the phenotype of an organism

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Gene interactions

Occur when two or more different genes influence the outcome of a single trait

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Epistasis

When the alleles of one gene mask the phenotypic effects of the alleles of another

Gene knockout

Geneticists have developed techniques to directly generate loss-of-function alleles

Maternal effect

An inheritance pattern for certain nuclear genes in which the genotype of the mother directly determines the phenotype of her offspring

Maternal effect and epigenetic inheritance involves..

Genes in the nucleus

Extranuclear inheritance involves..

Genes in organelles other than the nucleus

The non-Mendelian inheritance pattern of maternal effect genes can be explained by the process of ___ in female animals.

Oogenesis

Epigenetic inheritance

A pattern in which a modification occurs to a nuclear gene or chromosome that alters gene expression

Lyon hypothesis

Mechanism of X inactivation

The process of X inactivation can be divided into 3 stages:

Initiation Spreading Maintenance

Initiation

One of the X chromosomes is targeted for inactivation

Spreading

The chosen X chromosome is inactivated

Maintenance

The inactivated X chromosome is maintained as such during future cell divisions

Genomic imprinting

A phenomenon in which a segment of DNA is marked and the effect is maintained throughout the life of the organism inheriting the marked DNA

Monoallelic expression

Depending on how the genes are marked, the offspring expressed either the maternally-inherited or the paternally-inherited allele

Three stages of imprinting

1. Establishment of the imprint during gametogenisis 2. Maintenance of the imprint during embryogenesis and in the adult somatic cells 3. Erasure and reestablishment of the imprint in the germ cells

Genomic imprinting must involve a ___ ___.

Marking process

Genomic imprinting is permanent in the somatic cells of an ___ animal.

Individual

Extranuclear inheritance

Inheritance patterns involving genetic material outside the nucleus

The genetic material of mitochondria and chloroplasts is located in a region called the ___.

Nucleoid

The genome is composed of a single chromosome containing..

Double-stranded DNA

The two most important examples are due to genetic material with what two organelles?

Mitochondria and chloroplasts

The main function of choroplasts is ___

Photosynthesis

Species with maternal inheritance may, on occasion, exhibit ___ ___.

Paternal leakage

The paternal parent occasionally provides mitochondria through the sperm

Heteroplasmy

Important factor in mitochondrial disease

Endosymbiosis theory

Describes the evolutionary origin of mitochondria and chloroplasts

Bacteria reproduce ___

Asexually

Genetic transfer

A segment of bacterial DNA is transferred from one bacterium to another

Bacteriophages

Viruses that infect bacteria

Transfer of genetic material from one bacterium to another can occur in 3 ways:

Conjugation Transduction Transformation

Conjugation

Involves direct physical contact

Transduction

Involves viruses

Transformation

Involves uptake of genes from the environment

Auxotrophs

Cannot synthesize a needed nutrient

Prototrophs

Make all their nutrients from basic components

Genetic transfer in bacteria was discovered by who?

Lederberg and Tatum

U-tube

Large enough to allow the passage of the genetic material but small enough to prevent the passage of bacterial cells

Fertility plasmids

Allow conjugation

Resistance plasmids

Contain genes conferring resistance to antibiotics

Degradative plasmids

Carry genes allowing digestion of unusual substances

Col-plasmids

Contain genes for colicins, proteins that kill other bacteria

Virulence plasmids

Carry genes that turn bacterium into pathogenic strains

The ___ of ___ of the integrated F factor determines the starting point and direction of the transfer process.

Origin of transfer

thr+

Able to synthesize the essential amino acid threonine

leu+

Able to synthesize the essential amino acid leucine

azi^s

Sensitive to killing by azide

ton^s

Sensitive to infection by T1

lac+

Able to metabolize lactose and use it for growth

gal+

Able to metabolize galactose and use it for growth

str^s

Sensitive to killing by streptomycin

Cotransduction

The packaging and transfer of two closely-linked genes

Cotransduction frequency

(1-d/L)^3

Natural transformation

DNA uptake occurs without outside help

Artificial transformation

DNA uptake occurs with the help of special techniques

Competent cells

Bacterial cells able to take up DNA

"Illegitimate" recombination

The DNA that enters the cell is not homologous to any genes on the host chromosome

Test 2 Flashcards

(80 cards)