Chapter 03.1: Extensions To Mendel: Complexities In Relating Genotype To Phenotype

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succulence

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full of juice; juicy.

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legume

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the pod or seed vessel of such a plant; peas and beans

pron. leg-yoom

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multifactorial

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determined by two or more factors;

multiple genes interacting with each other or one or more genes interacting with the environment

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homogenized

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uniform

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advent

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a coming into place, view, or being; arrival

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What were alleles originally called? (before it was shortened)

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allelomorph

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entreat

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to ask (a person) earnestly; beseech; implore; beg

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Dominance is complete when:

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the hybrid resembles one of the two pure-breeding parents

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Dominance is incomplete when:

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the hybrid resembles neither parent; its novel phenotype is usually intermediate between the parental phenotypes

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codominances occurs when:

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the hybrid shows the trait from both pure-breeding parents

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incomplete dominance

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the hybrid does not resemble either pure-breeding parent; often express an intermediate

neither trait are recessive or dominant to the other

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In incomplete dominance and codominance, the phenotypic ratios are:

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exact reflection of the genotype ratios

e.g., 1:2:1

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codominant

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when both traits show up equally in the heterozygote's phenotype

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What type of dominance is exhibited by blood cells?

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codominance

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x

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x

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How many blood genotypes are there? What are they?

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6; A/A ; A/O; B/B ; B/O ; A/B ;O/O

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multiple alleles

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a given gene with more than two alleles

e.g., bloodtype, with IA, IB, i alleles

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True or false,

Dominance relations are unique to a pair of alleles

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True

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What are the blood groups (phenotypes)? How many types are there?

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4; A, B, AB, O

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What happens when type B blood is used in a transfusion into type A blood?

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The type A recipient produces type B anti-bodies, which act to coagulate the B blood

Note, an AB individual makes neither type of antibody; type O produces both anti-A and anti-B antibodies

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What blood type is consider the "universal donor"? Why?

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Those with type O blood; their red blood cells carry no surface molecules that will stimulate an antibody attack

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What blood type is consider the "universal recipient"? Why?

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those with type AB blood; they make neither anti-A nor anti-B antibodies

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dominance series

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alleles listed in order from most dominant to most recessive

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histocompatibility antigents

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encode a class of cell surface molecules; stimulate a proper immune response that destroys intruders while leaving the body's own tissue intact

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identical twins are:

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monozygotic

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mutations

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chance alteration of the genetic material

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to be inherited, mutations must occur in:

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gamete-producing cells

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Do all genes have the same mutation rates?

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No!

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deleterious

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harmful

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allele frequency

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each allele of the gene accounts for a percentage of the total number of gene copies

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wild-type allele

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an allele whose frequency is greater than 1%

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How is wild-type usually indicated?

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using the superscript plus sign,

X^+

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mutant allele

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an allele with a frequency of less than 1%

a mutation is a newly arisen mutant allele

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agouti

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Agouti fur contains a pattern of pigmentation in which individual hairs have several bands of light and dark pigment

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monomorphic

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a gene with only one wild-type allele

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What's the scientific name for the house mouse?

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Mus musculus

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polymorphic

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genes with more than one wild-type

e.g., with blood alleles IA, IB, i

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"incompatibility" gene

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a gene seen in wild species of tomatoes and petunias that prevent self-fertilization and promote outbreeding

a plant cannot accept pollen carrying an allele identical to either of its own incompatibility alleles

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pleiotropy

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a single gene determining a number of distinct and seemingly unrelated characteristics

e.g., in the Maori people of New Zealand, a recessive gene causes infertility AND respiratory issues. This is due to the gene not coding correctly for cilia and flagella

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A 2:1 ratio might imply?

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That the recessive trait is lethal when homozygous, skewing the ratios.

This is a recessive lethal allele

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recessive lethal allele

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An allele that negatively affects the survival of a homozygote

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in utero

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in the womb

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What are the symptoms of Tay Sachs?

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The newborn remains healthy for five to six months, but then develops blindness, paralysis, mental retardation, and other symptoms of a deteriorating nervous system

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Recessive alleles causing prenatal or early childhood lethality can only be passed on to to subsequent generations by _______

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heterozygous carriers

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A dominant allele causing death in in prepubescence must be:

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a new mutation (it has no way of being passed on otherwise)

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ataxia

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loss of muscle coordination

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Sickle-cell disease is the result of a faulty _______

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hemoglobin molecule

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Hemoglobin is composed of:

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α globin and β globin

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α

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alpha

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β

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beta

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hemolytic

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blood destroying

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β-thallasemia

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a hemolytic disease

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What is dangerous about sickled cells?

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They clog the blood vessels, reducing oxygen flow to the tissues and giving rise to muscle cramps, shortness of breath, and fatigue.

They're also very fragile.

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anemia

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low red blood cell count

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Can an allele have multiple phenotypic expressions?

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Yes! And can even show a mixture of a dominant phenotype, codominant phenotype, and/or incomplete dominant phenotype

For this reason, when discussing dominance relationships it is VITAL that the particular phenotype under analysis is defined

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endemic

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belonging exclusively or confined to a particular place

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when discussing dominance relationships it is VITAL that the particular phenotype under analysis is defined . Why?

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an allele can have multiple phenotypic expressions

And can even show a mixture of a dominant phenotype, codominant phenotype, and/or incomplete dominant phenotype

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An environmental condition that allows conditional lethals to live is called a:

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permissive condition

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When less than 100% of the individuals possessing a particular genotype express it in their phenotype, it is called:

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reduced penetrance

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A trait produced by the interactions of alleles of at least two genes or from interactions between gene and environment is called a:

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multifactorial trait

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Cell surface molecules that are involved in the immune system and are highly variable are called:

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histocompatibility antigents

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One gene affecting more than one genotype is called:

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pleiotropy

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Individuals with the same genotype have related phenotypes that vary in intensity. What is this called?

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variable expressivity.

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x

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x