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Flashcards in Genes & Gene Action Deck (38)
1

gene definition

a unit of information, coded in DNA on a chromosome

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all genes make ___ mostly for the reason of ____. Some genes make it just as an _____

RNA, making proteins

end product

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each gene has a specific location on a _____

chromosome

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gene location is called

locus (plural: loci)

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alternative versions of the same gene are called

alleles

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gene map definition

the loci of all the genes on a chromosome

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ie. all normal copies of chromosome 15 in humans have the same ____

map of loci

they are homologs (have the same genes)

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homologs may have the same genes in the same places, but maybe different ____

alleles

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each homolog can have its own ____ of the same gene

version

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allele definition

different version of the same gene

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sister chromatids in regard to alleles

have the same alleles b/c they are identical

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different alleles of the same gene may only have ____ differences in their effects

small

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how many alleles can there be for the same locus?

in a whole species ... infinite

in an individual diploid... one or two different alleles at the same time

14

how many differences do these infinite alleles in a species cause?

smaller than you would think b/c many alleles have similar effects

15

5-alpha-reductase type 2 gene

codes for a protein enzyme called 5-alpha-reductase type 2 that converts testosterone --> dihydrotestosterone

many different mutated/nonfunctional alleles of this gene have turned up

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when a male has no functional copy of 5-alpha-reductase type 2 gene

develops externally as a female, at least until puberty

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CFTR gene

cystic fibrosis transmembrane conductance regulator

causes cystic fibrosis when mutated to non-functional form

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in allele G551D of CFTR....

glycine in position 551 is replaced by aspartic acid (4%)

a drug can cure this!!

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a single base change in a gene may....

destroy its ability to make a working product

have no effect

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cytogenetic definition

chromosomal

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genotype definition

set of alleles carried by an organism at one or more loci

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homozygote

individual with a homozygous genotype

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heterozygote

individual with a heterozygous genotype

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homozygous

both alleles at the locus are the same (AA or aa)

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heterozygous

both alleles are not the same (Aa)

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phenotype

the effect of a genotype on an organism

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wild-type

a phenotype that is typical or normal

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recessive phenotypes are not seen unless...

the recessive allele is homozygous

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example of a genetic condition that is recessive

albinism

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for recessive genetic conditions...

a good copy of the gene for an enzyme is usually enough to give the wild-type phenotype

a mutated gene for an enzyme is usually involved

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dominant phenotypes are seen...

in heterozygotes for the dominant allele

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example of a genetic condition that is dominant

achondroplastic dwarfism

inactivates fibroblast growth factor receptor 3

this protein is a membrane signal receptor for growth factor hormone

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for dominant genetic conditions...

one bad allele is enough to give an abnormal phenotype

the homozygote is lethal

do not often involve a mutated gene for an enzme

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a recessive allele has to be ____ to cause its phenotype

homozygous

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a dominant allele causes its phenotype if ___

just one allele is present

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many dominant alleles cause the same ____

phenotype in heterozygotes and homozygotes

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Incomplete dominance definition

The phenotype of the heterozygote is intermediate between the two homozygotes

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Codominance

The phenotype of a heterozygote shows the effects of both alleles at the same time

ie. blood type AB