Genes & Gene Action

Question 1

gene definition

Answer 1

a unit of information, coded in DNA on a chromosome

Question 2

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

Answer 2

RNA, making proteins

end product

Question 3

each gene has a specific location on a _____

Answer 3

chromosome

Question 4

gene location is called

Answer 4

locus (plural: loci)

Question 5

alternative versions of the same gene are called

Answer 5

alleles

Question 6

gene map definition

Answer 6

the loci of all the genes on a chromosome

Question 7

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

Answer 7

map of loci

they are homologs (have the same genes)

Question 8

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

Answer 8

alleles

Question 9

each homolog can have its own ____ of the same gene

Answer 9

version

Question 10

allele definition

Answer 10

different version of the same gene

Question 11

sister chromatids in regard to alleles

Answer 11

have the same alleles b/c they are identical

Question 12

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

Answer 12

small

Question 13

how many alleles can there be for the same locus?

Answer 13

in a whole species … infinite

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

Question 14

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

Answer 14

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

Question 15

5-alpha-reductase type 2 gene

Answer 15

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

Question 16

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

Answer 16

develops externally as a female, at least until puberty

Question 17

CFTR gene

Answer 17

cystic fibrosis transmembrane conductance regulator

causes cystic fibrosis when mutated to non-functional form

Question 18

in allele G551D of CFTR….

Answer 18

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

a drug can cure this!!

Question 19

a single base change in a gene may….

Answer 19

destroy its ability to make a working product

have no effect

Question 20

cytogenetic definition

Answer 20

chromosomal

Question 21

genotype definition

Answer 21

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

Question 22

homozygote

Answer 22

individual with a homozygous genotype

Question 23

heterozygote

Answer 23

individual with a heterozygous genotype

Question 24

homozygous

Answer 24

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

Question 25

heterozygous

Answer 25

both alleles are not the same (Aa)

Question 26

phenotype

Answer 26

the effect of a genotype on an organism

Question 27

wild-type

Answer 27

a phenotype that is typical or normal

Question 28

recessive phenotypes are not seen unless…

Answer 28

the recessive allele is homozygous

Question 29

example of a genetic condition that is recessive

Answer 29

albinism

Question 30

for recessive genetic conditions…

Answer 30

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

Question 31

dominant phenotypes are seen…

Answer 31

in heterozygotes for the dominant allele

Question 32

example of a genetic condition that is dominant

Answer 32

achondroplastic dwarfism

inactivates fibroblast growth factor receptor 3

this protein is a membrane signal receptor for growth factor hormone

Question 33

for dominant genetic conditions…

Answer 33

one bad allele is enough to give an abnormal phenotype

the homozygote is lethal

do not often involve a mutated gene for an enzme

Question 34

a recessive allele has to be ____ to cause its phenotype

Answer 34

homozygous

Question 35

a dominant allele causes its phenotype if ___

Answer 35

just one allele is present

Question 36

many dominant alleles cause the same ____

Answer 36

phenotype in heterozygotes and homozygotes

Question 37

Incomplete dominance definition

Answer 37

The phenotype of the heterozygote is intermediate between the two homozygotes

Question 38

Codominance

Answer 38

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

ie. blood type AB