ch 4 extensions of mendelian inheritance

Question 1

mendelian inheritance

Answer 1

a pattern of inheritance that follows mendel’s laws; this pattern involves the transmission of eukaryotic genes that are located on the chromosomes found within the cell’s nucleus

Question 2

simple mendelian inheritance

Answer 2

an inheritance pattern involving simple, dominant/recessive relationship that produces observed ratios in the offspring that readily obey mendel’s laws

Question 3

wild-type alleles

Answer 3

an allele that is fairly prevalent in a natural population, generally found in more than 1% of the population; for polymorphic genes, there is more than one wild-type allele

Question 4

genetic polymorphism

Answer 4

when two or more alleles occur in population; each allele is found at a frequency of 1% or higher

Question 5

mutant allele

Answer 5

an allele that has been created by altering a wild-type allele by mutation

Question 6

gain-of-function mutations

Answer 6

a mutation that changes a gene product so that it gains a new or abnormal function

Question 7

dominant-negative mutations

Answer 7

a mutation that produces an altered gene product that acts antagonistically to the normal gene product; shows a dominant pattern of inheritance

Question 8

haploinsufficiency

Answer 8

the phenomenon in which an individual has only a single functional copy of a gene and that single functional copy does not produce a normal phenotype; shows a dominant pattern of inheritance

Question 9

incomplete penetrance

Answer 9

a situation in which an allele that is expected to cause a particular phenotype does not

Question 10

expressivity

Answer 10

the degree to which a trait is expressed; for example, flowers with deep read have a high expressivity of the red allele

Question 11

temperature-sensitive allele

Answer 11

an allele for which the resulting phenotype depends on the environmental temperature

Question 12

incomplete dominance

Answer 12

a pattern of inheritance in which a heterozygous that carries two different alleles exhibit a genotype that is intermediate to those of the corresponding homozygous individual; a heterozygous may have pink flowers, whereas the homozygous have red or white flowers

Question 13

overdominance (heterozygote advantage)

Answer 13

an inheritance pattern in which a heterozygous has greater reproductive success than either of the corresponding homozygous

Question 14

multiple alleles

Answer 14

two or more alleles of the same gene found within a population

Question 15

codominance

Answer 15

a pattern of inheritance in which two alleles are both expressed in the heterozygous condition; for example, a person with the genotype IA and IB has the blood type AB and expresses both surface antigens A and B

Question 16

x-linked inheritance

Answer 16

an inheritance pattern in certain species that involves genes that are located only on the X chromosome

Question 17

hemizygous

Answer 17

indicates that a male had a single copy of an x-linked gene; a male mammal is said to be hemizygous for x-linked genes

Question 18

x-linked recessive

Answer 18

an inheritance pattern in which a gene is found on the x-chromosome and the disease-causing allele is recessive relative to a corresponding dominant allele

Question 19

reciprocal cross

Answer 19

a pair of crosses in which the traits of the two parents differ with regard to sex; for example, one cross could be a red eyed female fly and a white eyed male fly the reciprocal cross would be a red eyed male fly and a white eyed female fly

Question 20

sex-linked genes

Answer 20

gene that is located on only one of the chromosomes

Question 21

y-linked genes (holandric genes)

Answer 21

genes (or alleles of genes) that are located only on the y chromosome

Question 22

pseudoautosomal inheritance

Answer 22

the inheritance pattern of genes that are found on both the x and y chromosomes; even though such genes are located physically on the sex chromosomes, their pattern of inheritance is identical to those of autosomal genes

Question 23

sex-influenced inheritance

Answer 23

an inheritance pattern in which an allele is dominant in one sex but recessive in the opposite sex

Question 24

sex-limited inheritance

Answer 24

an inheritance pattern in which a trait is only found in one of the two sexes (ie beard development)

Question 25

sexual dimorphism

Answer 25

phenomenon in which the males and females of a species are morphologically distinct

Question 26

lethal allele

Answer 26

an allele that may cause the death of an organism

Question 27

essential gene

Answer 27

a gene essential for survival

Question 28

nonessential genes

Answer 28

genes that are not absolutely required for survival although they are likely to be beneficial to the organism

Question 29

conditional lethal alleles

Answer 29

an allele that is lethal, but only under certain environment conditions

Question 30

temperature-sensitive (ts) lethal alleles

Answer 30

an allele that is lethal only in certain environmental temp range

Question 31

semilethal alleles

Answer 31

lethal alleles that kill some individuals but not all

Question 32

age of onset

Answer 32

the age at which symptoms of a disease first appears

Question 33

pleiotropy

Answer 33

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

Question 34

gene interaction

Answer 34

the phenomenon in which two or more different genes influence the outcome of a single trait

Question 35

epistasis

Answer 35

an inheritance pattern where one gene can mask the phenotypic effects of a different gene

Question 36

recessive epistasis

Answer 36

a form of epistasis in which an individual must be homozygous for either recessive allele to mask a particular phenotype

Question 37

complementation

Answer 37

a phenomenon in which the presence of two different mutant alleles in the same organism produces a wild-type phenotype; usually happens because the two mutations are in different genes so the organism carries one copy of each mutant allele and one copy of each wild-type allele

Question 38

gene modifier effect

Answer 38

an outcome in which the allele of one gene modifies the phenotypic effect of the allele of a different gene

Question 39

gene knockout

Answer 39

in the case of diploid species, the condition in which both copies of a gene have been altered to an inactive form

Question 40

gene redundancy

Answer 40

the phenomenon in which one gene compensates for the lost of function of another gene

Question 41

paralogs

Answer 41

homologous genes within a single species that constitute a gene family