ch 5 nonmendelian inheritance

Question 1

maternal effect

Answer 1

an inheritance pattern for certain nuclear genes in which the gene type of the mother directly determines the phenotypic traits of her offspring

Question 2

reciprocal cross

Answer 2

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. and the the reciprocal cross would be a red-eyed male fly and white-eyed female fly

Question 3

epigenetics

Answer 3

the study of mechanisms that lead to changes in gene expression that can be passed from cell to cell and are reversible but do not involve a change in the dna sequence

Question 4

dosage compensation

Answer 4

the phenomenon observed in species with sex chromosomes, in which one of the sex chromosomes is altered so that males and females have similar levels of gene expression, even though they do not have the same complement of sex chromosomes

Question 5

x-chromosome inactivation (XCI)

Answer 5

a process in which mammals equalize the expression of x-linked genes by randomly turning off one x chromosome in the somatic cells of females

Question 6

barr body

Answer 6

a structure in the interphase nuclei of somatic cells of female mammals that is a highly condensed x-chromosome

Question 7

lyon hypothesis

Answer 7

a hypothesis to explain the pattern of x-chromosome inactivation seen in mammals; initially, both x-chromosomes are inactive; however, at an early stage of embryonic development, one of the two x chromosomes is randomly inactivated in each somatic cell

Question 8

clone

Answer 8

1. a group of genetically identical cells that were derived from a single cell
2. an individual that has been produced from a somatic cell of another individual, such as the sheep dolly
3. many copies of dna fragment that are propagated within a vector or produced by pcr

Question 9

x-inactivation center (Xic)

Answer 9

a site on the x chromosome that appears to play a critical role in X-chromosome inactivation

Question 10

genomic imprinting

Answer 10

a pattern of inheritance that involves a change in a single gene or chromosome during gamete formation; depending on whether the modification occurs during spermatogenesis or oogenesis, imprinting governs whether an offspring will express a gene that has been inherited from its mother or father

Question 11

monoallelic expression

Answer 11

in the case of genomic imprinting. refers to the phenomenon that only one of the two alleles of a given gene is transcriptionally expressed

Question 12

dna methylation

Answer 12

a regulatory mechanism in which an enzyme covalently attaches a methyl group (–CH3) to a base in dna; in eukaryotes. the base is cytosine; in prokaryotes. both adenine and cytosine can be methylated

Question 13

imprinting control region (ICR)

Answer 13

a dna region that is differentially methylated and plays a role in genomic imprinting

Question 14

nuclear genes

Answer 14

genes that are located on chromosomes found in the cell nucleus of eukaryotic cells

Question 15

extranuclear inheritance

Answer 15

(also called cytoplasmic inheritance) the inheritance of genetic material that is not found within the cell nucleus

Question 16

nucleoid

Answer 16

a darkly staining region that contains the genetic material of mitochondria, chloroplasts. or bacteria

Question 17

mitochondrial dna (mtDNA)

Answer 17

the dna found within mitochondria

Question 18

chloroplast dna (cpDNA)

Answer 18

the genetic material found within chloroplast

Question 19

maternal inheritance

Answer 19

inheritance of dna that occurs through the cytoplasm of the egg

Question 20

heteroplasmy

Answer 20

a condition in which a cell has variation in a particular type of organelle; for example, a plant cell could contain some chloroplasts that make chlorophyll and other chloroplasts that don’t

Question 21

heterogamous

Answer 21

describes a species that produces two morphologically different types of gametes

Question 22

paternal leakage

Answer 22

the phenomenon in which maternal inheritance is generally observed in a species, but the male parent may, rare occasions, provide mitochondria or chloroplasts to the zygote

Question 23

endosymbiosis

Answer 23

a symbiotic relationship in which the symbiont actually lives inside the host

Question 24

endosymbiosis theory

Answer 24

the theory that the ancient origin of plastids and mitochondria was the result of certain species of bacteria taking up residence within primordial eukaryotic cells