Chapter 18 - epigenetic, linkage, and extranuclear inheritance

Question 1

epigenetic inheritance

Answer 1

• epigenetic changes that are passed from parents to offspring
• not all epigenetic changes are inherited from parents

Question 2

epimutation

Answer 2

• heritable change in gene expression that does not alter the sequence of DNA

Question 3

X-chromosome inactivation

Answer 3

• one X chromosome in the somatic cells of female mammals is inactivated

Question 4

evidence for X-chromosome

Answer 4

• burr bodies - found in female but not male cat cells
• calico cat pattern

Question 5

calico cat pattern and X inactivation

Answer 5

• the patchy pattern on calico cat is due to the permanent inactivation of one X chromosome in each skin cell
• early embryo has both X chromosomes active
• each embryonic cell randomly inactivates one of its X chromosomes
• as development proceeds, the pattern of X-chromosome inactivation is maintained during cell division

Question 6

mosaic

Answer 6

• female mammals heterozygous for X-linked genes have half their somatic cells expressing each allele

Question 7

dosage compensation

Answer 7

• inactivation of one X in female cells gives equal levels of expression of X-linked genes in male andfemale cells

Question 8

extranuclear inheritance

Answer 8

• mitochondria and chloroplasts contain their own genomes
• smaller than nuclear genome

Question 9

linkage

Answer 9

• when two genes are nearby on a chromosome, they are often transmitted together
• do not follow the law of independent assortment