15.1- Genomic Imprinting

Question 1

What is genomic imprinting?

Answer 1

Genomic imprinting is an epigenetic phenomenon in which expression of a gene depends on which parent it was inherited from

Question 2

Most genes are expressed from both chrosomes (T/F)

Answer 2

True

Question 3

What are paternally imprinted genes?

Answer 3

• A small number of genes that are turned off in the chromosomes inherited from our fathers
• we rely on expression from the maternally inherited copy

Question 4

What are maternally imprinted genes?

Answer 4

• A small number of genes are turned off in the chromosomes inherited from our mother
• we rely on expression from the gene inherited from our father

Question 5

Is imprinting a universal feature across biology?

Answer 5

• No, may be unique to mammals and flowering plants
• around 1 percent of mammalian genes are imprinted

Question 6

How does genomic imprinting work?

Answer 6

• epigenetic modifications such as DNA methylation can block transcription
• methylation patterns are used to establish imprinting

Question 7

What happens to methylation patterns during meiosis?

Answer 7

• all of the methylation patterns are erased
• next, methylation patterns are re-established on out gametes in a sex-specific manner (put on every single egg/sperm cell in sex-specific way, whether or not the gene came from the father or mother)

Question 8

How does genomic imprinting lead to monoallelic expression?

Answer 8

• Maternal imprinting: gene on maternally inherited allele is transcriptionally silent. The paternally inherited allele is expressed.
• Paternal imprinting: the gene on the paternally inherited allele is transcriptionally silent. The maternally inherited allele is expressed.

Question 9

Insulin-like growth factor example

Answer 9

• Lgf2 (insulin-like growth factor): maternally imprinted
• lgf2R (insulin-like growth factor receptor): paternally imprinted
• in mice, =levels is normal. More gf than receptor= large mouse