Beyond the Genome Sequence

Question 1

mitochondrial DNA is .. inherited

Answer 1

maternally

mitochondrial DNA
* circular
about 5 in mito matrix

Question 2

in a cell you have mitochondrial DNA and nuclear DNA, genes that are important for mitochondrial function are found in the .. & ..

Answer 2

mitochondrial and nuclear genomes

Question 3

loss of mitochondrial function, leads to interference with energy production in tissues causing severe illness

Answer 3

mitochondrial disease

• only mothers can pass this down
• Genes in both the mitochondrial and nuclear genomes are important for mitochondrial function, so many mitochondrial diseases can be caused by mitochondrial variants or nuclear variants.

can be treated with mitochondrial replacement therapy
* DNA coming from 3 different parents (controversial & new)

Question 4

… are prone to errors in DNA replication and repair, leading to expansion and contraction of repeats. An increase in the length of … can lead to disease phenotypes by a variety of mechanisms

Answer 4

unstable repeats

Question 5

…. is the tendency of a genetic condition to increase in severity and sometimes also decrease in age of onset, as it is passed from one generation to the next. It is typically associated with genetic conditions caused by unstable repeats, as these tend to change in length over generations.

Answer 5

anticipation

Question 6

DNA is wrapped around histones forming the chromatin environment. The DNA & histones are covalently modified with small chemical groups which influence gene expression. What are two modifications commonly used?

Answer 6

methylation (CH3)

acetylation (C=0 &CH3)

Question 7

K4 & K9 are two common lysines attached to chromatin that get methylated/acetylated

Question 8

.. methylation turns on nearby genes

.. methylation turns off nearby genes

Answer 8

K4

K9

Question 9

.. acetylation turns on nearby genes

Answer 9

K9

Question 10

methylation of DNA … genes

Answer 10

silences/represses

Question 11

… changes are heritable changes in gene function or expression that do not involve a DNA sequence change

Answer 11

epigenetic

Question 12

an epigenetic change that is parent-specific
* specific silencing of the paternally or maternally inherited copy of a gene

epigenetic marks are deposited at an imprinting center (IC), where the DNA is methylated during development of either the egg or the sperm
methylation of ICs can be passed down to next generation whereas methylation of other genes are reset

Answer 12

genomic imprinting

Question 13

… produces equal expression of X-linked genes in males and females. Females, because of this, are mosaics and can be manifesting carriers of X-linked traits

Answer 13

X-inactivation

Question 14

Females have two copies of the X chromosome while males have only one copy, so … is necessary to ensure equal expression levels. In humans, X-inactivation occurs, meaning that one copy of the X chromosome is silenced in each cell, leading to silencing of one copy of X-linked genes in females.

Answer 14

dosage compensation

Question 15

Females are effectively … for the X chromosome, because even though all of their cells have both of the X chromosomes, only one is expressed. This means that different cells will express different copies of the X, which encode different variants, or different alleles of the X-linked genes. This effectively means that those cells have different genotypes, making them X chromosome ….

Answer 15

mosaics