Functions and dysfunction in genomic regulation

Question 1

which amino acids make up a histone

Answer 1

the basic aa lysine and arginine

Question 2

how is the pairing of A-T and G-C different?

Answer 2

A-T pairs contain 2 hydrogen bonds and G-C contains three

Question 3

what is the exclusive carrier of information from DNA to protein?

Answer 3

RNA (mRNA)

Question 4

When can RNA be transcribed into DNA?

Answer 4

though an RNA virus (HIV) by using reverse transcriptase

which is an RNA-dependent DNA polymerase

Question 5

which part of DNA is the structural backbone?

Answer 5

sugar-phosphates; and give DNA its negative charge

Question 6

which basic residue of histone proteins is the target for posttranslational modifications?

Answer 6

lysine

Question 7

why are mitotic chromosomes condenses 500 times when compared with interphase chromosomes?

Answer 7

to prevent physical damage to the DNA as chromosomes are separated and passed on to daughter cells

Question 8

what is the basic unit of chromosome packing?

Answer 8

nucleosomes

Question 9

how many histone proteins make up the core particle of a nucleosome?

Answer 9

8

Question 10

what are the DNA binding proteins that are involved in forming chromosomes?

Answer 10

histones and non-histone chromosomal proteins

Question 11

what type of bonds are formed between DNA and the histone octamer in each necleosome

Answer 11

hydrogen bonds

Question 12

what type of chromatin is highly concentrated at the centromers and telomers of a chromosome?

Answer 12

heterochromatin

Question 13

euchromatin

Answer 13

refers to the transcriptionally active areas of the genome in which histone association with the DNA has been reduced

Question 14

what effect does heterochromatin have on actively expressed, nearby genes?

Answer 14

they will be silenced if relocated near heterochromatin

Question 15

where are long terminal repeats found and how are the formed?

Answer 15

at either end of retrotransposons (proviral DNA) and they are formed by reverse transcription of retroviral DNA

Question 16

what effect does histone deacetylase (HDAC) have on gene expression?

Answer 16

HDAC removes the acetate group from histones, thereby allowing histones to reassociate with DNAactively represses gene expression – deactylated chromatin is compact and transcriptionally repressed– aka: turns gene off

Question 17

function of histone acetyl transferase (HAT)

Answer 17

actively PROMOTES gene expression- mediated by binding of transcription factors - acetylated chromatin is open and transcriptionally active

HAT will acetylate lysine side chains on histones, which reduces the charge attraction between histones and DNA-

often associated with transcription factors that bind to the region of DNA that needs to be transcribed, facilitating the removal of histones from the DNA and binding of the transcription apparatus

Question 18

effect of methylation on PTM

Answer 18

represses gene transcription – the greater the extent of methylation, the less readily a gene is transcribed

ex: CpG islands within a promoter - cysteine gets hypermethylated at 5’ position – transcriptional silencing