Foundations of Medical Genetics

Question 1

Nucleotide =

Answer 1

sugar + base + Phosphate group

Question 2

purines vs pyramidines

Answer 2

purines = a,g. 2 heterocyclic rings
pyramidines = c, t. 1 heterocyclic ring

Question 3

Polymerization of DNA strand

Answer 3

-nucleotide triphosphate of the 4 bases join to form chains (2 phosphate remived). requires energy.

• through phosphodiester bond.
  chemical reaction between PO4- and OH- groups.

polymerization of sugar phosphate backbone with phosphodiester bond.

Question 4

DNA structure

Answer 4

right handed double helix. executes a turn every 10 bases. sugar phosphate backbone.

Question 5

DNA replication enzymes

Answer 5

Topoisomerase/gyrase = loosens the bonds

Helicase = unzips, form replication form

Primase = starts the process by making RNA primer

DNAp3 = binds to primer, only adds DNA bases in 5’ to 3’ direction.
but it READS in 3’ to 5’.

Exonuclease = removes primers

DNAp1 = fills up sections with DNA

DNA ligase = seals up the fragments in both strands.

Question 6

function of DNA

Answer 6

preservation of genetic material during replication and gene expression

Question 7

function of RNA

Answer 7

Coding RNA, to make proteins

Question 8

Organization of DNA within the nucleus

Answer 8

supercoiling.

DNA - nucleosome - chromatin - chromatin loops - condensed chromatin loops - chromosome

Question 9

function of chromosome

Answer 9

offspring, compactness, accuracy for replication

Question 10

chromosomes in humans

Answer 10

diploid number - 46. 22 autosome pairs. 2 sex chromosomes.

Question 11

euchromatin vs heterochromatin

Answer 11

eu: loosely packed. light staining. low DNA density. genetically active.
he: tightly packed. high DNA density. dark staining. found on outer sides. genetically inactive.

Question 12

Gene location for CFTR = 7q31.2

Answer 12

chromosome 7
long arm q
region 3
band 1
subband 2

Question 13

Haemoglobin gene clusters

Answer 13

gene expression changes over time,

eg from HbF to HbA2 to HbA in adult =
beta globin gene clusters: epsilon, beta, gamma, delta

alpha globin gene clusters = alpha 1 and 2, zeta 1 and 2

Question 14

gene activity varies by cell. can be:

Answer 14

• tissue specific

- developmental expression

Question 15

epigenetics

Answer 15

changes in how cells read the genes, not in the genes themselves.

Question 16

epigenetic processes include:

Answer 16

1. DNA methylation:
   unmethylated = open
   methylated = close
2. HISTONE modification
   = chromosome remodelling, unwinding of DNA.
   = enzyme HATs (acetylation = activation) // enzyme HDACs (deacetylation = silencing)
3. OTHERS (non coding RNA - associated gene silencing)
4. Some epigenetic changes inherited in gametes from parents

Question 17

Gene ON/activated

Answer 17

open chromatin, Unmethylated cytosines, acetylated histones

Question 18

Gene OFF/deactivated/silenced

Answer 18

closed chromatin, methylated cytosines, deacytylated histones