Genome Anatomy

Question 1

what is genome anatomy?

Answer 1

genome anatomy is how the genome is organised and how it functions

Question 2

how is almost all heritable information written and how is it organised?

Answer 2

in DNA sequences

3x10^9 nucleotides from father and mother and there is 750 megabytes of uncompressed date

Question 3

where is other information found?

Answer 3

in chromatin features such as in epigenetics

Question 4

where do data storage errors arise from?

Answer 4

genetic pathologies (genome goes wrong and genetic disease results) and this is why error correction methods (ensure that the DNA is copied correctly) are important

Question 5

what is epigenetics?

Answer 5

changes in the genome that influence the genome and are not included in the DNA code

Question 6

what is the difference between DNA and RNA?

Answer 6

the presence and absence of the hydroyxl group on the second carbon atom

Question 7

what is the effect of the chemical groups on the carbon atoms?

Answer 7

this changes the stability of the molecule - RNA is less stable as the breakage is faster in the phosphodiester bond (intramolecular nucleophilic attack)

Question 8

which direction are DNA sequences written in?

Answer 8

5’-3’ direction which is the direction that DNA and RNA are synthesised in

Question 9

what determines the sequences?

Answer 9

the order of purine and pyrimidine bases sticking out the side of the chain

Question 10

at which end do new nucleotides get added?

Answer 10

3’ end

Question 11

how are strands arranged and how are they matched?

Answer 11

they are antiparallel and matched by base pairing

Question 12

Abb(ns) nt and bp are what?

Answer 12

these are shorthand loosely interchangeable terms for DNA sequences

Question 13

how is shorthand usually written?

Answer 13

with the sense strands (which can also relate to antisense as well)

Question 14

in DNA replication what happens on the antisense (lagging) strand?

Answer 14

Okazaki fragments are found

Question 15

how do they replicate?

Answer 15

they unwind the structure using a helicase and then synthesise a complimentary daughter strand

Question 16

how long is DNA in one chromosome?

Answer 16

around 9 cm

Question 17

what are chromosomes?

Answer 17

they are the packages in which the DNA is organised as it must fit into the nucleus

Question 18

how many nucleotides are wrapped around histone proteins?

Answer 18

around 200

Question 19

what order is standard karyotype?

Answer 19

largest to smallest

Question 20

what does diploidy refer to?

Answer 20

diploidy is the human genome and means that we get one gene from mother and one from father

Question 21

what is the centromere?

Answer 21

the centromere is where the chromosomes are attached to the spindle during cell division

Question 22

what is found at the end of the chromosomes?

Answer 22

at the end of each arm of the chromosome (p being short and q long) there is a telomere - Ptel and Qtel are different

Question 23

what is the telomeric repeat sequence?

Answer 23

TTAGGG and includes specialised replication machinery with telomerase and TERT

Question 24

what happens in somatic cell division?

Answer 24

the telomeres shorter and therefore telomerase is inactive in somatic cells - there is a finite number of cell divisions until senescence known as ageing. Telomerase is only active in germ cells

Question 25

what happens in a cancerous mechanism?

Answer 25

TERT reactivates

Question 26

how does the end of the chromosome work?

Answer 26

it is single stranded and loops back round in a complex structure to stabilise the chromosome

Question 27

in the chromosome ideogram how can abnormal chromosomes be identified?

Answer 27

stretching of chromosomes determines the visibility of bands and therefore when there are abnormal chromosomes they are shown up in bands

Question 28

what does 2n=46 mean

Answer 28

the chromosome complement is diploid therefore n = 23 and 2n = 46.

Question 29

what does haploinsufficiency mean?

Answer 29

haploinsufficiency is when 2 copies are needed and one is insufficient - dosage is important in these genes - the exception is the X chromosome

Question 30

what are psudomonal regions?

Answer 30

information that is shared with the X and the Y regions

Question 31

why are males hemizygous?

Answer 31

they only have one X chromsome and therefore only have one copy of many genes that are only found on the X chromosome

Question 32

what happens to chromosomes after replication?

Answer 32

each chromosome becomes sister chromatids - 4n

Question 33

what is the Y chromosome composed of compared to X?

Answer 33

the Y has the pseudomonal regions and then mostly heterochromatin, the X has the pseudomonal regions and the X unique genes

Question 34

how much of the human genome is non coding?

Answer 34

>90% - short and long non coding genes

Question 35

how many protein coding genes are there?

Answer 35

around 20,000 with an average size of 50-100kb and average mRNA of 2kb

Question 36

what are three different sequences classes and examples?

Answer 36

single copy sequences such as genes repetitive sequences such as Alu repeats - interspersed repeats satellite DNA such as heterochromatin and large blocks of repetitive sequence

Question 37

describe mitochondrial genomes?

Answer 37

circular, not linear: this is an endosymbiotic remnant | cytoplasmic not nuclear due to maternal inheritance from oocyte

Question 38

what do the genes in mitochondria do?

Answer 38

they encode for mitochondrial roles such as components of oxidative phosphorylation

Question 39

how are mitochondrial pathologies inherited?

Answer 39

maternally

Question 40

what is a gene?

Answer 40

it is a functional unit of DNA

Question 41

what is the term used to describe the copying of DNA into RNA?

Answer 41

transcription. Translation is when RNA is turned into a protein.

Question 42

what are the components of genes?

Answer 42

introns, exons and regulatory sequences (promtores, enhancers and locus control regions)

Question 43

where is the DNA transported to after splicing?

Answer 43

after splicing the DNA is transported into the cytoplasm

Question 44

which regions gets removed in splicing?

Answer 44

the intronic region

Question 45

what is the term for when exons are spliced together in different orders or creating different proteins?

Answer 45

alternative splicing

Question 46

what happens to the genome through evolution?

Answer 46

duplication and divergence

Question 47

what does duplication produce?

Answer 47

two random arrangements of genes

Question 48

what do mutations lead to?

Answer 48

mutations over millions of years lead to two random arrangements of genes diverging and producing different functions

Question 49

what are pseudogenes?

Answer 49

they look the same as normal genes but they contain errors and are therefore non functional

Question 50

what are processed genes?

Answer 50

intronless copies of other genes that are usually remote from parent genes. They occur via reverse transcription and reintegration. They will occasional remain functional but most are non functional

Question 51

what are the classifications of repetitive DNA?

Answer 51

interspersed repeats (scattered around the genome) and satellite DNA

Question 52

where is satellite DNA found?

Answer 52

satellite DNA is found with large blocks at the centromeres and heterochromatin chromosomal regions

Question 53

what are simple tandemly repeated sequences?

Answer 53

there are many types - centromere repeats and chromosome specific

Question 54

what does polymorphic relate to?

Answer 54

polymorphic means that the blocks of satellite DNA may vary in size

Question 55

what type of satellite DNA is found at centromeres?

Answer 55

alphoid DNA - 171bp repeat unit. It is required for the assembly of the centromere and making it unique

Question 56

what type of variation does alphoid DNA show?

Answer 56

it shows chromosome specific sequence variation

Question 57

what is an alu repeat?

Answer 57

it i a SINE - short interspersed nuclear element that has a role in the generation of molecular pathology

Question 58

how are alu repeats dispersed?

Answer 58

retrotransposition