KH8

Question 1

What characteristic does the genome of each species of eukaryote consist of

Answer 1

A characteristic number of independent linear DNA molecules

Question 2

What do chromosomes never exist as and what do they exist as instead

Answer 2

Never exist as naked DNA but always as a DNA/protein complex called chromatin

Question 3

Hat is chromatin

Answer 3

DNA/protein complex

Question 4

What is a key feature of chromatin organization

Answer 4

Condensation or compacting

Question 5

When are chromosomes even more packed during mitosis and why

Answer 5

Metaphase to facilitate their equal distribution between the two daughter cells

Question 6

What does a centromere do

Answer 6

Joins two sister chromatids together

Question 7

What is the difference between condensation in metaphase vs interphase

Answer 7

Metaphase: highly condensed for transmission to daughter cells

Interphase: dynamic and controlled folding but not as condensed

Question 8

Difference between metaphase and interphase in terms of replication and transcription

Answer 8

M: No DNA replication or transcription

I: Real functional chromosome undergoing replication and transcription

Question 9

What happens to the chromosome in the transition from metaphase to interphase

Answer 9

Chromatin fibre of the chromosome unwinds to a degree

Question 10

What is a nuecleosome

Answer 10

DNA wrapped around a histone (protein) octanes

Question 11

What causes giant interphase chromosomes (polytene chromosomes of the fly salivary glands)

Answer 11

Driven by DNA: 10 cycles of DNA replication without cell division (1024 daughter chromatids)

Question 12

How are regional differences in chromatin condensation in giant interphase chromosomes shown

Answer 12

Dark bands: topological domains (condensed chromatids)
Light bands: boundary elements

Question 13

What do polytene chromosome puffs show

Answer 13

Chromatin decondensation with transcriptional activation, associated with active form of RNA polymerase II meaning active transcription

Question 14

What does red and green mean in polytene chromosome puffs

Answer 14

Red = active for transcription
Green = inactive

Question 15

What are the characteristics of the regulation of puffs

Answer 15

They are regions of active transcription done at different times in different regions

Question 16

What are metaphase sister chromatids

Answer 16

Identical products of the previous semi conservative replication of a single chromosomal DNA molecule

Question 17

What is a karyotype

Answer 17

The chromosomal complement of the species: the number, shape and size of the chromosomes are species specific

Question 18

What are translocations

Answer 18

Chromosomes breaking and rejoining

Question 19

When can translocation mutations happen and what can they cause

Answer 19

Can happen during a somatic cell division cycle and can cause disease

Question 20

Can chromosome rearrangement occur in the germ line

Answer 20

Yes

Question 21

What does chromosome rearrangement in the germ line do to gametes

Answer 21

Give them variant chromosomes

Question 22

Why is karyotype so consistent across a species

Answer 22

Germ line chromosome rearrangements are usually a dead end

Question 23

Is it possible for a chromosomal rearrangement variant to be successfully passed from one generation yo the next

Answer 23

Yes

Question 24

What are the elements required for replication and stable inheritance of linear chromosomes

Answer 24

1. Origin of replication
2. Centromere (gives equally to two daughters)
3. 2 telomeres (ends)

Question 25

Where can the leu plasmid replicate and not replicate in

Answer 25

R: bacteria NR: eukaryotes (bacterial origins of DNA replication do not work) plasmid cannot support leu- yeast growth in absence of leucine

Question 26

How can the plasmid leu- support yeast growth in absence of leucine in eukaryotes

Answer 26

If we insert a random piece of yeast in the plasmid that contained a yeast origin of replication

Question 27

What is ARS (autonomously replicating sequence)

Answer 27

Yeast origin on DNA replication

Question 28

What is the remaining issue even after yeast is added to plasmid

Answer 28

DNA not evenly partitioned between daughters, missing the centromere that drives mitosis segregation

Question 29

What is CEN

Answer 29

DNA sequence from a yeast chromosome centromere

Question 30

What is required for good segregation

Answer 30

Genomic fragment CEN (centromeric sequence)

Question 31

What is the kinetochore

Answer 31

Site where microtubule spindles attach to centromere

Question 32

What is CENP-A

Answer 32

A centromeric protein present on a nucleosome, it is a centromere-specific histone variant

Question 33

What does CENP-A do

Answer 33

Recruits the CBF3 complex which in turn recruits the Ndc80 complex which attaches to microtubles

Question 34

Does a plasmid with ARS and CEN that works well as an experimental circular chromosome in yeast also work well as a linear chromosome

Answer 34

No, they are made as circular and everything is lost when they are cut with a restriction endonuclease

Question 35

What are telomeres

Answer 35

Special sequences located at the end of eukaryotic chromosomes necessary for chromosome life

Question 36

How can linear plasmids containing ARS and CEN behave like normal chromosomes

Answer 36

If the genomic fragment telomerase (TEL) is added to both ends

Question 37

What is the function of telomeres

Answer 37

1. Protect from exonuclease 2. Prevent end-to-end fusion 3. Solve a replication problem faced by linear DNA

Question 38

What is the telomere problem

Answer 38

Because the lagging strand cannot be completed, chromosomes should shorten at the ends in each replication

Question 39

Why is chromosome shortening unsustainable

Answer 39

Because at some point you will lose an essential gene

Question 40

What is the solution to chromosome shortening

Answer 40

Telomerase, a DNA polymerase that can extend telomeres, restoring chromosome length to overcome lagging strand end-shortening

Question 41

What do telomeres contain

Answer 41

Simple repeat DNA sequences

Question 42

What is a reverse transcriptase

Answer 42

A DNA polymerase that uses RNA as a template

Question 43

What is telomerase

Answer 43

A reverse transcriptase that carries its own template RNA complementary to the telomeres DNA repeat

Question 44

What does extending the template strand by telomerase allow

Answer 44

The primate more template DNA to prime on

Question 45

Where is telomerase primarily active

Answer 45

In germ cells and stem cells (somatic cells divide only a few times so existing telomeres repeats are long enough