Chromosomes - important tings

Question 1

Tell me about the Necleolus Organiser regions
- what are they associated with
- what do they made up of.

Answer 1

• associated with the nucleolus.
• consist of tandem repeats of rDNA, and segements of chromosomes that contains genes for rRNA.

Question 2

what processes can chromatin undergo and what can it not undergo

Answer 2

can’t undergo translation, but undergoes everything else (transcrption, replication, repair, gene recombination and cell division.

Question 3

when do chromatids form

Answer 3

during the s phase when DNA is replicated

Question 4

what is an allele

Answer 4

variation of a gene

Question 4

what terminology (and how much of each) is used to describe genetic material during the following processes -
1. before rpelication
2. after replication
3. during prophase
4. after anaphase

Answer 4

1. 1 chromosome and 1 chromatid
2. 1 chromasome and 2 sister chromatids
3. 1 chromosome and 2 sister chromatids
4. 2 chromosomes and 1 chromatid each

Question 5

what is an locus

Answer 5

location of gene on a chromosome

Question 6

How many autosomal and sex chromosomes do cells have

Answer 6

we have 44 autosomes autosomal chromosomes.

And 2 sex chromosomes

46 in total.

Question 7

In what stage of cell divsion, aloows for karyotypes to be made of chromosomes. and what microscope is used.

Answer 7

Metaphase. using a light microscope.

Question 8

what are duplicated, condensed chromosomes called?

Answer 8

dyads.

Question 9

which classification of chromosomes can also be called sat-chromosomes and why.
Which species can they be found in.

Answer 9

Accrocentric Chromosomes, they have satellites and a secondary constriction - marking the site of NORs on their chromosomes.

found in rare species.

Question 10

what are satellites, and what can they be used for.

Answer 10

Tandem repeats - multiple repeats of a sequence of nucleotides.
the length of the sequence differs between individuals, but those that are closely related have more similar satellites. so can be used for DNA profiling.

Question 11

what are kinetchores, and how many base pairs are they made up of.

Answer 11

attachment site for the spindle fibres which help pull apart the sister chromatids at the centromere in anaphase.

• a complex made of about 80 different base pairs.

Question 12

the interphase chromosomes are in what structural state

Answer 12

a single strand of DNA wound around histones. - chromatin

Question 13

During mitosis, all synthetic processes stop. true or false

Answer 13

true, cos all other processes like transcription and some replication happens during the interphase of the cell cycle.

Question 14

what plays a majour role in chromosome condensation during mitosis

Answer 14

methylation, increases the hydrophic nature of the histones, making DNA tightly wound to them - forming heterchromatin again.

Question 15

what information can be read from a karyotype

Answer 15

• chromosomes morphological size
• number of chromosome
• chromosomes size

Question 16

How many copies of each chromosome are in the interphase nucleus

Answer 16

2 copies, a result of replication during synthesis or the interphase.

Question 17

what are cetromeres

Answer 17

the primary constriction on chromosomes, seperating the p and q arms

Question 18

what are centrosomes, describe their function

Answer 18

they are a component of the cells, replicate during the G1 or S ohase of cell division.
they are needed in mitosis, in the prometaphse phase, where they move to opposite poles and are the origin of the mitotic spindle.

Question 19

describe the structure of centrosomes and centrioles

Answer 19

Centrosome cosiest if centrioles at 90 degrees to each other.

Question 20

Where in the cell cycle does transcription occur

Answer 20

In the G2 phase