nucleus- week 1

Question 1

what are the regulator regions of genes known as

Answer 1

promoter/enhancer (where transcription starts)

Question 2

which of these statements are true?
1)prokaryotic genes are split into coding exons and non-coding introns
2)Eukaryotic genes are simultaneous transcribed and translated
3)Eukaryotic genes are split into coding exons and on-coding introns
4)Prokaryotic genes are simultaneous transcribed and translated

Answer 2

answers 3 &4

Question 3

1) how many chromosomes do we have (give diploid number)
2)Humans have 2 sex chromosomes; what are they called?
3)what are our remaining chromosomes called?

Answer 3

1) 46
2) X & Y
3) autosomes/autosomal chromosomes

Question 4

what are the 2 arms of a chromosomes called (give the short and long arm)

Answer 4

short arm: p arm
Long arm: q arm

Question 5

what is the name given to the regions of DNA where replication begins?

Answer 5

origin of replication/ Replication Origin/Origin

Question 6

which of the following are benefits of having separate, membrane bound nucleus? (Can pick more than 1)
1)Helped the evolution of cellular motility
2)Separation of delicate DNA from cytoskeletal filaments
3)Rapid response to the external environment
4)Enabled the evolution of split genes and alternative splicing

Answer 6

1, 2 & 4

Question 7

by which bonds are nucleotides bonded together in a strand of DNA

Answer 7

• nucleotides linked together by COVALENT BONDS between 5’ phosphate and 3’ OH group

Question 8

how many hydrogen bonds form between 1)thymine and adenine
2)Cytosine and Guanine

Answer 8

1)2 hydrogen bonds
2)3 hydrogen bonds- will require more energy to break

Question 9

what is the function of DNA

Answer 9

Storage of genetic information.
➢Replication
➢Gene expression

Question 10

what does each base pair contain in DNA and explain what each one is

Answer 10

1 purine (contains 2 nitrogen rings) and 1 small pyrimidine(contains 1 nitrogen ring)

Question 11

what enzyme is used in transcription when one strand serves as a template for RNA synthesis

Answer 11

RNA polymerase II : makes Pre-mRNA

Question 12

discuss the role of nuclear localisation signals (NLS)

Answer 12

usually short peptides which must be presesnted a set of certain amino acids that acts as a ‘key’ that act as a signal fragment which causes nuclear power complex change its shape which then allows for the protein to pass through which then that mediates the transport of proteins from the cytoplasm into the nucleus.

Question 13

what is the role of Importin (import receptor protein) in nuclear import

Answer 13

-Importin binds to NLS
-this complex then interact with the nuclear pore fibrils (cytosolic)
-enter the pore together as the pore increases in size
- once inside nucleus the importin returns back (to the outer nuclear membrane) which leaves the protein in the nucleus

Question 14

describe the structure and role of the nuclear lamina (what’s it made up of)

Answer 14

-its used for STRUCTURAL SUPPORT on both inside and outside the nuclear membrane
-nuclear lamina is made up of some proteins called LEHMANN’S LAMIN STRUCTURE
-it has GLOBULAR HEAD ENDS and ROD-LIKE CENTRAL DOMAIN-HELIX

Question 15

what are the 2 structural components of a chromosome

Answer 15

Telomeres and Centromeres

Question 16

what are the properties of the telomeres of a chromosome (3 points)

Answer 16

-it is the end of the chromosome (for protection gets shorter with age due to DNAase- why some genes are said to become a higher possibility as it becomes closer to the telomere)
-shorten with age
-special replication mechanism

Question 17

what are the purposes of the Centromeres in chromosomes (3 points)

Answer 17

-Hold metaphase chromosomes together
-attaches to mitotic spindle
-repetitive sequences highly packaged

Question 18

what is it called if the centromere is in the :
1) Middle
2)slightly closer to the end
3)the end of the chromosome

Answer 18

1) Middle= METACENTRIC
2)slightly closer to the end of chromosome= SUBMETACENTRIC
3)the end of the chromosome =ACROCENTIC

Question 19

what is the purpose of regulatory proteins in gene expression

Answer 19

make sure that the nucleosome binding isn’t disrupted or they might disband that protection which would disrupt nucleosome binding
(Gene regulatory proteins recognize short stretches of double-helical DNA of defined sequence and thereby determine which of the thousands of genes in a cell will be transcribed- they can create Looped domains)

Question 20

what is a Nucleosome

Answer 20

Eukaryotic DNA that is coiled/wrapped around Histone proteins- this is can be done as hydrogen bonds form between the +ve charged histones & the -ve charged phosphate backbone

Question 21

what is the role of the Nuclear envelope

Answer 21

separates the contents of the nucleus from the cytoplasm and provides the structural framework of the nucleus.

Question 22

Explain the advantage of evolution of the nucleus in eukaryotic cells, referring to its structure and linking this to its functions.

Answer 22

The presence of a nucleus in eukaryotic cells gives eukaryotes two advantages.
-The nucleus represents an additional protective enclosure of the DNA. As a result, eukaryotic DNA is less susceptible to mutations
-The nucleus also makes reproduction easier to control

Question 23

When is the highest level of DNA packaging achieved?

Answer 23

mitosis, metaphase

Question 24

DNA and associated proteins in the nucleus form a material known as Chromatin, TRUE or FALSE

Answer 24

TRUE

Question 25

What fold level of packaging does the beads-on-a-string form of chromatin cause? {type the number only}

Answer 25

3

Question 26

Which of the following histones are found in the nucleosome core? (Select all correct answers)

H1

H2A

H2B

H3

H4

Answer 26

H2A, H2B, H3, H4

Question 27

Which of these describe the nucleosome core?

A dimer

A tetramer

A pentamer

An octamer

A dodecamer

Answer 27

An octamer

Question 28

How much DNA is wound around the histone core in the nucleosome? (give number only)

Answer 28

146 nucleotides

Question 29

Which additional protein is used to twist the beads-on-a-string form of chromatin into the 30nm fibre?

Answer 29

histone, H1

Question 30

To what structure are chromatin loops attached?

Answer 30

Nuclear scaffold, scaffold

Question 31

What is active (expressed) DNA known as?

Answer 31

euchromatin (its chromatin loosely packed to enable transcription - active gene)

Question 32

What is highly packaged silent DNA known as?

Answer 32

heterochromatin

Question 33

Nuclear import receptors may be called ___Response and nuclear export receptors may be called ___

Answer 33

(importins)
(exportins)