nucleus- week 1 Flashcards
what are the regulator regions of genes known as
promoter/enhancer (where transcription starts)
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
answers 3 &4
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?
1) 46
2) X & Y
3) autosomes/autosomal chromosomes
what are the 2 arms of a chromosomes called (give the short and long arm)
short arm: p arm
Long arm: q arm
what is the name given to the regions of DNA where replication begins?
origin of replication/ Replication Origin/Origin
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
1, 2 & 4
by which bonds are nucleotides bonded together in a strand of DNA
- nucleotides linked together by COVALENT BONDS between 5’ phosphate and 3’ OH group
how many hydrogen bonds form between 1)thymine and adenine
2)Cytosine and Guanine
1)2 hydrogen bonds
2)3 hydrogen bonds- will require more energy to break
what is the function of DNA
Storage of genetic information.
➢Replication
➢Gene expression
what does each base pair contain in DNA and explain what each one is
1 purine (contains 2 nitrogen rings) and 1 small pyrimidine(contains 1 nitrogen ring)
what enzyme is used in transcription when one strand serves as a template for RNA synthesis
RNA polymerase II : makes Pre-mRNA
discuss the role of nuclear localisation signals (NLS)
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.
what is the role of Importin (import receptor protein) in nuclear import
-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
describe the structure and role of the nuclear lamina (what’s it made up of)
-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
what are the 2 structural components of a chromosome
Telomeres and Centromeres
what are the properties of the telomeres of a chromosome (3 points)
-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
what are the purposes of the Centromeres in chromosomes (3 points)
-Hold metaphase chromosomes together
-attaches to mitotic spindle
-repetitive sequences highly packaged
what is it called if the centromere is in the :
1) Middle
2)slightly closer to the end
3)the end of the chromosome
1) Middle= METACENTRIC
2)slightly closer to the end of chromosome= SUBMETACENTRIC
3)the end of the chromosome =ACROCENTIC
what is the purpose of regulatory proteins in gene expression
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)
what is a Nucleosome
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
what is the role of the Nuclear envelope
separates the contents of the nucleus from the cytoplasm and provides the structural framework of the nucleus.
Explain the advantage of evolution of the nucleus in eukaryotic cells, referring to its structure and linking this to its functions.
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
When is the highest level of DNA packaging achieved?
mitosis, metaphase
DNA and associated proteins in the nucleus form a material known as Chromatin, TRUE or FALSE
TRUE
What fold level of packaging does the beads-on-a-string form of chromatin cause? {type the number only}
3
Which of the following histones are found in the nucleosome core? (Select all correct answers)
H1
H2A
H2B
H3
H4
H2A, H2B, H3, H4
Which of these describe the nucleosome core?
A dimer
A tetramer
A pentamer
An octamer
A dodecamer
An octamer
How much DNA is wound around the histone core in the nucleosome? (give number only)
146 nucleotides
Which additional protein is used to twist the beads-on-a-string form of chromatin into the 30nm fibre?
histone, H1
To what structure are chromatin loops attached?
Nuclear scaffold, scaffold
What is active (expressed) DNA known as?
euchromatin (its chromatin loosely packed to enable transcription - active gene)
What is highly packaged silent DNA known as?
heterochromatin
Nuclear import receptors may be called ___Response and nuclear export receptors may be called ___
(importins)
(exportins)
