Lecture #11 - Nucleus stuff Flashcards
The Nucleus:
- the most p____ organelle (__-__μm dia.)
- one n____ per cell (in most cases)
- contains m__ (……….) of the cell’s genes
- serves as r_____ of genetic information
- and the cell’s c___ c___
- the most PROMINENT organelle (5-10μm dia. roughly spherical)
- one NUCLEUS per cell (in most cases - except RBC have none and muscle cells have multiple)
- contains MOST (but not all) of the cell’s genes
- serves as RESPOSITORY of genetic information
- and the cell’s CONTROL CENTRE (cell sends intructions to nucleus so cell controls nucleus lol)
What’s the nucleus surrounded by?
Nuclear envelope which is composed of two membranes (each is a lipid bilayer with proteins in them) - it’s another name for nuclear membrane.
Needs to have 2 layers because needs extra protection since it’s the control centre
In this image, the small thing is a nuclear pore that sits in the membrane
The inner surface of nuclear envelope is lined by the ……? Composed of? Helps to? And also?
Nuclear LAMINA
- composed of INTERMEDIATE FILAMENTS
- helps maintain SHAPE of nucleus
- and ORGANISES the PACKING of DNA
It’s like the steel meshwork before concrete poured - offers support and upholds structure. Intermediate filaments because cells wants it to remain stable for a long time.
Nuclear pore:
- What is it?
- It’s a hole but has extra ish for control:
- mRNA, rRNA and tRNA out of nucleus (DNA doesnt leave)
- CONTROL SIGNALS move into nuclues (testosterone turns shit on in nuc - steriods go straight thru bc lipophylic)
- ENERGY AND MATERIALS into nuclues (needs to make shit so these things needed)
From textbook:
The evenelope is perforated by pore structures that are about 100nm dia. An intricate protein strcuture called a PORE COMPLEX lines each pore and plays an imporant role in the cell by REGULATING THE ENTRY AND EXITS OF PROTEINS AND RNAs as well as large complexes of MACROMOLECULES
Nucleolus - what is it? rRNA and mRNA context
Here a type of RNA called rNA is synthesised from instructions in the DNA. Also, proteins imported from the cytoplasm are assembled with rNA into large and small subunits of ribosomes. These subunits then exit the nucelus through the nuclear pores to the cytoplasm where they assemble to become a ribsome.
The nucleus directs protein synthesis by synthesising mRNA which is transported to cyto via nuc pore
Appreicate this image
Yeah
DNA:
- How many m of DNA in one human cell? How many times the diameter of the nuc?
- DNA must be very well p___ but also a_____
- DNA double helix is combined with _____ ____ to form _____ ____
- Chromatin fibres undergo ……..
DNA:
- 2.5m of DNA and 250,000 X the dia. of nuc
- DNA must be very well PACKED but also ACCESSIBLE
- DNA double helix is combined with HISTONE PROTEINS to form CHROMATIN FIBRES
- Chromatin fibres undergo MULTI-LEVEL PACKAGING
The first stage of packaging:
- What’s the dia. of double helix?
- The helix interacts with….. to form ….. and each “bead” is called ____
- DNA double helix is about 2nm dia.
- The helix interacts with SPECIFIC HISTONE PROTEINS (H2-H4) to form a 10nm dia fibre and each “bead” is called a NUCLEOSOME (i.e helix coils around histone proteins and becomes a beaded structure)
Histone proteins; more than a fifth of a histone’s……..
more than a fifth of a histone’s aa’s are +vely charged and therefore bind tightly to the -vely charged DNA
Further interactions between the _____ and ……… cause the 10nm fibre to coil to form the ____ fibre.
The ____ fibre loops to form _____ fibre
First arrow: Further interactions between the DNA and another histone (H1) cause the 10nm fibre to coil to form the 30nm fibre.
Second arrow: The 30nm fibre loops to form 300nm fibre
During cell division, the 300nm fibres ___ to form _____ chromosomes
During cell division, the 300nm finres coil to form metaphase chromosomes (only time you get to see the chromosomes like that - interphase rest of time so has just chromatin
- During ______ some regions of chromatin are more _____ than others
- What’s the name of the region that’s less dense?
- Is this often genetically active?
- What’s the name of the region that’s more dense?
- Is this genetically active or inactive?
- What kind of relationship is there between euchromatin and heterochromatin
- Is the location of chromosome within the nucleus random?
- During INTERPHASE some regions of chromatin are more COMPACT than others
- Euchromatin - less dense and often genetically active (less dense so it’s accessible for transcription)
- Heterochromatin - more dense and genetically inactive (eg neurons dont need info to make RBCs etc so it’s genes that cell doesnt need)
- There is a DYNAMIC relationship between eu and heterochromatin (so interchangeable?)
- The location of chromasome within nucleus is NOT random DNA makes links with the inner surface of membrane (nuclear)
