Cell Biology Test 1.2 (prokaryotes and eukaryotes) ✅ Flashcards
What is the bacterial genome composed of?
single circular DNA molecule
some exceptions exist, ie. vibrio cholera with 2 dissimilar chromosomes.
What information does the bacterial genome hold?
directions for all necessary functions to maintain a functional and self-replicating cell.
What is in prokaryotic cells, that is similar to histones in eukaryotic cells?
nucleoid associated proteins
State the differences between eukaryotes and prokaryotic DNA.
Prokaryotes:
- not membrane bound
- nucleoid
- flows freely in the cytoplasm
- only 1
- circular
- no histones or introns
- has nucleoid assosiated proteins
Eukaryotes:
- membrane bound organelle
- more than one (chromosomes)
- located in the nucleus
- linear
- histones and introns
What is the function fo a genome?
it directs all growth and processes necessary to maintain a functional, self replicating system
What are plasmids?
small, usually circular, covalentry closed, double starnded DNA molecules
How do plasmids replicate?
replicate independent of the chromosome
What are the two types of plasmids?
TRANSMISSIBLE: transferred by conjugation
NON TRANSMISSIBLE: do not contain transfer genes
What are the key functions of plasmids?
1) antibiotic resistance
2) resistance to heavy metals
3) UV resistance
4) exotoxins
5) bacteriocins
6) pilli
What are transposons?
jumping genes.
- pieces of DNA that move readily from one site to another.
- jump between the DNA of bacteria, plasmids and bacteriophages.
What are the two ways of transposition?
1) Direct transposition: inserted into new site without replication
2) Replicative transposition: replicate their DNA and then insert the new copy into another site.
What is the nucleoid?
The region within a prokaryote where the genetic material is located.
What is a prokaryote?
An UNICELLULAR organism with no membrane-bound organelles.
In what forms does DNA exist in eukaryotes?
1) Nucleus
2) Mitochondria
3) Chloroplasts
all have double membranes
Explain mitochondrial DNA.
- small
- circular
- encodes for proteins
- allows pathways to produce energy (cellular respiration)
- mitochondrial DNA is inherited from the mother
how many genes exist in mitochondrial DNA?
around 37 genes.
rRNA < proteins < tRNA
Explain chloroplast DNA.
- small
- circular
- allows for photosynthesis
State the components of the nucleus.
- nuclear membrane
- nucleolus
- nucleoplasm
- inner membrane
- outer membrane
- nuclear pore
- chromatin
- rough ER surrounding
- nucleoporins
- ribosomes (on the surrounding rough ER)
- importin
- nuclear lamin
- lamins
State the two main function of the nucleus.
1) storage of genetic material.
2) protein synthesis (transcription)
State the function of nucleoporins.
- control the entry and exit from the cell
How do the nucleoporins look?
they have eight fold symmetry
What type of parts does the nucleus have? (texture wise)
globular and fibrous
State the function of the nuclear envelope.
forms a selectively permeable barrier.
State the function of the nuclear lamina.
stabilises the nuclear envelope.
laminate= stabilize paper
State the function of the lamins.
Lamins are associated with the chromatin.
State the function of importin.
- selective protein
- aids in the transport/movement of substances across the nuclear membrane
State the function of the nuclear pores.
- allow to movement across and into the nucleus
1) ions and solutes transfer using simple diffusion,
2) large macromolecules are regulated by nucleoporins
What does the large number of nuclear pores aid in?
simultaneous movement into and out of the cell.
What are large macromolecules regulated by in the nucleus?
by nucleoporins
State the function of chromatin.
allows for DNA replication, transcription, repair, cell division and genetic recombination.
How is chromatin formed?
DNA and proteins
What does chromatin change into?
chromosomes
What does basophilic mean?
easily stained
What moves into the nucleus?
- enzymes
- ribosomal proteins,
- chromatin
- transcription factors
What moves out of the nucleus?
- pre-mRNA
- ribosomal subunits
- RNA associated with proteins
What is the nucleoplasm? What is its function?
A gel-like matrix in which nuclear components are suspended. It functions to cushion and protect the insides of the nucleus, provides a mode of transportation for enzymes and aids to maintain the cells shape.
What is chromatin?
- complex of DNA and proteins
- forms chromosomes
What are the two types of chromatin?
1) Euchromatin: transcribable, active, less condensed.
2) Heterochromatin: not transcribable, highly condensed
What is the function of histone proteins?
help organise DNA.
- supercoil DNA
- allow for gene regulation (regulatory proteins)
- regulate transcription
How is DNA coiled?
8 histone proteins and 1 DNA strand wrapped around 1.75 times.
What is a nucleosome?
8 histone proteins (2H2A, 2H2B, 2H3, 2H4),
1.75 wrapped DNA strand.
What is a chromatosome?
8 histone proteins (2H2A, 2H2B, 2H3, 2H4),
1.75x wrapped around DNA strand,
Additional H1 histone protein
What does the H1 histone protein allow for?
higher order folding
(due to the ‘tail’ domains which cause interactions between nucleosomes and additional proteins)
What do multiple nucleosomes form?
nucleosome array
What do multiple chromatosomes form?
chromatin –> chromosome
What are the two forms in which nucleosome arrays exist? Which one is more folded?
Solenoid and zigzag. Zigzag is folded more deeply.
What is the interaction pattern in the solenoid form of nucleosome arrays?
What type of pattern (model) is the solenoid form?
interactions between histones occur sequentially (1,2,3,4 and so on)
The solenoid form is a “one start model”
What is the interaction pattern in the zigzag form of nucleosome arrays?
What type of pattern (model) is the solenoid form?
DNA connects two opposing nucleosomes
(1 and 3, 2 and 4, and so on)
The zigzag pattern is differently known as the “two start model”
When are chromosomes most compact?
during metaphase
What are the components of a chromosome?
- chromatid
- centromere
- chromatin
- pellicle
- matrix
- telomere
- chromonemata
- satellite
- primary constriction
- secondary constriction
What is the chromosome structure?
The chromosome is a supercoiled structure of chromatin.
What are the 4 shapes of chromosomes?
Metacentric (V shaped)
Submetacentric (L shaped)
Acrocentric (J shaped)
Telocentric (rod shaped)
State an example of a non typical chromosome.
Polytene chromosomes
Lampbrush chromosomes
Gender chromosomes
How are polytene chromosomes formed?
the products of multiple rounds of S-phase remain tightly associated to form one supersized chromosome.
What are polytene chromosomes? Which subset are they located in?
Polytene chromosomes are formed due to multiple products of S phase being tightly associated together.
they are part of the ENDOPOLYPLOID CELLS.
What is part of the endopolyploid cells?
polytene chromosomes
Explain the lampbrush chromosomes.
- present in oocytes of birds, lower Vertebrata and invertebrates
- form due to an active transcription of many genes
- during meiosis prophase 1
Explain how gender chromosomes are exceptions.
- sex chromosomes determine the gender of an organism
- XX is woman
- XY is male
- X is much bigger than Y
