Gene, Chromosomes, Mitosis And Meiosis Flashcards
(39 cards)
What are chromosomes made up of?
DNA, protein and RNA.
Name some features of the chromosome.
- karyotype
- centromere
- telomeres
- origins of replication (ori)
- chromosomes visible during metaphase (condensed)
- Banding pattern
- g banding- metaphase chromosomes treated with mild heat/proteogtic enzymes stained with giemsa producing dark bonds.
What is telocentric?
When the centromere is at one end.
What is acrocentric?
When centromere is off the center.
What is sub-metacentric?
When centromere is a bit off the center.
What is matacentric?
When the centromere is at the center.
What is diploid?
Human are diploid. 2n. 2 sets of chromosomes. 46 chromosomes in total.
What is haploid?
One set of chromosomes. 23 in humans.
What is homologous?
Pairs of chromosomes. All euk. are diploid or have a diploid phase.
Describe DNA packaging.
- Short region of DNA wraps around histones forming nucleosomes.
- 30nm chromatin fiber of packed nucleosomes.
- Forms condensed chromosomes.
- Chromosomes.
Describe the structure of chromosomes in eukaryotes.
Each chromosome has linear, unbroken double-stranded DNA molecule- contain twice as much protein by weight as DNA.
Chromosomes- complex of DNA, chromosomal protein and RNA- chromatin.
Name two types of chromatin.
Euchromatin and heterochromatin.
Describe euchromatin.
- stains lightly
- uncoiled during interphase, condensed during mitosis
- majority of genome
- genetically active (contains genes that are being expressed)
Describe heterochromatin.
- stains darkly, highly condensed
- genetically inactive (either contains no genes or genes cannot be expressed)
- replicates later in S phase of cell cycle due to a higher degree of condensation
- found near centromeres at telomeres and else where in species-soecies manner
Name two types of heterochromatin.
Constitutive and facultative.
Describe constitutive heterochromatin.
Genetically inactive, found at homologous sites of chromosome pairs (centromeric and telomeric heterochromatin, mostly X chromosome)
Describe facultative heterochromatin.
Potential to become to heterochromatin state. May become inactive when chromatin condenses. Eg. Barr bodies (inactive X chromosomes)
Describe histones.
- most abundant protein associated with chromosomes
- small, basic protein
- overall positive charge
- equal amount of histone and DNA in chromatic
- 5 main types associated with euk.DNA; H1, H2A, H2B, H3, and H4
How are nucleosomes formed?
- In the nucleus.
- DNA coiled in a non-random way.
- Simplest packaging’s winding of DNA around histones.
- 2 tight spherical turns of DNA, 146bp, are wrapped around octamer of 2 copies of each of the 4 core histones (H2A, H2B, H3, H4)
- each nucleosome is connected by 20-30 bp of linear DNA
CHROMATIN ORGANISATION?
Describe the euk. Cell cycle.
- G1 (gap phase 1)- primary growth phase, longest stage
- S (synthesis)- replication of DNA
- G2 (gap phase 2)- organelles replicate, microtubules organise
^interphase^
- M (mitosis)- subdivided into 5 phases, PMAT.
- C (cytokinesis)- 2 new cells separate.
Duration of cell cycle for fruit fly embryos?
8 mins
Duration of cell cycle for mammal cells?
24 hrs
Duration of cell cycle for liver cells?
+1 yr
