Final - Part 2 Flashcards
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Genome vs Genes
Genome: All the genetic material in a norganism
- Ex) genomes of kiwi consist of: nucleus, mitochondria.. bascially everything that is containing heretability).
Genes: a segment of genome that is transcribed into functional RNA (mRNA, tRNA, rRNA) and passed from parent to offspring.
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Where are genomes located in prokaryotes & eukaryotes?
Prokaryotes: in nucleoid (그 nucleus 대신 있는 거)
Eukaryotes:
- Plant cells: nuclear + mitochondria + choloroplast genomes
- Animal cells: nuclear + mictochondria
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How are genomes organized in prokaryotic genomes & eukaryotic genomes
They both have chromosomes.
Prokaryotic genomes: usually in a single circular chromosome.
Eukaryotic genomes: multiple linear chromosomes inside the nucleus.
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Chromosome
Chromatin
Define
Chromosome: a single long chain of DNA of 2 complementary strands.
- Made out of chromatins
Chromatins: A mixture of DNA and proteins that form the chromosome.
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Human genomes
Where? how many?
- 23 pairs of (mostly) homologous chromosomes.
- 46 chromosomes
- Most of our cells’ nuclei
- We should at least have 2 copies of any given gene in similar areas of eeach chromosome.
- Only 1 copy of each chromosome’s sequence is represented in the human genome
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What does homologous mean?
A chromosome is mostly identical in nucleotide sequence to its homomlogous pair.
they can’t be completely identical
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Which chromosome is not homologous?
Sex choromosomes
- Females: XY (not homologous)
- Males: XX (Homologous)
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What human genome project figured out
Most of the human genome is identical between individuals, but there are varations amongst individuals.
This is why wew don’t look the same
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Organization of Eukaryotic Chromosomes
- DNA
- DNA is coiled around histones: protein complex
- Nucleosomes coiled into a chromatin fiber.
- Further condensation of chromatin
- Duplicated chromosome
-> DNA coiled around histones, and these coils are pulled into further coils that help it fit into a nucleus.
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Is DNA always coiled?
DNA can be coiled and uncoiled as needed, so our cells can access the genetic information within.
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Organization of Prokaryotic Chromosomes
- Most prokaryotes’ genomes are one circular chromosome
- May contain plasmids: additional small circles of RNA that could be passed around between different bacterial cells.
- They twist up the chromosomes by the way of proteins and enzymes to fit into the cells.
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How do we physically grow up?
Combination of 2 things
Combination of cells dividing + growing
- Cuz the increase in # of cells make organisms physically grow.
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Cell cycle & 2 broad parts of the cell cycle
Define cell cycle and the parts
Cell cycle: process which describes how cells progress through their lives until division / reproduction
2 broad parts of the cell cycle:
1. Interphase - G1, S, G2 Phases
2. Mitosis + cytokinesis
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Interphase
Describe interphase and 3 major cellular processes
The majority of a cell’s life cycle is spend in interphase
- G1, S, G2
1. General growth (get to a certain size to be able to divide)
2. Replication of chromosomes
3. Preparation for cell division
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G1/G2 Phases
3 major cellular processes
G stands for Gap
1. Gathering up or synthesizing resources for growth
2. General cell growth
3. Growth/replication of organelles
(so that there is enough copied organelles for 2 cells in the future
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Difference between G1 & G2
Cells in G2 have twice as much DNA as cells in G1. Cuz S phrase replicates DNA!
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S Phase
S stands for Synthesis!
1. All the cell’s DNA is replicated
2. New DNA is synthesized
3. All of a cell’s chromosomes are replicated in preparationg for division
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Chromosomes replication during S phase
Don’t confuse the # of chromosomes
- There is an unduplicated chromosome
- Replicated chromosomes attached at the centromere
- While attached these are considered 1 chromosome
- Each half is called a sister chromatid
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After S phase, how many total chromosomes are there in a typical human cell?
46
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Before S phase, how many total chromosomes are there in a typical human cell?
46 (92 sister chromatids!)
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Cell Cyle Checkpoints
How many? why important?
3 Checkpoints: At the end of G1&G2&Metaphase
It’s important to know that the cell is ready to divide. (Are any components damaged? Enough resources in the environment? Are neighbouring cells signalling for or against division?)
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- G1 Checkpoint
- What does it check?
what is it?
It’s the main decision point for cells to progress on cell cycle.
Why? Cuz after this point, a cell is irreversibly committed to dividing cuz DNA is replicated
It checks: internl & external conditions
1. Size
2. Nutrients
3. Molecular signals from neighbours
4. DNA integrity (is any of the DNA damaged?
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G0 Phase
also why does it happen?
Cells may also be cued to leave the cell cycle and stop dividing
- It’s a resting state
- May be permanent or temporary
- Due to: not enough nutrients, neighbouring cells signal against division etc)
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G2 Checkpoint
final check of the genetic material before the chromosomes are separated into 2 cells
Checks:
1. DNA integrity
2. DNA replication (is DNA replication complete)