Chromosomes and Cell Division Flashcards by Jonathan Biss

Chromosomes and Cell Division

Primary function of genetic material

Store information

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Chromosomes and Cell Division

Histone

Protein

DNA wrapped around it

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Chromosomes and Cell Division

Why is the histone attracted to the DNA

DNA has a negative charge

Histone has a positive charge

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Chromosomes and Cell Division

By how much does DNA wrapping around histone shorten it?

Sevenfold

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Chromosomes and Cell Division

Nucleosome

Repeating unit of DNA wrapped around an octamer of histone proteins

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Chromosomes and Cell Division

How are nucleosomes organised?

Into an even more compact structure

30nm fibre

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Chromosomes and Cell Division

Radial loop domains

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Chromosomes and Cell Division

Two proposed models for structure of 30nm fibre

Three dimensional zig-zag model

Solenoid model

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Chromosomes and Cell Division

Why are we unsure about the structure of the 30nm fibre?

DNA conformation may be altered when extracted from living cells

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Chromosomes and Cell Division

Types of compaction of chromosomes

Heterochromatin

Euchromatin

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Chromosomes and Cell Division

Heterochromatin

Transcriptionally inactive

Very compact

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Chromosomes and Cell Division

Echaromatin

Less condensed than heterochromatin

Capable of gene transcription

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Chromosomes and Cell Division

Which type of chromsome compaction is most common in non-dividing cells?

Euchromatin

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Chromosomes and Cell Division

What happens to chromatin compaction during cell division?

All Euchromatin converted to heterochromatin

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Chromosomes and Cell Division

Individual chromosomes are located in their….

Discrete, non-overlapping territory

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Chromosomes and Cell Division

Chromosome compaction at metaphase

Radial loops remain anchored to scaffold formed from proteins in the nuclear matrix

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Chromosomes and Cell Division

How many different chromosomes do humans have?

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Chromosomes and Cell Division

How many chromosomes do humans have in total?

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Chromosomes and Cell Division

Haploid cells

Only have one member of a chromosome pair

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Chromosomes and Cell Division

Diploid cells

Have full set of chromosomes

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Chromosomes and Cell Division

When a species is diploid, members of a pair of chromosomes are called….

Homologues

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Chromosomes and Cell Division

Homologues

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Chromosomes and Cell Division

Cell cycle (time taken)

G1 (11 hours)

S (8 hours)

G2 (4 hours)

M (1 hour)

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Chromosomes and Cell Division

Cell cycle (shorthand and long)

First gap (G1)

DNA synthesis (S)

Second gap (G2)

Mitosis (M)

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# Chromosomes and Cell Division Shortest stage in cell cycle

Mitosis

# Chromosomes and Cell Division Checkpoint proteins

Act as sensors to determine if the cell is in proper condition to divide

# Chromosomes and Cell Division What happens if checkpoint proteins find a problem

Cell division is delayed until it's sorted or stopped entirely

# Chromosomes and Cell Division What does a loss of checkpoint function lead to

Mutation and cancer

# Chromosomes and Cell Division 3 checkpoints in eukaryotic cell division

G1 checkpoint/restriction point G2 checkpoint Metaphase checkpoint

# Chromosomes and Cell Division S phase of DNA replication

DNA is replicated Sister chromatids formed

# Chromosomes and Cell Division Sister chromatids

2 identical chromosomes copies Tightly associated at centromere

# Chromosomes and Cell Division Centromere

Acts as an attachment site for kinetochore

# Chromosomes and Cell Division What is responsible for organising and sorting chromosomes during miosis?

Mitotic spindle

# Chromosomes and Cell Division What is the spindle formed from?

Microtubules

# Chromosomes and Cell Division What are microtubules formed from?

Tybulin proteins

# Chromosomes and Cell Division 3 types of microtubules

Astral Polar Kinetichore

# Chromosomes and Cell Division Astral microtubules

Position spindle in the cell

# Chromosomes and Cell Division Polar microtubules

Seperate the 2 poles

# Chromosomes and Cell Division Kinetochore tubules

Attached to kinetochore of each chromosome

# Chromosomes and Cell Division Stages of mitosis

Prophase Metaphase Anaphase Teleophase

# Chromosomes and Cell Division Stage of mitosis that don't really need to know

Prometaphase

# Chromosomes and Cell Division What happens before mitosis?

Interphase

# Chromosomes and Cell Division Interphase

Phase where chromosomes are decondensed and found in nucleus G1, S, G2 phases of cell cycle

# Chromosomes and Cell Division What happens after mitosis?

Cytokinesis

# Chromosomes and Cell Division Prophase

Chromasomes have already replicated to produce sister chromatids Nuclear membrane dissociates into small vesicles Chromatids condense

# Chromosomes and Cell Division Prometaphase

Mitotic spindle is formed Centrosomes move apart and set boundries of the two poles Spindle fibres interact with sister chromatids 2 kinetichores on each pair of sister chromatids are attached to kinetochore microtubules from opposite poles

# Chromosomes and Cell Division Metaphase

Pairs of sister chromatids are aligned along metaphase plate Sister chromatids aligned into a single row Cell is in metaphase when alignment complete

# Chromosomes and Cell Division Metaphase plate

Plane halfway between the poles

# Chromosomes and Cell Division Anaphase

Connections between the pairs of sister chromatids broken Each individual chromosome is linked to one of the two poles by kinetichore microtubules Kinetochore microtubules shorten, pulling chromomes toward the pole it's attached to The poles move further away from each other as overlapping polar microtubules lengthen and push against each other

# Chromosomes and Cell Division Role of polar microtubules

They overlap and during anaphase lengthen and push against each other This forces the two poles to move further apart

# Chromosomes and Cell Division Which mircotubules pull the individual chromosomes to the poles?

Kinetochore microtubules

# Chromosomes and Cell Division Telophase

Chromosomes have reached their respective poles Chromosomes decondense Nuclear membranes reform to produce two seperate nuclei

# Chromosomes and Cell Division Cytokinesis

Stage where two nuclei are segregated into separate daughter cells

# Chromosomes and Cell Division Cytokinesis in animals

Cleavage furrow constricts like a drawstring to separate the cells

# Chromosomes and Cell Division Cytokinesis in plants

Cell plate forms a cell wall between the two daughter cells

# Chromosomes and Cell Division Meiosis

Process by which haploid cells are produced from a cell that was originally diploid

# Chromosomes and Cell Division How is meiosis different than mitosis?

Homologous pairs form a bivalent at prophase I Crossing over between homologous chromosome pairs

# Chromosomes and Cell Division What is the purpose of crossing over?

To form novel gene combinations

# Chromosomes and Cell Division When does crossing over happen?

Prophase I

# Chromosomes and Cell Division Crossing over (diagram)

# Chromosomes and Cell Division Meiosis I diagram

# Chromosomes and Cell Division Mieosis II diagram

# Chromosomes and Cell Division What type of daughter cells does mitosis produce?

2 diploid cells Identical

# Chromosomes and Cell Division How many chromosomes in a human diploid cell?

46 (2 sets of 23)

# Chromosomes and Cell Division How many chromosomes in a haploid human cell?

# Chromosomes and Cell Division What type of daughter cells does meiosis produce?

4 haploid daughter cells All slightly genetically different

# Chromosomes and Cell Division Which form of cell division produces identical daughter cells?

Mitosis

# Chromosomes and Cell Division What factors are chromosomes identified by?

Size Location of centromere Banding pattern

# Chromosomes and Cell Division Metacentric

Centromere is in the middle of the chromosome

# Chromosomes and Cell Division Submetacentric

Centromere is off centre

# Chromosomes and Cell Division Acrocentric

Centromere is near the end

# Chromosomes and Cell Division Telocentric

Centromere is at end

# Chromosomes and Cell Division When centromere is in the middle of the chromosome

Metacentric

# Chromosomes and Cell Division When centromere is off centre

Submetacentric

# Chromosomes and Cell Division When the centromere is positioned near the end

Acrocentric

# Chromosomes and Cell Division When the centromere is at the end

Telocentric

# Chromosomes and Cell Division Deletion mutation

Segment missing/deleted

# Chromosomes and Cell Division Duplication mutation

Section occurs 2 or more times in a row

# Chromosomes and Cell Division Inversion mutation

Change in direction along a single chromosome

# Chromosomes and Cell Division Translocation mutation

One segment becomes attached to another chromosome Either simple or reciprocal

# Chromosomes and Cell Division When the correct amount of chromosomes are present it is...

Euploid

# Chromosomes and Cell Division Polyploid

When 3 or more sets of chromosomes are present

# Chromosomes and Cell Division Triploid

3 sets of chromosomes present

# Chromosomes and Cell Division Tetraploid

4 sets of chromosomes present

# Chromosomes and Cell Division Hexaploid

6 sets of chromosomes present

# Chromosomes and Cell Division Trisomic

Normal 2 copies of a chromosome plus a 3^rd

# Chromosomes and Cell Division Aneuploidy

When total number of a particular chromosome isn't correct

# Chromosomes and Cell Division When missing one of a normal copies of a chromosome. (when only one of a pair is present)

Monosomic

# Chromosomes and Cell Division Non-disjunction

Chromosomes do not sort properly during cell division

# Chromosomes and Cell Division Effects of non-disjuntion

If occurs during meiosis it can produce gametes with too many or too few chromosomes

# Chromosomes and Cell Division In interspecies breeding when organisms have at least one set of chromosomes from 2 or more different species

Alloploid

# Chromosomes and Cell Division In interspecies breeding, 2 or more complete sets of chromosomes from 2 or more different species

Allopolyploidy

# Chromosomes and Cell Division In interspecies breeding when 2 complete sets of chromosomes from 2 different species are present, making a total of 4 sets

Allotetraploid

# Chromosomes and Cell Division Organism that commonly exhibit polyploidy

Plants

# Chromosomes and Cell Division Do animals usually tolerate deviations from diploidy?

No Usually lethal for offspring

# Chromosomes and Cell Division Synapsis

The process of forming a bivalent

Chromosomes and Cell Division Flashcards

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