Lecture 13 (Eukaryotic cell division - mitosis)

Question 1

What areas of human endeavour does genetics impact?

Answer 1

Medicine
Law 
Agriculture 
Sociology 
Philosophy 
Ecology 
Agriculture

Question 2

How do acellular life store genetic information?

Answer 2

Viruses generally store their genetic information as double-stranded or single-stranded, DNA or RNA

Question 3

How do prokaryotic organisms store genetic information?

Answer 3

Bacteria generally store their genetic information ass circular, single copy, naked (not surrounded by a vast amount of proteins like eukaryotes) double-stranded DNA

Question 4

How do eukaryotic organisms store genetic information?

Answer 4

Protists, animals, plants and fungi generally store their genetic information as linear, greater than or equal to one single copy, histone-bound DNA; sexual cycle

Question 5

How much DNA does a human have?

Answer 5

Each 3000 base pairs is approximately 1 micron. Humans have 3x10^9 base pairs therefore each human cell contains about 2 metres of DNA. Humans have approximately 21000 genes.

Question 6

Karyotype

Answer 6

An ordered, visual representation of chromosomes in a cell.

Question 7

Karyotype process

Answer 7

You start off by getting cells t a very particular stage in cell division (metaphse)

Take blood sample
Treat cells with mitogen
Then colchicine
Then stain

Question 8

Human chromosomes

Answer 8

1-22 are called autosomes

X and Y are sex chromosomes

Question 9

Autosome

Answer 9

An autosome is any chromosome that is not a sex chromosome

Question 10

Homologous pairs

Answer 10

Chromosome pairs of approximately the same length, centromere position, and staining pattern, for genes with the same corresponding loci. One homologous chromosome is inherited from the mother; the other is inherited from the father.

Question 11

Locus

Answer 11

Particular location where the gene is found

Question 12

Gene

Answer 12

a sequence of nucleotides in DNA or RNA that encodes the synthesis of a gene product, either RNA or protein

A gene is a section of DNA that codes for a protein

Question 13

Allele

Answer 13

Alternative form of a gene

Difference forms of a gene at that locus

Question 14

Homozygote

Answer 14

2 alleles are the same at that particular locus

Question 15

Heterozygote

Answer 15

2 alleles are different at that particular locus

Question 16

Multicellular organisms depend on cell division for …

Answer 16

Development from a fertilised cell (growth and development)

Growth to adult (10^14 - we get here because the original cell divided and the cell division of those products formed occurs etc. etc.)

Repair

Question 17

How does a eukaryotic cell divide its DNA equally?

Answer 17

Basically, all you cells (except a few that have mutations) have the same DNA sequence (same geners, same chromosomes). This occurs because of a specific way that chromosomes are organised during cell division so that every cell gets a copy of every chromosome. Makes sure cell division gives you products that are essentially genetically identical to the cells that they have come from…this is what mitosis does

Question 18

Stages of the cell cycle

Answer 18

G1, Synthesis phase, G2 and then mitosis

Question 19

Chromosome

Answer 19

A cellular structure consisting of one DNA molecule and associated protein molecules.

Question 20

Interphase

Answer 20

Interphase is the phase of the cell cycle in which a typical cell spends most of its life. During interphase, the cell copies its DNA in preparation for mitosis.

Question 21

G1 phase

Answer 21

A cell grows during this phase

Cellular growth and production of proteins and other materials

Question 22

Synthesis phase (S phase)

Answer 22

A cell continues to grow as it copies its chromosomes

Question 23

Cell replicates its DNA during S phase

Answer 23

The newly replicated chromosomes which are dispersed in the nucleus in the form of thread like strands of chromatin, slowly begin to coil and condense into a compact form which we can see under a light microscope. The condensed replicated chromosomes each consist of two replicates called chromatids joined together by a constricted area known as the centromere. At this constricted region, each of the two chromatids of a replicated chromosome has a kinetochore, a special structure of proteins and DNA

Question 24

G2 phase

Answer 24

A cell keeps on growing as it completes preparations for cell division

Question 25

Duplicated chromosome

Answer 25

Two sister chromatids, which later seperate during mitosis During the S phase of interphase, duplication occurs. Before this you have one copy of each chromosome and then this chromosome duplicates (to form two sister chromatids connected at the centromere) and in anaphase essentially that connection gets spilt apart with one of these chromatids in each cell.

Question 26

Mitosis

Answer 26

Cell division that produces two genetically identical daughter cells // the division of one nucleus into two genetically identical nuclei Consists of 5 phases - prophase, prometaphase, metaphase, anaphase, telophase

Question 27

Five phases of mitosis

Answer 27

prophase, prometaphase, metaphase, anaphase, telophase

Question 28

Prophase

Answer 28

Every chromosome has doubled into a pair of sister chromatids, so there are two sister chromatids that are genetically identical to one another The chromatin fibers become more tightly coiled, condensing into discrete chromosomes observable with a light microscope Spindle (made up of microtubules) begins to form This is the first stage of mitosis

Question 29

Prometaphase

Answer 29

Nuclear envelope fragments Chromosomes have become even more condensed A kinetochore, a specialised protein structure, has now formed at the centromere of each chromatid (therefore there are two per chromosome) Some of the microtubules attach to the kinetochores, becoming “kinetochore microtubules” which jerk the chromosomes back and forth Non-kinetochore microtubules interact with those from the opposite pole of the spindle, lengthening the cell

Question 30

Metaphase

Answer 30

Pairs of sister chromatids line up along the central part of the cell which is known as the metaphase plate (halfway between the two centrosomes) Chromosomes/pairs of sister chromatids line up in an organised way due to the connection via the kinetochore to the kinetochore microtubule, so the kinetochore microtubules act in such a way that all the chromosomes are lined up on the metaphase plate Spindles consist of both kinetochore microtubules and the non-kinetochore microtubules and the non-kinetochore microtubules as well as the centrosomes at opposite side of the cell The chromosomes’ centromeres now lie at the metaphase plate For each chromosome, the kinetochores of the sister chromatids are attached to kinetochore microtubules coming from opposite poles

Question 31

Anaphase

Answer 31

Mitosis works because in anaphase, the parts of sister chromatids get ripped apart, one going to one side and the other chromatid going to the opposite side. Remember that each sister chromatid is a copy of the other one so you are effectively sending one lot of genetic information one way and another lot in the opposite direction. This works because the kinetochore microtubules getting shorter which pulls the sister chromatids apart right at the centromere. The non kinetochore microtubules get longer and push the two ends of the cell apart By the end of anaphase, the two ends of the cell have equivalent and complete collections of chromosomes

Question 32

Telophase and cytokinesis

Answer 32

telophase - Furrow starts to form, nucleolus forming, nuclear envelope forming, chromosomes become less condensed, mitosis is now complete Cytokinesis - this is how the cytoplasm divides, eventually the two cells will seperate and there will be a cell membrane surrounding them (and if you are talking about plant cells then there could be a cell wall that forms as well). Cytokinesis involves the formation of a cleavage furrow, which pinches the cell in two

Question 33

Each daughter cell of mitosis has...

Answer 33

One copy of every chromosome (sister chromatids seperate during anaphase)

Question 34

Sister chromatids in mitosis each have...

Answer 34

1 double-stranded copy of their DNA molecule

Question 35

During mitotic anaphase what happens to non-kinetochore and kinetochore microtubules …

Answer 35

Non-kinetochore microtubules lengthen and kinetochore microtubules shorten

Question 36

Kinetochore microtubule

Answer 36

Spindle microtubules that attach to the kinetochores. The kinetochore microtubules attach to chromosomes and move them towards poles. A pair of sister chromatids are connected by the centromere and the centromere connects to the kinetochore which connects to the kinetochore microtubule.

Question 37

Non-kinetochore microtuble

Answer 37

Spindle microtubules that do not attach to kinetochores. Nonkinetochore microtubules are responsible for elongating the cell during anaphase.

Question 38

Kinetochore

Answer 38

a complex of proteins associated with the centromere of a chromosome during cell division, to which the microtubules of the spindle attach.

Question 39

Centrosome

Answer 39

an organelle that is the main place where cell microtubules are organized

Question 40

Centromere

Answer 40

The centromere is the specialized DNA sequence of a chromosome that links a pair of sister chromatids. During mitosis, spindle fibers attach to the centromere via the kinetochore.

Question 41

Mitosis rate in skin versus muscle and neurons

Answer 41

In humans, our skin cells have a high turnover rate due to wear and tear and go through mitosis very frequently whereas other cells such as adult neurons and muscle cells rarely divide

Question 42

Chromatin

Answer 42

Chromatin is a mass of genetic material composed of DNA and proteins that condense to form chromosomes during eukaryotic cell division. Chromatin is located in the nucleus of our cells.

Question 43

Replicated chromosome

Answer 43

A replicated chromosome is considered to be one chromosome consisting of two chromatids.

Question 44

Chromatid in anaphase

Answer 44

Remember that during anaphase each chromatid becomes a single chromosome