Chromosomes and Cell Division - First Lecture

Question 1

What are the stages of the cell cycle?

Answer 1

Interphase and mitosis then cytokinesis.

A cell spends most of its time in what is called interphase, and during this time it grows, replicates its chromosomes, and prepares for cell division. The cell then leaves interphase, undergoes mitosis, and completes its division.

Question 2

What are the different stages of interphase?

Answer 2

G1, S and G2

Question 3

What happens during the G1 stage of interphase?

Answer 3

Protein and RNA synthesis Growth and maturation of the cell occurs DNA checking and subsequent repair occurs during the pause between G1 and S

Question 4

What happens during the S phase of interphase?

Answer 4

DNA synthesis

S for synthesis🧬

Question 5

What happens during the G2 phase of interphase?

Answer 5

Further synthesis of RNA and proteins Further growth Organelles such as mitochondria grow and divide Followed by proof reading and subsequent repair of newly synthesised DNA

Question 6

What are the stages of Mitosis?

Answer 6

Prophase Metaphase Anaphase Telophase Cytokinesis

PMATC

Question 7

What happens during Prophase?

Answer 7

Chromosomes condense Nuclear membrane disappears Spindle fibres form from the centriole

Question 8

What happens during metaphase?

Answer 8

Chromosomes allign t the equator of the cell Attached by fibre to each centriole Maximum condensation of chromosome

Question 9

What happens during anaphase?

Answer 9

Sister chromatids separate at the centromere Move to opposite ends of the cell

Question 10

What happens during telophase?

Answer 10

Nuclear membranes form
And 2 diploid cells form (43) (43)

Question 11

What happens during cytokinesis?

Answer 11

Cytoplasm separates

Question 12

What is the structure of the centromere?

Answer 12

Repetitive DNA sequences (satellite DNA) Site of the kinetochore which is a protein complex that binds to microtubules

Question 13

What is the difference between Heterochromatin and Euchromatin?

Answer 13

Heterochromatin; is condensed structure, Silenced genes

Euchromatin; Open structure, Active genes

Question 14

Where can you find satellite DNA and what is it?

Answer 14

Tandemly repeated DNA sequences at the Centromeres and telomeres of chromosomes

Question 15

How is chromatin formed?

Answer 15

DNA packed within histone proteins

Question 16

What is the charge of histone?

Answer 16

Positively charged

Question 17

What is a nucleosome?

Answer 17

A unit of eukaryotic chromosome A length of DNA wrapped around a core of histones

Question 18

How is a solenoid structure formed?

Answer 18

Further wrapping of nucleosomes

Question 19

What are the different levels of structural elements of chromatin?

Answer 19

Nucleosome Chromatin fibre Fibre-scaffold complex Chromosome

Question 20

What is the purpose of packaging DNA?

Answer 20

Charge neutralised Takes up less space Inactive DNA can be folded into inaccessible locations until required

Question 21

What is the purpose of FISH (fluorescent In Situ Hybridisation)

Answer 21

Mark or tag a specific DNA sequence out of the whole genome

Question 22

What is the process of FISH?

Answer 22

Denature DNA into single strands Hybridise the DNA with fluorescent tag (tag complimentary to desired DNA sequence) Excess tags are washed away Tags are either fluorescent themselves or can attach to a fluorescent molecule The chromosome is then viewed under a fluorescence microscope revealing the physical location of the desired gene

Question 23

What are the different types of FISH probes?

Answer 23

Unique sequence probes
Centromeric probes
Telomeric probes
Whole chromosome probes

Question 24

What are the stages of meiosis?

Answer 24

DNA replication
Pairing of homologous chromosomes
Recombination takes place
Homologous chromosomes are separated by spindle fibres.
Cell division 1
Meitoic division 2 takes place

Question 25

What is the purpose of meiosis?

Answer 25

It is the cell division of germ cells to form haploid gamete cells ( egg or sperm) from diploid cells in ovaries and testes

Question 26

What are the different names given to egg formation and sperm formation?

Answer 26

oogenesis spermatogenesis

Question 27

When does gametogenesis begin in males and females?

Answer 27

Males - Puberty Females - Early embryonic life

Question 28

What determines the sex of the zygote?

Answer 28

Wether or not the sperm contains the y chromosome

Question 29

Where does mitochondrial DNA come from?

Answer 29

Only from the mother via the egg

Question 30

What happens to the X chromosome in females?

Answer 30

One of them is randomly inactivated

Question 31

Where are the telomeres of a chromosome?

Answer 31

At the end of the arms.

Question 32

What is the end replication problem?

Answer 32

Consecutive rounds of DNA replication cause the telomeres to become shorter and shorter.

Question 33

How do eukaryotes solve the end replication problem?

Answer 33

Telomerase can reverse transcribe its own RNA template to synthesis the additional DNA, increases the 3’ end of the parent strand, allowing the okasaki fragments and polymerase to extend the 5’ end if the other DHA strand.

Question 34

What is telomerase made up of?

Answer 34

Proteins and RNA