2 - Mitosis And Meiosis

Question 1

What is the structure of a chromosome with two DNA molecules?

Answer 1

Question 2

When looking at a eukaryotic cell under the microscope, why might there be no nuclear envelope?

Answer 2

Cell may be undergoing mitosis or meiosis

Question 3

What are the four types of centromere?

Answer 3

Question 4

How are chromosomes classified and what are X and why?

Answer 4

• Based on their size and centromere type
• Go in descending size from 1-22
• Grouped A-G
• X is C and Y is G

Question 5

How does DNA polymerase proof-read?

Answer 5

• Contains a restriction endonuclease

Question 6

What is the proccess and outcome of mitosis?

Answer 6

Outcome: 2 identical diploid daughter cells, somatic cell replication for growth and repair

Prophase: nuclear envelope disintegrates, chromosomes condense, centrioles move to opp ends

Prometaphase: spindle attach by kinetochore

Metaphase: chromosomes line up randomly on the equator

Anaphase: spindles contract, centromere splits, sister chromatids go to opposite poles of cell and they appear v-shaped

Telophase: two groups of chromosomes, new nuclear envelope surrounds each group. chromosomes uncondense.

Cytokenesis: from cleavage furrow

Question 7

Where are chromosomes during interphase?

Answer 7

In their own territories in the nucleus as chromatin

Question 8

What is a metaphase spread?

Answer 8

• Where chromosomes are analysed when the cell is arrested during metaphase as the chromosomes are highly condensed

Question 9

What are non-sister chromatids and what do they have in common?

Answer 9

Chromsomes in the same tetrad

Both have same genes but different alleles

Question 10

What is the outcome of meiosis and why is it carried out?

Answer 10

• 4 haploid non-identical daughter cells
• Used to create genetic diversity and maintain the chromosome number throughout generations

Question 11

What is the process of meiosis?

Answer 11

Question 12

What is crossing over?

Answer 12

• Homologous chromosomes in a bivalent
• Non sister chromatids form chiasmata and swap genetic information
• Essential, if didn’t occur may lead to both chromosomes ending up in one cell

Question 13

What is a karyotype?

Answer 13

• Can physically see all the bands and chromosomes

OR

• Chromosome number:

47,XY,+21

(no spaces, just commas)

Question 14

Why is the ova larger than the sperm?

Answer 14

Ova contains all the organelles and cytoplasm for cell growth but sperm just needs genetic material

Question 15

What generates genetic diversity?

Answer 15

• Independent assortment
• Crossing over

Question 16

What is the importance of G0?

Answer 16

• Stops cells over replicating
• If they recieve a signal, they can reenter the cell cycle for tissue repair

(neurones never can, liver can)

Question 17

How do autosomes pair up in meiosis?

Answer 17

• Contain similar DNA sequences so they pair up

Question 18

What is anaphase lag?

Answer 18

• Where chromosomes dont attach to the spindle fibre or they get left behind in the cytoplasm
• DNA lost as degraded in cytoplasm
• Aneuploidy

Question 19

Compare and contrast mitosis and meiosis?

Answer 19

Mitosis

• One division , one replication
• 2 identical diploid cells
• Has prometaphase

Meiosis:

• Two divisions, one replication
• 4 haploid non-identical daughter cells
• Crossing over
• Independent assortment
• Homologous chromosomes pair up

Question 20

What is the nucleolus and why isn’t it visible during mitosis?

Answer 20

• Contains DNA from five chromosomes. Used to produce ribosomal RNA
• During mitosis all DNA is condensed into chromosomes and they are on the equator of the cell

Question 21

What is the process of oogenesis?

Answer 21

Question 22

What is the process of spermogenesis?

Answer 22

Question 23

What is the SRY gene?

Answer 23

The gene that codes for male development

If crossing over occurs in a male, and SRY passed to X chromosome, daughter can inherit this and be intersex

• She has XX but no female development as presence of SRY gene
• Intersex children