Cell Division

Question 1

Where is DNA found?

Answer 1

In the nucleus

Question 2

Whats the function of DNA?

Answer 2

Control all cell activities ie cell division

Question 3

What is chromatin?

Answer 3

Long thread like DNA in a non dividing cell

Question 4

What is a chromosome?

Answer 4

Double coiled short DNA in a dividing cell

Question 5

What does a chromosome consist of?

Answer 5

Chromatids and a centromere.

Question 6

What is a gene?

Answer 6

A section of DNA which codes for one polypeptide chain.

Question 7

What is an allele?

Answer 7

A version of a gene

Question 8

Does a diploid have a homologous pairs?

Answer 8

yes

Question 9

Does a haploid have a homologous pairs?

Answer 9

no

Question 10

What are homologous pairs?

Answer 10

They are a pair of chromosomes which contain the same genes but possibly different alleles. One chromosome is paternal and one is maternal.

Question 11

How many sets of chromosomes does a haploid have?

Answer 11

One (n)

Question 12

How many sets of chromosomes does a diploid have?

Answer 12

Two (2n): total number of chromosomes before meiosis

Question 13

How many sets of chromosomes does a polyploid have?

Answer 13

Many sets of chromosomes

Question 14

How many divisions happen in mitosis and meiosis?

Answer 14

MITOSIS: one division results in two daughter cells.

MEIOSIS: two divisions results in four daughter cells

Question 15

What happens to the chromosome number in mitosis and meiosis?

Answer 15

MITOSIS: chromosome number remains unchanged: diploid daughter cells produced (each with 2 sets of chromosome)

MEIOSIS: chromosome number is halved: haploid daughter cells produced (each with only one set of chromosomes)

Question 16

What happens to the genetical identity in mitosis and meiosis?

Answer 16

MITOSIS: daughter cells are genetically identical to each other and to the parent cell.

MEIOSIS: daughter cells are genetically different from each other and the parent cell.

Question 17

What happens to the homologous pairs in mitosis and meiosis?

Answer 17

MITOSIS: Homologous pairs don’t pair up

MEIOSIS: Homologous chromosomes pair up to form bivalents via synapsis.

Question 18

When does crossing over occur in mitosis and meiosis?

Answer 18

MITOSIS: Doesn’t occur

MEIOSIS: it occurs at the chiasmata

Question 19

Does genetic variation occur in mitosis and meiosis?

Answer 19

MITOSIS: there’s no genetic variation

MEIOSIS: variation due to independent assortment

Question 20

What is the importance of meiosis?

Answer 20

• Produces variation.
• Homologous pairs of chromosomes are separated producing non-identical daughter cells.
• The production of haploid gametes (half chromosome number).
• Allows chromosome number to be maintained during sexual reproduction.
• Diploid number is restored in fertilisation (haploid gametes fuse and form a diploid zygote)

Question 21

When does genetic variation occur?

Answer 21

• During crossing over, parts of homologous chromosomes may be exchanged producing new allele combinations.
• During independent assortment of homologous pairs of chromosomes maternal and paternal chromosomes are mixed up.
• Independent assortment of chromatids.

Question 22

Why are the gametes haploid?

Answer 22

They fuse to form diploid zygote (restores chromosome number). If there was no reduction in chromosomes number would DOUBLE in each successive.