cell division 3.28, 3.29, 3.30, 3.31, 3.32, 3.33, 3.34, 3.36B, 3.37B

Question 1

how many chromosomes does the human body have?

Answer 1

23 pair of homologous chromsomes that contain the genes
23 chromosomes from the mothers egg cell
23 chromosomes from the fathers sperm cell

Question 2

what type of daughter cells does mitosis produce?

Answer 2

• produces genetically identical cells
• produces diploid cells (one pair of each chromosome in each nucleus)
• human diploid cells have 23 pairs of chromosomes 46 in total

Question 3

what is mitosis used for?

Answer 3

growth, repair and asexual reproduction

Question 4

what type of cells does meiosis produce?

Answer 4

• produces haploid gametes (sperm, egg and pollen)
• not genetically identical
• human haploid cells have 23 chromosomes in total (unpaired)
• halves the number of chromosomes

Question 5

what is meiosis used for?

Answer 5

only used to produce gametes for sexual reproduction

Question 6

what is the consequence of meiosis?

Answer 6

every gamete produced is genetically different and carries different alleles from every other gamete

Question 7

it is random which sperm/pollen grain fertilises an egg, therefore variation in offspring is produces by:

Answer 7

• genetic variation in gamete cells produced by meiosis cells
• random fertillisation of ova by male gamates

Question 8

how many cells does mitosis produce?

Answer 8

produces two cells

Question 9

how many cells does meiosis produce?

Answer 9

produces four cells

Question 10

how many cell divisions does mitosis involve?

Answer 10

involved one division

Question 11

how many cell divisions does meiosis involve?

Answer 11

involves two cell divisions

Question 12

what is the process of cell division with mitosis?

Answer 12

• the DNA replicates to form two copies of each chromosome, these copies (chromatids) are joined together at a single point (the centromere)
• the nuclear membrane breaks down and the chromosomes line up across the centre of the cell attached to spindle fibres
• the chromatids are pulled apart and move to opposite sides of the cell
• the cytoplasm and cell membrane divide to form two identical cells

Question 13

what is the process of cell division with meiosis?

Answer 13

• the DNA replicates to form two copies of each chromosome, these copies (chromatids) are joined together at a single point (the centromere)
• the nuclear membrane breaks down, the homologous pairs of chromosomes join together
• the homologous pairs of chromosomes exchange sections of DNA and they then attach to the spindle fibres in pairs at the centre of the cell
• the homologous pairs of chromosomes are pulled apart and move to opposite ends of the cell, the cell divides
• the chromosomes line up along the centre of the cell attached to the spindle fibres, and the chromatids separate and move to opposite ends of the cell, each cell divides again

Question 14

variation in a particular characteristic can be…

Answer 14

genetic, environmental or a combination of both

Question 15

what are the two types of variation?

Answer 15

continuous - where there is a smooth range of measurements/data
discontinuous - where there is distinct categories with no values in between

Question 16

what is a mutation?

Answer 16

a change in the sequence of bases in dna
- this can be due to a replacement of a single base pair with a different pair or the addition or deletion one or more base pairs

Question 17

are mutations common or rare?

Answer 17

rare in eukaryotes as our cells can detect and correct many mistakes in our dna sequence

Question 18

are chromosomal mutations harmful?

Answer 18

yes as they result in an over or under production of proteins

Question 19

what effect does a change in the dna sequence have?

Answer 19

no effect, but can less often be either positive or negative

Question 20

how is a mutation inherited?

Answer 20

if mutation occurs during meiosis in gamete formation it will affect all the cells in the individual which develops from the gamete

Question 21

how is a mutation not inherited?

Answer 21

if the mutation occurs in a body cell it will only affect those cells produced by mitosis from the affected cell, mutations in the body cells give rise to cancers of the cells affected

Question 22

what are mutagens?

Answer 22

chemicals which cause more frequent mutations

Question 23

examples of mutagens:

Answer 23

• ionising radiations (gamma, X-rays and uv)
• some chemicals like tobacco