Cell Division

Question 1

asexual reproduction

Answer 1

• only one parent is needed
• uses less energy and is faster
• lots of identical offspring

Question 2

sexual reproduction

Answer 2

• produces variation in offspring

- allows us to use selective breeding

Question 3

gamete

Answer 3

an organism’s reproductive cell which has half the number of chromosomes

Question 4

chromosome

Answer 4

a structure found in the nucleus which is made up of a long strand of DNA

Question 5

allele

Answer 5

the different forms of the gene

Question 6

dominant allele

Answer 6

only one allele is needed for it to be expressed and for the corresponding phenotype to be observed

Question 7

recessive allele

Answer 7

two copies are needed for it to be expressed and for the corresponding phenotype to be observed

Question 8

homozygous

Answer 8

when both inherited alleles are the same

Question 9

heterozygous

Answer 9

when one of the inherited alleles is dominant and the other is recessive

Question 10

genotype

Answer 10

the combination of alleles an individual has e.g. Aa

Question 11

phenotype

Answer 11

the physical characteristics that are observed in the individual e.g. eye colour

Question 12

codominance

Answer 12

when neither allele is dominant over the other, so both contribute to the phenotype

Question 13

mitosis (2)

Answer 13

STAGE 1 - interphase:
duplicate its DNA - so there’s one copy for each new cell, x-shaped chromosomes are formed

prophase:

• the chromosomes condense, getting shorter and fatter
• the membrane around nucleus breaks down and chromosomes lie free in cytoplasm

metaphase:
- chromosomes line up at the centre of the cell

anaphase:
- spindle fibres pull them apart

telophase:

• membranes form around each of the sets of chromosomes which become the nuclei of the two new cells
• cytoplasm divides

Question 14

mitosis (1)

Answer 14

• produces two daughter cells

- genetically identical to parent

Question 15

meiosis (1)

Answer 15

• produces four genetically different cells

Question 16

meiosis (2)

Answer 16

1) cell duplicates DNA so it has double the genetic information.
2) cell divides into two, each with 46 chromosomes (diploid).
3) cell divides in two again to produce 4 cells with 23 chromosomes (haploid)