3C Cell Differentiation

Question 1

cell differentiation

Answer 1

the process by which a less specialised cell becomes more specialised for a particular function

Question 2

how can the degree of differentiation between cells be measured? (2)

Answer 2

• by comparing the proteins contained in cells

- this enables us to work out which genes have been expressed and which have been supressed

Question 3

locus

Answer 3

place on a chromosome where any particular gene is found

Question 4

multiple alleles (3)

Answer 4

• some features are determined by multiple alleles, meaning that there are more than two possible variants
• no matter how many possible alleles there are, any one diploid individual will only inherit two of them
• example= human ABO blood group system, A and B are dominant to O, so the O blood group is recessive, but A and B are codominant

Question 5

codominant

Answer 5

both alleles are expressed in phenotype and produce a protein

Question 6

polygenic (3)

Answer 6

• characteristic is coded by more than one gene on different loci
• example= eye colour, weight
• further variety is added by interaction with environment

Question 7

what could some reasons for unexpected ratios be? (4)

Answer 7

• small sample size
• experimental error
• process is random so the unexpected can happen
• could mean that the genes being examined are both on the same chromosome (linked)

Question 8

what does crossing two heterozygotes in a dihybrid cross result in?

Answer 8

9:3:3:1

Question 9

gene linkage

Answer 9

when genes for two different characteristics are found on the same chromosome and are close together so they are linked and inherited as a single unit

Question 10

identifying linked genes (5)

Answer 10

• when genes are closely linked (located close to each other on the chromosome) then recombination events which separate them rarely occur during meiosis
• if the genes are located further appart on chromosome, then the number of recombination events in meiosis may be higher
• so the tightness of the linkage of a pair of genes is related to how close together the linked genes are located on the chromosome
• genes that are very close together are less likely to be split during the crossing over stage of meiosis than genes that are further appart
• if genes are further appart, crossing over is more likely to occur