3C

Question 1

cell differentiation

Answer 1

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

Question 2

locus

Answer 2

place on a chromosome where any particular gene is found

Question 3

multiple alleles

Answer 3

more than two possible variants at a particular locus

Question 4

codominant

Answer 4

both alleles are expressed in the phenotype

Question 5

codominant

Answer 5

both alleles are expressed in the phenotype

Question 6

gene linkage

Answer 6

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 7

polygenic

Answer 7

phenotypic characters determined by several interacting genes

Question 8

digenic (dihybrid)

Answer 8

inheritance the inheritance of two pairs of contrasting characteristics at the same time

Question 9

operon

Answer 9

a unit consisting of linked genes which is thought to regulate other genes responsible for protein synthesis

Question 10

discontinuous variation

Answer 10

phenotypic features which are either present or not, usually inherited on one or at most a small number of genes.

Question 11

continuous cariation

Answer 11

phenotypic features which show a huge range of values; they are usually polygenic and are also affected by environmental factors

Question 12

transcription factor

Answer 12

protein that binds to the DNA in the nucleus and affects the process of transcribing DNA into RNA

Question 13

promoter sequence

Answer 13

specific region on the DNA to which transcription factors bind to stimulate transcription

Question 14

enhancer sequence

Answer 14

specific region of DNA to which transcription factors bind and regulate the activity of the DNA by changing the structure of the chromatin

Question 15

exons

Answer 15

segments of a DNA or RNA molecule containing information coding for a protein or peptide sequence

Question 16

introns

Answer 16

segments of a DNA or RNA molecule containing information which does not code for a protein or peptide sequence

Question 17

pre-mRNA

Answer 17

mRNA that is transcribed directly from the DNA before it has been modified

Question 18

spliceosomes

Answer 18

enzyme complexes that act on pre-mRNA, joining exons together after the removal of the introns

Question 19

DNA methylation

Answer 19

methylation of DNA (addition of a methyl -CH group) to a cytosine in the DNA molecule next to a guanine in the
DNA chain and prevents the transcription of a gene

Question 20

DNA demethylation

Answer 20

removal of the methyl group from methylated
DNA enabling genes to become active so they can be transcribed

Question 21

heterochromatin

Answer 21

densely supercoiled and condensed chromatin where the genes are not available to be copied to make proteins

Question 22

histone acentylation

Answer 22

addition of an acetyl group (-COCH3) to one of the lysines in the histone structure, which opens up the structure and activates the chromatin, allowing genes in that area to be transcribed

Question 23

histone methylation

Answer 23

addition of a methyl group (-CHs) to a lysine in the histone; methylation may cause inactivation or activation of the region of DNA, depending on the position of the lysine

Question 24

non-coding RNA (ncRNA)

Answer 24

98% of the RNA, which does not code for proteins but affects the transcription of the DNA code, modifies the chromatin structure or modifies the products of transcription

Question 25

totipotent

Answer 25

an undifferentiated cell that can form any one of the different cell types needed for an entire new organism

Question 26

blastocyst

Answer 26

an early embryo consisting of a hollow ball of cells with an inner cell mass of pluripotent cells that will eventually form a new organism

Question 27

embryonic stem cells

Answer 27

the undifferentiated cells of the early human embryo with the potential to develop into many different types of specialised cell

Question 28

morula

Answer 28

an early embryo made up of a solid ball of 10-30 totipotent cells

Question 29

pluripotent

Answer 29

an undifferentiated cell that can form most of the cell types needed for an entire new organism

Question 30

adult stem cells (somatic stem cells)

Answer 30

undifferentiated cells found among the normal differentiated cells in a tissue or organ that can differentiate when needed to produce any one of the major cell types found in that particular tissue or organ

Question 31

multipotent

Answer 31

a cell that can form a very limited range of differentiated cells within a mature organism

Question 32

therapeutic cloning

Answer 32

an experimental technique used to produce embryonic stem cells from an adult cell donor

Question 33

induced pluripotent stem cells (iPS cells)

Answer 33

adult cells that have been reprogrammed by the introduction of new genes to become pluripotent again

Question 34

induced pluripotent stem cells (iPS cells)

Answer 34

adult cells that have been reprogrammed by the introduction of new genes to become pluripotent again

Question 35

what are benefits of embryonic stem cells?

Answer 35

- pluripotent - undifferentiated

Question 36

what are benefits of adult stem cells?

Answer 36

- undifferentiated - multipotent

Question 37

what are risks of embryonic stem cells?

Answer 37

- might be cancerous - ethical issues - unknown long-term effects

Question 38

what are risks of adult stem cells?

Answer 38

- difficult to extract - limited availability - more difficult to grow in the lab

Question 39

what are benefits of cord stem cells?

Answer 39

- possible to store

Question 40

what are disadvantages of cord stem cells?

Answer 40

- takes a lot of storage space - precancerous cells of conditions e.g. leukaemia might already be present - little evidence