topic 3C

Question 1

cell differentiation

Answer 1

is 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

gene linkage

Answer 5

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 6

Polygenic

Answer 6

phenotypic characters determined by several interacting genes

Question 7

digenic (dihybrid) inheritance

Answer 7

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

Question 8

operon

Answer 8

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

Question 9

discontinuous variation

Answer 9

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

Question 10

continuous variation

Answer 10

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

Question 11

transcription factor

Answer 11

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

Question 12

promoter sequence

Answer 12

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

Question 13

enhancer sequence

Answer 13

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

Question 14

exons

Answer 14

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

Question 15

introns

Answer 15

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

Question 16

pre-mRNA

Answer 16

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

Question 17

spliceosomes

Answer 17

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

Question 18

DNA methylation

Answer 18

methylation of DNA (addition of a methyl -CH3 group) to a cytosine in the DNA molecule next to a guanine in the
DNA chain and prevents the transcription of a gene

Question 19

DNA demethylation

Answer 19

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

Question 20

heterochromatin

Answer 20

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

Question 21

histone acetylation

Answer 21

addition of an acetyl group (-COCHs) 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 transcribedc

Question 22

histone methylation

Answer 22

addition of a methyl group (-CH3) 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 23

non-coding RNA (cRNA)

Answer 23

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 24

totipotent

Answer 24

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

Question 25

blastocyst

Answer 25

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 26

embryonic stem cells

Answer 26

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

Question 27

morula

Answer 27

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

Question 28

pluripotent

Answer 28

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

Question 29

adult stem cells (somatic stem cells)

Answer 29

are 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 30

multipotent

Answer 30

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

Question 31

therapeutic cloning

Answer 31

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

Question 32

induced pluripotent stem cells (iPS cells)

Answer 32

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