cell cycle , cellular ageing , cell death and gene expression

Question 1

what is a gene ?

Answer 1

A functional region of DNA which codes for a sequence of RNA

Question 2

what is an allele ?

Answer 2

An individual variant of a gene

Question 3

What is an exon ?

Answer 3

Portions of a gene product which are removed via splicing of RNA

Question 4

what is an intron?

Answer 4

Portions of a gene product which are retained following splicing

Question 5

what is the genotype?

Answer 5

The genes (and alleles of them) in a cell/organism

Question 6

what is the phenotype?

Answer 6

The physical features of an organism resulting from its genotype

Question 7

what is a mutation ?

Answer 7

Changes in the genetic sequence

Question 8

how is RNA produced from DNA?

Answer 8

Transcription

Question 9

what are the forms of RNA?

Answer 9

messanger RNA
transfer RNA [tRNA]
ribosomal RNA [rRNA]
short interferring and micro RNA [siRNA and miRNA]

Question 10

what is a substitution mutation ?

Answer 10

one base is replaced with another

Question 11

What are the 3 types of substitution mutations ?

Answer 11

Silent: New code is for same amino acid

Missense: The new code changes an amino acid

Nonsense: The new code is a STOP codon and stops the protein being produced

Question 12

What does the frameshift mutation do?

Answer 12

Frameshift: The triplet code is disrupted, so all amino acids after the mutation
change

Question 13

what are the types of frameshift mutations ?

Answer 13

Addition: A new base is added, shifting the rest forwards

Deletion: A base is removed, pulling the rest backwards
Mutations

Question 14

what is a germline mutation ?

Answer 14

cells that will give rise to gametes

have genes that can be passed on

can be passed down through families

Question 15

what is a somatic mutation ?

Answer 15

mutation does effect other cells only the ones it divides into

cannot be passed

Question 16

what is proliferation ?

Answer 16

growth
replace dead / injured cells
happens in mitosis

Question 17

when is proliferation vital?

Answer 17

plays a key role from embryogensis to whole organism

crititical in the maintenance of adult tissue homeostasis

Question 18

why do some cells divide at specific times ?

Answer 18

enviroment = nutrience , temp , ph , oxygen

interactions with other cells and signalling molecules

intracellular signalling

Question 19

what are the four stages of dividing cells ?

Answer 19

G1
S phase
G2
M phase

also G0 - for resting cells

Question 20

what happens in G1 ?

Answer 20

preparation for DNA synthesis [ s phase]

Question 21

what happens in G2 ?

Answer 21

preparation for cell division [ m phase ]

Question 22

If DNA damage is detected, the cell will not be able to proceed through the cell cycle until that damage is repaired. If it can not be repaired, what process will occcur ?

Answer 22

apoptosis

Question 23

What happens during s phase ?

Answer 23

DNA replication occur

DNA helicase breaks hydrogen bonds between DNA strand separating them

DNA polymerase catalyses addition polymerisation of DNA nucleotides

New nucleotides are added to the 3’ (“3 prime”)
end of the new strand. New nucleotides are
attached via their 5’ (“5 prime”) end

Question 24

how is cell cycle controlled ?

Answer 24

fixed amount of time for each event

information from cell cycle event and external environment

Question 25

what is s-phases ?

Answer 25

chromosomes undergo replication

new DNA is synthesised - duplicate chromosome constructed

chromosome only visible during division

after replication :
* Each chromosome is composed of two identical chromatids

• Chromatids are joined together at the centromere

Question 26

what is m-phase ?

Answer 26

how cells physically divide to produce two genetically identical daughter cells

Question 27

how many stages of mitosis are there and what are their names ?

Answer 27

5

prophase
prometaphase
metaphase
anaphase
telophase

Question 28

what is cytokinesis ?

Answer 28

cytoplasmic division divides cells in two

Question 29

what is prophase ?

Answer 29

chromosome condense and are visible and threadlike

nuclear membrane and nucleoli disappear

mitotic spindles begins to form

centrosomes move away from each other

Question 30

what is prometaphase ?

Answer 30

nuclear envelope fragments

microtubules attach to the chromatids at the kinetochores

other microtubules interact connecting from different poles

Question 31

what is metaphase ?

Answer 31

centrosomes are now at opposite poles

chromosomes are lined up on the metaphase plate

all chromosome are attached to each of the poles

Question 32

what is anaphase ?

Answer 32

connection between chromatids at the centromere is cleaved

each chromatid is now a daughter chromosome

chromosome are pulled to opposite poles as cell elongates

anaphase ends when chromosome reaches poles

Question 33

what is telophase ?

Answer 33

two daughter nuclei form

chromosomes become less dense

Contractile ring begins to assemble
* Actin and myosin filaments
* Cytoplasm is divided in two
* Creates two daughter cells, each with one nucleus

mitosis is complete

Question 34

what is meiosis necessary for ?

Answer 34

production and function of gametes

Question 35

why does meiosis cause a source of variation ?

Answer 35

• Fusion with different gamete for mixing of gene combinations
• Each gamete having a different combination of the parent’s genes
• Recombination resulting in new chromosomes

Question 36

what are the principles of meiosis ?

Answer 36

Meiosis I: Homologous (paired) chromosomes are separated from one another but remain intact (sister chromatids still attached to one another).

Meiosis II: Sister chromatids on each
chromosome are separated into the new cells

Question 37

what is the name of controlled cell death ?

Answer 37

Apoptosis

Question 38

what is the name of uncontrolled cell death ?

Answer 38

necrosis