Voice of the genome

Question 1

Structural differences between prokaryote and eukaryote cells

Answer 1

Circular DNA; linear DNA
Pili; no pili
70S ribosome; 80S ribosome
No nucleus; nucleus
Plasmid; no plasmid
Capsule; no capsule

Question 2

How proteins are made and transported out of the cell

Answer 2

Proteins produced by ribosomes
Folded in ER
Packaged in vesicles to Golgi apparatus
Vesicles fuse with Golgi apparatus
Proteins modified in Golgi apparatus and packaged in vesicle
Vesicle fuses with cell membrane
Exocytosis

Question 3

Sperm adaptation

Answer 3

Flagellum: movement by rotating
Acrosome: contains enzymes for digesting zona pellucida
Mitochondria: provide energy for flagellum

Question 4

Ovum adaptation

Answer 4

Follicle cells: release enzymes to attract sperms
Zona pellucida: thickens to prevent polyspermy
Lysosomes: release enzymes to thicken zona pellucida

Question 5

Genetic variation reasons

Answer 5

Independent assortment
Crossing over

Question 6

Stages in mitotic cell division

Answer 6

Interphase
Mitosis
Cytokinesis

Question 7

Interphase stages and function

Answer 7

G1: synthesis of new organelles and cell growth
S: DNA replication
G2: synthesis of new organelles and cell growth

Question 8

Prophase events

Answer 8

Chromosomes condense
Microtubules form spindle
Centrioles move to opposite poles
Spindle fibres form
Nuclear envelope breaks down
Nucleolus disappears

Question 9

Metaphase events

Answer 9

Chromosomes line up at equator of the cell
Centromeres attach to spindle fibres

Question 10

Anaphase events

Answer 10

Spindle fibres shorten, pulling sister chromatids apart to opposite poles
Spindle breaks down

Question 11

Telophase events

Answer 11

Chromosomes decondense
Nuclear envelope reforms around each group of chromosomes

Question 12

Cytokinesis events

Answer 12

Cell surface membrane constricts around centre of cell
Plant cell: cell plate synthesised between the two new cells

Question 13

Stem cell definition

Answer 13

Undifferentiated
Keep dividing (no Hayflick limit)
Give rise to specialised cells
Replace damaged cells

Question 14

Totipotent, pluripotent, multipotent meaning

Answer 14

Any cell type
Most cell type
Some cell type

Question 15

Embyronic stem cell issues

Answer 15

Ethical issue (kill embryo)
Rejection by immune system
Costly
Difficult

Question 16

Therapeutic cloning/somatic cell nuclear transfer meaning

Answer 16

Diploid cell nucleus removed
Ovum nucleus removed
Diploid cell nucleus fused with ovum
Cell undergoes mitosis to blastocyst
Stem cells isolated

Question 17

Epigenome definition

Answer 17

DNA, histones and chemical markers

Question 18

2 ways to prevent transcription

Answer 18

Methylation so RNA polymerase cannot bind
Modify histones to affect how tightly it is wound

Question 19

Differential gene expression meaning

Answer 19

Genes can be switched on and off/expressed

Question 20

Consequence of differential gene expression

Answer 20

Stimulus detected (hormone, environment)
Genes expressed/switched off
mRNA from expressed genes is produced and translated
Protein synthsised
Proteins permanently modify cell
Cell becomes specialised

Question 21

Causes for switching on/off genes

Answer 21

Protein repressor molecules attach to DNA of promotor region
Protein regulator (starts transcription) cannot attach
Protein repressor molecules attach to protein regulators, preventing them from attaching

Question 22

FOP cause

Answer 22

Gene mutation
Genes for making proteins for bone cell is not switched off in white blood cells
When tissue is damaged, white blood cells move to site of damage
Protein produced, diffusing into muscle cells
Muscle cells turn into bone cells

Question 23

Level of organisation in organisms

Answer 23

Cell
Tissue
Organ
Organ system

Question 24

Phenotype and genotype definition

Answer 24

Characteristics of organism resulting from interaction of the organism with environment and genotype
All the alleles of an organism

Question 25

Polygenic definition

Answer 25

More than one gene involved in inheritance of a characteristic
Continuous variation

Question 26

Multifactorial definition

Answer 26

Several genetic factor and environmental factors are involved

Question 27

How melanin is made in skin

Answer 27

Exposure to UV light
MSH is produced
MSH receptors form on surface of melanocytes
Melanin is produced and placed into melanosomes
Melanosomes collect around nucleus of skin cell to protect it from UV light damage

Question 28

Why only ears, paws and tail of Himalayan rabbit is dark

Answer 28

Mutant alleles for tyrosinase, which changes amino acid tyrosine into melanin
Tyrosinase made is unstable and inactivated at normal body temperature
Ears, paws and tail are cooler than body temperature
Tyrosinase active, melanin produced there

Question 29

Diet affects epigenome in mice

Answer 29

Agouti gene is normally methylated, leading to brown healthy mice
When agouti gene is expressed, agouti protein bind to MSH receptors and prevents production of melanin
Caused by lack of methyl in diet
Agouti protein binds to receptors in brain area involved in feeding bahaviour
Mice become obese and yellow

Question 30

Behaviour causes change in epigenome in rats

Answer 30

GR gene prevents stress
Methylated GR gene leads to stressed rats
Licking and grooming activates GR genes
Good mother with anxious pups: high licking and grooming, leads to activation of GR gene, so the pups are calm
Bad mother with good pups: low licking and grooming, leads to methylation of GR gene, so the pups are stressed

Question 31

Cause of cancer

Answer 31

When rate of cell multiplication is faster than the rate cell death
Tumour growth
Usually caused by damage to DNA

Question 32

Oncogene’s role in cancer

Answer 32

Code for proteins that stimulate transition from one stage to the next in mitosis
Less methylation causes cell cycle to be always active
More mitosis

Question 33

Tumour suppressor gene’s role in cancer

Answer 33

Produce suppressor proteins that stop the cycle
More methylation causes cell cycle to have no brake on mitosis

Question 34

Environmental factors for cancer

Answer 34

Smoking
UV light
Diet
Virus infection