week 3

Question 1

organelles

Answer 1

in euk cells
perform specific functions in the cell
all show links between structure and function

Question 2

nucleus

Answer 2

relatively large, spherical, located centrally within cell
contains cell genome controlling cellular activities
chromatin condenses to form chromosomes at cell division
nuclear envelope has nuclear pores to control passage

Question 3

nucleolus

Answer 3

region in nucleus
involved in ribosomal RNA synthesis
nuclear shape maintained by protein nuclear matrix

Question 4

ER

Answer 4

system of membranous tubules and sacs
amount in cell varies with cell activity
high levels in secretory cells

Question 5

RER

Answer 5

‘intracellular highway’
movement and processing of molecules within cell
studded with ribosomes
processes proteins for export from cell with chemical modification - occurs in ER lumen
- eg protein folding and sugar addition
has highly folded membranes with inner lumen

Question 6

SER

Answer 6

specialised metabolism and storage
involved in lipid/ carbohydrate processing, steroid synthesis and is main site of cll membrane synthesis
highly folded membranes with inner lumen

Question 7

golgi

Answer 7

piled system of membrane sacs (cisternae) and vesicles (smaller sacs)
cis (nearest cell centre) and trans faces
vesicles from ER fuse with cis face and further protein modification occurs- eg addition of sugars
final vesicles bud off for distribution in cell or export

Question 8

endosomes/ lysosomes

Answer 8

single membrane-bound compartments
most commonly observed in animal, fungi and protists
specialised membrane with transport protein
vesicles containing digestive enzymes produced from ER/ golgi fuse and mature to form lysosomes which have an acidic internal environment
- allows digestion of external/ internal material

Question 9

mitochondria

Answer 9

small- 1-4 x 0.2-1 micrometers
two membranes
inner membrane highly invaginated forming cristae with embedded proteins for metabolic processes such as ATP production
numbers variable according to cell type/ activity
has circular HA genome encoding some genes for metabolic activities (but not all)

Question 10

plastids

Answer 10

found in plants and algae
chloroplast is most common type
most plastids are more simple- smaller, lack chlorophyll and used for storage
- eg leucoplast for starch storage
plastids have circular DNA genome encoding some (not all) genes required for metabolism

Question 11

endosymbiont theory

Answer 11

from observation that both mitochondrion and chloroplasts have own genomes and bacterial-like DNA
states that m + c where originally independent prokaryotes engulfed by an ancestral eukaryotic cell

Question 12

vacuole

Answer 12

fluid filled membrane bound sacs
prominent in plant cells
storage area- may contain toxins or pigments
bound by tonoplast membrane with protein pumps to transport contents
turgor pressure gives plant cell strength
smaller in animal cells where used for food digestion (contractile vacuole)

Question 13

ribosomes

Answer 13

not membrane bound
numerous small granules
site of protein synthesis

Question 14

centrioles

Answer 14

found in animal cells
involved with cell division and microtubule formation

Question 15

cytoskeleton

Answer 15

composed of proteinaceous microtubules (form cilia and flagella), microfilaments and intermediate filaments
cell framework and motility

Question 16

genotype

Answer 16

set of genes inherited
determines phenotype (mostly)
- other factors could alter observed effects
more like fuzzy instructions- not blueprint

Question 17

phenotype

Answer 17

individual characteristics and appearance

Question 18

genes

Answer 18

unit which genetic information is stored in

Question 19

factors affecting phenotype

Answer 19

epigenetics

Question 20

epigenetics

Answer 20

chemical modifications to genes that turn them on/ off
heritable and passed on as cells divide

Question 21

environment

Answer 21

eg. malnutrition stunts growth + lowers final height
day length and temp cycles can affect flowering time

Question 22

randomness

Answer 22

during development, some processes do not repeat exactly
cell- cell interactions may be subtly different which alters final result

Question 23

how to study effects of genetics

Answer 23

take very similar genetic backgrounds and environments
- doing both at once is common to reduce the effects of phenotypic variation in animal studies
- use knockout or gene-edited animals to examine roles of genetic changes

Question 24

use of clones

Answer 24

genetically identical
could be used to study influence of environment
- widely done with bacteria, yeast and human cell lines
- animal clones have been created but they are not always identical

Question 25

how to clone mammal

Answer 25

remove genetic material from egg cell fuse enucleated egg with a cell from the animal to be cloned, or transfer the nucleus from the donor cell zap with an electrical pulse to activate the new hybrid cell implant into surrogate mother and wait for delivery

Question 26

identical twins

Answer 26

occurs when a fertilised egg splits early during development both genetically identical and usually share a very similar environment typically they are not fully identical and differences increase with age

Question 27

why are we not all clones

Answer 27

parental cells undergo meiosis to form gametes two gametes= offspring parental cell= 2n replication occurs, then recombination gametes consist of 4 chromatids

Question 28

how do genes influence phenotypes

Answer 28

DNA is informational carrier genes code for proteins proteins act inside cells cells interact with other cells organs and tissues are established organisms is assembles and grows

Question 29

genome

Answer 29

complete set of genetic material within one chromosome set varies hugely in size between different species, as does gene number

Question 30

mendel

Answer 30

born in 1822 experiments on inheritance using pea plants 1866- Experiments in Plant Hybridisation- contained his 3 principles of Inheritance work largely ignored until 1900 when 3 botanists rediscovered his work

Question 31

before mendel ideas

Answer 31

heredity seen as blending process offspring were a dilution of different parental characteristics

Question 32

mendels idea

Answer 32

instead of blending, characters are transmitted as 'particles' of information from one generation to the next called these characters 'factors' now know these are genes

Question 33

benefits of pea plant experiments

Answer 33

ideal for genetics strict control over with plants mated each plant has both male and female reproductive organs (stamens and pistil) can be self fertilised

Question 34

character

Answer 34

heritable feature

Question 35

trait

Answer 35

each variant of a character

Question 36

pea plant process

Answer 36

mendel grew true breeding plants (P generation) set up monohybrid crosses to produce F1 gen all F1 gen had purple flowers- purple flower colour is dom factor F1 gen self-fertilised and plants with white flowers reappeared in the F2 gen- approx 3:1 ratio

Question 37

true breeding plants

Answer 37

plants that always produce offspring with the same traits

Question 38

monohybrid cross

Answer 38

true bred plant with purple flower crossed with true bred plant with white flowers

Question 39

pea plant conclusion

Answer 39

an organism inherits 2 factors (alleles) for a characteristic hereditary particles= genes -alternative forms= alleles when the plant reproduces these 2 characters separate (segregate during gamete formation and end up in different gametes)

Question 40

mendel's law of segregation

Answer 40

each gamete (sex cell) gives one factor (allele) each offspring gets one factor (allele) from each parent random fusion occurs during fertilisation

Question 41

rules of dominance

Answer 41

if the organism has two dominant alleles then the dominant trait will be expressed (PP) is the organism has one dom and one rec allele the dominant trait will be expressed (Pp) if the org has 2 rec alleles the rec trait will be expressed (pp)

Question 42

phenotype

Answer 42

physical description of trait purple or white flowers

Question 43

genotype

Answer 43

genetic makeup purple flowers PP or Pp white flowers pp

Question 44

locus + allele

Answer 44

variation in the sequence of nucleotide bases at the specific locus on the gene the purple or white flower allele are different versions of a gene at the same location on homologous chromosomes (2 DNA variations at the flower colour locus)

Question 45

dihybrid crosses

Answer 45

experiments conducted on more than one trait observed that one trait did not affect another trait so different factors (genes) segregate independently from one another during the formation of gametes example- crossed true breeding yellow round peas with true breeding green wrinkled peas

Question 46

mendel's law of independent assortment

Answer 46

genes get shuffles these many combinations are one of the advantages of sexual reproduction

Question 47

pedigree analysis

Answer 47

used to map traits onto family tree