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Biology 101 flashcards
1
Q

what is the product of mitosis

A

chromatids decondensed
two separate nuclei

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2
Q

what is the difference between organs and tissue

A

organs have more functions than tissues
tissues made of cells, organs made of tissues
tissues are made up of the same type of specialised cell which carries out the same function whereas organs are made up of many different types of tissues

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3
Q

why do cells produced become smaller after each cell cycle in mitosis

A
  • fewer organelles
  • no time in G1 or G2 phase
  • cytoplasm is divided to form new cells
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4
Q

how can you tell whether an electron image is of the golgi apparatus

A
  • fluid-filled flattened sacs
  • separate cisternae
  • smooth membrane/ no ribosomes
  • sacs are in stacks
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5
Q

describe the structure of the cell wall of the xylem

A
  • lignin in rings in the cell wall
  • cellulose molecules are held by hydrogen bonds
  • presence of bordered pit
  • presence of pectin in the cell wall
  • xylem cell walls are contain lignin
    cell wall of xylem vessel is made up of cellulose
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6
Q

why do people with emphysema require air with a higher concentration of oxygen than those without emphysema

A
  • smaller surface area of alveoli with emphysema
  • therefore need larger concentration gradient to maintain the rate of diffusion
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7
Q

how is glycogen produced

A

alpha glucose molecules joins together by 1,4 and 1,6-glycosidic bonds to form glycogen
via condensation reactions

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8
Q

why is glycogen suitable for its role

A

branches molecule for more rapid hydrolysis
glycogen is a compact molecule which means that more of it can fit in a smaller amount of space
insoluble-> no osmotic effect

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9
Q

why do people with CF have thicker mucus

A
  • gene mutation causing a non-functioning CFTR protein channel
  • chloride ions cant move out of epithelial cells
  • accumulation of sodium and chloride ions in the cells which causes water to move out of the mucus by osmosis
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10
Q

why does the structure of arteries allow for it to maintain and withstand high pressures

A
  • more collagen provides strength to withstand high pressure
  • contraction of muscle allows constriction of lumen
  • elastic fibres for elastic recoil
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11
Q

why did meselson and stahl accept the semi conservative replication model

A
  • generation 1 has a single band which is halfway between 15N and 14N
  • DNA has one strand containing 15N and one strand containing 15N
  • in semi-conservative model further generations would have no band at 15N
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12
Q

compare and contras fibrous and globular proteins

A

both contain bonds such as disulphide bridges holding them together
both are chains of amino acids joined by peptide bonds
fibrous contains cross linkages whereas globular dont
both has a 3D structure

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13
Q

what does p^2 and q ^2 and 2pq represent in the hardy weinberg equation

A

p^2- homozygous dominant
q^2- homozygous recessive
2pq- heterozygous genotype

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14
Q

what is the effect of interbreeding on genetic diversity

A

would increase the genetic diversity
introduction of different alleles into the population

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15
Q

how can molecular phylogeny be used to determine relationships between organisms

A

sequencing bases in their DNA/ amino acids in proteins
the more similarities they have the more closely related they are

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16
Q

explain how preventing the shortening of spindle fibres effect mitosis

A

sister chromatids cant be separated
so chromosomes remain at the equator

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17
Q

how do you calculate tensile strength

A

force/ cross sectional area of the fibre

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18
Q

why does contamination of tissue cultures have to be avoided?

A

contaminants case disease of plant tissue
contaminants compete for nutrients
contaminants cause poor growth

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19
Q

why is a drug tested on animals and healthy volunteers?

A

testing on animals for toxicity
finding out how the drug is metabolised

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20
Q

how does lignin add to the strength of xylem tissue

A

lignin holds the fibres together and keeps fibres parallel

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21
Q

how does inbreeding lead to genetic defects?

A

closely related animals mated with each other
inbreeding depression
increased chance of homozygous recessive genotypes for genetic defects

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22
Q

how are breeding programmes at zoos designed to reduce the risk of inbreeding

A

exchange of gametes between zoos
ivf
studbooks
selection of unrelated mates
exchange of animals between zoos

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23
Q

what is the structure of lipids

A

only contains carbon, hydrogen and oxygen
fatty acids and glycerol joined by ester bonds

24
Q

how do you answer questions that give you ranges

A

smaller range -> more reliable
ranges overlap -> no significant difference
work out the maximum and minimum for each value if given ranges

25
Q

how do you increase validity

A

name controlled variables

26
Q

how is species richness counted

A

count the number of species in a known are using a quadrat

27
Q

why odes biodiversity need to be maintained

A

loss of biodiversity means there are fewer species
loss of endemic species leads to extinction
some species havent been discovered and may be useful

28
Q

why is little genetic diversity bad

A

no selective advantage when the environment changes
less likely to survive
increases the risk of extinction

29
Q

why is increased genetic diversity good

A

greater chance of survival as higher chance of having beneficial alleles
increased mating with genetically different individuals
different individuals decreases inbreeding

30
Q

how does the use of hardy weinberg equation allow us to see if evolution has occurred

A

identify changes in the allele frequency over time
if allele frequency has changed then evolution has occured
if theres no migration

31
Q

what is species evenness

A

relative abundance of each species

32
Q

describe the process of semi conservative replication

A

DNA helicase breaks H bonds between bases-. forms 2 strands
original strand acts as template and complementary base bairing occurs between free floating DNA Nucleotides and template strand
nucleotides join by condensation reactions catalysed by DNA polymerase
H bonds form between bases on original and new strand

33
Q

describe the experiment meselson and stahl used to show that DNA replicates semi-conservitavely

A

2 samples of bacteria grown- one in nutrient broth containing light nitrogen and other in heavy nitrogen
as bacteria reproduced -> took up nitrogen
sample of DNA taken and spun in centrifuge
DNA from heavy settled lower down than light
the bacteria grown in heavy were taken out and put in broth only containing light and left for one round of replication
another DNA sample taken and spun in centrifuge
DNA settled in the middle showing that DNA contained a mixture of heavy and light nitrogen which shows the DNA replicated semi-conservatively

34
Q

recall info on amniocentesis

A

carried out at 15-20 weeks
sample of amniotic fluid taken using fine needle
analyses foetal cell DNA
1% chance of miscarriage
results arent available until 2-3 weeks later

35
Q

recall info on chorionic villus sampling

A

carried out 11-14 weeks
earlier decision can be made so less traumatic
sample taken from chorionic villi
done via abdomen or catheter
1-2% chance of miscarriage
initial results available in a few days

36
Q

what happens in prophase

A

chromosomes condense
centrioles move to opposite ends of the cell
spindle fibres form
nuclear envelope breaks down

37
Q

what happens in anaphase

A

centromeres divide seperating sister chromatids
spindle fibres contract pulling chromatids to opposite ends

38
Q

what happens in telophase

A

chromatids decondense
nuclear envelope reforms
2 nuclei

39
Q

what are activators

A

factors that increase the rate of transcription
they help RNA polymerase bind to DNA and begin transcription

40
Q

what are repressors

A

prevent RNA polymerase from binding and stop transcription

41
Q

what is an operon

A

a section of DNA that contains a cluster of structural genes that are transcribed together as well as control elements and sometimes a regulatory gene

42
Q

what is a structural gene

A

code for useful proteins e.g enzymes

43
Q

what are control elements

A

include a promoter and and operator

44
Q

what is a promoter

A

a DNA sequence located before the structural genes that RNA polymerase binds to

45
Q

what is an operator

A

a DNA sequence that transcription factors bind to

46
Q

what is a regulatory gene

A

codes for an activator or repressor

47
Q

what is the lac operon in E. coli

A

E. coli can respire used lactose if glucose is unavailable
the genes that produce the enzymes needed to respire lactose are found on the lac operon
it has 3 structural genes- lacZ, lacY, lacA which produces proteins that help bacteria digest lactose including beta-galactosidase and lactose permease

48
Q

what happens in the lac operon when lactose isnt present

A

regulatory gene produces lac repressor which is a transcription factor that binds to the operator when no lactose isnt present
blocks transcription because RNA polymerase cant bind to promoter

49
Q

what happens in the lac operon when lactose is present

A

lactose binds to repressor
changes repressors shape
lac repressor can no longer bind to operator site
RNA polymerase can begin transcription of the structural genes

50
Q

what happens when theres increased methylation

A
51
Q

how does histone modification affect gene expression

A
52
Q

how does histone modification affect gene expression

A
53
Q

how can epigenetic changes be passed on

A
54
Q

what is monogenic and polygenic

A
55
Q

what is the role of oncogenes

A

they code for protein that stimulate the transition from one stage in the cell cycle to the next
DNA mutation of epigenetic changes in these genes can lead to the cycle being continually active - may cause excessive cell division

56
Q

what is the role of tumour suppressor genes

A

they produce proteins that stop the cell cycle e.g p53
inhibits G1 to S transition
if this gene becomes inactive theres no brake on the cell cycle - continuous division

[OBSELETE] S - Bio (5 decks)

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