Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

a level biology > Topic 2: Genes and Health Part 2 > Flashcards

Topic 2: Genes and Health Part 2 Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

what is exocytosis

A

the release of substances, usually proteins/polysaccharides. from the cell as vesicles (small membrane bound sacs) fuse with the cell membrane, the substance can thenn diffuse out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is endocytosis

A

when substances are taken into a cell by the creation of a vesicle from the cell membrane
part of the cell membrane engulfs the solid/liquid material to be transported

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are enzymes

A
  • globular proteins that act as biological catalysts
  • speed up reactions within cells that would otherwise occur very slowly
  • have an active site with a specific shape
  • intracellular/extracellular
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how is the active site of an enzyme made to be specific

A

the primary structure (initial sequence of amino acids) determines the enzymes tertiary structure which determines the shape

a change in a gene determining the primary structure could change the tertiary structure of the enzyme produced and therefore the specificity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the Induced Fit Model for enzymes

A

rather than only the shape of the substrate being specific to the active site, it has to be able to make the active site also change shape so it can lock the substrate more tightly in shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how do enzymes lower activation energy - the actual method

A
  1. if two substrate enzymes have to be joined to form the product, attaching them both to the enzyme can hold them closer together and reduce repulsion so that they bond more easily
  2. if they enzyme is catalysing a breakdown reaction, fitting into the active site will put more strain on bonds in the substrate so that it breaks up more easily
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how do charges affect enzyme-substrate complexes

A

many of the amino acids making up the enzyme have positively and negatively charged chemical groups

for the substrate to fit in the active site, electrical charges on the substrate molecule and the enzyme should be opposite so that they attract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what factors affect enzyme catalyzed reactions

A

inhibitors (non + competitive)
enzyme concentration
substrate concentration
temperature
pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how does a competitive inhibitor work

A

it blocks the substrate from binding to the active site by binding in it’s place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how does a non-competitive inhibitor work

A

it allows the substrate to bind to the active site but blocks the reaction from taking place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how does temperature affect enzyme catalyzed reactions

A

a soluble protein denatures and becomes insoluble as well as getting inactivated
an insoluble fibrous protein will lose it’s structural strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

why does a pH change affect enzyme catalysed reactions

A

pH change causes bonds maintaining the tertiary structure of the active site to break, causing the shape to distort

the charge on some amino acids making up the active site are also altered, so the substrate can’t be held in there the same way

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

how does substrate concentration affect enzyme catalyzed reaction

A

it increases the rate of reaction until a saturation point is reached

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how does enzyme concentration affect enzyme catalyzed reaction

A

it increases the rate of reaction until substrate concentration becomes the limiting factor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

where in a cell is DNA stored

A

it’s stored in almost every cell, in the nucleus
if a cell doesn’t have a nucleus then it is stored in the cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the components of a nucleotide

A

1 phosphate group
1 nitrogen-containing organic base
1 pentose sugar molecule (deoxyribose in DNA vs ribose in RNA)

all of which are linked by condensation reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

which are the purine bases

A

adenine and guanine; they have a double ring structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what are the pyrimidine bases

A

thymine, cytosine, uracil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what bases are used DNA

A

adenine, cytosine, guanine, thymine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what bases are used in RNA

A

adenine, guanine, cytosine, uracil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

how is DNA, a polynucleotide formed

A

phosphodiester bonds form between mononucleotides through condensation reactions, between the sugar of one nucleotide and the phosphate group of another

two antiparallel polynucleotides are twisted together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

describe transcription

A

in nucleus

  1. the enzyme RNA polymerase attaches to the DNA, at a start codon in front of a gene in a non coding region
  2. RNA polymerase separates the two DNA strands by breaking hydrogen bonds, the DNA molecule unwinds
  3. the RNA polymerase enzyme moves along one of the separate strands, the antisense strand, adding complementary RNA nucleotides (U instead of T)
  4. nucleotides link by phosphodiester bonds to form a strand of messenger RNA, mRNA
  5. when RNA polymerase reaches a stop codon, it stops making mRNA and detaches from the DNA
  6. the hydrogen bonds between the unwound DNA strands re-form, the DNA molecule ‘zips up’
  7. mRNA travels out of the nucleus via the nuclear pores to attach to a ribosome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what two words are used to describe the DNA code + what do they mean

A

degenerate - more than one triplet can code for the same amino acid

non-overlapping - each triplet is separate and bases aren’t shared

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is a gene

A

the sequence of bases on a DNA molecule that codes for the sequence of amino acids in a polypeptide chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

describe translation

A
  1. the mRNA carrying the genetic code leaves the nucleus and attaches to the ribosome in the cytoplasm, so the protein can be assembled
  2. the ribosome reads and moves along the mRNA strand a codon at a time
  3. a tRNA molecule brings the specific amino acid to the MRNA in the order of the codons
  4. as the ribosome moves along the mRNA hydrogen bonds form between the codon and anticodon (anticodon is part of tRNA structure which is complementary to the codons) of mRNA and tRNA
  5. peptide bonds form between the amino acids, forming a protein
  6. the process continues until a stop codon is reached on the mRNA, the polypeptide chain stops growing and detaches from the ribosome (bc tRNA doesn’t have an anticodon for a stop codon)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what comes first in protein synthesis, translation or transcription?

A

transcription, then translation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is a start codon

A

AUG

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what is a stop codon

A

a codon that has no tRNAs with complementary anticodons to these sequences, meaning no amino acid can be transferred

29
Q

genes, chromosomes and DNA relativity

A

DNA makes up genes which are carried in chromosomes which are kept in cells

30
Q

outline DNA replication

A

it has to occur before mitosis

  1. replication begins at a specific sequence on the DNA molecule
  2. DNA helicase unwinds and unzips the DNA, by breaking hydrogen bonds joining base pairs and forming to separate strands
  3. the new DNA is built up from ACGT that are abundant in the nucleoplasm; they attach to their complementary bases on the old strand
  4. DNA polymerase joins the new nucleotides to each other with phosphodiester bonds which forms the phosphate-sugar backbone
  5. a winding enzyme winds up the new strands to form double helices
  6. the two new molecules are identical to the old one
31
Q

what is the name of the accepted model for DNA replication

A

semi-conservative replication, a theory put forward by meselsohn and stahl

32
Q

how was the semi-conservative replication of DNA proven?

A

bacteria was grown in the broth of a heavy isotope of nitrogen, N15 (because all DNA bases contain nitrogen)
the DNA and it’s solution was centrifuged to see where the DNA strand would lie, it was low in the tube because it was heavy

The next generation was grown in an N14 broth and the same process was done but the DNA was now in the middle because the DNA was a hybrid between N14 and N15

it means that there is genetic continuity between generations

33
Q

define genotype

A

the genetic makeup of an organism

34
Q

what is incomplete dominance

A

the heterozygous genotype produces a phenotype that falls in-between that expected by the dominant and recessive (eg white is dominant and red is recessive, so it ends up pink)

35
Q

outline the experiment using catalase that looks at rate of product formation

A
  1. add a set volume and conc of hydrogen peroxide to a boiling tube with a suitable buffer solution to keep pH constant
  2. set up with a bung in the tube and a delivery tube going into an upside down measuring cylinder in a trough of water
  3. add a set volume of one of the catalase concs into the boiling tube and quickly replace the bung
  4. record volume of oxygen produced every 30 seconds for 5 minutes, measured in cm^2 and with a stopwatch
  5. repeat twice and then calculate mean for every 30 second interval
  6. plot data on graph with oxygen volume produced against time and determine initial rate using a tangent
  7. repeat the entire experiment with all other catalase concentrations
36
Q

outline the experiment that measures the rate of the removal of the substrate

A
  1. set up a colorimeter with a red filter and zero it using a cuvette containing iodine dissolved in potassium iodide solution (browny-orange)
  2. in another cuvette, pipette a set volume of one of the starch conc and a set volume of iodine dissolved in potassium iodide solution and mix which will turn the solution a dark blue-black. place cuvette in zeroed colorimeter and record percentage absorbance
  3. add a set volume and conc of amylase to the cuvette and start a stopwatch immediately
  4. every 10 seconds for 5 minutes, record absorbance on colorimeter
  5. repeat twice and then calculate mean absorbance for every 10 second interval
  6. plot absorbance (arbitrary units^-1) against time and draw a tangent to estimate initial rate of reaction
  7. repeat everything for other starch concentrations
37
Q

how many hydrogen bonds form between A and T

A

two

38
Q

how many hydrogen bonds form between C and G

A

three

c and g rhyme with 3

39
Q

what is mRNA

A

its made in the nucleus during transcription
three adjacent bases is a codon
it carried genetic code from DNA in nucleus to the cytoplasm where its used during translation to make a protein

40
Q

what is tRNA

A

it’s found in the cytoplasm
each tRNA carries a specific amino acid at one end and a sequence of three bases at the other end, called an anticodon which recognises codons on the mRNA
it carries amino acids used to make proteins to the ribosomes during translation

41
Q

define allele

A

alleles are different versions of the same gene found at the same locus on a chromosome

42
Q

what happens if a base is missing in a base sequence

A

the bases will move back one, causing the entire chain after that point to shift

43
Q

how can CF be tested for

A
  1. CF causes a higher salt concentration in sweat, so this is tested for
  2. there are higher levels of the protein trypsinogen in the blood of people with CF, it is tested for in all UK babies
44
Q

how is genetic screening used and for what

A

it identifies the presence of abnormal genes/alleles in the DNA of cells

it’s done to confirm a diagnosis, identify carriers and test embryos

45
Q

what are the two opportunities to take a sample for genetic screening

A

whilst in the womb or once born

46
Q

how can you take a sample whilst in the womb

A

remove a single cell
remove some fluid or blood (contains cells)
cut out a piece of tissue
drawblood from the umbilical cord

47
Q

how do you take a sample once born

A

use hair/ heel prick test (collects blood) / swab inside of cheek

48
Q

what are the 4 different types of genetic screening

A
  1. non-invasive prenatal diagnosis (NIPD)
  2. amniocentesis
  3. chorionic villus sampling (CVS)
  4. preimplantation genetic diagnosis (PGD)
49
Q

outline and evaluate preimplantation genetic diagnosis (PGD)

A

done with IVF, cell samples are taken from the embryo and analysed before implanting it
+ reduces chance of having a baby with a genetic disorder
+ avoids issues around abortion

– it could lead to designer babies in the future
– false results

50
Q

define pre-natal test

A

tests that occur once the embryo is developing inside the uterus

51
Q

outline and evaluate amniocentesis

A

it is usually carried out at 15-20 weeks of pregnancy
a fine needle obtains an amniotic fluid sample through the abdomen which contains foetal cells, these contain DNA that can be analysed

– 1% chance of miscarriage
– chance of bacterial infection

+ lower chance of miscarriage than CVS
+ there is a rapid test that only tests for a few, common disorders and takes 3-4 days

52
Q

outline and evaluate chorionic villus sampling (CVS)

A

11-14 weeks along
fine needle moves some cells from the placenta (chorionic villi)

  • 1-2% miscarriage chance
  • chance of causing infection when taking the sample
  • abortion can be encouraged if tests are positive

+ can be done earlier than amniocentesis, making it less traumatic physically

53
Q

outline non-invasive prenatal diagnosis (NIPD)

A

a new and rapidly developing procedure
DNA fragments in the mother’s blood during pregnancy are analysed
it can be detected at 4-5 weeks but there’s only enough to analyse at 7-8 weeks
only limited conditions can be screened for (currently)

54
Q

how is mRNA synthesised at a DNA template strand

A

RNA nucleotides align with complementary bases on DNA
RNA nucleotides joined together by RNA polymerase forming phosphodiester bonds

55
Q

what information does DNA store

A

genetic information

56
Q

what information does RNA contain

A

information about protein synthesis as one of its main functions is transferring genetic info from the DNA to ribosomes

57
Q

how do mononucleotides form DNA

A

condensation reactions occur between the phosphate of one mononucleotide and the sugar group of another

ester bonds

58
Q

briefy outline the structure of DNA

A

a polymer made of two antiparallel (running in opposite directions) polynucleotide strands, twisted to form the DNA double-helix

59
Q

outline the types of RNA

A

mRNA
- made in nucleus during transcription
- three adjacent bases is a codon
- carries genetic code from DNA in nucleus to the cytoplasm where it’s used in translation to make a protein

tRNA
- found in cytoplasm
- amino binding site at one end and anticodon at other end (3 base sequence)
- carries amino acids for proteins to the ribosomes during translation

60
Q

what is the part of DNA with a pentose sugar and phosphate group bound together known as

A

sugar-phosphate backbone

61
Q

what bonds are found in DNA

A

between nitrogenous bases: H bonds
between pentose sugar and nitrogenous base: glycosidic bonds
between phosphate group and pentose sugar: phosphodiester bonds

62
Q

what are features of dna

A

triplet code
non-overlapping
degenerate

63
Q

what is the best way to study enzymes and allow for fair comparison between conditions

A

look at initial rate

64
Q

explain how optimal temp affects rate of enzyme catalysed reaction

A

more kinetic energy
more frequent collisions between the enzymes and substrates
more enzyme-substrate complexes formed

65
Q

what is a recessive allele

A

a faulty version of the gene

66
Q

what do you bring up when talking about things that will stop mRNA

A

they’ll bind to either mRNA or ribosome, changing the shape and preventing the two from binding
translation can therefore not occur
tRNA then can’t bind to mRNA and so, the polypeptide isn’t synthesised

67
Q

what is the name of the centre of a chromosome and what is the name of where spindle fibres come from

A

centre: centromere
spindle: centrioles

68
Q

what is a centriole vs centromere

A

centromere: centre of chromosome
centriole: spindle fibres

a level biology (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions