2B & C Proteins, Genetics and Inheritance Flashcards
(64 cards)
1
Q
gene
A
seq. of bases on DNA molecule that code for a seq of a.a in a polypeptide chain
2
Q
allele
A
different form of a gene -> diff alleles = diff base seq.
found at same locus on chromosome
3
Q
genotype
A
alleles a person has eg. Bb/BB/bb
4
Q
phenotype
A
characteristic of organism eg. brown eyes
5
Q
dominant allele
A
allele that produces a characteristic when
1+ copy is present eg. BB
6
Q
recessive allele
A
allele that produces characteristic when
2 copies present eg. bb
7
Q
incomplete dominance
A
when dominant allele trait isn’t completely shown over recessive allele trait
-> both alleles expressed
eg. RR -> red flowers rr -> white flowers
Rr -> PINK FLOWERS
8
Q
homozygote
A
organism that has 2 identical alleles of particular gene -> eg. BB/bb
9
Q
heterozygote
A
organism that has 2 different alleles of particular gene -> eg. Bb
10
Q
carrier
A
organism that has 1 dominant, 1 recessive (hetero.) so DOESN’T have disease but carries copy of allele for disease
11
Q
mutation
A
changes to base seq of DNA
caused by errors in DNA replication
12
Q
what errors in DNA replication cause mutations?
A
- SUBSTITUTION -> change in 1 base
- DELETION -> deleting 1 base
- INSERTION -> adding 1 base
- DUPLICATION -> adding same base more than once
- INVERSION -> seq of bases REVERSED
ID IDs
13
Q
Order of DNA bases determines order of a.a in protein.
What happens if mutation is present?
A
- primary structure changed
- could change 3D shape of protein
- so doesn’t work properly
14
Q
what happens if there is a mutation in gene?
A
can cause genetic disorder eg. CF
15
Q
how is CF obtained?
A
caused by mutation in gene coding for
CTFR protein
16
Q
what is a CTFR protein?
A
- channel protein
- moves Cl⁻ ions from cells -> mucus
-> causes H₂O to move into mucus by osmosis
= watery mucus
17
Q
how does mutant CTFR affect its function?
A
less efficient at transporting Cl⁻ ions OUT of cell
= less water moves out by osmosis = THICK MUCUS
18
Q
how does CF affect respiratory system?
A
- buildup mucus in lungs traps bacteria = higher risk of infection
- buildup mucus in airways -> caused by cilia unable to move mucus
-> some airways blocked = gas exchange decreases
= less s.a for gas exchange = DIFFICULTY BREATHING
19
Q
how does CF affect digestive system?
A
- tube that goes from pancreas->small intestine can get blocked by mucus
-> prevents dig. enzymes reaching small intestine = less able to digest food so LESS NUTRIENTS ABSORBED - mucus can cause CYSTS IN PANCREAS = stops production of enzymes …
- mucus lining small intestine is v thick = STOPS ABSORPTION OF NUTRIENTS
20
Q
how does CF affect reproductive system?
A
mucus supposed to prevent infection and move sex cells
MEN: vas deferens (tube connecting balls to dick) is absent / blocked by mucus = SPERM NEVER REACHES DICK
WOMEN: thick cervical mucus prevents sperm reaching egg -> decreases mobility of sperm = DECREASES CHANCE OF MAKING IT TO EGG
21
Q
what are the main uses of genetic screening?
A
- identifying people carrying allele at locus for particular disorder
- screening embryos BEFORE IMPLANTATION in fertility treatment (PGD)
- testing foetus before birth -> PRENATAL TESTING
22
Q
what are there roles of tRNA?
A
- carries a.a to ribosomes (in translation)
- each tRNA carries a SPECIFIC A.A
- tRNAs ANTICODON BIND TO mRNAs CODON
23
Q
role of mRNA?
A
carries genetic code from DNA in nucleus -> cytoplasm where its used to make a PROTEIN during translation
24
Q
3 differences between replication of DNA and transcription of DNA
A
- replication inv. DNA NUCLEOTIDES whereas transcription inv. RNA NUCLEOTIDES
- replication: makes double stranded DNA whereas
transcription: makes single stranded RNA - replication: makes IDENTICAL COPIES whereas
transcription: makes COMPLIMENTARY COPIES
25
semi conservative DNA replication
**1/2** strands in new DNA mol. are from **o.g**
therefore **GENETIC CONTINUITY** between **generations of cells**
26
describe the process of DNA replication
1. **DNAhelicase** (enzyme) breaks **H-bonds** between bases on **2 POLYNUCLEOTIDE DNA STRANDS** -> makes helix **unravel**
2. **o.g** strand acts as **TEMPLATE** for new one -> **COMPLIMENTARY** BASE PAIRING = free DNA nucleotides **ATTRACTED to EXPOSED BASES**
3. **CONDENSATION** REACTIONS join nucleotides together (catalysed by **DNApolymerase**)
-> H-bonds form between o.g bases and new
27
describe the structure of DNA
- **complimentary base pairing** and **H-bonding** between 2 polynucleotide strands
- strands are **antiparallel**
- **phosphodiester bonds** between **deoxyribose** and **phosphate** (a.k.a backbone)
28
where does translation occur?
cytoplasm
29
describe **translation** in protein synthesis
1. mRNA molecule attaches to a ribosome
2. in cytoplasm: free molecules of tRNA
3. tRNA binds to **specific a.a** (also in cytoplasm) and bring them to mRNA on ribosome
4. **ANTICODON on each tRNA** pairs with **COMPLEMENTARY TRIPLET** on the **mRNA** = **CODON** (inc **start codon** on mRNA)
5. **2 tRNA** fit onto ribosome **at one time** -> bring a.a they are each carrying **side by side**
6. **PEPTIDE BOND** formed, via a **CONDENSATION REACTION**, **BETWEEN** the 2 a.a
7. process continues until **STOP CODON on the mRNA** reached
8. a.a is complete -> forms **FINAL POLYPEPTIDE**
30
describe the structure of tRNA
- **triplet** of **unpaired bases** at one end = **anticodon**
- region at the other end **where a specific a.a can attach**
31
what is a START CODON?
- Near beginning of the mRNA is a **triplet of bases** called the start codon **(AUG)**
- This is a **signal** to **START OFF TRANSLATION**
- AUG **codes** for **a.a METHIONINE**
32
how does a mutation prevent enzyme functioning properly?
1. if **folded incorrectly** -> substrate doesn't fit in active site
2. mutation leads to CHANGES IN **SEQ OF BASES**
3. ... leads to **DIFF A.A**
4. changes **3° STRUCTURE**
33
**non-overlapping genetic code**
each **3 a.a** are **DISTINCT** -> **base** is **only used once** in triplet
34
adv. of a.a having more than one code
- **effect of mutations reduced**
-> **a.a** may **not** be **altered**
- no affect on **protein**
35
how are a.a **joined together** in a polypeptide
- **PEPTIDE BOND** -> between **amine** and **carb. acid** group in **CONDENSATION** reaction
36
dipeptide
2 a.a bonded together
37
polypeptide
chain of 2+ a.a bonded together
38
degenerate code
**a.a** can be **coded for** by **more than one codon**
39
triplet code
3 bases (1 codon) code for 1 a.a
40
genetic code
**seq of base triplets** (codons) in **DNA** or **mRNA** which **codes for specific a.a**
- non-overlapping
- degenerate
41
what does gene therapy involve?
using various **mechanisms** to **alter person's genetic material** to treat / cure **diseases**
42
what are 4 factors that affect enzyme activity?
- temp
- enzyme conc
- substrate conc
- pH
43
how is initial rate of reaction calculated over time?
(enzyme practical)
1 / time
44
what is effect of enzyme conc on enzyme activity?
(enzyme practical)
as enzyme conc increases = **increased no. enzyme-substrate complexes** made
-> as more **frequent successful collisions** between **SUBSTRATE** and **ACTIVE SITE** form enzyme-substrate complexes
-> so **rate increases** to an **optimum**
45
describe the 2 types of test for screening fetuses for genetic disorders
| prenatal testing
***- AMNIOCENTESIS***
-> testing sample cells from **amniotic fluid** (contains **fetal cells which has DNA**)
-> sample obtained using v fine needle into abdomen
-> small risk miscarriage
***- CHORIONIC VILLI SAMPLING (CVS)***
-> testing sample cells from **chorionic villi** (part of **fetus connecting to mother**) containing **fetal DNA**
-> using v fine needle into abdomen OR vagina with catheter
-> small risk miscarriage
46
discuss the social / ethical viewpoints related to genetic screening
**identification of carriers**
PROS
-> allows ppl to make **informed decision** before having children
CONS
-> emotional distress
-> tests **aren't 100% accurate** = decisions made on false info
-> **genetic discrimination**
**PGD**
PROS
->** less chance** baby having **genetic disorder**
-> as before implantation = **avoids abortion issues**
CONS
-> used to find out **other characteristics**
= leads to **designer babies**
47
explain why the secondary structure of a protein is an **ɑ helix** or a **β pleated sheet**
**H-bonds** form **between a.a** in polypeptide chain
-> makes it **coil** (ɑ helix) or **fold** (β pleated sheet)
48
what determines the tertiary structure of a protein?
(4 marks)
- ionic bonds
- disulphide bonds
-> when 2 molecules of **a.a cysteine** get close: **sulphur** atom **bonds** to other **sulphur** in **other cysteine** -> forming disulphide bond
- hydrophobic/philic interactions -> hydrophobic groups **clump together** when close
-> so hydrophilic grouos more likely to be **pushed to outside**
-> affects **how protein folds up in final structure**
- H-bonds
49
explain how a protein's primary structure determines its 3D structure and properties
(3 marks)
- **a.a seq** of protein determines **what bonds** will form and how protein will **fold up into 3D structure**
- eg. if many cysteines -> form **disulphide bonds** **(keratin)**
with each other and protein **folds in certain way**
- **3D** structure (**globular / fibrous**) **determines properties** which relate to its **function** in body
50
describe the globular 3D structure of proteins
eg. haemoglobin
- **spherical** made of **multiple polypeptide chains**
- chains are **coiled up** so hydrophilic parts on outside of molecule and hydrophobic parts of chain face inwards
-> making molecules soluble so **easily transported in fluids**
51
**haemoglobin** is a **globular** protein. explain how this is useful for its function
- made of **4 polypeptide chains**
- carries **O₂** around body in **blood**
- chains **coiled up** so hydrophilic parts on **outside** and hydrophobic parts of chain face **inwards** ...
- ... making them **soluble** so **easily transported in blood**
- has **cooperative binding** so **changes shape** when it binds to O₂
-> makes it **easier** for **next one** to bind
- has **iron** containing **4 haem groups** that **bind to O₂**
52
**collagen** is a fibrous protein. explain how this is useful to its function
(4 marks)
- long **insoluble** (doesn't affect water potential of cells as it holds body cells together)
- **primary** structure twisted into **ɑ** **helix**
- **3 helixes** **twist** to form triple superhelix (also held together by H-bonds)
- chains held together by **lots of H-bonds**
-> makes protein **strong**
- collagen is strong and stable but **flexible** so good for **forming connective tissue**
53
describe the fibrous 3D structure of proteins
eg. collagen, keratin
- **long, insoluble polypeptide chains** that are tightly **coiled** to form **rope** shape
- chains held together by **lots of bonds** (disulphide, H-bonds)
-> makes protein **strong**
-> so found in **supportive tissue**
54
**describe what might happen to polypeptide to make it a** **functional enzyme**
## Footnote
is this right??
- **folded** to make **globular** shape which is **precise for function** as an enzyme
- **3D** shape held together by **bonds** **between R groups** (eg. ionic, disulphide) to **produce active site**
55
intracellular enzymes
catalyse reactions **inside** cells
56
extracellular enzymes
- **produced** and **secreted** by cells
- to catalyse reactions **outside** cells
57
what is an enzyme?
(2 marks)
- **proteins** that speed up chemical reactions ...
- by acting as **biological catalysts** that **reduce Ea**
58
explain how enzyme properties relate to their tertiary structure
(5 marks)
- enzymes are v **specific** -> usually **only catalyse 1 reaction** (eg. maltase only breaks down maltose)
- as **only 1 complementary substrate** will **fit** into **active site**
- active site shape **determined** by enzymes **tertiary** structure
- **tertiary** structure **determined by primary** structure
- so **each** enzyme has **diff tertiary** = **diff primary** structure = **diff active site shape**
- if substrate shape doesn't match active site = **enzyme-substrate complex not formed** = **reaction not catalysed**
59
what happens if the tertiary structure of an enzyme is **altered**?
(3 marks)
- **shape** of **active site changes** ...
- so **substrate won't fit** into active site ...
- so **enzyme-substrate complex not** formed ...
- so enzyme **cannot carry out its function** :(
60
what causes a change in tertiary structure?
- changes in **pH / temp**
- **primary** structure **determined by gene**
- if **mutation occurs in gene** -> could change **tertiary** structure of enzyme produced
61
(polyploidy)
occurs when an organism has **more than two sets** of **homologous chromosomes**
caused by **mutation**
62
design an experiment to investigate the effect of enzyme and substrate conc on initial rate of reaction
control variables
-> temp
-> vol enzyme sol - 2cm³ trypsin
-> vol substrate - 5cm³ casein
-> conc substrate
METHOD
1. set up **water bath** so temp kept **constant**
2. mark **X** on one side of test tube -> fill with **5cm³ casein sol** and place in water bath with 2nd test tube with **2cm³ trypsin** (start at lowest conc **0.2%**)
3. allow subs to **acclimatise** for **3 mins** so both at **same temp**
4. **add** test tube trypsin to casein and start **stopwatch** -> time how long until **casein** sol turns **transparent** (when you **clearly see X** mark)
5. **repeat** 2x more then repeat with other conc (**0.0%,** 0.4%, 0.6%, 0.8%, 1.0%)
initial rate of reaction 𝛼 enzyme conc
as **↑ enzymes present** = **↑ active sites available** to form **enzyme-sub complexes**
63
Meselson and Stahl provided evidence that DNA replication is **semi-conservative**.
describe how they proved this
(6 marks)
1. 2 samples bacteria grown -> 1 **in nutrient broth** containing light, other heavy
*-> as bacteria **reproduced**, **took up N** from broth to make **nucelotides** for **new DNA** -> so N became part of bacterial DNA*
2. **DNA contains Nitrogen** -> so used two **isotopes** ... **¹⁵N (heavy)** and **¹⁴N (light)**
3. light DNA settled at **top** of centrifuge, heavy settled near **bottom**
4. **heavy** N bacteria **replicated** in **light N broth**
5. if DNA conservative, heavy DNA would still be together and sit at **bottom** and **new light** N would settle at **top**
6. BUT semi-conservative DNA, **new** bacterial DNA would **contain 1 light, 1 heavy** strand ...
7. ... and DNA would **settle between** where light N DNA and heavy N DNA settled
64
describe **transcription** in protein synthesis
1. **RNA polymerase** (enzyme) attaches to DNA double helix at **start codon**
2. **H-bonds broken** between strands and **helix unravels**
3. one strand used as **template** to make mRNA copy
4. RNA polymerase **lines up RNA mononucleotides along template strand**
5. **complementary base pairing** means mRNA strand is **complimentary** copy of **DNA template (antisense) strand** -> bases **joined** by RNA polymerase, forming **mRNA** molecule
6. RNA polymerase **moves along DNA**, separating strand and making mRNA strand
7. H-bonds between DNA strands **reform** once RNA polymerase has **passed by** - reforms double helix
8. when RNA polymerase reaches **stop codon** -> stops making mRNA and **detaches from DNA**
9. mRNA moves from nucleus->cytoplasm through **nuclear pore**
