Genes And Health Flashcards
1
Q
What is another name for proteins
A
Polypeptides
2
Q
Describe what the primary structure of a protein is
A
A linear sequence of the amino acids in a protein
3
Q
Secondary structure is the _____________________ of parts of a _____________ due to ________ bonds between _______ bonds
A
- regular folding
- protein
- hydrogen
- peptide
4
Q
Alpha helix is a type of ________ structure
A
Secondary
5
Q
Alpha helixes are held together by _____________ bonds running __________ to the long ______________
A
- hydrogen
- parallel
- helical axis
6
Q
Why is alpha helix a stable and strong structure
A
Has many hydrogen bonds
7
Q
What is a beta pleated sheet
A
Another type of secondary structure
8
Q
A beta pleat sheet is when the polypeptide chain ___________ back and forth forming a sheet of _____________
A
- zig-zags
- antiparallel strands
9
Q
Beta pleated sheets strands are held together by ____________ bonds between ____________ bonds
A
- hydrogen
- peptide
10
Q
Tertiary structure is the __________________ structure of the whole protein chain formed by ________ between _____________
A
- overall 3D
- bonds
- R groups
11
Q
Hydrophobic interactions forming tertiary structures are between…
A
R groups
12
Q
Hydrogen bonds in tertiary groups are between…
A
H and O of R groups
13
Q
_________ in tertiary structures are between charged R groups
A
Ionic Bonds
14
Q
S-S bonds in tertiary structures are __________ and between ______________ R groups
A
- covalent
- two cysteine R groups
15
Q
Quaternary Structure is…
A
The 3D structure of several polypeptide chains interacting w/ each other via bonds between R
groups
16
Q
What are conjugated proteins?
A
- proteins that are joined to other non protein molecules
17
Q
What is another name for non protein molecules
A
Prosthetic groups
18
Q
Globular proteins have ________ structures
A
Primary, Secondary, Tertiary, Quaternary
19
Q
Fibrous Proteins have ______________ structure
A
Primary, Secondary, Quaternary
20
Q
Globular proteins have a _____________________ shape
A
- small spherical and compact
21
Q
Why are globular proteins soluble?
A
They have hydrophillic R groups outside
22
Q
Examples of Globular proteins
A
-Enzymes
-Antibodies
-Hormones
23
Q
What is the shape of fibrous proteins?
A
- Large long strong fibres
24
Q
Fibrous proteins are insoluble as ________________
A
Hydrophobic R groups are on the outside
25
Fibrous proteins have __________ roles
- Structural
- collagen, keratin
26
How are peptides made
Condensation
27
How are peptides broken
Hydrolysis
28
What happens when amino acids are dissolved in water?
- They become Zwitterions
- hydrogen gained on N terminus
- hydrogen lost on C terminus
29
what effects does cystic fibrosis have on the respiratory system?
- lung infections
- breathing problems
30
What effects does CF have on the digestive system
- impaired digestion
- damage to pancreas
31
C.F can cause _____________ in the reproductive system
Infertility
32
Cystic fibrosis can cause sweat to become…
Very salty
33
What does the plural membrane do?
Prevent friction between lungs and ribs
34
Name two components of the trachea
- smooth muscle ( not under conscious control )
- cartilage ring ( keeps it open)
35
Mucus is produced by __________ cells which are located between ______________________ lining ________ tract
- goblet
- ciliates epithelial cells
- respitory
36
The trachea, bronchi and bronchioles contain:
- goblet cells
- ciliated cells
37
Terminal bronchioles only contain:
- ciliated cells
38
Why are there no goblet/ciliated cells in the alveoli?
- they would reduce gas exchange
39
1. Cilia
2. Mucus
3. Goblet cell
4. Columnar epithelial cell
5. Basement membrane
6. Lung
7. Voice box
40
1. Vesicles with mucus
2. Goblet cell
3. ER and Golgi
4. Nucleus
41
What is the basement membrane?
- sticky anchor for cells
- holds cells in position
- made of a protein carbohydrate matrix
42
What’s is golgis role in goblet cells?
- exocytosis - transport protein out of cells
43
What is the ER role in goblet cell
- protein synthesis
44
What are the adaptations of goblet cells?
- large ER and Golgi apparatus
- many vesicles from which mucus is secreted out of cell
45
- Mucus traps ____________ ( dust, _________ ) and prevents them from entering alveoli
- _____________ inhaled air
- foreign particles
- bacteria
- moisturises
46
Epithelial cells line both the …….. and the …………
-outside (skin)
- inside of the body
47
Describe Psuedostratified epithelium structure
- consists of a single layer of cells
- nuclei are in different position giving the appearance of more than 1 year of cells ( therefore pseudostartified)
48
What type of epithelium lines trachea + bronchi
Pseudostratified columnar
49
What type of epithelia cells are in the bronchioles?
- pseudostratified columnar
50
How does cystic fibrosis cause lung infections?
- mucus traps bacteria but mucus is too sticky to be moved away by cilia
- low oxygen levels in mucus so anaerobic bacteria thrive
- WBC fighting bacteria dna and release DNA making mucus stickier
- leading inflammation and infection
51
Why does cystic fibrosis cause breathing difficulties?
- mucus blocks bronchioles so less/ no air
- leading to reduced gas exchange
52
What is the Ficks law of diffusion
= rate of diffusion is inversely proportional to the thickness of the gas exchange surface
Rate of diffusion = ( surface area * difference in concentration ) / diffusion distance
53
1 - branch of pulmonary vein
2 - branch of pulmonary artery
3 - terminal bronchiole
4 - capillary
5 - alveoli
54
Terminal Bronchiole
1 - capillary from pulmonary vein
2 - blood plasma
3 - endothelium ( capillary wall )
4 - red blood cell
5 - surfactant and moisture
6 - capillary to pulmonary artery
7 - simple squamous epithelium ( alveolar wall )
55
What is surfactant and what is its role?
= phospholipid
- prevents permanent collapse and sticking together of alveoli
56
What makes gas exchange from alveoli to blood efficient
- short diffusion distance
- large concentration gradient
- surface area
57
Short diffusion distance in the alveoli
- oxygen only diffuses through ____ cells (______________ and ______________ to reach the red blood cells)
- the _____________ epithelium of the alveoli is very ________
- capillaries have a very narrow _________ so distance to a RBC is short
- two
- epithelium
- endothelium
- squamos
- thin
- lumen
58
- In the alveoli oxy conc is ___% ( due to the mixing of inhaled air with _______ air)
- In the blood it is ____%
- The 8% difference in oxygen levels between the alveoli and blood provides a ______________
- 13
- 5
- large concentration gradient
59
How is surface area increased in the alveoli?
- many alveoli which are very short
60
How does cystic fibrosis reduce surface area
- mucus blocks bronchioles
- fewer alveoli available for gas exchange
61
Mucus fills alveoli _________ diffusion distance
- increasing
62
Why do people with cystic fibrosis have reduced elasticity in their lungs?
- they over inflate their lungs to try and get enough oxygen
63
How does cystic fibrosis overall cause tiredness?
- reduced gas exchange leading to an oxygen shortage
64
In the alveoli what type of epithelium cells are there?
- simple squamous
65
What does Glycosylated mean?
- A carbohydrate attached to an r group
66
What does phosphorylated mean?
- phosphoryl group attached to the r group
67
Describe the experiment that show membrane was fluid
- mouse cell and human cell membrane proteins were labelled with different dyes
- the cells were fused together
- after some time different proteins had mixed around in the membrane
68
What does the mouse cell + human cell membrane protein experiment show about membranes?
- proteins (and lipids) in membranes move
- membrane has fluid properties
69
Why is the fluid mosaic model described as fluid?
- two dimensional ‘liquid’ with lateral movement of lipids and proteins through layer
70
Why is the fluid mosaic model described as mosaic?
- composed of different types of macromolecules. For example integral/peripheral proteins, lipids and glycolipds.
71
What is the overall conclusion of lipids structure?
- lipids form two dimensional liquid in which lipids can move
- proteins attached to membrane
72
Lipid bilayer
1 - glycolipid
2 - channel protein
3 - integral protein
4 - integral transmembrane protein
5 - cholesterol
6 - peripheral protein
7- glycoprotein
73
Phospholipid
1 - Headgroup
2 - Phosphate
3 - Glycerol
4 - Fatty acid
74
Triglyceride
1 - glycerol
2 - fatty acid
75
What is the difference between triglycerides and phosopholipids
Phospholipid has only two fatty acids and replaces one with a phosphate
76
1 - head group
2 - phosphate
3 - glycerol
4 - saturated hydrocarbon fatty acid tails
5 - double bond ( gives bend )
77
Describe the nature of the head of the phospholipid
Hydropholic ( polar)
78
Describe the nature of the fatty acid tails
- hydrophobic
- non polar
79
Describe the arrangement of the phospholipid bilayer
- Hydropillic heads face towards solution
- Hydrophobic tails face away from solution
80
When a hydrocarbon is described as unsaturated it means that the hydrocarbon…
Contains double or triple bonds
81
If there are more unsaturated fatty acids phospholipids will be…
- Less tightly packed
- more movement possible
82
If there are more saturated fatty acids phospholipids will be…
- tightly packed
- less movement possible
83
If there is more cholesterol there is
- reduced movement of phospholipids
84
Describe membrane permeability in terms of non polar molecules
- non polar molecules can move through the membrane as they are not affected (repelled or attracted) by the hydrophilic heads
85
Describe membrane permeability in terms of polar molecules
- polar molecules cannot move through the membrane due to the charged phospholipid head
86
Why can water travel through the membrane?
- It is a very small and abundant molecule
87
Describe passive transport
- not energy dependent:
- diffusion
- facilitated diffusion
- osmosis
88
Describe active transport
- energy dependent:
- active transport
- bulk transport
- endocytosis
- exocytosis
89
Describe diffusion
- movement of molecules from an area where they are at high concentration to an area where they are at low concentration
90
Describe facilitated diffusion
- movement of molecules from an area of high conc. to an area of low conc. via a carrier or channel protein
91
What is a gated channel
- some channels can be opened by hormones or by a change in potential difference
92
1 - channel protein
2 - carrier protein
3 - polar molecules ( ions )
4 - larger molecules ( glucose )
93
describe osmosis
= movement of water molecules from a high water potential to a low water potential across a selectively permeable membrane
OR
= net movement of water into areas of high solute concentration across a selectively permeable membrane
94
How is movement of water molecules reduced by solute
- water forms H-bonds with solute molecules
95
define hypotonic
- solution with lower solute conc. than cell
96
What happens to animal cells if they are in a hypotonic solution
Lysed ( burst )
97
Define Isotonic
- solution with the same solute concentration as cell
98
Define hypertonic
- solution with higher solute conc than cell
99
What happens if an animal cell is in a hypertonic solution
- shrivelled (crenate)
100
An animal cell is turgid in a __________ solution
Hypertonic
101
An animal cell is flaccid in a ________ solution
Isotonic
102
A plant cell is plasmolysed in a __________ solution
Hypertonic
103
Describe Active transport
- movement from a low concentration to a high concentration via carrier proteins using energy from ATP
104
Define bulk transport
= energy dependent bulk transport out of and into cells
105
Exocytosis is the export of molecules out of cells involving _____________ that _________ with the cell membrane and ________ their contents
- vesicles
- fuse
- release
106
Describe endocytosis
- uptake of molecules by the creation of a vesicle from the cell membrane
- cell membrane engulfs the molecules to be transported
107
Phagocytosis is known as
- cell eating ( solid particle )
108
Placytosis is known as
- cell drinking
- extracellular fluid
109
Receptor mediated is
- specific form of endocytosis involving receptors and coat proteins
Q
110
What happens when there is too little water in the mucus of a healthy person ( non - CF )
1 - Cl ion are pumped into cell from tissue fluid across basal membrane against conc grad. Via ATP. They can’t go back through the basal membrane because they are polar
2 - CFTR channel is open causing Na+ channel to close. Cl- diffuses through the open CFTR channel
3 - Na+ diffuses down the electrochemical/ electrical gradient into the mucus ( where Cl- ions go Na+ will follow through the intercellular space/ tissue fluid)
4 - High salt conc. in the mucus draws water out of cells by osmosis - mucus becomes runny
5 - water is drawn into cells from tissue fluid by osmosis
111
Why is mucus so sticky in cystic fibrosis
1 - CTFR is absent or non-function
2 - Na+ channel is permanently open and Na+ diffuses into cells from mucus and is pumped into tissue fluid
3 - Cl - diffuses out of mucus towards basal membrane via the intercellular space down an electrical gradient
4 -Water is continually removed from mucus by osmosis: mucus becomes sticky
5 - bacteria and wbc gets trapped; dna released from dead wbc makes mucus even more sticky
112
How does CF affect digestion
- mucus blocks pancreatic duct
- macromolecules are not broken down
- protease cannot leave and damages organ resulting in fibrosis and cysts
- bile production/secretion is affected
- fat soluble vitamins ( A D E K) not enough of
113
Describe enzyme action
- substrate binds to active site
- enzyme substrates complex formed
- enzyme catalyses reaction and products are formed
- products no longer fit and are released
- enzyme remains unchanged and it is free to be used again
114
Active site
- part of the folded protein where substrate binds
115
Lock and Key theory
- substrate shape is complementary to shape of active site
116
Induced fit theory
- substrate binding induces shape change in active site which enables perfect fit and catalytic activity
117
How is activation energy lowered?
- attraction between charged r group of active site and substrate was may distort shape of substrate and assists in formation of bond or breaking of bonds
- ES complex restricts movement of substrate
118
`What is a cofactor
- non protein chemical compound that is bound to enzymes and required for enzyme action
119
What is an apoenzyme
- enzyme without its cofactor
120
What is a holoenzyme
- enzyme active because it has its cofactors
121
Co enzyme
- tightly bound cofactor
122
Prosthetic group
- loosely bound cofactor
123
Competitive inhibitor
Competes with substrate for active site
124
Non competitive inhibitor
- binds to allosteric site and changes shape of active site
125
The pyrimidines are single ring and include:
- thymine
- cytosine
126
Purines are double rings and include:
-adenine
-guanine
127
What is the first step in nucleotide formation?
- deoxyribose + base -> nucleoside
- condensation reaction
128
What is step two of nucleotide formation
-phosphate + nucleoside -> nucleotide
-condensation reaction
129
How are polynucleotides formed
- a phosphatediester bond is formed between the deoxyribose of one nucleotide and the oh of a phosphate group on a different nucleotide
130
What is the definition of transcription?
- copying of a length of DNA code one gene long into messenger RNA (MRNA)
- in the nucleus
- catalysed by RNA polymerase
131
Label these parts of DNA
1 - promoter (kicks starts transmission)
2 - gene
3 - terminator
132
What are regulatory sequences?
- promoter and terminator regions
133
Describe step 1 of transcription
Transcription initiation
- RNA polymerase binds to DNA and stands for promoter regions
- RNA polymerase partially unwinds the DNA double helix
- RNA polymerase starts to transcribe DNA sequence on the anti-sense (template) strand into RNA sequence (via complementary base pairing)
134
What is RNA synthesis?
- anti-sense strand transcribed
-> RNA has the same sequence as coding strand (U replaces T)
135
RNA polymerase has ………… activity (unwinding of DNA ………………)
- helicase
- double helix
136
What is polymerase activity?
- formation of phosphodiester bonds
- between RNA nucleotides in 5’ -> 3’ synthesis
137
What is step 2 in transcription
Transcription elongation
-transcription continues until the terminator is reached
138
What is step 3 in transcription
Transcription termination
-RNA polymerase reaches terminator
-transcription stops:
- RNA polymerase + transcript are released
139
Describe RNA Processing
-RNA transcript is SPLICED = Introns are removed
-RNA transcript receives CAP AND TAIL
-process RNA transcript = MRNA
140
What is rna export
-MRNA is exported out of the nucleus via pores in the nuclear membrane
1 - nucleus
2 - mrna
141
What is wrong in CF in terms of digestive system?
-thick sticky mucus in the pancreatic duct and small intensive
142
How is digestion affected by CF?
-digestive enzymes made in pancreas cannot reach the duodenum
-reduced absorption of food
-reduced absorption of nutrients (digestion products)
143
The pancreas is damaged due to CF because…
Trapped digestive enzymes damage pancreatic tissue
144
What is the result of trapped digestive enzymes damaging the pancreatic tissue?
-Islets of Langerhans get damaged
-insulin production reduced or stopped
-Type 1 Diabetes
145
How does cystic fibrosis cause infertility?
-thick sticky mucus in reproductive system
146
How does CF cause infertility in women?
-mucus blocks service
-pregnancy still possible but more likely with IVF (puberty delayed to age 15 on avg)
147
How does cystic fibrosis cause infertility in men?
-50% have no sperm duct
-if sperm duct is present, it is usually blocked w/ mucus
-95% of sperm produced is abnormal
-only 1-2% of CF men can reproduce naturally (without IVF)
148
How is sweat produced in healthy people?
-sweat is salty water made in sweat glands
-some salt is reabsorbed out of sweat duct into cells
(Cl- ions diffuse via CFTR, Na+ ions follow electrical gradient)
149
How is sweat produced in CF patients?
-no functional CFTR so Cl- and Na+ are not reabsorbed and instead are lost in sweat)
-Sweat has much higher concentration of salt
150
What is the definition of Translation?
= using the sequence of codons on mRNA to produce a sequence of amino acids in a protein
151
Where does translation take place?
-in the cytoplasm on free ribosomes or on the rER
152
What is translation catalysed by?
-ribosomes
-tRNA
-peptide synthetase
153
What is the genetic code?
-Bases (= codon) code for 1 specific amino acid
154
What is the definition of triplet code?
-3 bases code for 1 amino acid (AA)
155
Degenerate is when some AAs…
Can be coded for by several codons
156
What are the three stop codons?
-UAA
-UAG
-UGA
157
What is the definition of universal?
-Same code in all organisms
158
Each codons read separately because the codons are…
Non-overlapping
159
Why is important that the genetic code is universal?
-due to common ancestry
160
What are ribosomes?
=cell components responsible for protein synthesis
161
What are ribosomes made up of?
-protein and ribosomal RNA (rRNA)
162
Ribosomes contain small and…
Large subunits
163
What type of ribosomes are there in prokaryotes (bacteria)?
70S
164
What type of ribosomes are there in eukaryotes?
80S
165
What does the S in 70/80S mean?
How long the ribosomes will take to settle
166
The Svedberg unit (S) is a measure of ……………………. Time in a centrifuge.
Sedimentation
167
Why do the ribosomes in eukaryotic cells have a higher Svedberg unit?
-They are larger and therefore take longer to settle at the bottom of a solution
168
How do antibiotics work?
-They bind to the small subunit of bacterial ribosomes, stopping attachment of TRNA, therefore stopping protein synthesis
169
Why do antibiotics kill bacteria but not other organisms?
Antibiotics bind much less successfully with the 80S ribosomes in eukaryotes, so have little effect on protein synthesis.
170
TRNA has a ………………… shaped structure
Clover leaf
171
tRNA has anticodon sequence which is…
Complementary to the codon
172
tRNA binds to a ……………….. corresponding to anti-codon
Specific amino acid
173
What are the two steps of translation?
-Translation initiation
-Translation elongation
174
What happens in translation initiation?
-ribosome attaches to mRNA
-ribosome moves along mRNA (5’ -> 3’) to find first AUG (start codon)
-tRNA (carrying Met AA) with complementary anticodon pairs w/ codon through complementary base pairing
175
What happens in translation elongation (1)?
- next tRNA with anticodon complementary to next mRNA is loaded
-adjacent AAs joined via a peptide bond (catalysed by peptide synthesise)
-ribosome moves along mRNA and first tRNA is released
-next tRNA with anticodon complementary to next mRNA codon is loaded
176
What happens in translation elongation (2)
-adjacted AAS joined via a peptide bond (catalysed by peptide synthetase)
-ribosome moves along and second tRNA is released
-elongation continues until a stop codon is reached
-when the ribosome reaches a STOP codon a release factor is loaded and translation stops
-the ribosome and completed polypeptide are released from mRNA
177
What are polysomes
-several ribosomes can bind to the same mRNA forming a polysome
-> several polypeptide chains are made simultaneously
178
Proteins made on free ribosomes in the cytoplasm go to:
-cytoplasm
-nucleus
-mitochondria
-chloroplasts
179
What is the rER
-rough endoplasmic reticulum
180
Where do proteins on the rER go to?
-ER
-Golgi
-lysosomes
-plasma membrane
-secretory vesicles (exocytosis)
181
What type of proteins fold the polypetide into secondary and tertiary structure?
-chaperones
182
How many hydrogen bonds are between adenine and thymine?
2 hydrogen bonds
183
How many hydrogen bonds are between guanine and cytosine?
3
184
What is DNAs role?
-codes for amino acid sequence in proteins
185
What is the sugar in DNA?
Deoxyribos
186
What are the bases in DNA?
A C G T
187
What is the structure of DNA
Double standard (ds) double helix
188
IS DNA long or short?
Long
189
Where is DNA located?
In the nucleus
190
The amount of DNA is…
Constant in cells
191
DNA is chemically very…
Stable
192
What is RNAs role?
-component in mRNA and tRNA
193
What is the sugar in RNA
Ribose
194
What is the sugar in RNA
-ribose
195
What are the bases in RNA
-ACGU
196
What is the structure of RNA
-single stranded often secondary structure
197
What is DNA replication?
- copying of the entire genome in preparation for cell division
198
what is step 1 of dna replication?
- DNA helicase unwinds DNA double helix
199
What is step 2 of DNA replication?
- the two strands of the DNA double helix are separated by breaking hydrogen bonds between base pairs
200
What is step 3 in dna replication?
- parent strands act as template for new DNA strands
- free nucleotides pair with their complementary nucleotides
- dna polymerase forms phosphodiester bonds
201
What is step 4 in dna replication?
- two identical new strands of dna are made
202
What’s is step 5 of dna replication?
- newly formed DNA rewinds into helices
203
What does semi-conservative mean?:
- one strand of the original parental DNA
- one new DNA strand
204
DNA replication is semi…
Semi conservative
205
What are the two alternative models of DNA replication?
- conservative (1 old + 1 new DNA molecule)
- dispersive / fragmentary (DNA molecules made randomly of 50% old and 50% new)
206
What is the Meselson-stahl experiment?
- one set of bacteria is grown with heavy 15N
- another set of bacteria is grown with light 14N
- isolation of DNA + centrifugal ion
= DNA with heavy 15N at bottom
= DNA with light 14N at top
207
What type of DNA replication is this?
Semi-conservative
208
What type of DNA replication is this?
Dispersive
209
What type of DNA replication is this?
Conservative
210
1 mistake made per ………….. nucleotides during replication
100,000
211
What fixes 99% of mutations?
- DNA polymerase proofreading
212
What fixes mutations after DNA polymerase proofreading?
- post-replication repair enzymes
213
How many mutations are there per diploid cell per division?
- 4
214
What is a point mutation?
- change in a single nucleotide (base)
215
What happens if there a deletion mutation?
A nucleotide is missing
- frameshift mutation (reading frame changes - different AA sequence)
216
What happens if there is an insertion mutation?
An additional nucleotide in the sequence
= frameshift mutation
217
What happens if there is a substitution mutation?
A nucleotides is replaced by another
1. Silent mutation (degenerate code: no change in AA sequence)
2. Missense mutation (change in AA sequence)
3. Non-sense mutation (stop codon produces a truncated protein)
218
What’s happens if there is an inversion mutation?
Nucleotides swapped
- missense mutation (change in AA sequence)
219
What are the orgins of mutation?
- mutagens (X-rays, UV light, chemicals) induce chemical changes in bases
220
How many mutations are there for cystic fibrosis?
- 1400
- in 70% if cases its a F508 mutation
221
What is a F508 mutation?
- deletion of three nucleotides
- missense mutation because the AA sequence changes
- this causes a loss in the phenylanine amino acid which causes misfolding of the protein
222
What is a chromosome?
- a highly coiled linear strand of DNA and associated proteins (histones)
223
What is a chromatid?
- one of two strands of DNA that makes up a duplicated chromosome
224
What is a centromere?
- region where two sister chromatids attach
225
What is a telomere?
- protective region of repetitive nucleotide sequences at each end of a chromosome
226
What are histones?
- proteins that package and order the dna into chromosomes
227
What is a homologous chromosome?
- a pair of paternal and maternal chromosomes with same set of genes in same sequence
228
What is a gene?
- a region of DNA that codes for the amino acid sequence in a protein
229
What is a gene locus?
- specific location of a gene on a chromosome
230
What is an allele?
- a alternative form of a gene
231
What does homozygous mean?
- identical alleles on homologous chromsomes
232
What does heterozygous mean?
- different alleles on homologous chromosomes
233
What does haploid mean?
- one set of chromosomes (1n)
234
What does diploid mean?
- two sets of chromosomes (2n)
235
What is genotype?
- genetic make up/ alleles present
236
What is phenotype?
- visible characteristics caused by expression of alleles
237
What is a dominant allele?
- an allele that is always expressed in the phenotype
238
What is a recessive allele?
- an allele that is only expressed in the absence of a dominant allele/ when homozygous
239
What is genetic testing?
- dna is tested to see if it contains the most common mutations for a particular genetic disease
- sample of cheek cell or WBC tested (in blood test)
240
What is preimplantation genetic diagnosis? (PGD)
- fertilisation by IVF
- a cell is removed from the resulting embryos at the 8-16 stage
- DNA is analysed
241
Why is IVF required for PGD
- several embryos needed
- to be able to assess the embryos for testing
242
What is amniocentesis?
- during pregnancy 15-18 weeks
- needle used to remove often l cells from amniotic fluid
- DNA is analysed
243
What are the advantedges of amniocentesis?
- 1% chance of miscarriage
- results after 3 days
244
What are disadvantages of amniocentesis?
- only carried out later in pregnancy
- risk of false positives
245
What is chronic villi sampling?
- during pregnancy from 10 weeks
- suction tube used to remove foetal cells from chorion
- DNA is analysed
246
What are the advantedges of CVS?
- earlier in pregnancy
- results available in 3 days
247
What are disadvantages to do with CVS?
- 1-2% of miscarrriage
- risk of false positives
248
What is newborn screening?
- blood samples (heel prick test) at 5 days after birth
- DNA is analysed
