IMMS: Week 1 Flashcards
1
Q
Describe the structure of DNA
A
Double helix which complementary base pairing (A-T + G-C) -> nucleosomes -> supercoils -> chromosomes
2
Q
How many chromosomes are there in an individual
A
46
3
Q
What is an autosomal chromosome
A
One that is not sex-determining
4
Q
What are the sex chromosomes in males and females
A
Males - XY and Females - XX
5
Q
What is a karyotype
A
The number and appearance of a chromosome in a cell, arranged in order of size
6
Q
How are chromosomes arranged in a karyotype
A
Pair 1 is the LARGEST, pair 22 is the SMALLEST, sex pair is 23
7
Q
How many base pairs does each DNA duplex have
A
10^7 base pairs
8
Q
How many genes do we have
A
22,000
9
Q
Describe the arms of a chromosome
A
Each has a p (small) and a q (long) arm
10
Q
What is mitosis
A
The division of a parent cell into two identical diploid daughter cells
11
Q
What is DNA not in replication called
A
chromatin
12
Q
What is DNA during replication called
A
Chromosomes
13
Q
What is DNA following replication called
A
Chromatids
14
Q
What stage of the cell cycle do we have to be in so mitosis can occur
A
Interphase
15
Q
What is the longest phase of the cell cycle
A
Interphase
16
Q
What happens in G1
A
No visible activity: Rapid Growth Normal Metabolic Function New Organelles produced Protein synthesis of those involved in spindle formation
17
Q
What happens in synthesis
A
DNA doubles through DNA replication
Histone proteins double through protein synthesis
Centrosome replication
18
Q
What happens in G2
A
Chromosomes condense
Energy stores accumulate
Mitochondria and centrioles double
19
Q
What happens in prophase
A
Chromatin condenses into chromosomes
Centrosomes nucleate microtubules and move to opposite poles of the nucleus
20
Q
What happens in metaphase
A
Chromosomes line up along the equatorial plane
21
Q
What happens in anaphase
A
Sister chromatids separate and are pushed to opposite poles of the cells, centromere first as spindle fibres contract
22
Q
What happens in telophase
A
Nuclear membrane forms
Chromosomes unfold into chromatin
Cytokinesis begins
23
Q
What happens in cytokinesis
A
Cell organelles are distributes evenly across the two daughter cells
Cytoplasm divides
24
Q
What is Down Syndrome
A
An extra chromosome at 21 (trisomy 21)
25
How can we tell on histological slides if a cell is undergoing mitosis
Dark nuclei and if the nuclei are not all the same size
26
Is meiosis a cycle?
No
27
What is the product of meiosis
4 haploid daughter cells which are distinct from each other and the parent cell
28
Where does crossing over of sister chromatids occur
meiosis 1 when chromosomes pair up into homologous pairs
29
Where does random assortment of chromosomes occur
In metaphase 1
30
What is the product of oogenesis
One egg cell and two polar bodies
31
Define non-disjunction
Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division
32
Name the two types of non-disjunction
Failure of separation of homologous chromosomes - meiosis I
| Failure of sister chromatids to separate - meiosis II
33
What condition can this result in
Down Syndrome
34
Define Gonadal mosaicism
When precursor germline cells are a mixture of two or more genetically identical cell lines
One cell line is normal, the other is mutated
35
How can incidence of gonadal mosaicism increase
Increasing paternal age
36
Is gonadal mosaicism more common in males or females
Males
37
Is the parent also affected with gonadal mosaicism. Explain your answer
No because it results from mutation of the germline and not via inheritance
38
What inheritance pattern is usually seen with gonadal mosaicism
Autosomal dominant or X-linked
39
How common are genetic diseases
Not very rare but enough for us to make services which tailor to these conditions
40
Four examples of genetic diseases
Huntingtons
Cystic Fibrosis
Downs Syndrome
Haemophilia
41
What are multifactorial diseases
A combination of genetic and environmental factors
42
What is the main type of disease affecting developed countries
Multifactorial
43
Four examples of multifactorial diseases
Diabetes
Spina Bifida
Cleft Lip
Schizophrenia
44
What is the main cause of disease in third world and A&E
Environmental
45
What chromosomes are autosomal
1-22 (No sex chromosome)
46
What is a locus
The position of a gene/DNA on the genetic map
47
What is a genotype
Genetic constitution of an individual
48
What is a phenotype
Appearance of an individual which results from the interaction with the environment and genotype
49
What is an allele
One of several alternative forms of a gene at a specific locus
50
What is polymorphism
Frequent hereditary variations at a locus that do not cause problems.
51
How can polymorphisms affect you
Makes you more/less efficient or make you more/less susceptible to disease
52
Define consanguinity
Reproductive union between two relatives
53
Define autozygosity
Homozygous by descent (inheritance of the same mutant allele through two branches of a family tree)
54
Define homozygous
Both alleles at a specific locus are the same
55
Define heterozygous
Alleles at a locus are different
56
Define hemizygous
Describe that are carried on an unpaired chromosome (refers to X chromosome on a male)
57
Define penetrance
Proportion of people with a gene/genotype who show the expected phenotype
58
Define complete penetrance
Gene or genes for the trait are expressed in all the population
59
Define incomplete penetrance
Gene or genes for the trait are expressed only in parts of the population
60
Define variable expression
Variation in clinical features (type and severity) of a genetic disorder between individuals with the same gene alteration
61
Define sex limitation
Expression of a particular characteristic limited to one of the sexes
62
Define a multifactorial condition
Due to a combination of genetic and environmental factors
63
Define late-onset
Condition that hadn't manifested itself at birth
64
Define autosomal dominant
A disease that only manifests itself in the heterozygous state
65
Why can both parents be unaffected by a disease even if the son has it (3 reasons)
1. Gonadal mosaicism
2. Variable (incomplete) penetrance
3. Only way to pass it is from male to male
These are all seen with autosomal dominant conditions
66
Define autosomal recessive
A disease that manifests itself in the homozygous state only.
67
What is the chance of an offspring getting the disease if its autosomal recessive
25%
68
What is the chance of offspring being a carrier if its an autosomal recessive disease
50%
69
What is the chance of a healthy sibling being a carrier
2/3
70
What is the most common autosomal recessive disease in whites
Cystic Fibrosis
71
Does cystic fibrosis have complete or variable penetrance
Variable
72
Incidence of cystic fibrosis in the UK
1 in 25,000
73
Define X-Linked inheritance
Caused by a mutation in genes on the X-chromosome
74
Can an X-linked disease be passed on from father-to-son? and why?
No, never not even carriers
Because sons always get their X chromosomes from their mother
75
What are all daughters from an affected male (X-Linked disease)?
Carriers
NOTE: All males will be unaffected
76
What gender are X-linked disorders usually transmitted through
Females
77
Define lyonisation
The process of X chromosome inactivation
78
When is X chromosome inactivated
During embryological development
79
Why is the X chromosome inactivated during lyonisation
Prevents them from having a double number of X chromosome gene products compared to males
ONLY ONE X chromosome will be functional
80
What is a BARRBODY
Inactive X chromosome which is packaged in heterochromatin
81
What is the result of packaging an X-chromosome into heterochromatin
Prevents it from being transcripted
82
What is heterochromatin
Chromosome material of greater density than normal chromosome. Here the activity of genes are suppressed
83
What is imprinting (non-mendelian)
For some genes only 1 out of 2 alleles are active, the other is inactive (could be either that the maternal or paternal allele is inactive)
84
What is Knudson's 2-hit hypothesis
Gene mutations may either be inherited or acquired during a person''s life
85
What causes a sporadic cancer
2 acquired mutations
86
What causes hereditary cancers
1 inherited mutation + 1 acquired mutation
87
What is an 'ideogram'
Diagrammatic form of chromosome bands, bands are numbered according to distance to the centromere
88
What is the mendelian classification of genetic disease
Autosomal dominant/recessive or X-linked
89
What is a non-traditional genetic disease
Mitochondrial (all mitochondria is inherited by the mother), imprinting or mosaicism
90
What is a square in a genetic pedigree
```
Square = male
Circle = Female
```
91
What is epithelia needed for
Protection, absorption and secretion
92
What are four examples of supporting tissues
Blood, tendons, bones and cartilage
93
What are three types of muscle
Smooth, skeletal and heart
94
What does haematoxylin stain
Acids blue
95
What does eosin stain
Alkaline pink
96
What substances does haematoxylin stain
Cell nuclei and RNA blue
97
What does eosin stain
Cytoplasm and colloidal proteins pink
Keratin - Orange/red
ECF
98
Do water extra-cellular jelly and fat stain
No
99
What does Alcian Blue stain
GAG rich structures blue
Goblet cells blue
Mast cell granules blue
Stain cartilage matrix blue
100
What does iron haematoxylin stain
Nuclei and elastic fibres black
101
What does PAS stain
Hexose sugars (e.g. goblet cell mucous cartilage matrix, glycogen, basement membrane and glycocalyx) pink
102
What does touluidine blue stain
Nuclei, ribosomes and cytoplasm dark blue
Cartilage matrix and mast cell granules pale blue
GAG bright purple
103
Role of the nucleus
Houses DNA as chromatin within the nucleolus
Nucleolus produces RNA
104
Role of the mitochondria
Site of oxidative phosphorylation
Double membrane (highly folded inner)
105
What happens in the outer membrane of the mitochondria
Lipid synthesis and fatty acid metabolism
106
What happens in the inner membrane of the mitochondria
Respiratory chain (electron transport) ATP production
107
What happens in the mitochondrial matrix
Krebs' cycle
108
What take place in the mitochondrial intramembranous space
Nucleotide phosphorylation
109
Role of the RER
Site of protein synthesis
110
Role of SER
Site of membrane lipid synthesis
Processes and stores synthesised proteins
111
Role of the cis golgi
Receives SER vesicles and phosphorylates proteins
112
Role of medial golgi
Modifies products by adding sugars (to form oligosaccharides) to lipids and peptides
113
Role of the trans golgi network
Proteolysis of peptides into active forms and sorting of molecules into vesicles which bud from the surface
114
Where is the golgi apparatus located
Close to the cell nucleus
115
Can I see the golgi apparatus in most cells?
No, but seen clearly in plasma cells
